/*-------------------------------------------------------------------------
 *
 * tablecmds.c
 *	  Commands for creating and altering table structures and settings
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  src/backend/commands/tablecmds.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/attmap.h"
#include "access/genam.h"
#include "access/gist.h"
#include "access/heapam.h"
#include "access/heapam_xlog.h"
#include "access/multixact.h"
#include "access/reloptions.h"
#include "access/relscan.h"
#include "access/sysattr.h"
#include "access/tableam.h"
#include "access/toast_compression.h"
#include "access/xact.h"
#include "access/xlog.h"
#include "access/xloginsert.h"
#include "catalog/catalog.h"
#include "catalog/heap.h"
#include "catalog/index.h"
#include "catalog/namespace.h"
#include "catalog/objectaccess.h"
#include "catalog/partition.h"
#include "catalog/pg_am.h"
#include "catalog/pg_attrdef.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_depend.h"
#include "catalog/pg_foreign_table.h"
#include "catalog/pg_inherits.h"
#include "catalog/pg_largeobject.h"
#include "catalog/pg_namespace.h"
#include "catalog/pg_opclass.h"
#include "catalog/pg_policy.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_publication_rel.h"
#include "catalog/pg_rewrite.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_tablespace.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "catalog/storage.h"
#include "catalog/storage_xlog.h"
#include "catalog/toasting.h"
#include "commands/cluster.h"
#include "commands/comment.h"
#include "commands/defrem.h"
#include "commands/event_trigger.h"
#include "commands/sequence.h"
#include "commands/tablecmds.h"
#include "commands/tablespace.h"
#include "commands/trigger.h"
#include "commands/typecmds.h"
#include "commands/user.h"
#include "commands/vacuum.h"
#include "common/int.h"
#include "executor/executor.h"
#include "foreign/fdwapi.h"
#include "foreign/foreign.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/parsenodes.h"
#include "optimizer/optimizer.h"
#include "parser/parse_coerce.h"
#include "parser/parse_collate.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "parser/parse_type.h"
#include "parser/parse_utilcmd.h"
#include "parser/parser.h"
#include "partitioning/partbounds.h"
#include "partitioning/partdesc.h"
#include "pgstat.h"
#include "rewrite/rewriteDefine.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "storage/lock.h"
#include "storage/predicate.h"
#include "storage/smgr.h"
#include "tcop/utility.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/partcache.h"
#include "utils/relcache.h"
#include "utils/ruleutils.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/timestamp.h"
#include "utils/typcache.h"
#include "utils/usercontext.h"

/*
 * ON COMMIT action list
 */
typedef struct OnCommitItem
{
	Oid			relid;			/* relid of relation */
	OnCommitAction oncommit;	/* what to do at end of xact */

	/*
	 * If this entry was created during the current transaction,
	 * creating_subid is the ID of the creating subxact; if created in a prior
	 * transaction, creating_subid is zero.  If deleted during the current
	 * transaction, deleting_subid is the ID of the deleting subxact; if no
	 * deletion request is pending, deleting_subid is zero.
	 */
	SubTransactionId creating_subid;
	SubTransactionId deleting_subid;
} OnCommitItem;

static List *on_commits = NIL;


/*
 * State information for ALTER TABLE
 *
 * The pending-work queue for an ALTER TABLE is a List of AlteredTableInfo
 * structs, one for each table modified by the operation (the named table
 * plus any child tables that are affected).  We save lists of subcommands
 * to apply to this table (possibly modified by parse transformation steps);
 * these lists will be executed in Phase 2.  If a Phase 3 step is needed,
 * necessary information is stored in the constraints and newvals lists.
 *
 * Phase 2 is divided into multiple passes; subcommands are executed in
 * a pass determined by subcommand type.
 */

typedef enum AlterTablePass
{
	AT_PASS_UNSET = -1,			/* UNSET will cause ERROR */
	AT_PASS_DROP,				/* DROP (all flavors) */
	AT_PASS_ALTER_TYPE,			/* ALTER COLUMN TYPE */
	AT_PASS_ADD_COL,			/* ADD COLUMN */
	AT_PASS_SET_EXPRESSION,		/* ALTER SET EXPRESSION */
	AT_PASS_OLD_INDEX,			/* re-add existing indexes */
	AT_PASS_OLD_CONSTR,			/* re-add existing constraints */
	/* We could support a RENAME COLUMN pass here, but not currently used */
	AT_PASS_ADD_CONSTR,			/* ADD constraints (initial examination) */
	AT_PASS_COL_ATTRS,			/* set column attributes, eg NOT NULL */
	AT_PASS_ADD_INDEXCONSTR,	/* ADD index-based constraints */
	AT_PASS_ADD_INDEX,			/* ADD indexes */
	AT_PASS_ADD_OTHERCONSTR,	/* ADD other constraints, defaults */
	AT_PASS_MISC,				/* other stuff */
} AlterTablePass;

#define AT_NUM_PASSES			(AT_PASS_MISC + 1)

typedef struct AlteredTableInfo
{
	/* Information saved before any work commences: */
	Oid			relid;			/* Relation to work on */
	char		relkind;		/* Its relkind */
	TupleDesc	oldDesc;		/* Pre-modification tuple descriptor */

	/*
	 * Transiently set during Phase 2, normally set to NULL.
	 *
	 * ATRewriteCatalogs sets this when it starts, and closes when ATExecCmd
	 * returns control.  This can be exploited by ATExecCmd subroutines to
	 * close/reopen across transaction boundaries.
	 */
	Relation	rel;

	/* Information saved by Phase 1 for Phase 2: */
	List	   *subcmds[AT_NUM_PASSES]; /* Lists of AlterTableCmd */
	/* Information saved by Phases 1/2 for Phase 3: */
	List	   *constraints;	/* List of NewConstraint */
	List	   *newvals;		/* List of NewColumnValue */
	List	   *afterStmts;		/* List of utility command parsetrees */
	bool		verify_new_notnull; /* T if we should recheck NOT NULL */
	int			rewrite;		/* Reason for forced rewrite, if any */
	bool		chgAccessMethod;	/* T if SET ACCESS METHOD is used */
	Oid			newAccessMethod;	/* new access method; 0 means no change,
									 * if above is true */
	Oid			newTableSpace;	/* new tablespace; 0 means no change */
	bool		chgPersistence; /* T if SET LOGGED/UNLOGGED is used */
	char		newrelpersistence;	/* if above is true */
	Expr	   *partition_constraint;	/* for attach partition validation */
	/* true, if validating default due to some other attach/detach */
	bool		validate_default;
	/* Objects to rebuild after completing ALTER TYPE operations */
	List	   *changedConstraintOids;	/* OIDs of constraints to rebuild */
	List	   *changedConstraintDefs;	/* string definitions of same */
	List	   *changedIndexOids;	/* OIDs of indexes to rebuild */
	List	   *changedIndexDefs;	/* string definitions of same */
	char	   *replicaIdentityIndex;	/* index to reset as REPLICA IDENTITY */
	char	   *clusterOnIndex; /* index to use for CLUSTER */
	List	   *changedStatisticsOids;	/* OIDs of statistics to rebuild */
	List	   *changedStatisticsDefs;	/* string definitions of same */
} AlteredTableInfo;

/* Struct describing one new constraint to check in Phase 3 scan */
/* Note: new not-null constraints are handled elsewhere */
typedef struct NewConstraint
{
	char	   *name;			/* Constraint name, or NULL if none */
	ConstrType	contype;		/* CHECK or FOREIGN */
	Oid			refrelid;		/* PK rel, if FOREIGN */
	Oid			refindid;		/* OID of PK's index, if FOREIGN */
	bool		conwithperiod;	/* Whether the new FOREIGN KEY uses PERIOD */
	Oid			conid;			/* OID of pg_constraint entry, if FOREIGN */
	Node	   *qual;			/* Check expr or CONSTR_FOREIGN Constraint */
	ExprState  *qualstate;		/* Execution state for CHECK expr */
} NewConstraint;

/*
 * Struct describing one new column value that needs to be computed during
 * Phase 3 copy (this could be either a new column with a non-null default, or
 * a column that we're changing the type of).  Columns without such an entry
 * are just copied from the old table during ATRewriteTable.  Note that the
 * expr is an expression over *old* table values, except when is_generated
 * is true; then it is an expression over columns of the *new* tuple.
 */
typedef struct NewColumnValue
{
	AttrNumber	attnum;			/* which column */
	Expr	   *expr;			/* expression to compute */
	ExprState  *exprstate;		/* execution state */
	bool		is_generated;	/* is it a GENERATED expression? */
} NewColumnValue;

/*
 * Error-reporting support for RemoveRelations
 */
struct dropmsgstrings
{
	char		kind;
	int			nonexistent_code;
	const char *nonexistent_msg;
	const char *skipping_msg;
	const char *nota_msg;
	const char *drophint_msg;
};

static const struct dropmsgstrings dropmsgstringarray[] = {
	{RELKIND_RELATION,
		ERRCODE_UNDEFINED_TABLE,
		gettext_noop("table \"%s\" does not exist"),
		gettext_noop("table \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not a table"),
	gettext_noop("Use DROP TABLE to remove a table.")},
	{RELKIND_SEQUENCE,
		ERRCODE_UNDEFINED_TABLE,
		gettext_noop("sequence \"%s\" does not exist"),
		gettext_noop("sequence \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not a sequence"),
	gettext_noop("Use DROP SEQUENCE to remove a sequence.")},
	{RELKIND_VIEW,
		ERRCODE_UNDEFINED_TABLE,
		gettext_noop("view \"%s\" does not exist"),
		gettext_noop("view \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not a view"),
	gettext_noop("Use DROP VIEW to remove a view.")},
	{RELKIND_MATVIEW,
		ERRCODE_UNDEFINED_TABLE,
		gettext_noop("materialized view \"%s\" does not exist"),
		gettext_noop("materialized view \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not a materialized view"),
	gettext_noop("Use DROP MATERIALIZED VIEW to remove a materialized view.")},
	{RELKIND_INDEX,
		ERRCODE_UNDEFINED_OBJECT,
		gettext_noop("index \"%s\" does not exist"),
		gettext_noop("index \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not an index"),
	gettext_noop("Use DROP INDEX to remove an index.")},
	{RELKIND_COMPOSITE_TYPE,
		ERRCODE_UNDEFINED_OBJECT,
		gettext_noop("type \"%s\" does not exist"),
		gettext_noop("type \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not a type"),
	gettext_noop("Use DROP TYPE to remove a type.")},
	{RELKIND_FOREIGN_TABLE,
		ERRCODE_UNDEFINED_OBJECT,
		gettext_noop("foreign table \"%s\" does not exist"),
		gettext_noop("foreign table \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not a foreign table"),
	gettext_noop("Use DROP FOREIGN TABLE to remove a foreign table.")},
	{RELKIND_PARTITIONED_TABLE,
		ERRCODE_UNDEFINED_TABLE,
		gettext_noop("table \"%s\" does not exist"),
		gettext_noop("table \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not a table"),
	gettext_noop("Use DROP TABLE to remove a table.")},
	{RELKIND_PARTITIONED_INDEX,
		ERRCODE_UNDEFINED_OBJECT,
		gettext_noop("index \"%s\" does not exist"),
		gettext_noop("index \"%s\" does not exist, skipping"),
		gettext_noop("\"%s\" is not an index"),
	gettext_noop("Use DROP INDEX to remove an index.")},
	{'\0', 0, NULL, NULL, NULL, NULL}
};

/* communication between RemoveRelations and RangeVarCallbackForDropRelation */
struct DropRelationCallbackState
{
	/* These fields are set by RemoveRelations: */
	char		expected_relkind;
	LOCKMODE	heap_lockmode;
	/* These fields are state to track which subsidiary locks are held: */
	Oid			heapOid;
	Oid			partParentOid;
	/* These fields are passed back by RangeVarCallbackForDropRelation: */
	char		actual_relkind;
	char		actual_relpersistence;
};

/* Alter table target-type flags for ATSimplePermissions */
#define		ATT_TABLE				0x0001
#define		ATT_VIEW				0x0002
#define		ATT_MATVIEW				0x0004
#define		ATT_INDEX				0x0008
#define		ATT_COMPOSITE_TYPE		0x0010
#define		ATT_FOREIGN_TABLE		0x0020
#define		ATT_PARTITIONED_INDEX	0x0040
#define		ATT_SEQUENCE			0x0080
#define		ATT_PARTITIONED_TABLE	0x0100

/*
 * ForeignTruncateInfo
 *
 * Information related to truncation of foreign tables.  This is used for
 * the elements in a hash table. It uses the server OID as lookup key,
 * and includes a per-server list of all foreign tables involved in the
 * truncation.
 */
typedef struct ForeignTruncateInfo
{
	Oid			serverid;
	List	   *rels;
} ForeignTruncateInfo;

/* Partial or complete FK creation in addFkConstraint() */
typedef enum addFkConstraintSides
{
	addFkReferencedSide,
	addFkReferencingSide,
	addFkBothSides,
} addFkConstraintSides;

/*
 * Partition tables are expected to be dropped when the parent partitioned
 * table gets dropped. Hence for partitioning we use AUTO dependency.
 * Otherwise, for regular inheritance use NORMAL dependency.
 */
#define child_dependency_type(child_is_partition)	\
	((child_is_partition) ? DEPENDENCY_AUTO : DEPENDENCY_NORMAL)

static void truncate_check_rel(Oid relid, Form_pg_class reltuple);
static void truncate_check_perms(Oid relid, Form_pg_class reltuple);
static void truncate_check_activity(Relation rel);
static void RangeVarCallbackForTruncate(const RangeVar *relation,
										Oid relId, Oid oldRelId, void *arg);
static List *MergeAttributes(List *columns, const List *supers, char relpersistence,
							 bool is_partition, List **supconstr,
							 List **supnotnulls);
static List *MergeCheckConstraint(List *constraints, const char *name, Node *expr, bool is_enforced);
static void MergeChildAttribute(List *inh_columns, int exist_attno, int newcol_attno, const ColumnDef *newdef);
static ColumnDef *MergeInheritedAttribute(List *inh_columns, int exist_attno, const ColumnDef *newdef);
static void MergeAttributesIntoExisting(Relation child_rel, Relation parent_rel, bool ispartition);
static void MergeConstraintsIntoExisting(Relation child_rel, Relation parent_rel);
static void StoreCatalogInheritance(Oid relationId, List *supers,
									bool child_is_partition);
static void StoreCatalogInheritance1(Oid relationId, Oid parentOid,
									 int32 seqNumber, Relation inhRelation,
									 bool child_is_partition);
static int	findAttrByName(const char *attributeName, const List *columns);
static void AlterIndexNamespaces(Relation classRel, Relation rel,
								 Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved);
static void AlterSeqNamespaces(Relation classRel, Relation rel,
							   Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved,
							   LOCKMODE lockmode);
static ObjectAddress ATExecAlterConstraint(List **wqueue, Relation rel,
										   ATAlterConstraint *cmdcon,
										   bool recurse, LOCKMODE lockmode);
static bool ATExecAlterConstraintInternal(List **wqueue, ATAlterConstraint *cmdcon, Relation conrel,
										  Relation tgrel, Relation rel, HeapTuple contuple,
										  bool recurse, LOCKMODE lockmode);
static bool ATExecAlterConstrEnforceability(List **wqueue, ATAlterConstraint *cmdcon,
											Relation conrel, Relation tgrel,
											Oid fkrelid, Oid pkrelid,
											HeapTuple contuple, LOCKMODE lockmode,
											Oid ReferencedParentDelTrigger,
											Oid ReferencedParentUpdTrigger,
											Oid ReferencingParentInsTrigger,
											Oid ReferencingParentUpdTrigger);
static bool ATExecAlterConstrDeferrability(List **wqueue, ATAlterConstraint *cmdcon,
										   Relation conrel, Relation tgrel, Relation rel,
										   HeapTuple contuple, bool recurse,
										   List **otherrelids, LOCKMODE lockmode);
static bool ATExecAlterConstrInheritability(List **wqueue, ATAlterConstraint *cmdcon,
											Relation conrel, Relation rel,
											HeapTuple contuple, LOCKMODE lockmode);
static void AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Relation rel,
											bool deferrable, bool initdeferred,
											List **otherrelids);
static void AlterConstrEnforceabilityRecurse(List **wqueue, ATAlterConstraint *cmdcon,
											 Relation conrel, Relation tgrel,
											 Oid fkrelid, Oid pkrelid,
											 HeapTuple contuple, LOCKMODE lockmode,
											 Oid ReferencedParentDelTrigger,
											 Oid ReferencedParentUpdTrigger,
											 Oid ReferencingParentInsTrigger,
											 Oid ReferencingParentUpdTrigger);
static void AlterConstrDeferrabilityRecurse(List **wqueue, ATAlterConstraint *cmdcon,
											Relation conrel, Relation tgrel, Relation rel,
											HeapTuple contuple, bool recurse,
											List **otherrelids, LOCKMODE lockmode);
static void AlterConstrUpdateConstraintEntry(ATAlterConstraint *cmdcon, Relation conrel,
											 HeapTuple contuple);
static ObjectAddress ATExecValidateConstraint(List **wqueue,
											  Relation rel, char *constrName,
											  bool recurse, bool recursing, LOCKMODE lockmode);
static void QueueFKConstraintValidation(List **wqueue, Relation conrel, Relation fkrel,
										Oid pkrelid, HeapTuple contuple, LOCKMODE lockmode);
static void QueueCheckConstraintValidation(List **wqueue, Relation conrel, Relation rel,
										   char *constrName, HeapTuple contuple,
										   bool recurse, bool recursing, LOCKMODE lockmode);
static void QueueNNConstraintValidation(List **wqueue, Relation conrel, Relation rel,
										HeapTuple contuple, bool recurse, bool recursing,
										LOCKMODE lockmode);
static int	transformColumnNameList(Oid relId, List *colList,
									int16 *attnums, Oid *atttypids, Oid *attcollids);
static int	transformFkeyGetPrimaryKey(Relation pkrel, Oid *indexOid,
									   List **attnamelist,
									   int16 *attnums, Oid *atttypids, Oid *attcollids,
									   Oid *opclasses, bool *pk_has_without_overlaps);
static Oid	transformFkeyCheckAttrs(Relation pkrel,
									int numattrs, int16 *attnums,
									bool with_period, Oid *opclasses,
									bool *pk_has_without_overlaps);
static void checkFkeyPermissions(Relation rel, int16 *attnums, int natts);
static CoercionPathType findFkeyCast(Oid targetTypeId, Oid sourceTypeId,
									 Oid *funcid);
static void validateForeignKeyConstraint(char *conname,
										 Relation rel, Relation pkrel,
										 Oid pkindOid, Oid constraintOid, bool hasperiod);
static void CheckAlterTableIsSafe(Relation rel);
static void ATController(AlterTableStmt *parsetree,
						 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode,
						 AlterTableUtilityContext *context);
static void ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
					  bool recurse, bool recursing, LOCKMODE lockmode,
					  AlterTableUtilityContext *context);
static void ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
							  AlterTableUtilityContext *context);
static void ATExecCmd(List **wqueue, AlteredTableInfo *tab,
					  AlterTableCmd *cmd, LOCKMODE lockmode, AlterTablePass cur_pass,
					  AlterTableUtilityContext *context);
static AlterTableCmd *ATParseTransformCmd(List **wqueue, AlteredTableInfo *tab,
										  Relation rel, AlterTableCmd *cmd,
										  bool recurse, LOCKMODE lockmode,
										  AlterTablePass cur_pass,
										  AlterTableUtilityContext *context);
static void ATRewriteTables(AlterTableStmt *parsetree,
							List **wqueue, LOCKMODE lockmode,
							AlterTableUtilityContext *context);
static void ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap);
static AlteredTableInfo *ATGetQueueEntry(List **wqueue, Relation rel);
static void ATSimplePermissions(AlterTableType cmdtype, Relation rel, int allowed_targets);
static void ATSimpleRecursion(List **wqueue, Relation rel,
							  AlterTableCmd *cmd, bool recurse, LOCKMODE lockmode,
							  AlterTableUtilityContext *context);
static void ATCheckPartitionsNotInUse(Relation rel, LOCKMODE lockmode);
static void ATTypedTableRecursion(List **wqueue, Relation rel, AlterTableCmd *cmd,
								  LOCKMODE lockmode,
								  AlterTableUtilityContext *context);
static List *find_typed_table_dependencies(Oid typeOid, const char *typeName,
										   DropBehavior behavior);
static void ATPrepAddColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
							bool is_view, AlterTableCmd *cmd, LOCKMODE lockmode,
							AlterTableUtilityContext *context);
static ObjectAddress ATExecAddColumn(List **wqueue, AlteredTableInfo *tab,
									 Relation rel, AlterTableCmd **cmd,
									 bool recurse, bool recursing,
									 LOCKMODE lockmode, AlterTablePass cur_pass,
									 AlterTableUtilityContext *context);
static bool check_for_column_name_collision(Relation rel, const char *colname,
											bool if_not_exists);
static void add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid);
static void add_column_collation_dependency(Oid relid, int32 attnum, Oid collid);
static ObjectAddress ATExecDropNotNull(Relation rel, const char *colName, bool recurse,
									   LOCKMODE lockmode);
static void set_attnotnull(List **wqueue, Relation rel, AttrNumber attnum,
						   bool is_valid, bool queue_validation);
static ObjectAddress ATExecSetNotNull(List **wqueue, Relation rel,
									  char *conName, char *colName,
									  bool recurse, bool recursing,
									  LOCKMODE lockmode);
static bool NotNullImpliedByRelConstraints(Relation rel, Form_pg_attribute attr);
static bool ConstraintImpliedByRelConstraint(Relation scanrel,
											 List *testConstraint, List *provenConstraint);
static ObjectAddress ATExecColumnDefault(Relation rel, const char *colName,
										 Node *newDefault, LOCKMODE lockmode);
static ObjectAddress ATExecCookedColumnDefault(Relation rel, AttrNumber attnum,
											   Node *newDefault);
static ObjectAddress ATExecAddIdentity(Relation rel, const char *colName,
									   Node *def, LOCKMODE lockmode, bool recurse, bool recursing);
static ObjectAddress ATExecSetIdentity(Relation rel, const char *colName,
									   Node *def, LOCKMODE lockmode, bool recurse, bool recursing);
static ObjectAddress ATExecDropIdentity(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode,
										bool recurse, bool recursing);
static ObjectAddress ATExecSetExpression(AlteredTableInfo *tab, Relation rel, const char *colName,
										 Node *newExpr, LOCKMODE lockmode);
static void ATPrepDropExpression(Relation rel, AlterTableCmd *cmd, bool recurse, bool recursing, LOCKMODE lockmode);
static ObjectAddress ATExecDropExpression(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode);
static ObjectAddress ATExecSetStatistics(Relation rel, const char *colName, int16 colNum,
										 Node *newValue, LOCKMODE lockmode);
static ObjectAddress ATExecSetOptions(Relation rel, const char *colName,
									  Node *options, bool isReset, LOCKMODE lockmode);
static ObjectAddress ATExecSetStorage(Relation rel, const char *colName,
									  Node *newValue, LOCKMODE lockmode);
static void ATPrepDropColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
							 AlterTableCmd *cmd, LOCKMODE lockmode,
							 AlterTableUtilityContext *context);
static ObjectAddress ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
									  DropBehavior behavior,
									  bool recurse, bool recursing,
									  bool missing_ok, LOCKMODE lockmode,
									  ObjectAddresses *addrs);
static void ATPrepAddPrimaryKey(List **wqueue, Relation rel, AlterTableCmd *cmd,
								bool recurse, LOCKMODE lockmode,
								AlterTableUtilityContext *context);
static void verifyNotNullPKCompatible(HeapTuple tuple, const char *colname);
static ObjectAddress ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
									IndexStmt *stmt, bool is_rebuild, LOCKMODE lockmode);
static ObjectAddress ATExecAddStatistics(AlteredTableInfo *tab, Relation rel,
										 CreateStatsStmt *stmt, bool is_rebuild, LOCKMODE lockmode);
static ObjectAddress ATExecAddConstraint(List **wqueue,
										 AlteredTableInfo *tab, Relation rel,
										 Constraint *newConstraint, bool recurse, bool is_readd,
										 LOCKMODE lockmode);
static char *ChooseForeignKeyConstraintNameAddition(List *colnames);
static ObjectAddress ATExecAddIndexConstraint(AlteredTableInfo *tab, Relation rel,
											  IndexStmt *stmt, LOCKMODE lockmode);
static ObjectAddress ATAddCheckNNConstraint(List **wqueue,
											AlteredTableInfo *tab, Relation rel,
											Constraint *constr,
											bool recurse, bool recursing, bool is_readd,
											LOCKMODE lockmode);
static ObjectAddress ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab,
											   Relation rel, Constraint *fkconstraint,
											   bool recurse, bool recursing,
											   LOCKMODE lockmode);
static int	validateFkOnDeleteSetColumns(int numfks, const int16 *fkattnums,
										 int numfksetcols, int16 *fksetcolsattnums,
										 List *fksetcols);
static ObjectAddress addFkConstraint(addFkConstraintSides fkside,
									 char *constraintname,
									 Constraint *fkconstraint, Relation rel,
									 Relation pkrel, Oid indexOid,
									 Oid parentConstr,
									 int numfks, int16 *pkattnum, int16 *fkattnum,
									 Oid *pfeqoperators, Oid *ppeqoperators,
									 Oid *ffeqoperators, int numfkdelsetcols,
									 int16 *fkdelsetcols, bool is_internal,
									 bool with_period);
static void addFkRecurseReferenced(Constraint *fkconstraint,
								   Relation rel, Relation pkrel, Oid indexOid, Oid parentConstr,
								   int numfks, int16 *pkattnum, int16 *fkattnum,
								   Oid *pfeqoperators, Oid *ppeqoperators, Oid *ffeqoperators,
								   int numfkdelsetcols, int16 *fkdelsetcols,
								   bool old_check_ok,
								   Oid parentDelTrigger, Oid parentUpdTrigger,
								   bool with_period);
static void addFkRecurseReferencing(List **wqueue, Constraint *fkconstraint,
									Relation rel, Relation pkrel, Oid indexOid, Oid parentConstr,
									int numfks, int16 *pkattnum, int16 *fkattnum,
									Oid *pfeqoperators, Oid *ppeqoperators, Oid *ffeqoperators,
									int numfkdelsetcols, int16 *fkdelsetcols,
									bool old_check_ok, LOCKMODE lockmode,
									Oid parentInsTrigger, Oid parentUpdTrigger,
									bool with_period);
static void CloneForeignKeyConstraints(List **wqueue, Relation parentRel,
									   Relation partitionRel);
static void CloneFkReferenced(Relation parentRel, Relation partitionRel);
static void CloneFkReferencing(List **wqueue, Relation parentRel,
							   Relation partRel);
static void createForeignKeyCheckTriggers(Oid myRelOid, Oid refRelOid,
										  Constraint *fkconstraint, Oid constraintOid,
										  Oid indexOid,
										  Oid parentInsTrigger, Oid parentUpdTrigger,
										  Oid *insertTrigOid, Oid *updateTrigOid);
static void createForeignKeyActionTriggers(Oid myRelOid, Oid refRelOid,
										   Constraint *fkconstraint, Oid constraintOid,
										   Oid indexOid,
										   Oid parentDelTrigger, Oid parentUpdTrigger,
										   Oid *deleteTrigOid, Oid *updateTrigOid);
static bool tryAttachPartitionForeignKey(List **wqueue,
										 ForeignKeyCacheInfo *fk,
										 Relation partition,
										 Oid parentConstrOid, int numfks,
										 AttrNumber *mapped_conkey, AttrNumber *confkey,
										 Oid *conpfeqop,
										 Oid parentInsTrigger,
										 Oid parentUpdTrigger,
										 Relation trigrel);
static void AttachPartitionForeignKey(List **wqueue, Relation partition,
									  Oid partConstrOid, Oid parentConstrOid,
									  Oid parentInsTrigger, Oid parentUpdTrigger,
									  Relation trigrel);
static void RemoveInheritedConstraint(Relation conrel, Relation trigrel,
									  Oid conoid, Oid conrelid);
static void DropForeignKeyConstraintTriggers(Relation trigrel, Oid conoid,
											 Oid confrelid, Oid conrelid);
static void GetForeignKeyActionTriggers(Relation trigrel,
										Oid conoid, Oid confrelid, Oid conrelid,
										Oid *deleteTriggerOid,
										Oid *updateTriggerOid);
static void GetForeignKeyCheckTriggers(Relation trigrel,
									   Oid conoid, Oid confrelid, Oid conrelid,
									   Oid *insertTriggerOid,
									   Oid *updateTriggerOid);
static void ATExecDropConstraint(Relation rel, const char *constrName,
								 DropBehavior behavior, bool recurse,
								 bool missing_ok, LOCKMODE lockmode);
static ObjectAddress dropconstraint_internal(Relation rel,
											 HeapTuple constraintTup, DropBehavior behavior,
											 bool recurse, bool recursing,
											 bool missing_ok, LOCKMODE lockmode);
static void ATPrepAlterColumnType(List **wqueue,
								  AlteredTableInfo *tab, Relation rel,
								  bool recurse, bool recursing,
								  AlterTableCmd *cmd, LOCKMODE lockmode,
								  AlterTableUtilityContext *context);
static bool ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno);
static ObjectAddress ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
										   AlterTableCmd *cmd, LOCKMODE lockmode);
static void RememberAllDependentForRebuilding(AlteredTableInfo *tab, AlterTableType subtype,
											  Relation rel, AttrNumber attnum, const char *colName);
static void RememberConstraintForRebuilding(Oid conoid, AlteredTableInfo *tab);
static void RememberIndexForRebuilding(Oid indoid, AlteredTableInfo *tab);
static void RememberStatisticsForRebuilding(Oid stxoid, AlteredTableInfo *tab);
static void ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab,
								   LOCKMODE lockmode);
static void ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId,
								 char *cmd, List **wqueue, LOCKMODE lockmode,
								 bool rewrite);
static void RebuildConstraintComment(AlteredTableInfo *tab, AlterTablePass pass,
									 Oid objid, Relation rel, List *domname,
									 const char *conname);
static void TryReuseIndex(Oid oldId, IndexStmt *stmt);
static void TryReuseForeignKey(Oid oldId, Constraint *con);
static ObjectAddress ATExecAlterColumnGenericOptions(Relation rel, const char *colName,
													 List *options, LOCKMODE lockmode);
static void change_owner_fix_column_acls(Oid relationOid,
										 Oid oldOwnerId, Oid newOwnerId);
static void change_owner_recurse_to_sequences(Oid relationOid,
											  Oid newOwnerId, LOCKMODE lockmode);
static ObjectAddress ATExecClusterOn(Relation rel, const char *indexName,
									 LOCKMODE lockmode);
static void ATExecDropCluster(Relation rel, LOCKMODE lockmode);
static void ATPrepSetAccessMethod(AlteredTableInfo *tab, Relation rel, const char *amname);
static void ATExecSetAccessMethodNoStorage(Relation rel, Oid newAccessMethodId);
static void ATPrepChangePersistence(AlteredTableInfo *tab, Relation rel,
									bool toLogged);
static void ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel,
								const char *tablespacename, LOCKMODE lockmode);
static void ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode);
static void ATExecSetTableSpaceNoStorage(Relation rel, Oid newTableSpace);
static void ATExecSetRelOptions(Relation rel, List *defList,
								AlterTableType operation,
								LOCKMODE lockmode);
static void ATExecEnableDisableTrigger(Relation rel, const char *trigname,
									   char fires_when, bool skip_system, bool recurse,
									   LOCKMODE lockmode);
static void ATExecEnableDisableRule(Relation rel, const char *rulename,
									char fires_when, LOCKMODE lockmode);
static void ATPrepAddInherit(Relation child_rel);
static ObjectAddress ATExecAddInherit(Relation child_rel, RangeVar *parent, LOCKMODE lockmode);
static ObjectAddress ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode);
static void drop_parent_dependency(Oid relid, Oid refclassid, Oid refobjid,
								   DependencyType deptype);
static ObjectAddress ATExecAddOf(Relation rel, const TypeName *ofTypename, LOCKMODE lockmode);
static void ATExecDropOf(Relation rel, LOCKMODE lockmode);
static void ATExecReplicaIdentity(Relation rel, ReplicaIdentityStmt *stmt, LOCKMODE lockmode);
static void ATExecGenericOptions(Relation rel, List *options);
static void ATExecSetRowSecurity(Relation rel, bool rls);
static void ATExecForceNoForceRowSecurity(Relation rel, bool force_rls);
static ObjectAddress ATExecSetCompression(Relation rel,
										  const char *column, Node *newValue, LOCKMODE lockmode);

static void index_copy_data(Relation rel, RelFileLocator newrlocator);
static const char *storage_name(char c);

static void RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid,
											Oid oldRelOid, void *arg);
static void RangeVarCallbackForAlterRelation(const RangeVar *rv, Oid relid,
											 Oid oldrelid, void *arg);
static PartitionSpec *transformPartitionSpec(Relation rel, PartitionSpec *partspec);
static void ComputePartitionAttrs(ParseState *pstate, Relation rel, List *partParams, AttrNumber *partattrs,
								  List **partexprs, Oid *partopclass, Oid *partcollation,
								  PartitionStrategy strategy);
static void CreateInheritance(Relation child_rel, Relation parent_rel, bool ispartition);
static void RemoveInheritance(Relation child_rel, Relation parent_rel,
							  bool expect_detached);
static ObjectAddress ATExecAttachPartition(List **wqueue, Relation rel,
										   PartitionCmd *cmd,
										   AlterTableUtilityContext *context);
static void AttachPartitionEnsureIndexes(List **wqueue, Relation rel, Relation attachrel);
static void QueuePartitionConstraintValidation(List **wqueue, Relation scanrel,
											   List *partConstraint,
											   bool validate_default);
static void CloneRowTriggersToPartition(Relation parent, Relation partition);
static void DetachAddConstraintIfNeeded(List **wqueue, Relation partRel);
static void DropClonedTriggersFromPartition(Oid partitionId);
static ObjectAddress ATExecDetachPartition(List **wqueue, AlteredTableInfo *tab,
										   Relation rel, RangeVar *name,
										   bool concurrent);
static void DetachPartitionFinalize(Relation rel, Relation partRel,
									bool concurrent, Oid defaultPartOid);
static ObjectAddress ATExecDetachPartitionFinalize(Relation rel, RangeVar *name);
static ObjectAddress ATExecAttachPartitionIdx(List **wqueue, Relation parentIdx,
											  RangeVar *name);
static void validatePartitionedIndex(Relation partedIdx, Relation partedTbl);
static void refuseDupeIndexAttach(Relation parentIdx, Relation partIdx,
								  Relation partitionTbl);
static void verifyPartitionIndexNotNull(IndexInfo *iinfo, Relation partition);
static List *GetParentedForeignKeyRefs(Relation partition);
static void ATDetachCheckNoForeignKeyRefs(Relation partition);
static char GetAttributeCompression(Oid atttypid, const char *compression);
static char GetAttributeStorage(Oid atttypid, const char *storagemode);


/* ----------------------------------------------------------------
 *		DefineRelation
 *				Creates a new relation.
 *
 * stmt carries parsetree information from an ordinary CREATE TABLE statement.
 * The other arguments are used to extend the behavior for other cases:
 * relkind: relkind to assign to the new relation
 * ownerId: if not InvalidOid, use this as the new relation's owner.
 * typaddress: if not null, it's set to the pg_type entry's address.
 * queryString: for error reporting
 *
 * Note that permissions checks are done against current user regardless of
 * ownerId.  A nonzero ownerId is used when someone is creating a relation
 * "on behalf of" someone else, so we still want to see that the current user
 * has permissions to do it.
 *
 * If successful, returns the address of the new relation.
 * ----------------------------------------------------------------
 */
ObjectAddress
DefineRelation(CreateStmt *stmt, char relkind, Oid ownerId,
			   ObjectAddress *typaddress, const char *queryString)
{
	char		relname[NAMEDATALEN];
	Oid			namespaceId;
	Oid			relationId;
	Oid			tablespaceId;
	Relation	rel;
	TupleDesc	descriptor;
	List	   *inheritOids;
	List	   *old_constraints;
	List	   *old_notnulls;
	List	   *rawDefaults;
	List	   *cookedDefaults;
	List	   *nncols;
	List	   *connames = NIL;
	Datum		reloptions;
	ListCell   *listptr;
	AttrNumber	attnum;
	bool		partitioned;
	const char *const validnsps[] = HEAP_RELOPT_NAMESPACES;
	Oid			ofTypeId;
	ObjectAddress address;
	LOCKMODE	parentLockmode;
	Oid			accessMethodId = InvalidOid;

	/*
	 * Truncate relname to appropriate length (probably a waste of time, as
	 * parser should have done this already).
	 */
	strlcpy(relname, stmt->relation->relname, NAMEDATALEN);

	/*
	 * Check consistency of arguments
	 */
	if (stmt->oncommit != ONCOMMIT_NOOP
		&& stmt->relation->relpersistence != RELPERSISTENCE_TEMP)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("ON COMMIT can only be used on temporary tables")));

	if (stmt->partspec != NULL)
	{
		if (relkind != RELKIND_RELATION)
			elog(ERROR, "unexpected relkind: %d", (int) relkind);

		relkind = RELKIND_PARTITIONED_TABLE;
		partitioned = true;
	}
	else
		partitioned = false;

	if (relkind == RELKIND_PARTITIONED_TABLE &&
		stmt->relation->relpersistence == RELPERSISTENCE_UNLOGGED)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("partitioned tables cannot be unlogged")));

	/*
	 * Look up the namespace in which we are supposed to create the relation,
	 * check we have permission to create there, lock it against concurrent
	 * drop, and mark stmt->relation as RELPERSISTENCE_TEMP if a temporary
	 * namespace is selected.
	 */
	namespaceId =
		RangeVarGetAndCheckCreationNamespace(stmt->relation, NoLock, NULL);

	/*
	 * Security check: disallow creating temp tables from security-restricted
	 * code.  This is needed because calling code might not expect untrusted
	 * tables to appear in pg_temp at the front of its search path.
	 */
	if (stmt->relation->relpersistence == RELPERSISTENCE_TEMP
		&& InSecurityRestrictedOperation())
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("cannot create temporary table within security-restricted operation")));

	/*
	 * Determine the lockmode to use when scanning parents.  A self-exclusive
	 * lock is needed here.
	 *
	 * For regular inheritance, if two backends attempt to add children to the
	 * same parent simultaneously, and that parent has no pre-existing
	 * children, then both will attempt to update the parent's relhassubclass
	 * field, leading to a "tuple concurrently updated" error.  Also, this
	 * interlocks against a concurrent ANALYZE on the parent table, which
	 * might otherwise be attempting to clear the parent's relhassubclass
	 * field, if its previous children were recently dropped.
	 *
	 * If the child table is a partition, then we instead grab an exclusive
	 * lock on the parent because its partition descriptor will be changed by
	 * addition of the new partition.
	 */
	parentLockmode = (stmt->partbound != NULL ? AccessExclusiveLock :
					  ShareUpdateExclusiveLock);

	/* Determine the list of OIDs of the parents. */
	inheritOids = NIL;
	foreach(listptr, stmt->inhRelations)
	{
		RangeVar   *rv = (RangeVar *) lfirst(listptr);
		Oid			parentOid;

		parentOid = RangeVarGetRelid(rv, parentLockmode, false);

		/*
		 * Reject duplications in the list of parents.
		 */
		if (list_member_oid(inheritOids, parentOid))
			ereport(ERROR,
					(errcode(ERRCODE_DUPLICATE_TABLE),
					 errmsg("relation \"%s\" would be inherited from more than once",
							get_rel_name(parentOid))));

		inheritOids = lappend_oid(inheritOids, parentOid);
	}

	/*
	 * Select tablespace to use: an explicitly indicated one, or (in the case
	 * of a partitioned table) the parent's, if it has one.
	 */
	if (stmt->tablespacename)
	{
		tablespaceId = get_tablespace_oid(stmt->tablespacename, false);

		if (partitioned && tablespaceId == MyDatabaseTableSpace)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot specify default tablespace for partitioned relations")));
	}
	else if (stmt->partbound)
	{
		Assert(list_length(inheritOids) == 1);
		tablespaceId = get_rel_tablespace(linitial_oid(inheritOids));
	}
	else
		tablespaceId = InvalidOid;

	/* still nothing? use the default */
	if (!OidIsValid(tablespaceId))
		tablespaceId = GetDefaultTablespace(stmt->relation->relpersistence,
											partitioned);

	/* Check permissions except when using database's default */
	if (OidIsValid(tablespaceId) && tablespaceId != MyDatabaseTableSpace)
	{
		AclResult	aclresult;

		aclresult = object_aclcheck(TableSpaceRelationId, tablespaceId, GetUserId(),
									ACL_CREATE);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error(aclresult, OBJECT_TABLESPACE,
						   get_tablespace_name(tablespaceId));
	}

	/* In all cases disallow placing user relations in pg_global */
	if (tablespaceId == GLOBALTABLESPACE_OID)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("only shared relations can be placed in pg_global tablespace")));

	/* Identify user ID that will own the table */
	if (!OidIsValid(ownerId))
		ownerId = GetUserId();

	/*
	 * Parse and validate reloptions, if any.
	 */
	reloptions = transformRelOptions((Datum) 0, stmt->options, NULL, validnsps,
									 true, false);

	switch (relkind)
	{
		case RELKIND_VIEW:
			(void) view_reloptions(reloptions, true);
			break;
		case RELKIND_PARTITIONED_TABLE:
			(void) partitioned_table_reloptions(reloptions, true);
			break;
		default:
			(void) heap_reloptions(relkind, reloptions, true);
	}

	if (stmt->ofTypename)
	{
		AclResult	aclresult;

		ofTypeId = typenameTypeId(NULL, stmt->ofTypename);

		aclresult = object_aclcheck(TypeRelationId, ofTypeId, GetUserId(), ACL_USAGE);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error_type(aclresult, ofTypeId);
	}
	else
		ofTypeId = InvalidOid;

	/*
	 * Look up inheritance ancestors and generate relation schema, including
	 * inherited attributes.  (Note that stmt->tableElts is destructively
	 * modified by MergeAttributes.)
	 */
	stmt->tableElts =
		MergeAttributes(stmt->tableElts, inheritOids,
						stmt->relation->relpersistence,
						stmt->partbound != NULL,
						&old_constraints, &old_notnulls);

	/*
	 * Create a tuple descriptor from the relation schema.  Note that this
	 * deals with column names, types, and in-descriptor NOT NULL flags, but
	 * not default values, NOT NULL or CHECK constraints; we handle those
	 * below.
	 */
	descriptor = BuildDescForRelation(stmt->tableElts);

	/*
	 * Find columns with default values and prepare for insertion of the
	 * defaults.  Pre-cooked (that is, inherited) defaults go into a list of
	 * CookedConstraint structs that we'll pass to heap_create_with_catalog,
	 * while raw defaults go into a list of RawColumnDefault structs that will
	 * be processed by AddRelationNewConstraints.  (We can't deal with raw
	 * expressions until we can do transformExpr.)
	 */
	rawDefaults = NIL;
	cookedDefaults = NIL;
	attnum = 0;

	foreach(listptr, stmt->tableElts)
	{
		ColumnDef  *colDef = lfirst(listptr);

		attnum++;
		if (colDef->raw_default != NULL)
		{
			RawColumnDefault *rawEnt;

			Assert(colDef->cooked_default == NULL);

			rawEnt = (RawColumnDefault *) palloc(sizeof(RawColumnDefault));
			rawEnt->attnum = attnum;
			rawEnt->raw_default = colDef->raw_default;
			rawEnt->generated = colDef->generated;
			rawDefaults = lappend(rawDefaults, rawEnt);
		}
		else if (colDef->cooked_default != NULL)
		{
			CookedConstraint *cooked;

			cooked = (CookedConstraint *) palloc(sizeof(CookedConstraint));
			cooked->contype = CONSTR_DEFAULT;
			cooked->conoid = InvalidOid;	/* until created */
			cooked->name = NULL;
			cooked->attnum = attnum;
			cooked->expr = colDef->cooked_default;
			cooked->is_enforced = true;
			cooked->skip_validation = false;
			cooked->is_local = true;	/* not used for defaults */
			cooked->inhcount = 0;	/* ditto */
			cooked->is_no_inherit = false;
			cookedDefaults = lappend(cookedDefaults, cooked);
		}
	}

	/*
	 * For relations with table AM and partitioned tables, select access
	 * method to use: an explicitly indicated one, or (in the case of a
	 * partitioned table) the parent's, if it has one.
	 */
	if (stmt->accessMethod != NULL)
	{
		Assert(RELKIND_HAS_TABLE_AM(relkind) || relkind == RELKIND_PARTITIONED_TABLE);
		accessMethodId = get_table_am_oid(stmt->accessMethod, false);
	}
	else if (RELKIND_HAS_TABLE_AM(relkind) || relkind == RELKIND_PARTITIONED_TABLE)
	{
		if (stmt->partbound)
		{
			Assert(list_length(inheritOids) == 1);
			accessMethodId = get_rel_relam(linitial_oid(inheritOids));
		}

		if (RELKIND_HAS_TABLE_AM(relkind) && !OidIsValid(accessMethodId))
			accessMethodId = get_table_am_oid(default_table_access_method, false);
	}

	/*
	 * Create the relation.  Inherited defaults and CHECK constraints are
	 * passed in for immediate handling --- since they don't need parsing,
	 * they can be stored immediately.
	 */
	relationId = heap_create_with_catalog(relname,
										  namespaceId,
										  tablespaceId,
										  InvalidOid,
										  InvalidOid,
										  ofTypeId,
										  ownerId,
										  accessMethodId,
										  descriptor,
										  list_concat(cookedDefaults,
													  old_constraints),
										  relkind,
										  stmt->relation->relpersistence,
										  false,
										  false,
										  stmt->oncommit,
										  reloptions,
										  true,
										  allowSystemTableMods,
										  false,
										  InvalidOid,
										  typaddress);

	/*
	 * We must bump the command counter to make the newly-created relation
	 * tuple visible for opening.
	 */
	CommandCounterIncrement();

	/*
	 * Open the new relation and acquire exclusive lock on it.  This isn't
	 * really necessary for locking out other backends (since they can't see
	 * the new rel anyway until we commit), but it keeps the lock manager from
	 * complaining about deadlock risks.
	 */
	rel = relation_open(relationId, AccessExclusiveLock);

	/*
	 * Now add any newly specified column default and generation expressions
	 * to the new relation.  These are passed to us in the form of raw
	 * parsetrees; we need to transform them to executable expression trees
	 * before they can be added. The most convenient way to do that is to
	 * apply the parser's transformExpr routine, but transformExpr doesn't
	 * work unless we have a pre-existing relation. So, the transformation has
	 * to be postponed to this final step of CREATE TABLE.
	 *
	 * This needs to be before processing the partitioning clauses because
	 * those could refer to generated columns.
	 */
	if (rawDefaults)
		AddRelationNewConstraints(rel, rawDefaults, NIL,
								  true, true, false, queryString);

	/*
	 * Make column generation expressions visible for use by partitioning.
	 */
	CommandCounterIncrement();

	/* Process and store partition bound, if any. */
	if (stmt->partbound)
	{
		PartitionBoundSpec *bound;
		ParseState *pstate;
		Oid			parentId = linitial_oid(inheritOids),
					defaultPartOid;
		Relation	parent,
					defaultRel = NULL;
		ParseNamespaceItem *nsitem;

		/* Already have strong enough lock on the parent */
		parent = table_open(parentId, NoLock);

		/*
		 * We are going to try to validate the partition bound specification
		 * against the partition key of parentRel, so it better have one.
		 */
		if (parent->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
					 errmsg("\"%s\" is not partitioned",
							RelationGetRelationName(parent))));

		/*
		 * The partition constraint of the default partition depends on the
		 * partition bounds of every other partition. It is possible that
		 * another backend might be about to execute a query on the default
		 * partition table, and that the query relies on previously cached
		 * default partition constraints. We must therefore take a table lock
		 * strong enough to prevent all queries on the default partition from
		 * proceeding until we commit and send out a shared-cache-inval notice
		 * that will make them update their index lists.
		 *
		 * Order of locking: The relation being added won't be visible to
		 * other backends until it is committed, hence here in
		 * DefineRelation() the order of locking the default partition and the
		 * relation being added does not matter. But at all other places we
		 * need to lock the default relation before we lock the relation being
		 * added or removed i.e. we should take the lock in same order at all
		 * the places such that lock parent, lock default partition and then
		 * lock the partition so as to avoid a deadlock.
		 */
		defaultPartOid =
			get_default_oid_from_partdesc(RelationGetPartitionDesc(parent,
																   true));
		if (OidIsValid(defaultPartOid))
			defaultRel = table_open(defaultPartOid, AccessExclusiveLock);

		/* Transform the bound values */
		pstate = make_parsestate(NULL);
		pstate->p_sourcetext = queryString;

		/*
		 * Add an nsitem containing this relation, so that transformExpr
		 * called on partition bound expressions is able to report errors
		 * using a proper context.
		 */
		nsitem = addRangeTableEntryForRelation(pstate, rel, AccessShareLock,
											   NULL, false, false);
		addNSItemToQuery(pstate, nsitem, false, true, true);

		bound = transformPartitionBound(pstate, parent, stmt->partbound);

		/*
		 * Check first that the new partition's bound is valid and does not
		 * overlap with any of existing partitions of the parent.
		 */
		check_new_partition_bound(relname, parent, bound, pstate);

		/*
		 * If the default partition exists, its partition constraints will
		 * change after the addition of this new partition such that it won't
		 * allow any row that qualifies for this new partition. So, check that
		 * the existing data in the default partition satisfies the constraint
		 * as it will exist after adding this partition.
		 */
		if (OidIsValid(defaultPartOid))
		{
			check_default_partition_contents(parent, defaultRel, bound);
			/* Keep the lock until commit. */
			table_close(defaultRel, NoLock);
		}

		/* Update the pg_class entry. */
		StorePartitionBound(rel, parent, bound);

		table_close(parent, NoLock);
	}

	/* Store inheritance information for new rel. */
	StoreCatalogInheritance(relationId, inheritOids, stmt->partbound != NULL);

	/*
	 * Process the partitioning specification (if any) and store the partition
	 * key information into the catalog.
	 */
	if (partitioned)
	{
		ParseState *pstate;
		int			partnatts;
		AttrNumber	partattrs[PARTITION_MAX_KEYS];
		Oid			partopclass[PARTITION_MAX_KEYS];
		Oid			partcollation[PARTITION_MAX_KEYS];
		List	   *partexprs = NIL;

		pstate = make_parsestate(NULL);
		pstate->p_sourcetext = queryString;

		partnatts = list_length(stmt->partspec->partParams);

		/* Protect fixed-size arrays here and in executor */
		if (partnatts > PARTITION_MAX_KEYS)
			ereport(ERROR,
					(errcode(ERRCODE_TOO_MANY_COLUMNS),
					 errmsg("cannot partition using more than %d columns",
							PARTITION_MAX_KEYS)));

		/*
		 * We need to transform the raw parsetrees corresponding to partition
		 * expressions into executable expression trees.  Like column defaults
		 * and CHECK constraints, we could not have done the transformation
		 * earlier.
		 */
		stmt->partspec = transformPartitionSpec(rel, stmt->partspec);

		ComputePartitionAttrs(pstate, rel, stmt->partspec->partParams,
							  partattrs, &partexprs, partopclass,
							  partcollation, stmt->partspec->strategy);

		StorePartitionKey(rel, stmt->partspec->strategy, partnatts, partattrs,
						  partexprs,
						  partopclass, partcollation);

		/* make it all visible */
		CommandCounterIncrement();
	}

	/*
	 * If we're creating a partition, create now all the indexes, triggers,
	 * FKs defined in the parent.
	 *
	 * We can't do it earlier, because DefineIndex wants to know the partition
	 * key which we just stored.
	 */
	if (stmt->partbound)
	{
		Oid			parentId = linitial_oid(inheritOids);
		Relation	parent;
		List	   *idxlist;
		ListCell   *cell;

		/* Already have strong enough lock on the parent */
		parent = table_open(parentId, NoLock);
		idxlist = RelationGetIndexList(parent);

		/*
		 * For each index in the parent table, create one in the partition
		 */
		foreach(cell, idxlist)
		{
			Relation	idxRel = index_open(lfirst_oid(cell), AccessShareLock);
			AttrMap    *attmap;
			IndexStmt  *idxstmt;
			Oid			constraintOid;

			if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
			{
				if (idxRel->rd_index->indisunique)
					ereport(ERROR,
							(errcode(ERRCODE_WRONG_OBJECT_TYPE),
							 errmsg("cannot create foreign partition of partitioned table \"%s\"",
									RelationGetRelationName(parent)),
							 errdetail("Table \"%s\" contains indexes that are unique.",
									   RelationGetRelationName(parent))));
				else
				{
					index_close(idxRel, AccessShareLock);
					continue;
				}
			}

			attmap = build_attrmap_by_name(RelationGetDescr(rel),
										   RelationGetDescr(parent),
										   false);
			idxstmt =
				generateClonedIndexStmt(NULL, idxRel,
										attmap, &constraintOid);
			DefineIndex(RelationGetRelid(rel),
						idxstmt,
						InvalidOid,
						RelationGetRelid(idxRel),
						constraintOid,
						-1,
						false, false, false, false, false);

			index_close(idxRel, AccessShareLock);
		}

		list_free(idxlist);

		/*
		 * If there are any row-level triggers, clone them to the new
		 * partition.
		 */
		if (parent->trigdesc != NULL)
			CloneRowTriggersToPartition(parent, rel);

		/*
		 * And foreign keys too.  Note that because we're freshly creating the
		 * table, there is no need to verify these new constraints.
		 */
		CloneForeignKeyConstraints(NULL, parent, rel);

		table_close(parent, NoLock);
	}

	/*
	 * Now add any newly specified CHECK constraints to the new relation. Same
	 * as for defaults above, but these need to come after partitioning is set
	 * up.  We save the constraint names that were used, to avoid dupes below.
	 */
	if (stmt->constraints)
	{
		List	   *conlist;

		conlist = AddRelationNewConstraints(rel, NIL, stmt->constraints,
											true, true, false, queryString);
		foreach_ptr(CookedConstraint, cons, conlist)
		{
			if (cons->name != NULL)
				connames = lappend(connames, cons->name);
		}
	}

	/*
	 * Finally, merge the not-null constraints that are declared directly with
	 * those that come from parent relations (making sure to count inheritance
	 * appropriately for each), create them, and set the attnotnull flag on
	 * columns that don't yet have it.
	 */
	nncols = AddRelationNotNullConstraints(rel, stmt->nnconstraints,
										   old_notnulls, connames);
	foreach_int(attrnum, nncols)
		set_attnotnull(NULL, rel, attrnum, true, false);

	ObjectAddressSet(address, RelationRelationId, relationId);

	/*
	 * Clean up.  We keep lock on new relation (although it shouldn't be
	 * visible to anyone else anyway, until commit).
	 */
	relation_close(rel, NoLock);

	return address;
}

/*
 * BuildDescForRelation
 *
 * Given a list of ColumnDef nodes, build a TupleDesc.
 *
 * Note: This is only for the limited purpose of table and view creation.  Not
 * everything is filled in.  A real tuple descriptor should be obtained from
 * the relcache.
 */
TupleDesc
BuildDescForRelation(const List *columns)
{
	int			natts;
	AttrNumber	attnum;
	ListCell   *l;
	TupleDesc	desc;
	char	   *attname;
	Oid			atttypid;
	int32		atttypmod;
	Oid			attcollation;
	int			attdim;

	/*
	 * allocate a new tuple descriptor
	 */
	natts = list_length(columns);
	desc = CreateTemplateTupleDesc(natts);

	attnum = 0;

	foreach(l, columns)
	{
		ColumnDef  *entry = lfirst(l);
		AclResult	aclresult;
		Form_pg_attribute att;

		/*
		 * for each entry in the list, get the name and type information from
		 * the list and have TupleDescInitEntry fill in the attribute
		 * information we need.
		 */
		attnum++;

		attname = entry->colname;
		typenameTypeIdAndMod(NULL, entry->typeName, &atttypid, &atttypmod);

		aclresult = object_aclcheck(TypeRelationId, atttypid, GetUserId(), ACL_USAGE);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error_type(aclresult, atttypid);

		attcollation = GetColumnDefCollation(NULL, entry, atttypid);
		attdim = list_length(entry->typeName->arrayBounds);
		if (attdim > PG_INT16_MAX)
			ereport(ERROR,
					errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
					errmsg("too many array dimensions"));

		if (entry->typeName->setof)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("column \"%s\" cannot be declared SETOF",
							attname)));

		TupleDescInitEntry(desc, attnum, attname,
						   atttypid, atttypmod, attdim);
		att = TupleDescAttr(desc, attnum - 1);

		/* Override TupleDescInitEntry's settings as requested */
		TupleDescInitEntryCollation(desc, attnum, attcollation);

		/* Fill in additional stuff not handled by TupleDescInitEntry */
		att->attnotnull = entry->is_not_null;
		att->attislocal = entry->is_local;
		att->attinhcount = entry->inhcount;
		att->attidentity = entry->identity;
		att->attgenerated = entry->generated;
		att->attcompression = GetAttributeCompression(att->atttypid, entry->compression);
		if (entry->storage)
			att->attstorage = entry->storage;
		else if (entry->storage_name)
			att->attstorage = GetAttributeStorage(att->atttypid, entry->storage_name);

		populate_compact_attribute(desc, attnum - 1);
	}

	return desc;
}

/*
 * Emit the right error or warning message for a "DROP" command issued on a
 * non-existent relation
 */
static void
DropErrorMsgNonExistent(RangeVar *rel, char rightkind, bool missing_ok)
{
	const struct dropmsgstrings *rentry;

	if (rel->schemaname != NULL &&
		!OidIsValid(LookupNamespaceNoError(rel->schemaname)))
	{
		if (!missing_ok)
		{
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_SCHEMA),
					 errmsg("schema \"%s\" does not exist", rel->schemaname)));
		}
		else
		{
			ereport(NOTICE,
					(errmsg("schema \"%s\" does not exist, skipping",
							rel->schemaname)));
		}
		return;
	}

	for (rentry = dropmsgstringarray; rentry->kind != '\0'; rentry++)
	{
		if (rentry->kind == rightkind)
		{
			if (!missing_ok)
			{
				ereport(ERROR,
						(errcode(rentry->nonexistent_code),
						 errmsg(rentry->nonexistent_msg, rel->relname)));
			}
			else
			{
				ereport(NOTICE, (errmsg(rentry->skipping_msg, rel->relname)));
				break;
			}
		}
	}

	Assert(rentry->kind != '\0');	/* Should be impossible */
}

/*
 * Emit the right error message for a "DROP" command issued on a
 * relation of the wrong type
 */
static void
DropErrorMsgWrongType(const char *relname, char wrongkind, char rightkind)
{
	const struct dropmsgstrings *rentry;
	const struct dropmsgstrings *wentry;

	for (rentry = dropmsgstringarray; rentry->kind != '\0'; rentry++)
		if (rentry->kind == rightkind)
			break;
	Assert(rentry->kind != '\0');

	for (wentry = dropmsgstringarray; wentry->kind != '\0'; wentry++)
		if (wentry->kind == wrongkind)
			break;
	/* wrongkind could be something we don't have in our table... */

	ereport(ERROR,
			(errcode(ERRCODE_WRONG_OBJECT_TYPE),
			 errmsg(rentry->nota_msg, relname),
			 (wentry->kind != '\0') ? errhint("%s", _(wentry->drophint_msg)) : 0));
}

/*
 * RemoveRelations
 *		Implements DROP TABLE, DROP INDEX, DROP SEQUENCE, DROP VIEW,
 *		DROP MATERIALIZED VIEW, DROP FOREIGN TABLE
 */
void
RemoveRelations(DropStmt *drop)
{
	ObjectAddresses *objects;
	char		relkind;
	ListCell   *cell;
	int			flags = 0;
	LOCKMODE	lockmode = AccessExclusiveLock;

	/* DROP CONCURRENTLY uses a weaker lock, and has some restrictions */
	if (drop->concurrent)
	{
		/*
		 * Note that for temporary relations this lock may get upgraded later
		 * on, but as no other session can access a temporary relation, this
		 * is actually fine.
		 */
		lockmode = ShareUpdateExclusiveLock;
		Assert(drop->removeType == OBJECT_INDEX);
		if (list_length(drop->objects) != 1)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("DROP INDEX CONCURRENTLY does not support dropping multiple objects")));
		if (drop->behavior == DROP_CASCADE)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("DROP INDEX CONCURRENTLY does not support CASCADE")));
	}

	/*
	 * First we identify all the relations, then we delete them in a single
	 * performMultipleDeletions() call.  This is to avoid unwanted DROP
	 * RESTRICT errors if one of the relations depends on another.
	 */

	/* Determine required relkind */
	switch (drop->removeType)
	{
		case OBJECT_TABLE:
			relkind = RELKIND_RELATION;
			break;

		case OBJECT_INDEX:
			relkind = RELKIND_INDEX;
			break;

		case OBJECT_SEQUENCE:
			relkind = RELKIND_SEQUENCE;
			break;

		case OBJECT_VIEW:
			relkind = RELKIND_VIEW;
			break;

		case OBJECT_MATVIEW:
			relkind = RELKIND_MATVIEW;
			break;

		case OBJECT_FOREIGN_TABLE:
			relkind = RELKIND_FOREIGN_TABLE;
			break;

		default:
			elog(ERROR, "unrecognized drop object type: %d",
				 (int) drop->removeType);
			relkind = 0;		/* keep compiler quiet */
			break;
	}

	/* Lock and validate each relation; build a list of object addresses */
	objects = new_object_addresses();

	foreach(cell, drop->objects)
	{
		RangeVar   *rel = makeRangeVarFromNameList((List *) lfirst(cell));
		Oid			relOid;
		ObjectAddress obj;
		struct DropRelationCallbackState state;

		/*
		 * These next few steps are a great deal like relation_openrv, but we
		 * don't bother building a relcache entry since we don't need it.
		 *
		 * Check for shared-cache-inval messages before trying to access the
		 * relation.  This is needed to cover the case where the name
		 * identifies a rel that has been dropped and recreated since the
		 * start of our transaction: if we don't flush the old syscache entry,
		 * then we'll latch onto that entry and suffer an error later.
		 */
		AcceptInvalidationMessages();

		/* Look up the appropriate relation using namespace search. */
		state.expected_relkind = relkind;
		state.heap_lockmode = drop->concurrent ?
			ShareUpdateExclusiveLock : AccessExclusiveLock;
		/* We must initialize these fields to show that no locks are held: */
		state.heapOid = InvalidOid;
		state.partParentOid = InvalidOid;

		relOid = RangeVarGetRelidExtended(rel, lockmode, RVR_MISSING_OK,
										  RangeVarCallbackForDropRelation,
										  &state);

		/* Not there? */
		if (!OidIsValid(relOid))
		{
			DropErrorMsgNonExistent(rel, relkind, drop->missing_ok);
			continue;
		}

		/*
		 * Decide if concurrent mode needs to be used here or not.  The
		 * callback retrieved the rel's persistence for us.
		 */
		if (drop->concurrent &&
			state.actual_relpersistence != RELPERSISTENCE_TEMP)
		{
			Assert(list_length(drop->objects) == 1 &&
				   drop->removeType == OBJECT_INDEX);
			flags |= PERFORM_DELETION_CONCURRENTLY;
		}

		/*
		 * Concurrent index drop cannot be used with partitioned indexes,
		 * either.
		 */
		if ((flags & PERFORM_DELETION_CONCURRENTLY) != 0 &&
			state.actual_relkind == RELKIND_PARTITIONED_INDEX)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot drop partitioned index \"%s\" concurrently",
							rel->relname)));

		/*
		 * If we're told to drop a partitioned index, we must acquire lock on
		 * all the children of its parent partitioned table before proceeding.
		 * Otherwise we'd try to lock the child index partitions before their
		 * tables, leading to potential deadlock against other sessions that
		 * will lock those objects in the other order.
		 */
		if (state.actual_relkind == RELKIND_PARTITIONED_INDEX)
			(void) find_all_inheritors(state.heapOid,
									   state.heap_lockmode,
									   NULL);

		/* OK, we're ready to delete this one */
		obj.classId = RelationRelationId;
		obj.objectId = relOid;
		obj.objectSubId = 0;

		add_exact_object_address(&obj, objects);
	}

	performMultipleDeletions(objects, drop->behavior, flags);

	free_object_addresses(objects);
}

/*
 * Before acquiring a table lock, check whether we have sufficient rights.
 * In the case of DROP INDEX, also try to lock the table before the index.
 * Also, if the table to be dropped is a partition, we try to lock the parent
 * first.
 */
static void
RangeVarCallbackForDropRelation(const RangeVar *rel, Oid relOid, Oid oldRelOid,
								void *arg)
{
	HeapTuple	tuple;
	struct DropRelationCallbackState *state;
	char		expected_relkind;
	bool		is_partition;
	Form_pg_class classform;
	LOCKMODE	heap_lockmode;
	bool		invalid_system_index = false;

	state = (struct DropRelationCallbackState *) arg;
	heap_lockmode = state->heap_lockmode;

	/*
	 * If we previously locked some other index's heap, and the name we're
	 * looking up no longer refers to that relation, release the now-useless
	 * lock.
	 */
	if (relOid != oldRelOid && OidIsValid(state->heapOid))
	{
		UnlockRelationOid(state->heapOid, heap_lockmode);
		state->heapOid = InvalidOid;
	}

	/*
	 * Similarly, if we previously locked some other partition's heap, and the
	 * name we're looking up no longer refers to that relation, release the
	 * now-useless lock.
	 */
	if (relOid != oldRelOid && OidIsValid(state->partParentOid))
	{
		UnlockRelationOid(state->partParentOid, AccessExclusiveLock);
		state->partParentOid = InvalidOid;
	}

	/* Didn't find a relation, so no need for locking or permission checks. */
	if (!OidIsValid(relOid))
		return;

	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relOid));
	if (!HeapTupleIsValid(tuple))
		return;					/* concurrently dropped, so nothing to do */
	classform = (Form_pg_class) GETSTRUCT(tuple);
	is_partition = classform->relispartition;

	/* Pass back some data to save lookups in RemoveRelations */
	state->actual_relkind = classform->relkind;
	state->actual_relpersistence = classform->relpersistence;

	/*
	 * Both RELKIND_RELATION and RELKIND_PARTITIONED_TABLE are OBJECT_TABLE,
	 * but RemoveRelations() can only pass one relkind for a given relation.
	 * It chooses RELKIND_RELATION for both regular and partitioned tables.
	 * That means we must be careful before giving the wrong type error when
	 * the relation is RELKIND_PARTITIONED_TABLE.  An equivalent problem
	 * exists with indexes.
	 */
	if (classform->relkind == RELKIND_PARTITIONED_TABLE)
		expected_relkind = RELKIND_RELATION;
	else if (classform->relkind == RELKIND_PARTITIONED_INDEX)
		expected_relkind = RELKIND_INDEX;
	else
		expected_relkind = classform->relkind;

	if (state->expected_relkind != expected_relkind)
		DropErrorMsgWrongType(rel->relname, classform->relkind,
							  state->expected_relkind);

	/* Allow DROP to either table owner or schema owner */
	if (!object_ownercheck(RelationRelationId, relOid, GetUserId()) &&
		!object_ownercheck(NamespaceRelationId, classform->relnamespace, GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER,
					   get_relkind_objtype(classform->relkind),
					   rel->relname);

	/*
	 * Check the case of a system index that might have been invalidated by a
	 * failed concurrent process and allow its drop. For the time being, this
	 * only concerns indexes of toast relations that became invalid during a
	 * REINDEX CONCURRENTLY process.
	 */
	if (IsSystemClass(relOid, classform) && classform->relkind == RELKIND_INDEX)
	{
		HeapTuple	locTuple;
		Form_pg_index indexform;
		bool		indisvalid;

		locTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(relOid));
		if (!HeapTupleIsValid(locTuple))
		{
			ReleaseSysCache(tuple);
			return;
		}

		indexform = (Form_pg_index) GETSTRUCT(locTuple);
		indisvalid = indexform->indisvalid;
		ReleaseSysCache(locTuple);

		/* Mark object as being an invalid index of system catalogs */
		if (!indisvalid)
			invalid_system_index = true;
	}

	/* In the case of an invalid index, it is fine to bypass this check */
	if (!invalid_system_index && !allowSystemTableMods && IsSystemClass(relOid, classform))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						rel->relname)));

	ReleaseSysCache(tuple);

	/*
	 * In DROP INDEX, attempt to acquire lock on the parent table before
	 * locking the index.  index_drop() will need this anyway, and since
	 * regular queries lock tables before their indexes, we risk deadlock if
	 * we do it the other way around.  No error if we don't find a pg_index
	 * entry, though --- the relation may have been dropped.  Note that this
	 * code will execute for either plain or partitioned indexes.
	 */
	if (expected_relkind == RELKIND_INDEX &&
		relOid != oldRelOid)
	{
		state->heapOid = IndexGetRelation(relOid, true);
		if (OidIsValid(state->heapOid))
			LockRelationOid(state->heapOid, heap_lockmode);
	}

	/*
	 * Similarly, if the relation is a partition, we must acquire lock on its
	 * parent before locking the partition.  That's because queries lock the
	 * parent before its partitions, so we risk deadlock if we do it the other
	 * way around.
	 */
	if (is_partition && relOid != oldRelOid)
	{
		state->partParentOid = get_partition_parent(relOid, true);
		if (OidIsValid(state->partParentOid))
			LockRelationOid(state->partParentOid, AccessExclusiveLock);
	}
}

/*
 * ExecuteTruncate
 *		Executes a TRUNCATE command.
 *
 * This is a multi-relation truncate.  We first open and grab exclusive
 * lock on all relations involved, checking permissions and otherwise
 * verifying that the relation is OK for truncation.  Note that if relations
 * are foreign tables, at this stage, we have not yet checked that their
 * foreign data in external data sources are OK for truncation.  These are
 * checked when foreign data are actually truncated later.  In CASCADE mode,
 * relations having FK references to the targeted relations are automatically
 * added to the group; in RESTRICT mode, we check that all FK references are
 * internal to the group that's being truncated.  Finally all the relations
 * are truncated and reindexed.
 */
void
ExecuteTruncate(TruncateStmt *stmt)
{
	List	   *rels = NIL;
	List	   *relids = NIL;
	List	   *relids_logged = NIL;
	ListCell   *cell;

	/*
	 * Open, exclusive-lock, and check all the explicitly-specified relations
	 */
	foreach(cell, stmt->relations)
	{
		RangeVar   *rv = lfirst(cell);
		Relation	rel;
		bool		recurse = rv->inh;
		Oid			myrelid;
		LOCKMODE	lockmode = AccessExclusiveLock;

		myrelid = RangeVarGetRelidExtended(rv, lockmode,
										   0, RangeVarCallbackForTruncate,
										   NULL);

		/* don't throw error for "TRUNCATE foo, foo" */
		if (list_member_oid(relids, myrelid))
			continue;

		/* open the relation, we already hold a lock on it */
		rel = table_open(myrelid, NoLock);

		/*
		 * RangeVarGetRelidExtended() has done most checks with its callback,
		 * but other checks with the now-opened Relation remain.
		 */
		truncate_check_activity(rel);

		rels = lappend(rels, rel);
		relids = lappend_oid(relids, myrelid);

		/* Log this relation only if needed for logical decoding */
		if (RelationIsLogicallyLogged(rel))
			relids_logged = lappend_oid(relids_logged, myrelid);

		if (recurse)
		{
			ListCell   *child;
			List	   *children;

			children = find_all_inheritors(myrelid, lockmode, NULL);

			foreach(child, children)
			{
				Oid			childrelid = lfirst_oid(child);

				if (list_member_oid(relids, childrelid))
					continue;

				/* find_all_inheritors already got lock */
				rel = table_open(childrelid, NoLock);

				/*
				 * It is possible that the parent table has children that are
				 * temp tables of other backends.  We cannot safely access
				 * such tables (because of buffering issues), and the best
				 * thing to do is to silently ignore them.  Note that this
				 * check is the same as one of the checks done in
				 * truncate_check_activity() called below, still it is kept
				 * here for simplicity.
				 */
				if (RELATION_IS_OTHER_TEMP(rel))
				{
					table_close(rel, lockmode);
					continue;
				}

				/*
				 * Inherited TRUNCATE commands perform access permission
				 * checks on the parent table only. So we skip checking the
				 * children's permissions and don't call
				 * truncate_check_perms() here.
				 */
				truncate_check_rel(RelationGetRelid(rel), rel->rd_rel);
				truncate_check_activity(rel);

				rels = lappend(rels, rel);
				relids = lappend_oid(relids, childrelid);

				/* Log this relation only if needed for logical decoding */
				if (RelationIsLogicallyLogged(rel))
					relids_logged = lappend_oid(relids_logged, childrelid);
			}
		}
		else if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot truncate only a partitioned table"),
					 errhint("Do not specify the ONLY keyword, or use TRUNCATE ONLY on the partitions directly.")));
	}

	ExecuteTruncateGuts(rels, relids, relids_logged,
						stmt->behavior, stmt->restart_seqs, false);

	/* And close the rels */
	foreach(cell, rels)
	{
		Relation	rel = (Relation) lfirst(cell);

		table_close(rel, NoLock);
	}
}

/*
 * ExecuteTruncateGuts
 *
 * Internal implementation of TRUNCATE.  This is called by the actual TRUNCATE
 * command (see above) as well as replication subscribers that execute a
 * replicated TRUNCATE action.
 *
 * explicit_rels is the list of Relations to truncate that the command
 * specified.  relids is the list of Oids corresponding to explicit_rels.
 * relids_logged is the list of Oids (a subset of relids) that require
 * WAL-logging.  This is all a bit redundant, but the existing callers have
 * this information handy in this form.
 */
void
ExecuteTruncateGuts(List *explicit_rels,
					List *relids,
					List *relids_logged,
					DropBehavior behavior, bool restart_seqs,
					bool run_as_table_owner)
{
	List	   *rels;
	List	   *seq_relids = NIL;
	HTAB	   *ft_htab = NULL;
	EState	   *estate;
	ResultRelInfo *resultRelInfos;
	ResultRelInfo *resultRelInfo;
	SubTransactionId mySubid;
	ListCell   *cell;
	Oid		   *logrelids;

	/*
	 * Check the explicitly-specified relations.
	 *
	 * In CASCADE mode, suck in all referencing relations as well.  This
	 * requires multiple iterations to find indirectly-dependent relations. At
	 * each phase, we need to exclusive-lock new rels before looking for their
	 * dependencies, else we might miss something.  Also, we check each rel as
	 * soon as we open it, to avoid a faux pas such as holding lock for a long
	 * time on a rel we have no permissions for.
	 */
	rels = list_copy(explicit_rels);
	if (behavior == DROP_CASCADE)
	{
		for (;;)
		{
			List	   *newrelids;

			newrelids = heap_truncate_find_FKs(relids);
			if (newrelids == NIL)
				break;			/* nothing else to add */

			foreach(cell, newrelids)
			{
				Oid			relid = lfirst_oid(cell);
				Relation	rel;

				rel = table_open(relid, AccessExclusiveLock);
				ereport(NOTICE,
						(errmsg("truncate cascades to table \"%s\"",
								RelationGetRelationName(rel))));
				truncate_check_rel(relid, rel->rd_rel);
				truncate_check_perms(relid, rel->rd_rel);
				truncate_check_activity(rel);
				rels = lappend(rels, rel);
				relids = lappend_oid(relids, relid);

				/* Log this relation only if needed for logical decoding */
				if (RelationIsLogicallyLogged(rel))
					relids_logged = lappend_oid(relids_logged, relid);
			}
		}
	}

	/*
	 * Check foreign key references.  In CASCADE mode, this should be
	 * unnecessary since we just pulled in all the references; but as a
	 * cross-check, do it anyway if in an Assert-enabled build.
	 */
#ifdef USE_ASSERT_CHECKING
	heap_truncate_check_FKs(rels, false);
#else
	if (behavior == DROP_RESTRICT)
		heap_truncate_check_FKs(rels, false);
#endif

	/*
	 * If we are asked to restart sequences, find all the sequences, lock them
	 * (we need AccessExclusiveLock for ResetSequence), and check permissions.
	 * We want to do this early since it's pointless to do all the truncation
	 * work only to fail on sequence permissions.
	 */
	if (restart_seqs)
	{
		foreach(cell, rels)
		{
			Relation	rel = (Relation) lfirst(cell);
			List	   *seqlist = getOwnedSequences(RelationGetRelid(rel));
			ListCell   *seqcell;

			foreach(seqcell, seqlist)
			{
				Oid			seq_relid = lfirst_oid(seqcell);
				Relation	seq_rel;

				seq_rel = relation_open(seq_relid, AccessExclusiveLock);

				/* This check must match AlterSequence! */
				if (!object_ownercheck(RelationRelationId, seq_relid, GetUserId()))
					aclcheck_error(ACLCHECK_NOT_OWNER, OBJECT_SEQUENCE,
								   RelationGetRelationName(seq_rel));

				seq_relids = lappend_oid(seq_relids, seq_relid);

				relation_close(seq_rel, NoLock);
			}
		}
	}

	/* Prepare to catch AFTER triggers. */
	AfterTriggerBeginQuery();

	/*
	 * To fire triggers, we'll need an EState as well as a ResultRelInfo for
	 * each relation.  We don't need to call ExecOpenIndices, though.
	 *
	 * We put the ResultRelInfos in the es_opened_result_relations list, even
	 * though we don't have a range table and don't populate the
	 * es_result_relations array.  That's a bit bogus, but it's enough to make
	 * ExecGetTriggerResultRel() find them.
	 */
	estate = CreateExecutorState();
	resultRelInfos = (ResultRelInfo *)
		palloc(list_length(rels) * sizeof(ResultRelInfo));
	resultRelInfo = resultRelInfos;
	foreach(cell, rels)
	{
		Relation	rel = (Relation) lfirst(cell);

		InitResultRelInfo(resultRelInfo,
						  rel,
						  0,	/* dummy rangetable index */
						  NULL,
						  0);
		estate->es_opened_result_relations =
			lappend(estate->es_opened_result_relations, resultRelInfo);
		resultRelInfo++;
	}

	/*
	 * Process all BEFORE STATEMENT TRUNCATE triggers before we begin
	 * truncating (this is because one of them might throw an error). Also, if
	 * we were to allow them to prevent statement execution, that would need
	 * to be handled here.
	 */
	resultRelInfo = resultRelInfos;
	foreach(cell, rels)
	{
		UserContext ucxt;

		if (run_as_table_owner)
			SwitchToUntrustedUser(resultRelInfo->ri_RelationDesc->rd_rel->relowner,
								  &ucxt);
		ExecBSTruncateTriggers(estate, resultRelInfo);
		if (run_as_table_owner)
			RestoreUserContext(&ucxt);
		resultRelInfo++;
	}

	/*
	 * OK, truncate each table.
	 */
	mySubid = GetCurrentSubTransactionId();

	foreach(cell, rels)
	{
		Relation	rel = (Relation) lfirst(cell);

		/* Skip partitioned tables as there is nothing to do */
		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
			continue;

		/*
		 * Build the lists of foreign tables belonging to each foreign server
		 * and pass each list to the foreign data wrapper's callback function,
		 * so that each server can truncate its all foreign tables in bulk.
		 * Each list is saved as a single entry in a hash table that uses the
		 * server OID as lookup key.
		 */
		if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
		{
			Oid			serverid = GetForeignServerIdByRelId(RelationGetRelid(rel));
			bool		found;
			ForeignTruncateInfo *ft_info;

			/* First time through, initialize hashtable for foreign tables */
			if (!ft_htab)
			{
				HASHCTL		hctl;

				memset(&hctl, 0, sizeof(HASHCTL));
				hctl.keysize = sizeof(Oid);
				hctl.entrysize = sizeof(ForeignTruncateInfo);
				hctl.hcxt = CurrentMemoryContext;

				ft_htab = hash_create("TRUNCATE for Foreign Tables",
									  32,	/* start small and extend */
									  &hctl,
									  HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
			}

			/* Find or create cached entry for the foreign table */
			ft_info = hash_search(ft_htab, &serverid, HASH_ENTER, &found);
			if (!found)
				ft_info->rels = NIL;

			/*
			 * Save the foreign table in the entry of the server that the
			 * foreign table belongs to.
			 */
			ft_info->rels = lappend(ft_info->rels, rel);
			continue;
		}

		/*
		 * Normally, we need a transaction-safe truncation here.  However, if
		 * the table was either created in the current (sub)transaction or has
		 * a new relfilenumber in the current (sub)transaction, then we can
		 * just truncate it in-place, because a rollback would cause the whole
		 * table or the current physical file to be thrown away anyway.
		 */
		if (rel->rd_createSubid == mySubid ||
			rel->rd_newRelfilelocatorSubid == mySubid)
		{
			/* Immediate, non-rollbackable truncation is OK */
			heap_truncate_one_rel(rel);
		}
		else
		{
			Oid			heap_relid;
			Oid			toast_relid;
			ReindexParams reindex_params = {0};

			/*
			 * This effectively deletes all rows in the table, and may be done
			 * in a serializable transaction.  In that case we must record a
			 * rw-conflict in to this transaction from each transaction
			 * holding a predicate lock on the table.
			 */
			CheckTableForSerializableConflictIn(rel);

			/*
			 * Need the full transaction-safe pushups.
			 *
			 * Create a new empty storage file for the relation, and assign it
			 * as the relfilenumber value. The old storage file is scheduled
			 * for deletion at commit.
			 */
			RelationSetNewRelfilenumber(rel, rel->rd_rel->relpersistence);

			heap_relid = RelationGetRelid(rel);

			/*
			 * The same for the toast table, if any.
			 */
			toast_relid = rel->rd_rel->reltoastrelid;
			if (OidIsValid(toast_relid))
			{
				Relation	toastrel = relation_open(toast_relid,
													 AccessExclusiveLock);

				RelationSetNewRelfilenumber(toastrel,
											toastrel->rd_rel->relpersistence);
				table_close(toastrel, NoLock);
			}

			/*
			 * Reconstruct the indexes to match, and we're done.
			 */
			reindex_relation(NULL, heap_relid, REINDEX_REL_PROCESS_TOAST,
							 &reindex_params);
		}

		pgstat_count_truncate(rel);
	}

	/* Now go through the hash table, and truncate foreign tables */
	if (ft_htab)
	{
		ForeignTruncateInfo *ft_info;
		HASH_SEQ_STATUS seq;

		hash_seq_init(&seq, ft_htab);

		PG_TRY();
		{
			while ((ft_info = hash_seq_search(&seq)) != NULL)
			{
				FdwRoutine *routine = GetFdwRoutineByServerId(ft_info->serverid);

				/* truncate_check_rel() has checked that already */
				Assert(routine->ExecForeignTruncate != NULL);

				routine->ExecForeignTruncate(ft_info->rels,
											 behavior,
											 restart_seqs);
			}
		}
		PG_FINALLY();
		{
			hash_destroy(ft_htab);
		}
		PG_END_TRY();
	}

	/*
	 * Restart owned sequences if we were asked to.
	 */
	foreach(cell, seq_relids)
	{
		Oid			seq_relid = lfirst_oid(cell);

		ResetSequence(seq_relid);
	}

	/*
	 * Write a WAL record to allow this set of actions to be logically
	 * decoded.
	 *
	 * Assemble an array of relids so we can write a single WAL record for the
	 * whole action.
	 */
	if (relids_logged != NIL)
	{
		xl_heap_truncate xlrec;
		int			i = 0;

		/* should only get here if wal_level >= logical */
		Assert(XLogLogicalInfoActive());

		logrelids = palloc(list_length(relids_logged) * sizeof(Oid));
		foreach(cell, relids_logged)
			logrelids[i++] = lfirst_oid(cell);

		xlrec.dbId = MyDatabaseId;
		xlrec.nrelids = list_length(relids_logged);
		xlrec.flags = 0;
		if (behavior == DROP_CASCADE)
			xlrec.flags |= XLH_TRUNCATE_CASCADE;
		if (restart_seqs)
			xlrec.flags |= XLH_TRUNCATE_RESTART_SEQS;

		XLogBeginInsert();
		XLogRegisterData(&xlrec, SizeOfHeapTruncate);
		XLogRegisterData(logrelids, list_length(relids_logged) * sizeof(Oid));

		XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);

		(void) XLogInsert(RM_HEAP_ID, XLOG_HEAP_TRUNCATE);
	}

	/*
	 * Process all AFTER STATEMENT TRUNCATE triggers.
	 */
	resultRelInfo = resultRelInfos;
	foreach(cell, rels)
	{
		UserContext ucxt;

		if (run_as_table_owner)
			SwitchToUntrustedUser(resultRelInfo->ri_RelationDesc->rd_rel->relowner,
								  &ucxt);
		ExecASTruncateTriggers(estate, resultRelInfo);
		if (run_as_table_owner)
			RestoreUserContext(&ucxt);
		resultRelInfo++;
	}

	/* Handle queued AFTER triggers */
	AfterTriggerEndQuery(estate);

	/* We can clean up the EState now */
	FreeExecutorState(estate);

	/*
	 * Close any rels opened by CASCADE (can't do this while EState still
	 * holds refs)
	 */
	rels = list_difference_ptr(rels, explicit_rels);
	foreach(cell, rels)
	{
		Relation	rel = (Relation) lfirst(cell);

		table_close(rel, NoLock);
	}
}

/*
 * Check that a given relation is safe to truncate.  Subroutine for
 * ExecuteTruncate() and RangeVarCallbackForTruncate().
 */
static void
truncate_check_rel(Oid relid, Form_pg_class reltuple)
{
	char	   *relname = NameStr(reltuple->relname);

	/*
	 * Only allow truncate on regular tables, foreign tables using foreign
	 * data wrappers supporting TRUNCATE and partitioned tables (although, the
	 * latter are only being included here for the following checks; no
	 * physical truncation will occur in their case.).
	 */
	if (reltuple->relkind == RELKIND_FOREIGN_TABLE)
	{
		Oid			serverid = GetForeignServerIdByRelId(relid);
		FdwRoutine *fdwroutine = GetFdwRoutineByServerId(serverid);

		if (!fdwroutine->ExecForeignTruncate)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot truncate foreign table \"%s\"",
							relname)));
	}
	else if (reltuple->relkind != RELKIND_RELATION &&
			 reltuple->relkind != RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a table", relname)));

	/*
	 * Most system catalogs can't be truncated at all, or at least not unless
	 * allow_system_table_mods=on. As an exception, however, we allow
	 * pg_largeobject to be truncated as part of pg_upgrade, because we need
	 * to change its relfilenode to match the old cluster, and allowing a
	 * TRUNCATE command to be executed is the easiest way of doing that.
	 */
	if (!allowSystemTableMods && IsSystemClass(relid, reltuple)
		&& (!IsBinaryUpgrade || relid != LargeObjectRelationId))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						relname)));

	InvokeObjectTruncateHook(relid);
}

/*
 * Check that current user has the permission to truncate given relation.
 */
static void
truncate_check_perms(Oid relid, Form_pg_class reltuple)
{
	char	   *relname = NameStr(reltuple->relname);
	AclResult	aclresult;

	/* Permissions checks */
	aclresult = pg_class_aclcheck(relid, GetUserId(), ACL_TRUNCATE);
	if (aclresult != ACLCHECK_OK)
		aclcheck_error(aclresult, get_relkind_objtype(reltuple->relkind),
					   relname);
}

/*
 * Set of extra sanity checks to check if a given relation is safe to
 * truncate.  This is split with truncate_check_rel() as
 * RangeVarCallbackForTruncate() cannot open a Relation yet.
 */
static void
truncate_check_activity(Relation rel)
{
	/*
	 * Don't allow truncate on temp tables of other backends ... their local
	 * buffer manager is not going to cope.
	 */
	if (RELATION_IS_OTHER_TEMP(rel))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot truncate temporary tables of other sessions")));

	/*
	 * Also check for active uses of the relation in the current transaction,
	 * including open scans and pending AFTER trigger events.
	 */
	CheckTableNotInUse(rel, "TRUNCATE");
}

/*
 * storage_name
 *	  returns the name corresponding to a typstorage/attstorage enum value
 */
static const char *
storage_name(char c)
{
	switch (c)
	{
		case TYPSTORAGE_PLAIN:
			return "PLAIN";
		case TYPSTORAGE_EXTERNAL:
			return "EXTERNAL";
		case TYPSTORAGE_EXTENDED:
			return "EXTENDED";
		case TYPSTORAGE_MAIN:
			return "MAIN";
		default:
			return "???";
	}
}

/*----------
 * MergeAttributes
 *		Returns new schema given initial schema and superclasses.
 *
 * Input arguments:
 * 'columns' is the column/attribute definition for the table. (It's a list
 *		of ColumnDef's.) It is destructively changed.
 * 'supers' is a list of OIDs of parent relations, already locked by caller.
 * 'relpersistence' is the persistence type of the table.
 * 'is_partition' tells if the table is a partition.
 *
 * Output arguments:
 * 'supconstr' receives a list of CookedConstraint representing
 *		CHECK constraints belonging to parent relations, updated as
 *		necessary to be valid for the child.
 * 'supnotnulls' receives a list of CookedConstraint representing
 *		not-null constraints based on those from parent relations.
 *
 * Return value:
 * Completed schema list.
 *
 * Notes:
 *	  The order in which the attributes are inherited is very important.
 *	  Intuitively, the inherited attributes should come first. If a table
 *	  inherits from multiple parents, the order of those attributes are
 *	  according to the order of the parents specified in CREATE TABLE.
 *
 *	  Here's an example:
 *
 *		create table person (name text, age int4, location point);
 *		create table emp (salary int4, manager text) inherits(person);
 *		create table student (gpa float8) inherits (person);
 *		create table stud_emp (percent int4) inherits (emp, student);
 *
 *	  The order of the attributes of stud_emp is:
 *
 *							person {1:name, 2:age, 3:location}
 *							/	 \
 *			   {6:gpa}	student   emp {4:salary, 5:manager}
 *							\	 /
 *						   stud_emp {7:percent}
 *
 *	   If the same attribute name appears multiple times, then it appears
 *	   in the result table in the proper location for its first appearance.
 *
 *	   Constraints (including not-null constraints) for the child table
 *	   are the union of all relevant constraints, from both the child schema
 *	   and parent tables.  In addition, in legacy inheritance, each column that
 *	   appears in a primary key in any of the parents also gets a NOT NULL
 *	   constraint (partitioning doesn't need this, because the PK itself gets
 *	   inherited.)
 *
 *	   The default value for a child column is defined as:
 *		(1) If the child schema specifies a default, that value is used.
 *		(2) If neither the child nor any parent specifies a default, then
 *			the column will not have a default.
 *		(3) If conflicting defaults are inherited from different parents
 *			(and not overridden by the child), an error is raised.
 *		(4) Otherwise the inherited default is used.
 *
 *		Note that the default-value infrastructure is used for generated
 *		columns' expressions too, so most of the preceding paragraph applies
 *		to generation expressions too.  We insist that a child column be
 *		generated if and only if its parent(s) are, but it need not have
 *		the same generation expression.
 *----------
 */
static List *
MergeAttributes(List *columns, const List *supers, char relpersistence,
				bool is_partition, List **supconstr, List **supnotnulls)
{
	List	   *inh_columns = NIL;
	List	   *constraints = NIL;
	List	   *nnconstraints = NIL;
	bool		have_bogus_defaults = false;
	int			child_attno;
	static Node bogus_marker = {0}; /* marks conflicting defaults */
	List	   *saved_columns = NIL;
	ListCell   *lc;

	/*
	 * Check for and reject tables with too many columns. We perform this
	 * check relatively early for two reasons: (a) we don't run the risk of
	 * overflowing an AttrNumber in subsequent code (b) an O(n^2) algorithm is
	 * okay if we're processing <= 1600 columns, but could take minutes to
	 * execute if the user attempts to create a table with hundreds of
	 * thousands of columns.
	 *
	 * Note that we also need to check that we do not exceed this figure after
	 * including columns from inherited relations.
	 */
	if (list_length(columns) > MaxHeapAttributeNumber)
		ereport(ERROR,
				(errcode(ERRCODE_TOO_MANY_COLUMNS),
				 errmsg("tables can have at most %d columns",
						MaxHeapAttributeNumber)));

	/*
	 * Check for duplicate names in the explicit list of attributes.
	 *
	 * Although we might consider merging such entries in the same way that we
	 * handle name conflicts for inherited attributes, it seems to make more
	 * sense to assume such conflicts are errors.
	 *
	 * We don't use foreach() here because we have two nested loops over the
	 * columns list, with possible element deletions in the inner one.  If we
	 * used foreach_delete_current() it could only fix up the state of one of
	 * the loops, so it seems cleaner to use looping over list indexes for
	 * both loops.  Note that any deletion will happen beyond where the outer
	 * loop is, so its index never needs adjustment.
	 */
	for (int coldefpos = 0; coldefpos < list_length(columns); coldefpos++)
	{
		ColumnDef  *coldef = list_nth_node(ColumnDef, columns, coldefpos);

		if (!is_partition && coldef->typeName == NULL)
		{
			/*
			 * Typed table column option that does not belong to a column from
			 * the type.  This works because the columns from the type come
			 * first in the list.  (We omit this check for partition column
			 * lists; those are processed separately below.)
			 */
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_COLUMN),
					 errmsg("column \"%s\" does not exist",
							coldef->colname)));
		}

		/* restpos scans all entries beyond coldef; incr is in loop body */
		for (int restpos = coldefpos + 1; restpos < list_length(columns);)
		{
			ColumnDef  *restdef = list_nth_node(ColumnDef, columns, restpos);

			if (strcmp(coldef->colname, restdef->colname) == 0)
			{
				if (coldef->is_from_type)
				{
					/*
					 * merge the column options into the column from the type
					 */
					coldef->is_not_null = restdef->is_not_null;
					coldef->raw_default = restdef->raw_default;
					coldef->cooked_default = restdef->cooked_default;
					coldef->constraints = restdef->constraints;
					coldef->is_from_type = false;
					columns = list_delete_nth_cell(columns, restpos);
				}
				else
					ereport(ERROR,
							(errcode(ERRCODE_DUPLICATE_COLUMN),
							 errmsg("column \"%s\" specified more than once",
									coldef->colname)));
			}
			else
				restpos++;
		}
	}

	/*
	 * In case of a partition, there are no new column definitions, only dummy
	 * ColumnDefs created for column constraints.  Set them aside for now and
	 * process them at the end.
	 */
	if (is_partition)
	{
		saved_columns = columns;
		columns = NIL;
	}

	/*
	 * Scan the parents left-to-right, and merge their attributes to form a
	 * list of inherited columns (inh_columns).
	 */
	child_attno = 0;
	foreach(lc, supers)
	{
		Oid			parent = lfirst_oid(lc);
		Relation	relation;
		TupleDesc	tupleDesc;
		TupleConstr *constr;
		AttrMap    *newattmap;
		List	   *inherited_defaults;
		List	   *cols_with_defaults;
		List	   *nnconstrs;
		ListCell   *lc1;
		ListCell   *lc2;
		Bitmapset  *nncols = NULL;

		/* caller already got lock */
		relation = table_open(parent, NoLock);

		/*
		 * Check for active uses of the parent partitioned table in the
		 * current transaction, such as being used in some manner by an
		 * enclosing command.
		 */
		if (is_partition)
			CheckTableNotInUse(relation, "CREATE TABLE .. PARTITION OF");

		/*
		 * We do not allow partitioned tables and partitions to participate in
		 * regular inheritance.
		 */
		if (relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE && !is_partition)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot inherit from partitioned table \"%s\"",
							RelationGetRelationName(relation))));
		if (relation->rd_rel->relispartition && !is_partition)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot inherit from partition \"%s\"",
							RelationGetRelationName(relation))));

		if (relation->rd_rel->relkind != RELKIND_RELATION &&
			relation->rd_rel->relkind != RELKIND_FOREIGN_TABLE &&
			relation->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("inherited relation \"%s\" is not a table or foreign table",
							RelationGetRelationName(relation))));

		/*
		 * If the parent is permanent, so must be all of its partitions.  Note
		 * that inheritance allows that case.
		 */
		if (is_partition &&
			relation->rd_rel->relpersistence != RELPERSISTENCE_TEMP &&
			relpersistence == RELPERSISTENCE_TEMP)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot create a temporary relation as partition of permanent relation \"%s\"",
							RelationGetRelationName(relation))));

		/* Permanent rels cannot inherit from temporary ones */
		if (relpersistence != RELPERSISTENCE_TEMP &&
			relation->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg(!is_partition
							? "cannot inherit from temporary relation \"%s\""
							: "cannot create a permanent relation as partition of temporary relation \"%s\"",
							RelationGetRelationName(relation))));

		/* If existing rel is temp, it must belong to this session */
		if (relation->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
			!relation->rd_islocaltemp)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg(!is_partition
							? "cannot inherit from temporary relation of another session"
							: "cannot create as partition of temporary relation of another session")));

		/*
		 * We should have an UNDER permission flag for this, but for now,
		 * demand that creator of a child table own the parent.
		 */
		if (!object_ownercheck(RelationRelationId, RelationGetRelid(relation), GetUserId()))
			aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(relation->rd_rel->relkind),
						   RelationGetRelationName(relation));

		tupleDesc = RelationGetDescr(relation);
		constr = tupleDesc->constr;

		/*
		 * newattmap->attnums[] will contain the child-table attribute numbers
		 * for the attributes of this parent table.  (They are not the same
		 * for parents after the first one, nor if we have dropped columns.)
		 */
		newattmap = make_attrmap(tupleDesc->natts);

		/* We can't process inherited defaults until newattmap is complete. */
		inherited_defaults = cols_with_defaults = NIL;

		/*
		 * Request attnotnull on columns that have a not-null constraint
		 * that's not marked NO INHERIT (even if not valid).
		 */
		nnconstrs = RelationGetNotNullConstraints(RelationGetRelid(relation),
												  true, false);
		foreach_ptr(CookedConstraint, cc, nnconstrs)
			nncols = bms_add_member(nncols, cc->attnum);

		for (AttrNumber parent_attno = 1; parent_attno <= tupleDesc->natts;
			 parent_attno++)
		{
			Form_pg_attribute attribute = TupleDescAttr(tupleDesc,
														parent_attno - 1);
			char	   *attributeName = NameStr(attribute->attname);
			int			exist_attno;
			ColumnDef  *newdef;
			ColumnDef  *mergeddef;

			/*
			 * Ignore dropped columns in the parent.
			 */
			if (attribute->attisdropped)
				continue;		/* leave newattmap->attnums entry as zero */

			/*
			 * Create new column definition
			 */
			newdef = makeColumnDef(attributeName, attribute->atttypid,
								   attribute->atttypmod, attribute->attcollation);
			newdef->storage = attribute->attstorage;
			newdef->generated = attribute->attgenerated;
			if (CompressionMethodIsValid(attribute->attcompression))
				newdef->compression =
					pstrdup(GetCompressionMethodName(attribute->attcompression));

			/*
			 * Regular inheritance children are independent enough not to
			 * inherit identity columns.  But partitions are integral part of
			 * a partitioned table and inherit identity column.
			 */
			if (is_partition)
				newdef->identity = attribute->attidentity;

			/*
			 * Does it match some previously considered column from another
			 * parent?
			 */
			exist_attno = findAttrByName(attributeName, inh_columns);
			if (exist_attno > 0)
			{
				/*
				 * Yes, try to merge the two column definitions.
				 */
				mergeddef = MergeInheritedAttribute(inh_columns, exist_attno, newdef);

				newattmap->attnums[parent_attno - 1] = exist_attno;

				/*
				 * Partitions have only one parent, so conflict should never
				 * occur.
				 */
				Assert(!is_partition);
			}
			else
			{
				/*
				 * No, create a new inherited column
				 */
				newdef->inhcount = 1;
				newdef->is_local = false;
				inh_columns = lappend(inh_columns, newdef);

				newattmap->attnums[parent_attno - 1] = ++child_attno;
				mergeddef = newdef;
			}

			/*
			 * mark attnotnull if parent has it
			 */
			if (bms_is_member(parent_attno, nncols))
				mergeddef->is_not_null = true;

			/*
			 * Locate default/generation expression if any
			 */
			if (attribute->atthasdef)
			{
				Node	   *this_default;

				this_default = TupleDescGetDefault(tupleDesc, parent_attno);
				if (this_default == NULL)
					elog(ERROR, "default expression not found for attribute %d of relation \"%s\"",
						 parent_attno, RelationGetRelationName(relation));

				/*
				 * If it's a GENERATED default, it might contain Vars that
				 * need to be mapped to the inherited column(s)' new numbers.
				 * We can't do that till newattmap is ready, so just remember
				 * all the inherited default expressions for the moment.
				 */
				inherited_defaults = lappend(inherited_defaults, this_default);
				cols_with_defaults = lappend(cols_with_defaults, mergeddef);
			}
		}

		/*
		 * Now process any inherited default expressions, adjusting attnos
		 * using the completed newattmap map.
		 */
		forboth(lc1, inherited_defaults, lc2, cols_with_defaults)
		{
			Node	   *this_default = (Node *) lfirst(lc1);
			ColumnDef  *def = (ColumnDef *) lfirst(lc2);
			bool		found_whole_row;

			/* Adjust Vars to match new table's column numbering */
			this_default = map_variable_attnos(this_default,
											   1, 0,
											   newattmap,
											   InvalidOid, &found_whole_row);

			/*
			 * For the moment we have to reject whole-row variables.  We could
			 * convert them, if we knew the new table's rowtype OID, but that
			 * hasn't been assigned yet.  (A variable could only appear in a
			 * generation expression, so the error message is correct.)
			 */
			if (found_whole_row)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot convert whole-row table reference"),
						 errdetail("Generation expression for column \"%s\" contains a whole-row reference to table \"%s\".",
								   def->colname,
								   RelationGetRelationName(relation))));

			/*
			 * If we already had a default from some prior parent, check to
			 * see if they are the same.  If so, no problem; if not, mark the
			 * column as having a bogus default.  Below, we will complain if
			 * the bogus default isn't overridden by the child columns.
			 */
			Assert(def->raw_default == NULL);
			if (def->cooked_default == NULL)
				def->cooked_default = this_default;
			else if (!equal(def->cooked_default, this_default))
			{
				def->cooked_default = &bogus_marker;
				have_bogus_defaults = true;
			}
		}

		/*
		 * Now copy the CHECK constraints of this parent, adjusting attnos
		 * using the completed newattmap map.  Identically named constraints
		 * are merged if possible, else we throw error.
		 */
		if (constr && constr->num_check > 0)
		{
			ConstrCheck *check = constr->check;

			for (int i = 0; i < constr->num_check; i++)
			{
				char	   *name = check[i].ccname;
				Node	   *expr;
				bool		found_whole_row;

				/* ignore if the constraint is non-inheritable */
				if (check[i].ccnoinherit)
					continue;

				/* Adjust Vars to match new table's column numbering */
				expr = map_variable_attnos(stringToNode(check[i].ccbin),
										   1, 0,
										   newattmap,
										   InvalidOid, &found_whole_row);

				/*
				 * For the moment we have to reject whole-row variables. We
				 * could convert them, if we knew the new table's rowtype OID,
				 * but that hasn't been assigned yet.
				 */
				if (found_whole_row)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot convert whole-row table reference"),
							 errdetail("Constraint \"%s\" contains a whole-row reference to table \"%s\".",
									   name,
									   RelationGetRelationName(relation))));

				constraints = MergeCheckConstraint(constraints, name, expr,
												   check[i].ccenforced);
			}
		}

		/*
		 * Also copy the not-null constraints from this parent.  The
		 * attnotnull markings were already installed above.
		 */
		foreach_ptr(CookedConstraint, nn, nnconstrs)
		{
			Assert(nn->contype == CONSTR_NOTNULL);

			nn->attnum = newattmap->attnums[nn->attnum - 1];

			nnconstraints = lappend(nnconstraints, nn);
		}

		free_attrmap(newattmap);

		/*
		 * Close the parent rel, but keep our lock on it until xact commit.
		 * That will prevent someone else from deleting or ALTERing the parent
		 * before the child is committed.
		 */
		table_close(relation, NoLock);
	}

	/*
	 * If we had no inherited attributes, the result columns are just the
	 * explicitly declared columns.  Otherwise, we need to merge the declared
	 * columns into the inherited column list.  Although, we never have any
	 * explicitly declared columns if the table is a partition.
	 */
	if (inh_columns != NIL)
	{
		int			newcol_attno = 0;

		foreach(lc, columns)
		{
			ColumnDef  *newdef = lfirst_node(ColumnDef, lc);
			char	   *attributeName = newdef->colname;
			int			exist_attno;

			/*
			 * Partitions have only one parent and have no column definitions
			 * of their own, so conflict should never occur.
			 */
			Assert(!is_partition);

			newcol_attno++;

			/*
			 * Does it match some inherited column?
			 */
			exist_attno = findAttrByName(attributeName, inh_columns);
			if (exist_attno > 0)
			{
				/*
				 * Yes, try to merge the two column definitions.
				 */
				MergeChildAttribute(inh_columns, exist_attno, newcol_attno, newdef);
			}
			else
			{
				/*
				 * No, attach new column unchanged to result columns.
				 */
				inh_columns = lappend(inh_columns, newdef);
			}
		}

		columns = inh_columns;

		/*
		 * Check that we haven't exceeded the legal # of columns after merging
		 * in inherited columns.
		 */
		if (list_length(columns) > MaxHeapAttributeNumber)
			ereport(ERROR,
					(errcode(ERRCODE_TOO_MANY_COLUMNS),
					 errmsg("tables can have at most %d columns",
							MaxHeapAttributeNumber)));
	}

	/*
	 * Now that we have the column definition list for a partition, we can
	 * check whether the columns referenced in the column constraint specs
	 * actually exist.  Also, merge column defaults.
	 */
	if (is_partition)
	{
		foreach(lc, saved_columns)
		{
			ColumnDef  *restdef = lfirst(lc);
			bool		found = false;
			ListCell   *l;

			foreach(l, columns)
			{
				ColumnDef  *coldef = lfirst(l);

				if (strcmp(coldef->colname, restdef->colname) == 0)
				{
					found = true;

					/*
					 * Check for conflicts related to generated columns.
					 *
					 * Same rules as above: generated-ness has to match the
					 * parent, but the contents of the generation expression
					 * can be different.
					 */
					if (coldef->generated)
					{
						if (restdef->raw_default && !restdef->generated)
							ereport(ERROR,
									(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
									 errmsg("column \"%s\" inherits from generated column but specifies default",
											restdef->colname)));
						if (restdef->identity)
							ereport(ERROR,
									(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
									 errmsg("column \"%s\" inherits from generated column but specifies identity",
											restdef->colname)));
					}
					else
					{
						if (restdef->generated)
							ereport(ERROR,
									(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
									 errmsg("child column \"%s\" specifies generation expression",
											restdef->colname),
									 errhint("A child table column cannot be generated unless its parent column is.")));
					}

					if (coldef->generated && restdef->generated && coldef->generated != restdef->generated)
						ereport(ERROR,
								(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
								 errmsg("column \"%s\" inherits from generated column of different kind",
										restdef->colname),
								 errdetail("Parent column is %s, child column is %s.",
										   coldef->generated == ATTRIBUTE_GENERATED_STORED ? "STORED" : "VIRTUAL",
										   restdef->generated == ATTRIBUTE_GENERATED_STORED ? "STORED" : "VIRTUAL")));

					/*
					 * Override the parent's default value for this column
					 * (coldef->cooked_default) with the partition's local
					 * definition (restdef->raw_default), if there's one. It
					 * should be physically impossible to get a cooked default
					 * in the local definition or a raw default in the
					 * inherited definition, but make sure they're nulls, for
					 * future-proofing.
					 */
					Assert(restdef->cooked_default == NULL);
					Assert(coldef->raw_default == NULL);
					if (restdef->raw_default)
					{
						coldef->raw_default = restdef->raw_default;
						coldef->cooked_default = NULL;
					}
				}
			}

			/* complain for constraints on columns not in parent */
			if (!found)
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_COLUMN),
						 errmsg("column \"%s\" does not exist",
								restdef->colname)));
		}
	}

	/*
	 * If we found any conflicting parent default values, check to make sure
	 * they were overridden by the child.
	 */
	if (have_bogus_defaults)
	{
		foreach(lc, columns)
		{
			ColumnDef  *def = lfirst(lc);

			if (def->cooked_default == &bogus_marker)
			{
				if (def->generated)
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
							 errmsg("column \"%s\" inherits conflicting generation expressions",
									def->colname),
							 errhint("To resolve the conflict, specify a generation expression explicitly.")));
				else
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
							 errmsg("column \"%s\" inherits conflicting default values",
									def->colname),
							 errhint("To resolve the conflict, specify a default explicitly.")));
			}
		}
	}

	*supconstr = constraints;
	*supnotnulls = nnconstraints;

	return columns;
}


/*
 * MergeCheckConstraint
 *		Try to merge an inherited CHECK constraint with previous ones
 *
 * If we inherit identically-named constraints from multiple parents, we must
 * merge them, or throw an error if they don't have identical definitions.
 *
 * constraints is a list of CookedConstraint structs for previous constraints.
 *
 * If the new constraint matches an existing one, then the existing
 * constraint's inheritance count is updated.  If there is a conflict (same
 * name but different expression), throw an error.  If the constraint neither
 * matches nor conflicts with an existing one, a new constraint is appended to
 * the list.
 */
static List *
MergeCheckConstraint(List *constraints, const char *name, Node *expr, bool is_enforced)
{
	ListCell   *lc;
	CookedConstraint *newcon;

	foreach(lc, constraints)
	{
		CookedConstraint *ccon = (CookedConstraint *) lfirst(lc);

		Assert(ccon->contype == CONSTR_CHECK);

		/* Non-matching names never conflict */
		if (strcmp(ccon->name, name) != 0)
			continue;

		if (equal(expr, ccon->expr))
		{
			/* OK to merge constraint with existing */
			if (pg_add_s16_overflow(ccon->inhcount, 1,
									&ccon->inhcount))
				ereport(ERROR,
						errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
						errmsg("too many inheritance parents"));

			/*
			 * When enforceability differs, the merged constraint should be
			 * marked as ENFORCED because one of the parents is ENFORCED.
			 */
			if (!ccon->is_enforced && is_enforced)
			{
				ccon->is_enforced = true;
				ccon->skip_validation = false;
			}

			return constraints;
		}

		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_OBJECT),
				 errmsg("check constraint name \"%s\" appears multiple times but with different expressions",
						name)));
	}

	/*
	 * Constraint couldn't be merged with an existing one and also didn't
	 * conflict with an existing one, so add it as a new one to the list.
	 */
	newcon = palloc0_object(CookedConstraint);
	newcon->contype = CONSTR_CHECK;
	newcon->name = pstrdup(name);
	newcon->expr = expr;
	newcon->inhcount = 1;
	newcon->is_enforced = is_enforced;
	newcon->skip_validation = !is_enforced;
	return lappend(constraints, newcon);
}

/*
 * MergeChildAttribute
 *		Merge given child attribute definition into given inherited attribute.
 *
 * Input arguments:
 * 'inh_columns' is the list of inherited ColumnDefs.
 * 'exist_attno' is the number of the inherited attribute in inh_columns
 * 'newcol_attno' is the attribute number in child table's schema definition
 * 'newdef' is the column/attribute definition from the child table.
 *
 * The ColumnDef in 'inh_columns' list is modified.  The child attribute's
 * ColumnDef remains unchanged.
 *
 * Notes:
 * - The attribute is merged according to the rules laid out in the prologue
 *   of MergeAttributes().
 * - If matching inherited attribute exists but the child attribute can not be
 *   merged into it, the function throws respective errors.
 * - A partition can not have its own column definitions. Hence this function
 *   is applicable only to a regular inheritance child.
 */
static void
MergeChildAttribute(List *inh_columns, int exist_attno, int newcol_attno, const ColumnDef *newdef)
{
	char	   *attributeName = newdef->colname;
	ColumnDef  *inhdef;
	Oid			inhtypeid,
				newtypeid;
	int32		inhtypmod,
				newtypmod;
	Oid			inhcollid,
				newcollid;

	if (exist_attno == newcol_attno)
		ereport(NOTICE,
				(errmsg("merging column \"%s\" with inherited definition",
						attributeName)));
	else
		ereport(NOTICE,
				(errmsg("moving and merging column \"%s\" with inherited definition", attributeName),
				 errdetail("User-specified column moved to the position of the inherited column.")));

	inhdef = list_nth_node(ColumnDef, inh_columns, exist_attno - 1);

	/*
	 * Must have the same type and typmod
	 */
	typenameTypeIdAndMod(NULL, inhdef->typeName, &inhtypeid, &inhtypmod);
	typenameTypeIdAndMod(NULL, newdef->typeName, &newtypeid, &newtypmod);
	if (inhtypeid != newtypeid || inhtypmod != newtypmod)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("column \"%s\" has a type conflict",
						attributeName),
				 errdetail("%s versus %s",
						   format_type_with_typemod(inhtypeid, inhtypmod),
						   format_type_with_typemod(newtypeid, newtypmod))));

	/*
	 * Must have the same collation
	 */
	inhcollid = GetColumnDefCollation(NULL, inhdef, inhtypeid);
	newcollid = GetColumnDefCollation(NULL, newdef, newtypeid);
	if (inhcollid != newcollid)
		ereport(ERROR,
				(errcode(ERRCODE_COLLATION_MISMATCH),
				 errmsg("column \"%s\" has a collation conflict",
						attributeName),
				 errdetail("\"%s\" versus \"%s\"",
						   get_collation_name(inhcollid),
						   get_collation_name(newcollid))));

	/*
	 * Identity is never inherited by a regular inheritance child. Pick
	 * child's identity definition if there's one.
	 */
	inhdef->identity = newdef->identity;

	/*
	 * Copy storage parameter
	 */
	if (inhdef->storage == 0)
		inhdef->storage = newdef->storage;
	else if (newdef->storage != 0 && inhdef->storage != newdef->storage)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("column \"%s\" has a storage parameter conflict",
						attributeName),
				 errdetail("%s versus %s",
						   storage_name(inhdef->storage),
						   storage_name(newdef->storage))));

	/*
	 * Copy compression parameter
	 */
	if (inhdef->compression == NULL)
		inhdef->compression = newdef->compression;
	else if (newdef->compression != NULL)
	{
		if (strcmp(inhdef->compression, newdef->compression) != 0)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("column \"%s\" has a compression method conflict",
							attributeName),
					 errdetail("%s versus %s", inhdef->compression, newdef->compression)));
	}

	/*
	 * Merge of not-null constraints = OR 'em together
	 */
	inhdef->is_not_null |= newdef->is_not_null;

	/*
	 * Check for conflicts related to generated columns.
	 *
	 * If the parent column is generated, the child column will be made a
	 * generated column if it isn't already.  If it is a generated column,
	 * we'll take its generation expression in preference to the parent's.  We
	 * must check that the child column doesn't specify a default value or
	 * identity, which matches the rules for a single column in
	 * parse_utilcmd.c.
	 *
	 * Conversely, if the parent column is not generated, the child column
	 * can't be either.  (We used to allow that, but it results in being able
	 * to override the generation expression via UPDATEs through the parent.)
	 */
	if (inhdef->generated)
	{
		if (newdef->raw_default && !newdef->generated)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
					 errmsg("column \"%s\" inherits from generated column but specifies default",
							inhdef->colname)));
		if (newdef->identity)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
					 errmsg("column \"%s\" inherits from generated column but specifies identity",
							inhdef->colname)));
	}
	else
	{
		if (newdef->generated)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
					 errmsg("child column \"%s\" specifies generation expression",
							inhdef->colname),
					 errhint("A child table column cannot be generated unless its parent column is.")));
	}

	if (inhdef->generated && newdef->generated && newdef->generated != inhdef->generated)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
				 errmsg("column \"%s\" inherits from generated column of different kind",
						inhdef->colname),
				 errdetail("Parent column is %s, child column is %s.",
						   inhdef->generated == ATTRIBUTE_GENERATED_STORED ? "STORED" : "VIRTUAL",
						   newdef->generated == ATTRIBUTE_GENERATED_STORED ? "STORED" : "VIRTUAL")));

	/*
	 * If new def has a default, override previous default
	 */
	if (newdef->raw_default != NULL)
	{
		inhdef->raw_default = newdef->raw_default;
		inhdef->cooked_default = newdef->cooked_default;
	}

	/* Mark the column as locally defined */
	inhdef->is_local = true;
}

/*
 * MergeInheritedAttribute
 *		Merge given parent attribute definition into specified attribute
 *		inherited from the previous parents.
 *
 * Input arguments:
 * 'inh_columns' is the list of previously inherited ColumnDefs.
 * 'exist_attno' is the number the existing matching attribute in inh_columns.
 * 'newdef' is the new parent column/attribute definition to be merged.
 *
 * The matching ColumnDef in 'inh_columns' list is modified and returned.
 *
 * Notes:
 * - The attribute is merged according to the rules laid out in the prologue
 *   of MergeAttributes().
 * - If matching inherited attribute exists but the new attribute can not be
 *   merged into it, the function throws respective errors.
 * - A partition inherits from only a single parent. Hence this function is
 *   applicable only to a regular inheritance.
 */
static ColumnDef *
MergeInheritedAttribute(List *inh_columns,
						int exist_attno,
						const ColumnDef *newdef)
{
	char	   *attributeName = newdef->colname;
	ColumnDef  *prevdef;
	Oid			prevtypeid,
				newtypeid;
	int32		prevtypmod,
				newtypmod;
	Oid			prevcollid,
				newcollid;

	ereport(NOTICE,
			(errmsg("merging multiple inherited definitions of column \"%s\"",
					attributeName)));
	prevdef = list_nth_node(ColumnDef, inh_columns, exist_attno - 1);

	/*
	 * Must have the same type and typmod
	 */
	typenameTypeIdAndMod(NULL, prevdef->typeName, &prevtypeid, &prevtypmod);
	typenameTypeIdAndMod(NULL, newdef->typeName, &newtypeid, &newtypmod);
	if (prevtypeid != newtypeid || prevtypmod != newtypmod)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("inherited column \"%s\" has a type conflict",
						attributeName),
				 errdetail("%s versus %s",
						   format_type_with_typemod(prevtypeid, prevtypmod),
						   format_type_with_typemod(newtypeid, newtypmod))));

	/*
	 * Must have the same collation
	 */
	prevcollid = GetColumnDefCollation(NULL, prevdef, prevtypeid);
	newcollid = GetColumnDefCollation(NULL, newdef, newtypeid);
	if (prevcollid != newcollid)
		ereport(ERROR,
				(errcode(ERRCODE_COLLATION_MISMATCH),
				 errmsg("inherited column \"%s\" has a collation conflict",
						attributeName),
				 errdetail("\"%s\" versus \"%s\"",
						   get_collation_name(prevcollid),
						   get_collation_name(newcollid))));

	/*
	 * Copy/check storage parameter
	 */
	if (prevdef->storage == 0)
		prevdef->storage = newdef->storage;
	else if (prevdef->storage != newdef->storage)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("inherited column \"%s\" has a storage parameter conflict",
						attributeName),
				 errdetail("%s versus %s",
						   storage_name(prevdef->storage),
						   storage_name(newdef->storage))));

	/*
	 * Copy/check compression parameter
	 */
	if (prevdef->compression == NULL)
		prevdef->compression = newdef->compression;
	else if (newdef->compression != NULL)
	{
		if (strcmp(prevdef->compression, newdef->compression) != 0)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("column \"%s\" has a compression method conflict",
							attributeName),
					 errdetail("%s versus %s",
							   prevdef->compression, newdef->compression)));
	}

	/*
	 * Check for GENERATED conflicts
	 */
	if (prevdef->generated != newdef->generated)
		ereport(ERROR,
				(errcode(ERRCODE_DATATYPE_MISMATCH),
				 errmsg("inherited column \"%s\" has a generation conflict",
						attributeName)));

	/*
	 * Default and other constraints are handled by the caller.
	 */

	if (pg_add_s16_overflow(prevdef->inhcount, 1,
							&prevdef->inhcount))
		ereport(ERROR,
				errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				errmsg("too many inheritance parents"));

	return prevdef;
}

/*
 * StoreCatalogInheritance
 *		Updates the system catalogs with proper inheritance information.
 *
 * supers is a list of the OIDs of the new relation's direct ancestors.
 */
static void
StoreCatalogInheritance(Oid relationId, List *supers,
						bool child_is_partition)
{
	Relation	relation;
	int32		seqNumber;
	ListCell   *entry;

	/*
	 * sanity checks
	 */
	Assert(OidIsValid(relationId));

	if (supers == NIL)
		return;

	/*
	 * Store INHERITS information in pg_inherits using direct ancestors only.
	 * Also enter dependencies on the direct ancestors, and make sure they are
	 * marked with relhassubclass = true.
	 *
	 * (Once upon a time, both direct and indirect ancestors were found here
	 * and then entered into pg_ipl.  Since that catalog doesn't exist
	 * anymore, there's no need to look for indirect ancestors.)
	 */
	relation = table_open(InheritsRelationId, RowExclusiveLock);

	seqNumber = 1;
	foreach(entry, supers)
	{
		Oid			parentOid = lfirst_oid(entry);

		StoreCatalogInheritance1(relationId, parentOid, seqNumber, relation,
								 child_is_partition);
		seqNumber++;
	}

	table_close(relation, RowExclusiveLock);
}

/*
 * Make catalog entries showing relationId as being an inheritance child
 * of parentOid.  inhRelation is the already-opened pg_inherits catalog.
 */
static void
StoreCatalogInheritance1(Oid relationId, Oid parentOid,
						 int32 seqNumber, Relation inhRelation,
						 bool child_is_partition)
{
	ObjectAddress childobject,
				parentobject;

	/* store the pg_inherits row */
	StoreSingleInheritance(relationId, parentOid, seqNumber);

	/*
	 * Store a dependency too
	 */
	parentobject.classId = RelationRelationId;
	parentobject.objectId = parentOid;
	parentobject.objectSubId = 0;
	childobject.classId = RelationRelationId;
	childobject.objectId = relationId;
	childobject.objectSubId = 0;

	recordDependencyOn(&childobject, &parentobject,
					   child_dependency_type(child_is_partition));

	/*
	 * Post creation hook of this inheritance. Since object_access_hook
	 * doesn't take multiple object identifiers, we relay oid of parent
	 * relation using auxiliary_id argument.
	 */
	InvokeObjectPostAlterHookArg(InheritsRelationId,
								 relationId, 0,
								 parentOid, false);

	/*
	 * Mark the parent as having subclasses.
	 */
	SetRelationHasSubclass(parentOid, true);
}

/*
 * Look for an existing column entry with the given name.
 *
 * Returns the index (starting with 1) if attribute already exists in columns,
 * 0 if it doesn't.
 */
static int
findAttrByName(const char *attributeName, const List *columns)
{
	ListCell   *lc;
	int			i = 1;

	foreach(lc, columns)
	{
		if (strcmp(attributeName, lfirst_node(ColumnDef, lc)->colname) == 0)
			return i;

		i++;
	}
	return 0;
}


/*
 * SetRelationHasSubclass
 *		Set the value of the relation's relhassubclass field in pg_class.
 *
 * It's always safe to set this field to true, because all SQL commands are
 * ready to see true and then find no children.  On the other hand, commands
 * generally assume zero children if this is false.
 *
 * Caller must hold any self-exclusive lock until end of transaction.  If the
 * new value is false, caller must have acquired that lock before reading the
 * evidence that justified the false value.  That way, it properly waits if
 * another backend is simultaneously concluding no need to change the tuple
 * (new and old values are true).
 *
 * NOTE: an important side-effect of this operation is that an SI invalidation
 * message is sent out to all backends --- including me --- causing plans
 * referencing the relation to be rebuilt with the new list of children.
 * This must happen even if we find that no change is needed in the pg_class
 * row.
 */
void
SetRelationHasSubclass(Oid relationId, bool relhassubclass)
{
	Relation	relationRelation;
	HeapTuple	tuple;
	Form_pg_class classtuple;

	Assert(CheckRelationOidLockedByMe(relationId,
									  ShareUpdateExclusiveLock, false) ||
		   CheckRelationOidLockedByMe(relationId,
									  ShareRowExclusiveLock, true));

	/*
	 * Fetch a modifiable copy of the tuple, modify it, update pg_class.
	 */
	relationRelation = table_open(RelationRelationId, RowExclusiveLock);
	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relationId));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", relationId);
	classtuple = (Form_pg_class) GETSTRUCT(tuple);

	if (classtuple->relhassubclass != relhassubclass)
	{
		classtuple->relhassubclass = relhassubclass;
		CatalogTupleUpdate(relationRelation, &tuple->t_self, tuple);
	}
	else
	{
		/* no need to change tuple, but force relcache rebuild anyway */
		CacheInvalidateRelcacheByTuple(tuple);
	}

	heap_freetuple(tuple);
	table_close(relationRelation, RowExclusiveLock);
}

/*
 * CheckRelationTableSpaceMove
 *		Check if relation can be moved to new tablespace.
 *
 * NOTE: The caller must hold AccessExclusiveLock on the relation.
 *
 * Returns true if the relation can be moved to the new tablespace; raises
 * an error if it is not possible to do the move; returns false if the move
 * would have no effect.
 */
bool
CheckRelationTableSpaceMove(Relation rel, Oid newTableSpaceId)
{
	Oid			oldTableSpaceId;

	/*
	 * No work if no change in tablespace.  Note that MyDatabaseTableSpace is
	 * stored as 0.
	 */
	oldTableSpaceId = rel->rd_rel->reltablespace;
	if (newTableSpaceId == oldTableSpaceId ||
		(newTableSpaceId == MyDatabaseTableSpace && oldTableSpaceId == 0))
		return false;

	/*
	 * We cannot support moving mapped relations into different tablespaces.
	 * (In particular this eliminates all shared catalogs.)
	 */
	if (RelationIsMapped(rel))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot move system relation \"%s\"",
						RelationGetRelationName(rel))));

	/* Cannot move a non-shared relation into pg_global */
	if (newTableSpaceId == GLOBALTABLESPACE_OID)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("only shared relations can be placed in pg_global tablespace")));

	/*
	 * Do not allow moving temp tables of other backends ... their local
	 * buffer manager is not going to cope.
	 */
	if (RELATION_IS_OTHER_TEMP(rel))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot move temporary tables of other sessions")));

	return true;
}

/*
 * SetRelationTableSpace
 *		Set new reltablespace and relfilenumber in pg_class entry.
 *
 * newTableSpaceId is the new tablespace for the relation, and
 * newRelFilenumber its new filenumber.  If newRelFilenumber is
 * InvalidRelFileNumber, this field is not updated.
 *
 * NOTE: The caller must hold AccessExclusiveLock on the relation.
 *
 * The caller of this routine had better check if a relation can be
 * moved to this new tablespace by calling CheckRelationTableSpaceMove()
 * first, and is responsible for making the change visible with
 * CommandCounterIncrement().
 */
void
SetRelationTableSpace(Relation rel,
					  Oid newTableSpaceId,
					  RelFileNumber newRelFilenumber)
{
	Relation	pg_class;
	HeapTuple	tuple;
	ItemPointerData otid;
	Form_pg_class rd_rel;
	Oid			reloid = RelationGetRelid(rel);

	Assert(CheckRelationTableSpaceMove(rel, newTableSpaceId));

	/* Get a modifiable copy of the relation's pg_class row. */
	pg_class = table_open(RelationRelationId, RowExclusiveLock);

	tuple = SearchSysCacheLockedCopy1(RELOID, ObjectIdGetDatum(reloid));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", reloid);
	otid = tuple->t_self;
	rd_rel = (Form_pg_class) GETSTRUCT(tuple);

	/* Update the pg_class row. */
	rd_rel->reltablespace = (newTableSpaceId == MyDatabaseTableSpace) ?
		InvalidOid : newTableSpaceId;
	if (RelFileNumberIsValid(newRelFilenumber))
		rd_rel->relfilenode = newRelFilenumber;
	CatalogTupleUpdate(pg_class, &otid, tuple);
	UnlockTuple(pg_class, &otid, InplaceUpdateTupleLock);

	/*
	 * Record dependency on tablespace.  This is only required for relations
	 * that have no physical storage.
	 */
	if (!RELKIND_HAS_STORAGE(rel->rd_rel->relkind))
		changeDependencyOnTablespace(RelationRelationId, reloid,
									 rd_rel->reltablespace);

	heap_freetuple(tuple);
	table_close(pg_class, RowExclusiveLock);
}

/*
 *		renameatt_check			- basic sanity checks before attribute rename
 */
static void
renameatt_check(Oid myrelid, Form_pg_class classform, bool recursing)
{
	char		relkind = classform->relkind;

	if (classform->reloftype && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot rename column of typed table")));

	/*
	 * Renaming the columns of sequences or toast tables doesn't actually
	 * break anything from the system's point of view, since internal
	 * references are by attnum.  But it doesn't seem right to allow users to
	 * change names that are hardcoded into the system, hence the following
	 * restriction.
	 */
	if (relkind != RELKIND_RELATION &&
		relkind != RELKIND_VIEW &&
		relkind != RELKIND_MATVIEW &&
		relkind != RELKIND_COMPOSITE_TYPE &&
		relkind != RELKIND_INDEX &&
		relkind != RELKIND_PARTITIONED_INDEX &&
		relkind != RELKIND_FOREIGN_TABLE &&
		relkind != RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot rename columns of relation \"%s\"",
						NameStr(classform->relname)),
				 errdetail_relkind_not_supported(relkind)));

	/*
	 * permissions checking.  only the owner of a class can change its schema.
	 */
	if (!object_ownercheck(RelationRelationId, myrelid, GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(myrelid)),
					   NameStr(classform->relname));
	if (!allowSystemTableMods && IsSystemClass(myrelid, classform))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						NameStr(classform->relname))));
}

/*
 *		renameatt_internal		- workhorse for renameatt
 *
 * Return value is the attribute number in the 'myrelid' relation.
 */
static AttrNumber
renameatt_internal(Oid myrelid,
				   const char *oldattname,
				   const char *newattname,
				   bool recurse,
				   bool recursing,
				   int expected_parents,
				   DropBehavior behavior)
{
	Relation	targetrelation;
	Relation	attrelation;
	HeapTuple	atttup;
	Form_pg_attribute attform;
	AttrNumber	attnum;

	/*
	 * Grab an exclusive lock on the target table, which we will NOT release
	 * until end of transaction.
	 */
	targetrelation = relation_open(myrelid, AccessExclusiveLock);
	renameatt_check(myrelid, RelationGetForm(targetrelation), recursing);

	/*
	 * if the 'recurse' flag is set then we are supposed to rename this
	 * attribute in all classes that inherit from 'relname' (as well as in
	 * 'relname').
	 *
	 * any permissions or problems with duplicate attributes will cause the
	 * whole transaction to abort, which is what we want -- all or nothing.
	 */
	if (recurse)
	{
		List	   *child_oids,
				   *child_numparents;
		ListCell   *lo,
				   *li;

		/*
		 * we need the number of parents for each child so that the recursive
		 * calls to renameatt() can determine whether there are any parents
		 * outside the inheritance hierarchy being processed.
		 */
		child_oids = find_all_inheritors(myrelid, AccessExclusiveLock,
										 &child_numparents);

		/*
		 * find_all_inheritors does the recursive search of the inheritance
		 * hierarchy, so all we have to do is process all of the relids in the
		 * list that it returns.
		 */
		forboth(lo, child_oids, li, child_numparents)
		{
			Oid			childrelid = lfirst_oid(lo);
			int			numparents = lfirst_int(li);

			if (childrelid == myrelid)
				continue;
			/* note we need not recurse again */
			renameatt_internal(childrelid, oldattname, newattname, false, true, numparents, behavior);
		}
	}
	else
	{
		/*
		 * If we are told not to recurse, there had better not be any child
		 * tables; else the rename would put them out of step.
		 *
		 * expected_parents will only be 0 if we are not already recursing.
		 */
		if (expected_parents == 0 &&
			find_inheritance_children(myrelid, NoLock) != NIL)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("inherited column \"%s\" must be renamed in child tables too",
							oldattname)));
	}

	/* rename attributes in typed tables of composite type */
	if (targetrelation->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
	{
		List	   *child_oids;
		ListCell   *lo;

		child_oids = find_typed_table_dependencies(targetrelation->rd_rel->reltype,
												   RelationGetRelationName(targetrelation),
												   behavior);

		foreach(lo, child_oids)
			renameatt_internal(lfirst_oid(lo), oldattname, newattname, true, true, 0, behavior);
	}

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);

	atttup = SearchSysCacheCopyAttName(myrelid, oldattname);
	if (!HeapTupleIsValid(atttup))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" does not exist",
						oldattname)));
	attform = (Form_pg_attribute) GETSTRUCT(atttup);

	attnum = attform->attnum;
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot rename system column \"%s\"",
						oldattname)));

	/*
	 * if the attribute is inherited, forbid the renaming.  if this is a
	 * top-level call to renameatt(), then expected_parents will be 0, so the
	 * effect of this code will be to prohibit the renaming if the attribute
	 * is inherited at all.  if this is a recursive call to renameatt(),
	 * expected_parents will be the number of parents the current relation has
	 * within the inheritance hierarchy being processed, so we'll prohibit the
	 * renaming only if there are additional parents from elsewhere.
	 */
	if (attform->attinhcount > expected_parents)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot rename inherited column \"%s\"",
						oldattname)));

	/* new name should not already exist */
	(void) check_for_column_name_collision(targetrelation, newattname, false);

	/* apply the update */
	namestrcpy(&(attform->attname), newattname);

	CatalogTupleUpdate(attrelation, &atttup->t_self, atttup);

	InvokeObjectPostAlterHook(RelationRelationId, myrelid, attnum);

	heap_freetuple(atttup);

	table_close(attrelation, RowExclusiveLock);

	relation_close(targetrelation, NoLock); /* close rel but keep lock */

	return attnum;
}

/*
 * Perform permissions and integrity checks before acquiring a relation lock.
 */
static void
RangeVarCallbackForRenameAttribute(const RangeVar *rv, Oid relid, Oid oldrelid,
								   void *arg)
{
	HeapTuple	tuple;
	Form_pg_class form;

	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
	if (!HeapTupleIsValid(tuple))
		return;					/* concurrently dropped */
	form = (Form_pg_class) GETSTRUCT(tuple);
	renameatt_check(relid, form, false);
	ReleaseSysCache(tuple);
}

/*
 *		renameatt		- changes the name of an attribute in a relation
 *
 * The returned ObjectAddress is that of the renamed column.
 */
ObjectAddress
renameatt(RenameStmt *stmt)
{
	Oid			relid;
	AttrNumber	attnum;
	ObjectAddress address;

	/* lock level taken here should match renameatt_internal */
	relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
									 stmt->missing_ok ? RVR_MISSING_OK : 0,
									 RangeVarCallbackForRenameAttribute,
									 NULL);

	if (!OidIsValid(relid))
	{
		ereport(NOTICE,
				(errmsg("relation \"%s\" does not exist, skipping",
						stmt->relation->relname)));
		return InvalidObjectAddress;
	}

	attnum =
		renameatt_internal(relid,
						   stmt->subname,	/* old att name */
						   stmt->newname,	/* new att name */
						   stmt->relation->inh, /* recursive? */
						   false,	/* recursing? */
						   0,	/* expected inhcount */
						   stmt->behavior);

	ObjectAddressSubSet(address, RelationRelationId, relid, attnum);

	return address;
}

/*
 * same logic as renameatt_internal
 */
static ObjectAddress
rename_constraint_internal(Oid myrelid,
						   Oid mytypid,
						   const char *oldconname,
						   const char *newconname,
						   bool recurse,
						   bool recursing,
						   int expected_parents)
{
	Relation	targetrelation = NULL;
	Oid			constraintOid;
	HeapTuple	tuple;
	Form_pg_constraint con;
	ObjectAddress address;

	Assert(!myrelid || !mytypid);

	if (mytypid)
	{
		constraintOid = get_domain_constraint_oid(mytypid, oldconname, false);
	}
	else
	{
		targetrelation = relation_open(myrelid, AccessExclusiveLock);

		/*
		 * don't tell it whether we're recursing; we allow changing typed
		 * tables here
		 */
		renameatt_check(myrelid, RelationGetForm(targetrelation), false);

		constraintOid = get_relation_constraint_oid(myrelid, oldconname, false);
	}

	tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constraintOid));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for constraint %u",
			 constraintOid);
	con = (Form_pg_constraint) GETSTRUCT(tuple);

	if (myrelid &&
		(con->contype == CONSTRAINT_CHECK ||
		 con->contype == CONSTRAINT_NOTNULL) &&
		!con->connoinherit)
	{
		if (recurse)
		{
			List	   *child_oids,
					   *child_numparents;
			ListCell   *lo,
					   *li;

			child_oids = find_all_inheritors(myrelid, AccessExclusiveLock,
											 &child_numparents);

			forboth(lo, child_oids, li, child_numparents)
			{
				Oid			childrelid = lfirst_oid(lo);
				int			numparents = lfirst_int(li);

				if (childrelid == myrelid)
					continue;

				rename_constraint_internal(childrelid, InvalidOid, oldconname, newconname, false, true, numparents);
			}
		}
		else
		{
			if (expected_parents == 0 &&
				find_inheritance_children(myrelid, NoLock) != NIL)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
						 errmsg("inherited constraint \"%s\" must be renamed in child tables too",
								oldconname)));
		}

		if (con->coninhcount > expected_parents)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("cannot rename inherited constraint \"%s\"",
							oldconname)));
	}

	if (con->conindid
		&& (con->contype == CONSTRAINT_PRIMARY
			|| con->contype == CONSTRAINT_UNIQUE
			|| con->contype == CONSTRAINT_EXCLUSION))
		/* rename the index; this renames the constraint as well */
		RenameRelationInternal(con->conindid, newconname, false, true);
	else
		RenameConstraintById(constraintOid, newconname);

	ObjectAddressSet(address, ConstraintRelationId, constraintOid);

	ReleaseSysCache(tuple);

	if (targetrelation)
	{
		/*
		 * Invalidate relcache so as others can see the new constraint name.
		 */
		CacheInvalidateRelcache(targetrelation);

		relation_close(targetrelation, NoLock); /* close rel but keep lock */
	}

	return address;
}

ObjectAddress
RenameConstraint(RenameStmt *stmt)
{
	Oid			relid = InvalidOid;
	Oid			typid = InvalidOid;

	if (stmt->renameType == OBJECT_DOMCONSTRAINT)
	{
		Relation	rel;
		HeapTuple	tup;

		typid = typenameTypeId(NULL, makeTypeNameFromNameList(castNode(List, stmt->object)));
		rel = table_open(TypeRelationId, RowExclusiveLock);
		tup = SearchSysCache1(TYPEOID, ObjectIdGetDatum(typid));
		if (!HeapTupleIsValid(tup))
			elog(ERROR, "cache lookup failed for type %u", typid);
		checkDomainOwner(tup);
		ReleaseSysCache(tup);
		table_close(rel, NoLock);
	}
	else
	{
		/* lock level taken here should match rename_constraint_internal */
		relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
										 stmt->missing_ok ? RVR_MISSING_OK : 0,
										 RangeVarCallbackForRenameAttribute,
										 NULL);
		if (!OidIsValid(relid))
		{
			ereport(NOTICE,
					(errmsg("relation \"%s\" does not exist, skipping",
							stmt->relation->relname)));
			return InvalidObjectAddress;
		}
	}

	return
		rename_constraint_internal(relid, typid,
								   stmt->subname,
								   stmt->newname,
								   (stmt->relation &&
									stmt->relation->inh),	/* recursive? */
								   false,	/* recursing? */
								   0 /* expected inhcount */ );
}

/*
 * Execute ALTER TABLE/INDEX/SEQUENCE/VIEW/MATERIALIZED VIEW/FOREIGN TABLE
 * RENAME
 */
ObjectAddress
RenameRelation(RenameStmt *stmt)
{
	bool		is_index_stmt = stmt->renameType == OBJECT_INDEX;
	Oid			relid;
	ObjectAddress address;

	/*
	 * Grab an exclusive lock on the target table, index, sequence, view,
	 * materialized view, or foreign table, which we will NOT release until
	 * end of transaction.
	 *
	 * Lock level used here should match RenameRelationInternal, to avoid lock
	 * escalation.  However, because ALTER INDEX can be used with any relation
	 * type, we mustn't believe without verification.
	 */
	for (;;)
	{
		LOCKMODE	lockmode;
		char		relkind;
		bool		obj_is_index;

		lockmode = is_index_stmt ? ShareUpdateExclusiveLock : AccessExclusiveLock;

		relid = RangeVarGetRelidExtended(stmt->relation, lockmode,
										 stmt->missing_ok ? RVR_MISSING_OK : 0,
										 RangeVarCallbackForAlterRelation,
										 stmt);

		if (!OidIsValid(relid))
		{
			ereport(NOTICE,
					(errmsg("relation \"%s\" does not exist, skipping",
							stmt->relation->relname)));
			return InvalidObjectAddress;
		}

		/*
		 * We allow mismatched statement and object types (e.g., ALTER INDEX
		 * to rename a table), but we might've used the wrong lock level.  If
		 * that happens, retry with the correct lock level.  We don't bother
		 * if we already acquired AccessExclusiveLock with an index, however.
		 */
		relkind = get_rel_relkind(relid);
		obj_is_index = (relkind == RELKIND_INDEX ||
						relkind == RELKIND_PARTITIONED_INDEX);
		if (obj_is_index || is_index_stmt == obj_is_index)
			break;

		UnlockRelationOid(relid, lockmode);
		is_index_stmt = obj_is_index;
	}

	/* Do the work */
	RenameRelationInternal(relid, stmt->newname, false, is_index_stmt);

	ObjectAddressSet(address, RelationRelationId, relid);

	return address;
}

/*
 *		RenameRelationInternal - change the name of a relation
 */
void
RenameRelationInternal(Oid myrelid, const char *newrelname, bool is_internal, bool is_index)
{
	Relation	targetrelation;
	Relation	relrelation;	/* for RELATION relation */
	ItemPointerData otid;
	HeapTuple	reltup;
	Form_pg_class relform;
	Oid			namespaceId;

	/*
	 * Grab a lock on the target relation, which we will NOT release until end
	 * of transaction.  We need at least a self-exclusive lock so that
	 * concurrent DDL doesn't overwrite the rename if they start updating
	 * while still seeing the old version.  The lock also guards against
	 * triggering relcache reloads in concurrent sessions, which might not
	 * handle this information changing under them.  For indexes, we can use a
	 * reduced lock level because RelationReloadIndexInfo() handles indexes
	 * specially.
	 */
	targetrelation = relation_open(myrelid, is_index ? ShareUpdateExclusiveLock : AccessExclusiveLock);
	namespaceId = RelationGetNamespace(targetrelation);

	/*
	 * Find relation's pg_class tuple, and make sure newrelname isn't in use.
	 */
	relrelation = table_open(RelationRelationId, RowExclusiveLock);

	reltup = SearchSysCacheLockedCopy1(RELOID, ObjectIdGetDatum(myrelid));
	if (!HeapTupleIsValid(reltup))	/* shouldn't happen */
		elog(ERROR, "cache lookup failed for relation %u", myrelid);
	otid = reltup->t_self;
	relform = (Form_pg_class) GETSTRUCT(reltup);

	if (get_relname_relid(newrelname, namespaceId) != InvalidOid)
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_TABLE),
				 errmsg("relation \"%s\" already exists",
						newrelname)));

	/*
	 * RenameRelation is careful not to believe the caller's idea of the
	 * relation kind being handled.  We don't have to worry about this, but
	 * let's not be totally oblivious to it.  We can process an index as
	 * not-an-index, but not the other way around.
	 */
	Assert(!is_index ||
		   is_index == (targetrelation->rd_rel->relkind == RELKIND_INDEX ||
						targetrelation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX));

	/*
	 * Update pg_class tuple with new relname.  (Scribbling on reltup is OK
	 * because it's a copy...)
	 */
	namestrcpy(&(relform->relname), newrelname);

	CatalogTupleUpdate(relrelation, &otid, reltup);
	UnlockTuple(relrelation, &otid, InplaceUpdateTupleLock);

	InvokeObjectPostAlterHookArg(RelationRelationId, myrelid, 0,
								 InvalidOid, is_internal);

	heap_freetuple(reltup);
	table_close(relrelation, RowExclusiveLock);

	/*
	 * Also rename the associated type, if any.
	 */
	if (OidIsValid(targetrelation->rd_rel->reltype))
		RenameTypeInternal(targetrelation->rd_rel->reltype,
						   newrelname, namespaceId);

	/*
	 * Also rename the associated constraint, if any.
	 */
	if (targetrelation->rd_rel->relkind == RELKIND_INDEX ||
		targetrelation->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
	{
		Oid			constraintId = get_index_constraint(myrelid);

		if (OidIsValid(constraintId))
			RenameConstraintById(constraintId, newrelname);
	}

	/*
	 * Close rel, but keep lock!
	 */
	relation_close(targetrelation, NoLock);
}

/*
 *		ResetRelRewrite - reset relrewrite
 */
void
ResetRelRewrite(Oid myrelid)
{
	Relation	relrelation;	/* for RELATION relation */
	HeapTuple	reltup;
	Form_pg_class relform;

	/*
	 * Find relation's pg_class tuple.
	 */
	relrelation = table_open(RelationRelationId, RowExclusiveLock);

	reltup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(myrelid));
	if (!HeapTupleIsValid(reltup))	/* shouldn't happen */
		elog(ERROR, "cache lookup failed for relation %u", myrelid);
	relform = (Form_pg_class) GETSTRUCT(reltup);

	/*
	 * Update pg_class tuple.
	 */
	relform->relrewrite = InvalidOid;

	CatalogTupleUpdate(relrelation, &reltup->t_self, reltup);

	heap_freetuple(reltup);
	table_close(relrelation, RowExclusiveLock);
}

/*
 * Disallow ALTER TABLE (and similar commands) when the current backend has
 * any open reference to the target table besides the one just acquired by
 * the calling command; this implies there's an open cursor or active plan.
 * We need this check because our lock doesn't protect us against stomping
 * on our own foot, only other people's feet!
 *
 * For ALTER TABLE, the only case known to cause serious trouble is ALTER
 * COLUMN TYPE, and some changes are obviously pretty benign, so this could
 * possibly be relaxed to only error out for certain types of alterations.
 * But the use-case for allowing any of these things is not obvious, so we
 * won't work hard at it for now.
 *
 * We also reject these commands if there are any pending AFTER trigger events
 * for the rel.  This is certainly necessary for the rewriting variants of
 * ALTER TABLE, because they don't preserve tuple TIDs and so the pending
 * events would try to fetch the wrong tuples.  It might be overly cautious
 * in other cases, but again it seems better to err on the side of paranoia.
 *
 * REINDEX calls this with "rel" referencing the index to be rebuilt; here
 * we are worried about active indexscans on the index.  The trigger-event
 * check can be skipped, since we are doing no damage to the parent table.
 *
 * The statement name (eg, "ALTER TABLE") is passed for use in error messages.
 */
void
CheckTableNotInUse(Relation rel, const char *stmt)
{
	int			expected_refcnt;

	expected_refcnt = rel->rd_isnailed ? 2 : 1;
	if (rel->rd_refcnt != expected_refcnt)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_IN_USE),
		/* translator: first %s is a SQL command, eg ALTER TABLE */
				 errmsg("cannot %s \"%s\" because it is being used by active queries in this session",
						stmt, RelationGetRelationName(rel))));

	if (rel->rd_rel->relkind != RELKIND_INDEX &&
		rel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX &&
		AfterTriggerPendingOnRel(RelationGetRelid(rel)))
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_IN_USE),
		/* translator: first %s is a SQL command, eg ALTER TABLE */
				 errmsg("cannot %s \"%s\" because it has pending trigger events",
						stmt, RelationGetRelationName(rel))));
}

/*
 * CheckAlterTableIsSafe
 *		Verify that it's safe to allow ALTER TABLE on this relation.
 *
 * This consists of CheckTableNotInUse() plus a check that the relation
 * isn't another session's temp table.  We must split out the temp-table
 * check because there are callers of CheckTableNotInUse() that don't want
 * that, notably DROP TABLE.  (We must allow DROP or we couldn't clean out
 * an orphaned temp schema.)  Compare truncate_check_activity().
 */
static void
CheckAlterTableIsSafe(Relation rel)
{
	/*
	 * Don't allow ALTER on temp tables of other backends.  Their local buffer
	 * manager is not going to cope if we need to change the table's contents.
	 * Even if we don't, there may be optimizations that assume temp tables
	 * aren't subject to such interference.
	 */
	if (RELATION_IS_OTHER_TEMP(rel))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter temporary tables of other sessions")));

	/*
	 * Also check for active uses of the relation in the current transaction,
	 * including open scans and pending AFTER trigger events.
	 */
	CheckTableNotInUse(rel, "ALTER TABLE");
}

/*
 * AlterTableLookupRelation
 *		Look up, and lock, the OID for the relation named by an alter table
 *		statement.
 */
Oid
AlterTableLookupRelation(AlterTableStmt *stmt, LOCKMODE lockmode)
{
	return RangeVarGetRelidExtended(stmt->relation, lockmode,
									stmt->missing_ok ? RVR_MISSING_OK : 0,
									RangeVarCallbackForAlterRelation,
									stmt);
}

/*
 * AlterTable
 *		Execute ALTER TABLE, which can be a list of subcommands
 *
 * ALTER TABLE is performed in three phases:
 *		1. Examine subcommands and perform pre-transformation checking.
 *		2. Validate and transform subcommands, and update system catalogs.
 *		3. Scan table(s) to check new constraints, and optionally recopy
 *		   the data into new table(s).
 * Phase 3 is not performed unless one or more of the subcommands requires
 * it.  The intention of this design is to allow multiple independent
 * updates of the table schema to be performed with only one pass over the
 * data.
 *
 * ATPrepCmd performs phase 1.  A "work queue" entry is created for
 * each table to be affected (there may be multiple affected tables if the
 * commands traverse a table inheritance hierarchy).  Also we do preliminary
 * validation of the subcommands.  Because earlier subcommands may change
 * the catalog state seen by later commands, there are limits to what can
 * be done in this phase.  Generally, this phase acquires table locks,
 * checks permissions and relkind, and recurses to find child tables.
 *
 * ATRewriteCatalogs performs phase 2 for each affected table.
 * Certain subcommands need to be performed before others to avoid
 * unnecessary conflicts; for example, DROP COLUMN should come before
 * ADD COLUMN.  Therefore phase 1 divides the subcommands into multiple
 * lists, one for each logical "pass" of phase 2.
 *
 * ATRewriteTables performs phase 3 for those tables that need it.
 *
 * For most subcommand types, phases 2 and 3 do no explicit recursion,
 * since phase 1 already does it.  However, for certain subcommand types
 * it is only possible to determine how to recurse at phase 2 time; for
 * those cases, phase 1 sets the cmd->recurse flag.
 *
 * Thanks to the magic of MVCC, an error anywhere along the way rolls back
 * the whole operation; we don't have to do anything special to clean up.
 *
 * The caller must lock the relation, with an appropriate lock level
 * for the subcommands requested, using AlterTableGetLockLevel(stmt->cmds)
 * or higher. We pass the lock level down
 * so that we can apply it recursively to inherited tables. Note that the
 * lock level we want as we recurse might well be higher than required for
 * that specific subcommand. So we pass down the overall lock requirement,
 * rather than reassess it at lower levels.
 *
 * The caller also provides a "context" which is to be passed back to
 * utility.c when we need to execute a subcommand such as CREATE INDEX.
 * Some of the fields therein, such as the relid, are used here as well.
 */
void
AlterTable(AlterTableStmt *stmt, LOCKMODE lockmode,
		   AlterTableUtilityContext *context)
{
	Relation	rel;

	/* Caller is required to provide an adequate lock. */
	rel = relation_open(context->relid, NoLock);

	CheckAlterTableIsSafe(rel);

	ATController(stmt, rel, stmt->cmds, stmt->relation->inh, lockmode, context);
}

/*
 * AlterTableInternal
 *
 * ALTER TABLE with target specified by OID
 *
 * We do not reject if the relation is already open, because it's quite
 * likely that one or more layers of caller have it open.  That means it
 * is unsafe to use this entry point for alterations that could break
 * existing query plans.  On the assumption it's not used for such, we
 * don't have to reject pending AFTER triggers, either.
 *
 * Also, since we don't have an AlterTableUtilityContext, this cannot be
 * used for any subcommand types that require parse transformation or
 * could generate subcommands that have to be passed to ProcessUtility.
 */
void
AlterTableInternal(Oid relid, List *cmds, bool recurse)
{
	Relation	rel;
	LOCKMODE	lockmode = AlterTableGetLockLevel(cmds);

	rel = relation_open(relid, lockmode);

	EventTriggerAlterTableRelid(relid);

	ATController(NULL, rel, cmds, recurse, lockmode, NULL);
}

/*
 * AlterTableGetLockLevel
 *
 * Sets the overall lock level required for the supplied list of subcommands.
 * Policy for doing this set according to needs of AlterTable(), see
 * comments there for overall explanation.
 *
 * Function is called before and after parsing, so it must give same
 * answer each time it is called. Some subcommands are transformed
 * into other subcommand types, so the transform must never be made to a
 * lower lock level than previously assigned. All transforms are noted below.
 *
 * Since this is called before we lock the table we cannot use table metadata
 * to influence the type of lock we acquire.
 *
 * There should be no lockmodes hardcoded into the subcommand functions. All
 * lockmode decisions for ALTER TABLE are made here only. The one exception is
 * ALTER TABLE RENAME which is treated as a different statement type T_RenameStmt
 * and does not travel through this section of code and cannot be combined with
 * any of the subcommands given here.
 *
 * Note that Hot Standby only knows about AccessExclusiveLocks on the primary
 * so any changes that might affect SELECTs running on standbys need to use
 * AccessExclusiveLocks even if you think a lesser lock would do, unless you
 * have a solution for that also.
 *
 * Also note that pg_dump uses only an AccessShareLock, meaning that anything
 * that takes a lock less than AccessExclusiveLock can change object definitions
 * while pg_dump is running. Be careful to check that the appropriate data is
 * derived by pg_dump using an MVCC snapshot, rather than syscache lookups,
 * otherwise we might end up with an inconsistent dump that can't restore.
 */
LOCKMODE
AlterTableGetLockLevel(List *cmds)
{
	/*
	 * This only works if we read catalog tables using MVCC snapshots.
	 */
	ListCell   *lcmd;
	LOCKMODE	lockmode = ShareUpdateExclusiveLock;

	foreach(lcmd, cmds)
	{
		AlterTableCmd *cmd = (AlterTableCmd *) lfirst(lcmd);
		LOCKMODE	cmd_lockmode = AccessExclusiveLock; /* default for compiler */

		switch (cmd->subtype)
		{
				/*
				 * These subcommands rewrite the heap, so require full locks.
				 */
			case AT_AddColumn:	/* may rewrite heap, in some cases and visible
								 * to SELECT */
			case AT_SetAccessMethod:	/* must rewrite heap */
			case AT_SetTableSpace:	/* must rewrite heap */
			case AT_AlterColumnType:	/* must rewrite heap */
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * These subcommands may require addition of toast tables. If
				 * we add a toast table to a table currently being scanned, we
				 * might miss data added to the new toast table by concurrent
				 * insert transactions.
				 */
			case AT_SetStorage: /* may add toast tables, see
								 * ATRewriteCatalogs() */
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * Removing constraints can affect SELECTs that have been
				 * optimized assuming the constraint holds true. See also
				 * CloneFkReferenced.
				 */
			case AT_DropConstraint: /* as DROP INDEX */
			case AT_DropNotNull:	/* may change some SQL plans */
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * Subcommands that may be visible to concurrent SELECTs
				 */
			case AT_DropColumn: /* change visible to SELECT */
			case AT_AddColumnToView:	/* CREATE VIEW */
			case AT_DropOids:	/* used to equiv to DropColumn */
			case AT_EnableAlwaysRule:	/* may change SELECT rules */
			case AT_EnableReplicaRule:	/* may change SELECT rules */
			case AT_EnableRule: /* may change SELECT rules */
			case AT_DisableRule:	/* may change SELECT rules */
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * Changing owner may remove implicit SELECT privileges
				 */
			case AT_ChangeOwner:	/* change visible to SELECT */
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * Changing foreign table options may affect optimization.
				 */
			case AT_GenericOptions:
			case AT_AlterColumnGenericOptions:
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * These subcommands affect write operations only.
				 */
			case AT_EnableTrig:
			case AT_EnableAlwaysTrig:
			case AT_EnableReplicaTrig:
			case AT_EnableTrigAll:
			case AT_EnableTrigUser:
			case AT_DisableTrig:
			case AT_DisableTrigAll:
			case AT_DisableTrigUser:
				cmd_lockmode = ShareRowExclusiveLock;
				break;

				/*
				 * These subcommands affect write operations only. XXX
				 * Theoretically, these could be ShareRowExclusiveLock.
				 */
			case AT_ColumnDefault:
			case AT_CookedColumnDefault:
			case AT_AlterConstraint:
			case AT_AddIndex:	/* from ADD CONSTRAINT */
			case AT_AddIndexConstraint:
			case AT_ReplicaIdentity:
			case AT_SetNotNull:
			case AT_EnableRowSecurity:
			case AT_DisableRowSecurity:
			case AT_ForceRowSecurity:
			case AT_NoForceRowSecurity:
			case AT_AddIdentity:
			case AT_DropIdentity:
			case AT_SetIdentity:
			case AT_SetExpression:
			case AT_DropExpression:
			case AT_SetCompression:
				cmd_lockmode = AccessExclusiveLock;
				break;

			case AT_AddConstraint:
			case AT_ReAddConstraint:	/* becomes AT_AddConstraint */
			case AT_ReAddDomainConstraint:	/* becomes AT_AddConstraint */
				if (IsA(cmd->def, Constraint))
				{
					Constraint *con = (Constraint *) cmd->def;

					switch (con->contype)
					{
						case CONSTR_EXCLUSION:
						case CONSTR_PRIMARY:
						case CONSTR_UNIQUE:

							/*
							 * Cases essentially the same as CREATE INDEX. We
							 * could reduce the lock strength to ShareLock if
							 * we can work out how to allow concurrent catalog
							 * updates. XXX Might be set down to
							 * ShareRowExclusiveLock but requires further
							 * analysis.
							 */
							cmd_lockmode = AccessExclusiveLock;
							break;
						case CONSTR_FOREIGN:

							/*
							 * We add triggers to both tables when we add a
							 * Foreign Key, so the lock level must be at least
							 * as strong as CREATE TRIGGER.
							 */
							cmd_lockmode = ShareRowExclusiveLock;
							break;

						default:
							cmd_lockmode = AccessExclusiveLock;
					}
				}
				break;

				/*
				 * These subcommands affect inheritance behaviour. Queries
				 * started before us will continue to see the old inheritance
				 * behaviour, while queries started after we commit will see
				 * new behaviour. No need to prevent reads or writes to the
				 * subtable while we hook it up though. Changing the TupDesc
				 * may be a problem, so keep highest lock.
				 */
			case AT_AddInherit:
			case AT_DropInherit:
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * These subcommands affect implicit row type conversion. They
				 * have affects similar to CREATE/DROP CAST on queries. don't
				 * provide for invalidating parse trees as a result of such
				 * changes, so we keep these at AccessExclusiveLock.
				 */
			case AT_AddOf:
			case AT_DropOf:
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * Only used by CREATE OR REPLACE VIEW which must conflict
				 * with an SELECTs currently using the view.
				 */
			case AT_ReplaceRelOptions:
				cmd_lockmode = AccessExclusiveLock;
				break;

				/*
				 * These subcommands affect general strategies for performance
				 * and maintenance, though don't change the semantic results
				 * from normal data reads and writes. Delaying an ALTER TABLE
				 * behind currently active writes only delays the point where
				 * the new strategy begins to take effect, so there is no
				 * benefit in waiting. In this case the minimum restriction
				 * applies: we don't currently allow concurrent catalog
				 * updates.
				 */
			case AT_SetStatistics:	/* Uses MVCC in getTableAttrs() */
			case AT_ClusterOn:	/* Uses MVCC in getIndexes() */
			case AT_DropCluster:	/* Uses MVCC in getIndexes() */
			case AT_SetOptions: /* Uses MVCC in getTableAttrs() */
			case AT_ResetOptions:	/* Uses MVCC in getTableAttrs() */
				cmd_lockmode = ShareUpdateExclusiveLock;
				break;

			case AT_SetLogged:
			case AT_SetUnLogged:
				cmd_lockmode = AccessExclusiveLock;
				break;

			case AT_ValidateConstraint: /* Uses MVCC in getConstraints() */
				cmd_lockmode = ShareUpdateExclusiveLock;
				break;

				/*
				 * Rel options are more complex than first appears. Options
				 * are set here for tables, views and indexes; for historical
				 * reasons these can all be used with ALTER TABLE, so we can't
				 * decide between them using the basic grammar.
				 */
			case AT_SetRelOptions:	/* Uses MVCC in getIndexes() and
									 * getTables() */
			case AT_ResetRelOptions:	/* Uses MVCC in getIndexes() and
										 * getTables() */
				cmd_lockmode = AlterTableGetRelOptionsLockLevel((List *) cmd->def);
				break;

			case AT_AttachPartition:
				cmd_lockmode = ShareUpdateExclusiveLock;
				break;

			case AT_DetachPartition:
				if (((PartitionCmd *) cmd->def)->concurrent)
					cmd_lockmode = ShareUpdateExclusiveLock;
				else
					cmd_lockmode = AccessExclusiveLock;
				break;

			case AT_DetachPartitionFinalize:
				cmd_lockmode = ShareUpdateExclusiveLock;
				break;

			default:			/* oops */
				elog(ERROR, "unrecognized alter table type: %d",
					 (int) cmd->subtype);
				break;
		}

		/*
		 * Take the greatest lockmode from any subcommand
		 */
		if (cmd_lockmode > lockmode)
			lockmode = cmd_lockmode;
	}

	return lockmode;
}

/*
 * ATController provides top level control over the phases.
 *
 * parsetree is passed in to allow it to be passed to event triggers
 * when requested.
 */
static void
ATController(AlterTableStmt *parsetree,
			 Relation rel, List *cmds, bool recurse, LOCKMODE lockmode,
			 AlterTableUtilityContext *context)
{
	List	   *wqueue = NIL;
	ListCell   *lcmd;

	/* Phase 1: preliminary examination of commands, create work queue */
	foreach(lcmd, cmds)
	{
		AlterTableCmd *cmd = (AlterTableCmd *) lfirst(lcmd);

		ATPrepCmd(&wqueue, rel, cmd, recurse, false, lockmode, context);
	}

	/* Close the relation, but keep lock until commit */
	relation_close(rel, NoLock);

	/* Phase 2: update system catalogs */
	ATRewriteCatalogs(&wqueue, lockmode, context);

	/* Phase 3: scan/rewrite tables as needed, and run afterStmts */
	ATRewriteTables(parsetree, &wqueue, lockmode, context);
}

/*
 * ATPrepCmd
 *
 * Traffic cop for ALTER TABLE Phase 1 operations, including simple
 * recursion and permission checks.
 *
 * Caller must have acquired appropriate lock type on relation already.
 * This lock should be held until commit.
 */
static void
ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
		  bool recurse, bool recursing, LOCKMODE lockmode,
		  AlterTableUtilityContext *context)
{
	AlteredTableInfo *tab;
	AlterTablePass pass = AT_PASS_UNSET;

	/* Find or create work queue entry for this table */
	tab = ATGetQueueEntry(wqueue, rel);

	/*
	 * Disallow any ALTER TABLE other than ALTER TABLE DETACH FINALIZE on
	 * partitions that are pending detach.
	 */
	if (rel->rd_rel->relispartition &&
		cmd->subtype != AT_DetachPartitionFinalize &&
		PartitionHasPendingDetach(RelationGetRelid(rel)))
		ereport(ERROR,
				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				errmsg("cannot alter partition \"%s\" with an incomplete detach",
					   RelationGetRelationName(rel)),
				errhint("Use ALTER TABLE ... DETACH PARTITION ... FINALIZE to complete the pending detach operation."));

	/*
	 * Copy the original subcommand for each table, so we can scribble on it.
	 * This avoids conflicts when different child tables need to make
	 * different parse transformations (for example, the same column may have
	 * different column numbers in different children).
	 */
	cmd = copyObject(cmd);

	/*
	 * Do permissions and relkind checking, recursion to child tables if
	 * needed, and any additional phase-1 processing needed.  (But beware of
	 * adding any processing that looks at table details that another
	 * subcommand could change.  In some cases we reject multiple subcommands
	 * that could try to change the same state in contrary ways.)
	 */
	switch (cmd->subtype)
	{
		case AT_AddColumn:		/* ADD COLUMN */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE |
								ATT_COMPOSITE_TYPE | ATT_FOREIGN_TABLE);
			ATPrepAddColumn(wqueue, rel, recurse, recursing, false, cmd,
							lockmode, context);
			/* Recursion occurs during execution phase */
			pass = AT_PASS_ADD_COL;
			break;
		case AT_AddColumnToView:	/* add column via CREATE OR REPLACE VIEW */
			ATSimplePermissions(cmd->subtype, rel, ATT_VIEW);
			ATPrepAddColumn(wqueue, rel, recurse, recursing, true, cmd,
							lockmode, context);
			/* Recursion occurs during execution phase */
			pass = AT_PASS_ADD_COL;
			break;
		case AT_ColumnDefault:	/* ALTER COLUMN DEFAULT */

			/*
			 * We allow defaults on views so that INSERT into a view can have
			 * default-ish behavior.  This works because the rewriter
			 * substitutes default values into INSERTs before it expands
			 * rules.
			 */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_VIEW |
								ATT_FOREIGN_TABLE);
			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode, context);
			/* No command-specific prep needed */
			pass = cmd->def ? AT_PASS_ADD_OTHERCONSTR : AT_PASS_DROP;
			break;
		case AT_CookedColumnDefault:	/* add a pre-cooked default */
			/* This is currently used only in CREATE TABLE */
			/* (so the permission check really isn't necessary) */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			/* This command never recurses */
			pass = AT_PASS_ADD_OTHERCONSTR;
			break;
		case AT_AddIdentity:
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_VIEW |
								ATT_FOREIGN_TABLE);
			/* Set up recursion for phase 2; no other prep needed */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_ADD_OTHERCONSTR;
			break;
		case AT_SetIdentity:
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_VIEW |
								ATT_FOREIGN_TABLE);
			/* Set up recursion for phase 2; no other prep needed */
			if (recurse)
				cmd->recurse = true;
			/* This should run after AddIdentity, so do it in MISC pass */
			pass = AT_PASS_MISC;
			break;
		case AT_DropIdentity:
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_VIEW |
								ATT_FOREIGN_TABLE);
			/* Set up recursion for phase 2; no other prep needed */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_DROP;
			break;
		case AT_DropNotNull:	/* ALTER COLUMN DROP NOT NULL */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			/* Set up recursion for phase 2; no other prep needed */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_DROP;
			break;
		case AT_SetNotNull:		/* ALTER COLUMN SET NOT NULL */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			/* Set up recursion for phase 2; no other prep needed */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_COL_ATTRS;
			break;
		case AT_SetExpression:	/* ALTER COLUMN SET EXPRESSION */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode, context);
			pass = AT_PASS_SET_EXPRESSION;
			break;
		case AT_DropExpression: /* ALTER COLUMN DROP EXPRESSION */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode, context);
			ATPrepDropExpression(rel, cmd, recurse, recursing, lockmode);
			pass = AT_PASS_DROP;
			break;
		case AT_SetStatistics:	/* ALTER COLUMN SET STATISTICS */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_MATVIEW |
								ATT_INDEX | ATT_PARTITIONED_INDEX | ATT_FOREIGN_TABLE);
			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode, context);
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_SetOptions:		/* ALTER COLUMN SET ( options ) */
		case AT_ResetOptions:	/* ALTER COLUMN RESET ( options ) */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE |
								ATT_MATVIEW | ATT_FOREIGN_TABLE);
			/* This command never recurses */
			pass = AT_PASS_MISC;
			break;
		case AT_SetStorage:		/* ALTER COLUMN SET STORAGE */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE |
								ATT_MATVIEW | ATT_FOREIGN_TABLE);
			ATSimpleRecursion(wqueue, rel, cmd, recurse, lockmode, context);
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_SetCompression: /* ALTER COLUMN SET COMPRESSION */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_MATVIEW);
			/* This command never recurses */
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_DropColumn:		/* DROP COLUMN */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE |
								ATT_COMPOSITE_TYPE | ATT_FOREIGN_TABLE);
			ATPrepDropColumn(wqueue, rel, recurse, recursing, cmd,
							 lockmode, context);
			/* Recursion occurs during execution phase */
			pass = AT_PASS_DROP;
			break;
		case AT_AddIndex:		/* ADD INDEX */
			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_PARTITIONED_TABLE);
			/* This command never recurses */
			/* No command-specific prep needed */
			pass = AT_PASS_ADD_INDEX;
			break;
		case AT_AddConstraint:	/* ADD CONSTRAINT */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			ATPrepAddPrimaryKey(wqueue, rel, cmd, recurse, lockmode, context);
			if (recurse)
			{
				/* recurses at exec time; lock descendants and set flag */
				(void) find_all_inheritors(RelationGetRelid(rel), lockmode, NULL);
				cmd->recurse = true;
			}
			pass = AT_PASS_ADD_CONSTR;
			break;
		case AT_AddIndexConstraint: /* ADD CONSTRAINT USING INDEX */
			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_PARTITIONED_TABLE);
			/* This command never recurses */
			/* No command-specific prep needed */
			pass = AT_PASS_ADD_INDEXCONSTR;
			break;
		case AT_DropConstraint: /* DROP CONSTRAINT */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			ATCheckPartitionsNotInUse(rel, lockmode);
			/* Other recursion occurs during execution phase */
			/* No command-specific prep needed except saving recurse flag */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_DROP;
			break;
		case AT_AlterColumnType:	/* ALTER COLUMN TYPE */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE |
								ATT_COMPOSITE_TYPE | ATT_FOREIGN_TABLE);
			/* See comments for ATPrepAlterColumnType */
			cmd = ATParseTransformCmd(wqueue, tab, rel, cmd, recurse, lockmode,
									  AT_PASS_UNSET, context);
			Assert(cmd != NULL);
			/* Performs own recursion */
			ATPrepAlterColumnType(wqueue, tab, rel, recurse, recursing, cmd,
								  lockmode, context);
			pass = AT_PASS_ALTER_TYPE;
			break;
		case AT_AlterColumnGenericOptions:
			ATSimplePermissions(cmd->subtype, rel, ATT_FOREIGN_TABLE);
			/* This command never recurses */
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_ChangeOwner:	/* ALTER OWNER */
			/* This command never recurses */
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_ClusterOn:		/* CLUSTER ON */
		case AT_DropCluster:	/* SET WITHOUT CLUSTER */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_MATVIEW);
			/* These commands never recurse */
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_SetLogged:		/* SET LOGGED */
		case AT_SetUnLogged:	/* SET UNLOGGED */
			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_SEQUENCE);
			if (tab->chgPersistence)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot change persistence setting twice")));
			ATPrepChangePersistence(tab, rel, cmd->subtype == AT_SetLogged);
			pass = AT_PASS_MISC;
			break;
		case AT_DropOids:		/* SET WITHOUT OIDS */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			pass = AT_PASS_DROP;
			break;
		case AT_SetAccessMethod:	/* SET ACCESS METHOD */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_MATVIEW);

			/* check if another access method change was already requested */
			if (tab->chgAccessMethod)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot have multiple SET ACCESS METHOD subcommands")));

			ATPrepSetAccessMethod(tab, rel, cmd->name);
			pass = AT_PASS_MISC;	/* does not matter; no work in Phase 2 */
			break;
		case AT_SetTableSpace:	/* SET TABLESPACE */
			ATSimplePermissions(cmd->subtype, rel, ATT_TABLE | ATT_PARTITIONED_TABLE |
								ATT_MATVIEW | ATT_INDEX | ATT_PARTITIONED_INDEX);
			/* This command never recurses */
			ATPrepSetTableSpace(tab, rel, cmd->name, lockmode);
			pass = AT_PASS_MISC;	/* doesn't actually matter */
			break;
		case AT_SetRelOptions:	/* SET (...) */
		case AT_ResetRelOptions:	/* RESET (...) */
		case AT_ReplaceRelOptions:	/* reset them all, then set just these */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_VIEW |
								ATT_MATVIEW | ATT_INDEX);
			/* This command never recurses */
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_AddInherit:		/* INHERIT */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			/* This command never recurses */
			ATPrepAddInherit(rel);
			pass = AT_PASS_MISC;
			break;
		case AT_DropInherit:	/* NO INHERIT */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			/* This command never recurses */
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_AlterConstraint:	/* ALTER CONSTRAINT */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE);
			/* Recursion occurs during execution phase */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_MISC;
			break;
		case AT_ValidateConstraint: /* VALIDATE CONSTRAINT */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			/* Recursion occurs during execution phase */
			/* No command-specific prep needed except saving recurse flag */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_MISC;
			break;
		case AT_ReplicaIdentity:	/* REPLICA IDENTITY ... */
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_MATVIEW);
			pass = AT_PASS_MISC;
			/* This command never recurses */
			/* No command-specific prep needed */
			break;
		case AT_EnableTrig:		/* ENABLE TRIGGER variants */
		case AT_EnableAlwaysTrig:
		case AT_EnableReplicaTrig:
		case AT_EnableTrigAll:
		case AT_EnableTrigUser:
		case AT_DisableTrig:	/* DISABLE TRIGGER variants */
		case AT_DisableTrigAll:
		case AT_DisableTrigUser:
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);
			/* Set up recursion for phase 2; no other prep needed */
			if (recurse)
				cmd->recurse = true;
			pass = AT_PASS_MISC;
			break;
		case AT_EnableRule:		/* ENABLE/DISABLE RULE variants */
		case AT_EnableAlwaysRule:
		case AT_EnableReplicaRule:
		case AT_DisableRule:
		case AT_AddOf:			/* OF */
		case AT_DropOf:			/* NOT OF */
		case AT_EnableRowSecurity:
		case AT_DisableRowSecurity:
		case AT_ForceRowSecurity:
		case AT_NoForceRowSecurity:
			ATSimplePermissions(cmd->subtype, rel,
								ATT_TABLE | ATT_PARTITIONED_TABLE);
			/* These commands never recurse */
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_GenericOptions:
			ATSimplePermissions(cmd->subtype, rel, ATT_FOREIGN_TABLE);
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_AttachPartition:
			ATSimplePermissions(cmd->subtype, rel,
								ATT_PARTITIONED_TABLE | ATT_PARTITIONED_INDEX);
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_DetachPartition:
			ATSimplePermissions(cmd->subtype, rel, ATT_PARTITIONED_TABLE);
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		case AT_DetachPartitionFinalize:
			ATSimplePermissions(cmd->subtype, rel, ATT_PARTITIONED_TABLE);
			/* No command-specific prep needed */
			pass = AT_PASS_MISC;
			break;
		default:				/* oops */
			elog(ERROR, "unrecognized alter table type: %d",
				 (int) cmd->subtype);
			pass = AT_PASS_UNSET;	/* keep compiler quiet */
			break;
	}
	Assert(pass > AT_PASS_UNSET);

	/* Add the subcommand to the appropriate list for phase 2 */
	tab->subcmds[pass] = lappend(tab->subcmds[pass], cmd);
}

/*
 * ATRewriteCatalogs
 *
 * Traffic cop for ALTER TABLE Phase 2 operations.  Subcommands are
 * dispatched in a "safe" execution order (designed to avoid unnecessary
 * conflicts).
 */
static void
ATRewriteCatalogs(List **wqueue, LOCKMODE lockmode,
				  AlterTableUtilityContext *context)
{
	ListCell   *ltab;

	/*
	 * We process all the tables "in parallel", one pass at a time.  This is
	 * needed because we may have to propagate work from one table to another
	 * (specifically, ALTER TYPE on a foreign key's PK has to dispatch the
	 * re-adding of the foreign key constraint to the other table).  Work can
	 * only be propagated into later passes, however.
	 */
	for (AlterTablePass pass = 0; pass < AT_NUM_PASSES; pass++)
	{
		/* Go through each table that needs to be processed */
		foreach(ltab, *wqueue)
		{
			AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
			List	   *subcmds = tab->subcmds[pass];
			ListCell   *lcmd;

			if (subcmds == NIL)
				continue;

			/*
			 * Open the relation and store it in tab.  This allows subroutines
			 * close and reopen, if necessary.  Appropriate lock was obtained
			 * by phase 1, needn't get it again.
			 */
			tab->rel = relation_open(tab->relid, NoLock);

			foreach(lcmd, subcmds)
				ATExecCmd(wqueue, tab,
						  lfirst_node(AlterTableCmd, lcmd),
						  lockmode, pass, context);

			/*
			 * After the ALTER TYPE or SET EXPRESSION pass, do cleanup work
			 * (this is not done in ATExecAlterColumnType since it should be
			 * done only once if multiple columns of a table are altered).
			 */
			if (pass == AT_PASS_ALTER_TYPE || pass == AT_PASS_SET_EXPRESSION)
				ATPostAlterTypeCleanup(wqueue, tab, lockmode);

			if (tab->rel)
			{
				relation_close(tab->rel, NoLock);
				tab->rel = NULL;
			}
		}
	}

	/* Check to see if a toast table must be added. */
	foreach(ltab, *wqueue)
	{
		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);

		/*
		 * If the table is source table of ATTACH PARTITION command, we did
		 * not modify anything about it that will change its toasting
		 * requirement, so no need to check.
		 */
		if (((tab->relkind == RELKIND_RELATION ||
			  tab->relkind == RELKIND_PARTITIONED_TABLE) &&
			 tab->partition_constraint == NULL) ||
			tab->relkind == RELKIND_MATVIEW)
			AlterTableCreateToastTable(tab->relid, (Datum) 0, lockmode);
	}
}

/*
 * ATExecCmd: dispatch a subcommand to appropriate execution routine
 */
static void
ATExecCmd(List **wqueue, AlteredTableInfo *tab,
		  AlterTableCmd *cmd, LOCKMODE lockmode, AlterTablePass cur_pass,
		  AlterTableUtilityContext *context)
{
	ObjectAddress address = InvalidObjectAddress;
	Relation	rel = tab->rel;

	switch (cmd->subtype)
	{
		case AT_AddColumn:		/* ADD COLUMN */
		case AT_AddColumnToView:	/* add column via CREATE OR REPLACE VIEW */
			address = ATExecAddColumn(wqueue, tab, rel, &cmd,
									  cmd->recurse, false,
									  lockmode, cur_pass, context);
			break;
		case AT_ColumnDefault:	/* ALTER COLUMN DEFAULT */
			address = ATExecColumnDefault(rel, cmd->name, cmd->def, lockmode);
			break;
		case AT_CookedColumnDefault:	/* add a pre-cooked default */
			address = ATExecCookedColumnDefault(rel, cmd->num, cmd->def);
			break;
		case AT_AddIdentity:
			cmd = ATParseTransformCmd(wqueue, tab, rel, cmd, false, lockmode,
									  cur_pass, context);
			Assert(cmd != NULL);
			address = ATExecAddIdentity(rel, cmd->name, cmd->def, lockmode, cmd->recurse, false);
			break;
		case AT_SetIdentity:
			cmd = ATParseTransformCmd(wqueue, tab, rel, cmd, false, lockmode,
									  cur_pass, context);
			Assert(cmd != NULL);
			address = ATExecSetIdentity(rel, cmd->name, cmd->def, lockmode, cmd->recurse, false);
			break;
		case AT_DropIdentity:
			address = ATExecDropIdentity(rel, cmd->name, cmd->missing_ok, lockmode, cmd->recurse, false);
			break;
		case AT_DropNotNull:	/* ALTER COLUMN DROP NOT NULL */
			address = ATExecDropNotNull(rel, cmd->name, cmd->recurse, lockmode);
			break;
		case AT_SetNotNull:		/* ALTER COLUMN SET NOT NULL */
			address = ATExecSetNotNull(wqueue, rel, NULL, cmd->name,
									   cmd->recurse, false, lockmode);
			break;
		case AT_SetExpression:
			address = ATExecSetExpression(tab, rel, cmd->name, cmd->def, lockmode);
			break;
		case AT_DropExpression:
			address = ATExecDropExpression(rel, cmd->name, cmd->missing_ok, lockmode);
			break;
		case AT_SetStatistics:	/* ALTER COLUMN SET STATISTICS */
			address = ATExecSetStatistics(rel, cmd->name, cmd->num, cmd->def, lockmode);
			break;
		case AT_SetOptions:		/* ALTER COLUMN SET ( options ) */
			address = ATExecSetOptions(rel, cmd->name, cmd->def, false, lockmode);
			break;
		case AT_ResetOptions:	/* ALTER COLUMN RESET ( options ) */
			address = ATExecSetOptions(rel, cmd->name, cmd->def, true, lockmode);
			break;
		case AT_SetStorage:		/* ALTER COLUMN SET STORAGE */
			address = ATExecSetStorage(rel, cmd->name, cmd->def, lockmode);
			break;
		case AT_SetCompression: /* ALTER COLUMN SET COMPRESSION */
			address = ATExecSetCompression(rel, cmd->name, cmd->def,
										   lockmode);
			break;
		case AT_DropColumn:		/* DROP COLUMN */
			address = ATExecDropColumn(wqueue, rel, cmd->name,
									   cmd->behavior, cmd->recurse, false,
									   cmd->missing_ok, lockmode,
									   NULL);
			break;
		case AT_AddIndex:		/* ADD INDEX */
			address = ATExecAddIndex(tab, rel, (IndexStmt *) cmd->def, false,
									 lockmode);
			break;
		case AT_ReAddIndex:		/* ADD INDEX */
			address = ATExecAddIndex(tab, rel, (IndexStmt *) cmd->def, true,
									 lockmode);
			break;
		case AT_ReAddStatistics:	/* ADD STATISTICS */
			address = ATExecAddStatistics(tab, rel, (CreateStatsStmt *) cmd->def,
										  true, lockmode);
			break;
		case AT_AddConstraint:	/* ADD CONSTRAINT */
			/* Transform the command only during initial examination */
			if (cur_pass == AT_PASS_ADD_CONSTR)
				cmd = ATParseTransformCmd(wqueue, tab, rel, cmd,
										  cmd->recurse, lockmode,
										  cur_pass, context);
			/* Depending on constraint type, might be no more work to do now */
			if (cmd != NULL)
				address =
					ATExecAddConstraint(wqueue, tab, rel,
										(Constraint *) cmd->def,
										cmd->recurse, false, lockmode);
			break;
		case AT_ReAddConstraint:	/* Re-add pre-existing check constraint */
			address =
				ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
									true, true, lockmode);
			break;
		case AT_ReAddDomainConstraint:	/* Re-add pre-existing domain check
										 * constraint */
			address =
				AlterDomainAddConstraint(((AlterDomainStmt *) cmd->def)->typeName,
										 ((AlterDomainStmt *) cmd->def)->def,
										 NULL);
			break;
		case AT_ReAddComment:	/* Re-add existing comment */
			address = CommentObject((CommentStmt *) cmd->def);
			break;
		case AT_AddIndexConstraint: /* ADD CONSTRAINT USING INDEX */
			address = ATExecAddIndexConstraint(tab, rel, (IndexStmt *) cmd->def,
											   lockmode);
			break;
		case AT_AlterConstraint:	/* ALTER CONSTRAINT */
			address = ATExecAlterConstraint(wqueue, rel,
											castNode(ATAlterConstraint, cmd->def),
											cmd->recurse, lockmode);
			break;
		case AT_ValidateConstraint: /* VALIDATE CONSTRAINT */
			address = ATExecValidateConstraint(wqueue, rel, cmd->name, cmd->recurse,
											   false, lockmode);
			break;
		case AT_DropConstraint: /* DROP CONSTRAINT */
			ATExecDropConstraint(rel, cmd->name, cmd->behavior,
								 cmd->recurse,
								 cmd->missing_ok, lockmode);
			break;
		case AT_AlterColumnType:	/* ALTER COLUMN TYPE */
			/* parse transformation was done earlier */
			address = ATExecAlterColumnType(tab, rel, cmd, lockmode);
			break;
		case AT_AlterColumnGenericOptions:	/* ALTER COLUMN OPTIONS */
			address =
				ATExecAlterColumnGenericOptions(rel, cmd->name,
												(List *) cmd->def, lockmode);
			break;
		case AT_ChangeOwner:	/* ALTER OWNER */
			ATExecChangeOwner(RelationGetRelid(rel),
							  get_rolespec_oid(cmd->newowner, false),
							  false, lockmode);
			break;
		case AT_ClusterOn:		/* CLUSTER ON */
			address = ATExecClusterOn(rel, cmd->name, lockmode);
			break;
		case AT_DropCluster:	/* SET WITHOUT CLUSTER */
			ATExecDropCluster(rel, lockmode);
			break;
		case AT_SetLogged:		/* SET LOGGED */
		case AT_SetUnLogged:	/* SET UNLOGGED */
			break;
		case AT_DropOids:		/* SET WITHOUT OIDS */
			/* nothing to do here, oid columns don't exist anymore */
			break;
		case AT_SetAccessMethod:	/* SET ACCESS METHOD */

			/*
			 * Only do this for partitioned tables, for which this is just a
			 * catalog change.  Tables with storage are handled by Phase 3.
			 */
			if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
				tab->chgAccessMethod)
				ATExecSetAccessMethodNoStorage(rel, tab->newAccessMethod);
			break;
		case AT_SetTableSpace:	/* SET TABLESPACE */

			/*
			 * Only do this for partitioned tables and indexes, for which this
			 * is just a catalog change.  Other relation types which have
			 * storage are handled by Phase 3.
			 */
			if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
				rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
				ATExecSetTableSpaceNoStorage(rel, tab->newTableSpace);

			break;
		case AT_SetRelOptions:	/* SET (...) */
		case AT_ResetRelOptions:	/* RESET (...) */
		case AT_ReplaceRelOptions:	/* replace entire option list */
			ATExecSetRelOptions(rel, (List *) cmd->def, cmd->subtype, lockmode);
			break;
		case AT_EnableTrig:		/* ENABLE TRIGGER name */
			ATExecEnableDisableTrigger(rel, cmd->name,
									   TRIGGER_FIRES_ON_ORIGIN, false,
									   cmd->recurse,
									   lockmode);
			break;
		case AT_EnableAlwaysTrig:	/* ENABLE ALWAYS TRIGGER name */
			ATExecEnableDisableTrigger(rel, cmd->name,
									   TRIGGER_FIRES_ALWAYS, false,
									   cmd->recurse,
									   lockmode);
			break;
		case AT_EnableReplicaTrig:	/* ENABLE REPLICA TRIGGER name */
			ATExecEnableDisableTrigger(rel, cmd->name,
									   TRIGGER_FIRES_ON_REPLICA, false,
									   cmd->recurse,
									   lockmode);
			break;
		case AT_DisableTrig:	/* DISABLE TRIGGER name */
			ATExecEnableDisableTrigger(rel, cmd->name,
									   TRIGGER_DISABLED, false,
									   cmd->recurse,
									   lockmode);
			break;
		case AT_EnableTrigAll:	/* ENABLE TRIGGER ALL */
			ATExecEnableDisableTrigger(rel, NULL,
									   TRIGGER_FIRES_ON_ORIGIN, false,
									   cmd->recurse,
									   lockmode);
			break;
		case AT_DisableTrigAll: /* DISABLE TRIGGER ALL */
			ATExecEnableDisableTrigger(rel, NULL,
									   TRIGGER_DISABLED, false,
									   cmd->recurse,
									   lockmode);
			break;
		case AT_EnableTrigUser: /* ENABLE TRIGGER USER */
			ATExecEnableDisableTrigger(rel, NULL,
									   TRIGGER_FIRES_ON_ORIGIN, true,
									   cmd->recurse,
									   lockmode);
			break;
		case AT_DisableTrigUser:	/* DISABLE TRIGGER USER */
			ATExecEnableDisableTrigger(rel, NULL,
									   TRIGGER_DISABLED, true,
									   cmd->recurse,
									   lockmode);
			break;

		case AT_EnableRule:		/* ENABLE RULE name */
			ATExecEnableDisableRule(rel, cmd->name,
									RULE_FIRES_ON_ORIGIN, lockmode);
			break;
		case AT_EnableAlwaysRule:	/* ENABLE ALWAYS RULE name */
			ATExecEnableDisableRule(rel, cmd->name,
									RULE_FIRES_ALWAYS, lockmode);
			break;
		case AT_EnableReplicaRule:	/* ENABLE REPLICA RULE name */
			ATExecEnableDisableRule(rel, cmd->name,
									RULE_FIRES_ON_REPLICA, lockmode);
			break;
		case AT_DisableRule:	/* DISABLE RULE name */
			ATExecEnableDisableRule(rel, cmd->name,
									RULE_DISABLED, lockmode);
			break;

		case AT_AddInherit:
			address = ATExecAddInherit(rel, (RangeVar *) cmd->def, lockmode);
			break;
		case AT_DropInherit:
			address = ATExecDropInherit(rel, (RangeVar *) cmd->def, lockmode);
			break;
		case AT_AddOf:
			address = ATExecAddOf(rel, (TypeName *) cmd->def, lockmode);
			break;
		case AT_DropOf:
			ATExecDropOf(rel, lockmode);
			break;
		case AT_ReplicaIdentity:
			ATExecReplicaIdentity(rel, (ReplicaIdentityStmt *) cmd->def, lockmode);
			break;
		case AT_EnableRowSecurity:
			ATExecSetRowSecurity(rel, true);
			break;
		case AT_DisableRowSecurity:
			ATExecSetRowSecurity(rel, false);
			break;
		case AT_ForceRowSecurity:
			ATExecForceNoForceRowSecurity(rel, true);
			break;
		case AT_NoForceRowSecurity:
			ATExecForceNoForceRowSecurity(rel, false);
			break;
		case AT_GenericOptions:
			ATExecGenericOptions(rel, (List *) cmd->def);
			break;
		case AT_AttachPartition:
			cmd = ATParseTransformCmd(wqueue, tab, rel, cmd, false, lockmode,
									  cur_pass, context);
			Assert(cmd != NULL);
			if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
				address = ATExecAttachPartition(wqueue, rel, (PartitionCmd *) cmd->def,
												context);
			else
				address = ATExecAttachPartitionIdx(wqueue, rel,
												   ((PartitionCmd *) cmd->def)->name);
			break;
		case AT_DetachPartition:
			cmd = ATParseTransformCmd(wqueue, tab, rel, cmd, false, lockmode,
									  cur_pass, context);
			Assert(cmd != NULL);
			/* ATPrepCmd ensures it must be a table */
			Assert(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
			address = ATExecDetachPartition(wqueue, tab, rel,
											((PartitionCmd *) cmd->def)->name,
											((PartitionCmd *) cmd->def)->concurrent);
			break;
		case AT_DetachPartitionFinalize:
			address = ATExecDetachPartitionFinalize(rel, ((PartitionCmd *) cmd->def)->name);
			break;
		default:				/* oops */
			elog(ERROR, "unrecognized alter table type: %d",
				 (int) cmd->subtype);
			break;
	}

	/*
	 * Report the subcommand to interested event triggers.
	 */
	if (cmd)
		EventTriggerCollectAlterTableSubcmd((Node *) cmd, address);

	/*
	 * Bump the command counter to ensure the next subcommand in the sequence
	 * can see the changes so far
	 */
	CommandCounterIncrement();
}

/*
 * ATParseTransformCmd: perform parse transformation for one subcommand
 *
 * Returns the transformed subcommand tree, if there is one, else NULL.
 *
 * The parser may hand back additional AlterTableCmd(s) and/or other
 * utility statements, either before or after the original subcommand.
 * Other AlterTableCmds are scheduled into the appropriate slot of the
 * AlteredTableInfo (they had better be for later passes than the current one).
 * Utility statements that are supposed to happen before the AlterTableCmd
 * are executed immediately.  Those that are supposed to happen afterwards
 * are added to the tab->afterStmts list to be done at the very end.
 */
static AlterTableCmd *
ATParseTransformCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
					AlterTableCmd *cmd, bool recurse, LOCKMODE lockmode,
					AlterTablePass cur_pass, AlterTableUtilityContext *context)
{
	AlterTableCmd *newcmd = NULL;
	AlterTableStmt *atstmt = makeNode(AlterTableStmt);
	List	   *beforeStmts;
	List	   *afterStmts;
	ListCell   *lc;

	/* Gin up an AlterTableStmt with just this subcommand and this table */
	atstmt->relation =
		makeRangeVar(get_namespace_name(RelationGetNamespace(rel)),
					 pstrdup(RelationGetRelationName(rel)),
					 -1);
	atstmt->relation->inh = recurse;
	atstmt->cmds = list_make1(cmd);
	atstmt->objtype = OBJECT_TABLE; /* needn't be picky here */
	atstmt->missing_ok = false;

	/* Transform the AlterTableStmt */
	atstmt = transformAlterTableStmt(RelationGetRelid(rel),
									 atstmt,
									 context->queryString,
									 &beforeStmts,
									 &afterStmts);

	/* Execute any statements that should happen before these subcommand(s) */
	foreach(lc, beforeStmts)
	{
		Node	   *stmt = (Node *) lfirst(lc);

		ProcessUtilityForAlterTable(stmt, context);
		CommandCounterIncrement();
	}

	/* Examine the transformed subcommands and schedule them appropriately */
	foreach(lc, atstmt->cmds)
	{
		AlterTableCmd *cmd2 = lfirst_node(AlterTableCmd, lc);
		AlterTablePass pass;

		/*
		 * This switch need only cover the subcommand types that can be added
		 * by parse_utilcmd.c; otherwise, we'll use the default strategy of
		 * executing the subcommand immediately, as a substitute for the
		 * original subcommand.  (Note, however, that this does cause
		 * AT_AddConstraint subcommands to be rescheduled into later passes,
		 * which is important for index and foreign key constraints.)
		 *
		 * We assume we needn't do any phase-1 checks for added subcommands.
		 */
		switch (cmd2->subtype)
		{
			case AT_AddIndex:
				pass = AT_PASS_ADD_INDEX;
				break;
			case AT_AddIndexConstraint:
				pass = AT_PASS_ADD_INDEXCONSTR;
				break;
			case AT_AddConstraint:
				/* Recursion occurs during execution phase */
				if (recurse)
					cmd2->recurse = true;
				switch (castNode(Constraint, cmd2->def)->contype)
				{
					case CONSTR_NOTNULL:
						pass = AT_PASS_COL_ATTRS;
						break;
					case CONSTR_PRIMARY:
					case CONSTR_UNIQUE:
					case CONSTR_EXCLUSION:
						pass = AT_PASS_ADD_INDEXCONSTR;
						break;
					default:
						pass = AT_PASS_ADD_OTHERCONSTR;
						break;
				}
				break;
			case AT_AlterColumnGenericOptions:
				/* This command never recurses */
				/* No command-specific prep needed */
				pass = AT_PASS_MISC;
				break;
			default:
				pass = cur_pass;
				break;
		}

		if (pass < cur_pass)
		{
			/* Cannot schedule into a pass we already finished */
			elog(ERROR, "ALTER TABLE scheduling failure: too late for pass %d",
				 pass);
		}
		else if (pass > cur_pass)
		{
			/* OK, queue it up for later */
			tab->subcmds[pass] = lappend(tab->subcmds[pass], cmd2);
		}
		else
		{
			/*
			 * We should see at most one subcommand for the current pass,
			 * which is the transformed version of the original subcommand.
			 */
			if (newcmd == NULL && cmd->subtype == cmd2->subtype)
			{
				/* Found the transformed version of our subcommand */
				newcmd = cmd2;
			}
			else
				elog(ERROR, "ALTER TABLE scheduling failure: bogus item for pass %d",
					 pass);
		}
	}

	/* Queue up any after-statements to happen at the end */
	tab->afterStmts = list_concat(tab->afterStmts, afterStmts);

	return newcmd;
}

/*
 * ATRewriteTables: ALTER TABLE phase 3
 */
static void
ATRewriteTables(AlterTableStmt *parsetree, List **wqueue, LOCKMODE lockmode,
				AlterTableUtilityContext *context)
{
	ListCell   *ltab;

	/* Go through each table that needs to be checked or rewritten */
	foreach(ltab, *wqueue)
	{
		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);

		/* Relations without storage may be ignored here */
		if (!RELKIND_HAS_STORAGE(tab->relkind))
			continue;

		/*
		 * If we change column data types, the operation has to be propagated
		 * to tables that use this table's rowtype as a column type.
		 * tab->newvals will also be non-NULL in the case where we're adding a
		 * column with a default.  We choose to forbid that case as well,
		 * since composite types might eventually support defaults.
		 *
		 * (Eventually we'll probably need to check for composite type
		 * dependencies even when we're just scanning the table without a
		 * rewrite, but at the moment a composite type does not enforce any
		 * constraints, so it's not necessary/appropriate to enforce them just
		 * during ALTER.)
		 */
		if (tab->newvals != NIL || tab->rewrite > 0)
		{
			Relation	rel;

			rel = table_open(tab->relid, NoLock);
			find_composite_type_dependencies(rel->rd_rel->reltype, rel, NULL);
			table_close(rel, NoLock);
		}

		/*
		 * We only need to rewrite the table if at least one column needs to
		 * be recomputed, or we are changing its persistence or access method.
		 *
		 * There are two reasons for requiring a rewrite when changing
		 * persistence: on one hand, we need to ensure that the buffers
		 * belonging to each of the two relations are marked with or without
		 * BM_PERMANENT properly.  On the other hand, since rewriting creates
		 * and assigns a new relfilenumber, we automatically create or drop an
		 * init fork for the relation as appropriate.
		 */
		if (tab->rewrite > 0 && tab->relkind != RELKIND_SEQUENCE)
		{
			/* Build a temporary relation and copy data */
			Relation	OldHeap;
			Oid			OIDNewHeap;
			Oid			NewAccessMethod;
			Oid			NewTableSpace;
			char		persistence;

			OldHeap = table_open(tab->relid, NoLock);

			/*
			 * We don't support rewriting of system catalogs; there are too
			 * many corner cases and too little benefit.  In particular this
			 * is certainly not going to work for mapped catalogs.
			 */
			if (IsSystemRelation(OldHeap))
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot rewrite system relation \"%s\"",
								RelationGetRelationName(OldHeap))));

			if (RelationIsUsedAsCatalogTable(OldHeap))
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot rewrite table \"%s\" used as a catalog table",
								RelationGetRelationName(OldHeap))));

			/*
			 * Don't allow rewrite on temp tables of other backends ... their
			 * local buffer manager is not going to cope.  (This is redundant
			 * with the check in CheckAlterTableIsSafe, but for safety we'll
			 * check here too.)
			 */
			if (RELATION_IS_OTHER_TEMP(OldHeap))
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot rewrite temporary tables of other sessions")));

			/*
			 * Select destination tablespace (same as original unless user
			 * requested a change)
			 */
			if (tab->newTableSpace)
				NewTableSpace = tab->newTableSpace;
			else
				NewTableSpace = OldHeap->rd_rel->reltablespace;

			/*
			 * Select destination access method (same as original unless user
			 * requested a change)
			 */
			if (tab->chgAccessMethod)
				NewAccessMethod = tab->newAccessMethod;
			else
				NewAccessMethod = OldHeap->rd_rel->relam;

			/*
			 * Select persistence of transient table (same as original unless
			 * user requested a change)
			 */
			persistence = tab->chgPersistence ?
				tab->newrelpersistence : OldHeap->rd_rel->relpersistence;

			table_close(OldHeap, NoLock);

			/*
			 * Fire off an Event Trigger now, before actually rewriting the
			 * table.
			 *
			 * We don't support Event Trigger for nested commands anywhere,
			 * here included, and parsetree is given NULL when coming from
			 * AlterTableInternal.
			 *
			 * And fire it only once.
			 */
			if (parsetree)
				EventTriggerTableRewrite((Node *) parsetree,
										 tab->relid,
										 tab->rewrite);

			/*
			 * Create transient table that will receive the modified data.
			 *
			 * Ensure it is marked correctly as logged or unlogged.  We have
			 * to do this here so that buffers for the new relfilenumber will
			 * have the right persistence set, and at the same time ensure
			 * that the original filenumbers's buffers will get read in with
			 * the correct setting (i.e. the original one).  Otherwise a
			 * rollback after the rewrite would possibly result with buffers
			 * for the original filenumbers having the wrong persistence
			 * setting.
			 *
			 * NB: This relies on swap_relation_files() also swapping the
			 * persistence. That wouldn't work for pg_class, but that can't be
			 * unlogged anyway.
			 */
			OIDNewHeap = make_new_heap(tab->relid, NewTableSpace, NewAccessMethod,
									   persistence, lockmode);

			/*
			 * Copy the heap data into the new table with the desired
			 * modifications, and test the current data within the table
			 * against new constraints generated by ALTER TABLE commands.
			 */
			ATRewriteTable(tab, OIDNewHeap);

			/*
			 * Swap the physical files of the old and new heaps, then rebuild
			 * indexes and discard the old heap.  We can use RecentXmin for
			 * the table's new relfrozenxid because we rewrote all the tuples
			 * in ATRewriteTable, so no older Xid remains in the table.  Also,
			 * we never try to swap toast tables by content, since we have no
			 * interest in letting this code work on system catalogs.
			 */
			finish_heap_swap(tab->relid, OIDNewHeap,
							 false, false, true,
							 !OidIsValid(tab->newTableSpace),
							 RecentXmin,
							 ReadNextMultiXactId(),
							 persistence);

			InvokeObjectPostAlterHook(RelationRelationId, tab->relid, 0);
		}
		else if (tab->rewrite > 0 && tab->relkind == RELKIND_SEQUENCE)
		{
			if (tab->chgPersistence)
				SequenceChangePersistence(tab->relid, tab->newrelpersistence);
		}
		else
		{
			/*
			 * If required, test the current data within the table against new
			 * constraints generated by ALTER TABLE commands, but don't
			 * rebuild data.
			 */
			if (tab->constraints != NIL || tab->verify_new_notnull ||
				tab->partition_constraint != NULL)
				ATRewriteTable(tab, InvalidOid);

			/*
			 * If we had SET TABLESPACE but no reason to reconstruct tuples,
			 * just do a block-by-block copy.
			 */
			if (tab->newTableSpace)
				ATExecSetTableSpace(tab->relid, tab->newTableSpace, lockmode);
		}

		/*
		 * Also change persistence of owned sequences, so that it matches the
		 * table persistence.
		 */
		if (tab->chgPersistence)
		{
			List	   *seqlist = getOwnedSequences(tab->relid);
			ListCell   *lc;

			foreach(lc, seqlist)
			{
				Oid			seq_relid = lfirst_oid(lc);

				SequenceChangePersistence(seq_relid, tab->newrelpersistence);
			}
		}
	}

	/*
	 * Foreign key constraints are checked in a final pass, since (a) it's
	 * generally best to examine each one separately, and (b) it's at least
	 * theoretically possible that we have changed both relations of the
	 * foreign key, and we'd better have finished both rewrites before we try
	 * to read the tables.
	 */
	foreach(ltab, *wqueue)
	{
		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
		Relation	rel = NULL;
		ListCell   *lcon;

		/* Relations without storage may be ignored here too */
		if (!RELKIND_HAS_STORAGE(tab->relkind))
			continue;

		foreach(lcon, tab->constraints)
		{
			NewConstraint *con = lfirst(lcon);

			if (con->contype == CONSTR_FOREIGN)
			{
				Constraint *fkconstraint = (Constraint *) con->qual;
				Relation	refrel;

				if (rel == NULL)
				{
					/* Long since locked, no need for another */
					rel = table_open(tab->relid, NoLock);
				}

				refrel = table_open(con->refrelid, RowShareLock);

				validateForeignKeyConstraint(fkconstraint->conname, rel, refrel,
											 con->refindid,
											 con->conid,
											 con->conwithperiod);

				/*
				 * No need to mark the constraint row as validated, we did
				 * that when we inserted the row earlier.
				 */

				table_close(refrel, NoLock);
			}
		}

		if (rel)
			table_close(rel, NoLock);
	}

	/* Finally, run any afterStmts that were queued up */
	foreach(ltab, *wqueue)
	{
		AlteredTableInfo *tab = (AlteredTableInfo *) lfirst(ltab);
		ListCell   *lc;

		foreach(lc, tab->afterStmts)
		{
			Node	   *stmt = (Node *) lfirst(lc);

			ProcessUtilityForAlterTable(stmt, context);
			CommandCounterIncrement();
		}
	}
}

/*
 * ATRewriteTable: scan or rewrite one table
 *
 * A rewrite is requested by passing a valid OIDNewHeap; in that case, caller
 * must already hold AccessExclusiveLock on it.
 */
static void
ATRewriteTable(AlteredTableInfo *tab, Oid OIDNewHeap)
{
	Relation	oldrel;
	Relation	newrel;
	TupleDesc	oldTupDesc;
	TupleDesc	newTupDesc;
	bool		needscan = false;
	List	   *notnull_attrs;
	List	   *notnull_virtual_attrs;
	int			i;
	ListCell   *l;
	EState	   *estate;
	CommandId	mycid;
	BulkInsertState bistate;
	int			ti_options;
	ExprState  *partqualstate = NULL;

	/*
	 * Open the relation(s).  We have surely already locked the existing
	 * table.
	 */
	oldrel = table_open(tab->relid, NoLock);
	oldTupDesc = tab->oldDesc;
	newTupDesc = RelationGetDescr(oldrel);	/* includes all mods */

	if (OidIsValid(OIDNewHeap))
	{
		Assert(CheckRelationOidLockedByMe(OIDNewHeap, AccessExclusiveLock,
										  false));
		newrel = table_open(OIDNewHeap, NoLock);
	}
	else
		newrel = NULL;

	/*
	 * Prepare a BulkInsertState and options for table_tuple_insert.  The FSM
	 * is empty, so don't bother using it.
	 */
	if (newrel)
	{
		mycid = GetCurrentCommandId(true);
		bistate = GetBulkInsertState();
		ti_options = TABLE_INSERT_SKIP_FSM;
	}
	else
	{
		/* keep compiler quiet about using these uninitialized */
		mycid = 0;
		bistate = NULL;
		ti_options = 0;
	}

	/*
	 * Generate the constraint and default execution states
	 */

	estate = CreateExecutorState();

	/* Build the needed expression execution states */
	foreach(l, tab->constraints)
	{
		NewConstraint *con = lfirst(l);

		switch (con->contype)
		{
			case CONSTR_CHECK:
				needscan = true;
				con->qualstate = ExecPrepareExpr((Expr *) expand_generated_columns_in_expr(con->qual, oldrel, 1), estate);
				break;
			case CONSTR_FOREIGN:
				/* Nothing to do here */
				break;
			default:
				elog(ERROR, "unrecognized constraint type: %d",
					 (int) con->contype);
		}
	}

	/* Build expression execution states for partition check quals */
	if (tab->partition_constraint)
	{
		needscan = true;
		partqualstate = ExecPrepareExpr(tab->partition_constraint, estate);
	}

	foreach(l, tab->newvals)
	{
		NewColumnValue *ex = lfirst(l);

		/* expr already planned */
		ex->exprstate = ExecInitExpr((Expr *) ex->expr, NULL);
	}

	notnull_attrs = notnull_virtual_attrs = NIL;
	if (newrel || tab->verify_new_notnull)
	{
		/*
		 * If we are rebuilding the tuples OR if we added any new but not
		 * verified not-null constraints, check all *valid* not-null
		 * constraints. This is a bit of overkill but it minimizes risk of
		 * bugs.
		 *
		 * notnull_attrs does *not* collect attribute numbers for valid
		 * not-null constraints over virtual generated columns; instead, they
		 * are collected in notnull_virtual_attrs for verification elsewhere.
		 */
		for (i = 0; i < newTupDesc->natts; i++)
		{
			CompactAttribute *attr = TupleDescCompactAttr(newTupDesc, i);

			if (attr->attnullability == ATTNULLABLE_VALID &&
				!attr->attisdropped)
			{
				Form_pg_attribute wholeatt = TupleDescAttr(newTupDesc, i);

				if (wholeatt->attgenerated != ATTRIBUTE_GENERATED_VIRTUAL)
					notnull_attrs = lappend_int(notnull_attrs, wholeatt->attnum);
				else
					notnull_virtual_attrs = lappend_int(notnull_virtual_attrs,
														wholeatt->attnum);
			}
		}
		if (notnull_attrs || notnull_virtual_attrs)
			needscan = true;
	}

	if (newrel || needscan)
	{
		ExprContext *econtext;
		TupleTableSlot *oldslot;
		TupleTableSlot *newslot;
		TableScanDesc scan;
		MemoryContext oldCxt;
		List	   *dropped_attrs = NIL;
		ListCell   *lc;
		Snapshot	snapshot;
		ResultRelInfo *rInfo = NULL;

		/*
		 * When adding or changing a virtual generated column with a not-null
		 * constraint, we need to evaluate whether the generation expression
		 * is null.  For that, we borrow ExecRelGenVirtualNotNull().  Here, we
		 * prepare a dummy ResultRelInfo.
		 */
		if (notnull_virtual_attrs != NIL)
		{
			MemoryContext oldcontext;

			Assert(newTupDesc->constr->has_generated_virtual);
			Assert(newTupDesc->constr->has_not_null);
			oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
			rInfo = makeNode(ResultRelInfo);
			InitResultRelInfo(rInfo,
							  oldrel,
							  0,	/* dummy rangetable index */
							  NULL,
							  estate->es_instrument);
			MemoryContextSwitchTo(oldcontext);
		}

		if (newrel)
			ereport(DEBUG1,
					(errmsg_internal("rewriting table \"%s\"",
									 RelationGetRelationName(oldrel))));
		else
			ereport(DEBUG1,
					(errmsg_internal("verifying table \"%s\"",
									 RelationGetRelationName(oldrel))));

		if (newrel)
		{
			/*
			 * All predicate locks on the tuples or pages are about to be made
			 * invalid, because we move tuples around.  Promote them to
			 * relation locks.
			 */
			TransferPredicateLocksToHeapRelation(oldrel);
		}

		econtext = GetPerTupleExprContext(estate);

		/*
		 * Create necessary tuple slots. When rewriting, two slots are needed,
		 * otherwise one suffices. In the case where one slot suffices, we
		 * need to use the new tuple descriptor, otherwise some constraints
		 * can't be evaluated.  Note that even when the tuple layout is the
		 * same and no rewrite is required, the tupDescs might not be
		 * (consider ADD COLUMN without a default).
		 */
		if (tab->rewrite)
		{
			Assert(newrel != NULL);
			oldslot = MakeSingleTupleTableSlot(oldTupDesc,
											   table_slot_callbacks(oldrel));
			newslot = MakeSingleTupleTableSlot(newTupDesc,
											   table_slot_callbacks(newrel));

			/*
			 * Set all columns in the new slot to NULL initially, to ensure
			 * columns added as part of the rewrite are initialized to NULL.
			 * That is necessary as tab->newvals will not contain an
			 * expression for columns with a NULL default, e.g. when adding a
			 * column without a default together with a column with a default
			 * requiring an actual rewrite.
			 */
			ExecStoreAllNullTuple(newslot);
		}
		else
		{
			oldslot = MakeSingleTupleTableSlot(newTupDesc,
											   table_slot_callbacks(oldrel));
			newslot = NULL;
		}

		/*
		 * Any attributes that are dropped according to the new tuple
		 * descriptor can be set to NULL. We precompute the list of dropped
		 * attributes to avoid needing to do so in the per-tuple loop.
		 */
		for (i = 0; i < newTupDesc->natts; i++)
		{
			if (TupleDescAttr(newTupDesc, i)->attisdropped)
				dropped_attrs = lappend_int(dropped_attrs, i);
		}

		/*
		 * Scan through the rows, generating a new row if needed and then
		 * checking all the constraints.
		 */
		snapshot = RegisterSnapshot(GetLatestSnapshot());
		scan = table_beginscan(oldrel, snapshot, 0, NULL);

		/*
		 * Switch to per-tuple memory context and reset it for each tuple
		 * produced, so we don't leak memory.
		 */
		oldCxt = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));

		while (table_scan_getnextslot(scan, ForwardScanDirection, oldslot))
		{
			TupleTableSlot *insertslot;

			if (tab->rewrite > 0)
			{
				/* Extract data from old tuple */
				slot_getallattrs(oldslot);
				ExecClearTuple(newslot);

				/* copy attributes */
				memcpy(newslot->tts_values, oldslot->tts_values,
					   sizeof(Datum) * oldslot->tts_nvalid);
				memcpy(newslot->tts_isnull, oldslot->tts_isnull,
					   sizeof(bool) * oldslot->tts_nvalid);

				/* Set dropped attributes to null in new tuple */
				foreach(lc, dropped_attrs)
					newslot->tts_isnull[lfirst_int(lc)] = true;

				/*
				 * Constraints and GENERATED expressions might reference the
				 * tableoid column, so fill tts_tableOid with the desired
				 * value.  (We must do this each time, because it gets
				 * overwritten with newrel's OID during storing.)
				 */
				newslot->tts_tableOid = RelationGetRelid(oldrel);

				/*
				 * Process supplied expressions to replace selected columns.
				 *
				 * First, evaluate expressions whose inputs come from the old
				 * tuple.
				 */
				econtext->ecxt_scantuple = oldslot;

				foreach(l, tab->newvals)
				{
					NewColumnValue *ex = lfirst(l);

					if (ex->is_generated)
						continue;

					newslot->tts_values[ex->attnum - 1]
						= ExecEvalExpr(ex->exprstate,
									   econtext,
									   &newslot->tts_isnull[ex->attnum - 1]);
				}

				ExecStoreVirtualTuple(newslot);

				/*
				 * Now, evaluate any expressions whose inputs come from the
				 * new tuple.  We assume these columns won't reference each
				 * other, so that there's no ordering dependency.
				 */
				econtext->ecxt_scantuple = newslot;

				foreach(l, tab->newvals)
				{
					NewColumnValue *ex = lfirst(l);

					if (!ex->is_generated)
						continue;

					newslot->tts_values[ex->attnum - 1]
						= ExecEvalExpr(ex->exprstate,
									   econtext,
									   &newslot->tts_isnull[ex->attnum - 1]);
				}

				insertslot = newslot;
			}
			else
			{
				/*
				 * If there's no rewrite, old and new table are guaranteed to
				 * have the same AM, so we can just use the old slot to verify
				 * new constraints etc.
				 */
				insertslot = oldslot;
			}

			/* Now check any constraints on the possibly-changed tuple */
			econtext->ecxt_scantuple = insertslot;

			foreach_int(attn, notnull_attrs)
			{
				if (slot_attisnull(insertslot, attn))
				{
					Form_pg_attribute attr = TupleDescAttr(newTupDesc, attn - 1);

					ereport(ERROR,
							(errcode(ERRCODE_NOT_NULL_VIOLATION),
							 errmsg("column \"%s\" of relation \"%s\" contains null values",
									NameStr(attr->attname),
									RelationGetRelationName(oldrel)),
							 errtablecol(oldrel, attn)));
				}
			}

			if (notnull_virtual_attrs != NIL)
			{
				AttrNumber	attnum;

				attnum = ExecRelGenVirtualNotNull(rInfo, insertslot,
												  estate,
												  notnull_virtual_attrs);
				if (attnum != InvalidAttrNumber)
				{
					Form_pg_attribute attr = TupleDescAttr(newTupDesc, attnum - 1);

					ereport(ERROR,
							errcode(ERRCODE_NOT_NULL_VIOLATION),
							errmsg("column \"%s\" of relation \"%s\" contains null values",
								   NameStr(attr->attname),
								   RelationGetRelationName(oldrel)),
							errtablecol(oldrel, attnum));
				}
			}

			foreach(l, tab->constraints)
			{
				NewConstraint *con = lfirst(l);

				switch (con->contype)
				{
					case CONSTR_CHECK:
						if (!ExecCheck(con->qualstate, econtext))
							ereport(ERROR,
									(errcode(ERRCODE_CHECK_VIOLATION),
									 errmsg("check constraint \"%s\" of relation \"%s\" is violated by some row",
											con->name,
											RelationGetRelationName(oldrel)),
									 errtableconstraint(oldrel, con->name)));
						break;
					case CONSTR_NOTNULL:
					case CONSTR_FOREIGN:
						/* Nothing to do here */
						break;
					default:
						elog(ERROR, "unrecognized constraint type: %d",
							 (int) con->contype);
				}
			}

			if (partqualstate && !ExecCheck(partqualstate, econtext))
			{
				if (tab->validate_default)
					ereport(ERROR,
							(errcode(ERRCODE_CHECK_VIOLATION),
							 errmsg("updated partition constraint for default partition \"%s\" would be violated by some row",
									RelationGetRelationName(oldrel)),
							 errtable(oldrel)));
				else
					ereport(ERROR,
							(errcode(ERRCODE_CHECK_VIOLATION),
							 errmsg("partition constraint of relation \"%s\" is violated by some row",
									RelationGetRelationName(oldrel)),
							 errtable(oldrel)));
			}

			/* Write the tuple out to the new relation */
			if (newrel)
				table_tuple_insert(newrel, insertslot, mycid,
								   ti_options, bistate);

			ResetExprContext(econtext);

			CHECK_FOR_INTERRUPTS();
		}

		MemoryContextSwitchTo(oldCxt);
		table_endscan(scan);
		UnregisterSnapshot(snapshot);

		ExecDropSingleTupleTableSlot(oldslot);
		if (newslot)
			ExecDropSingleTupleTableSlot(newslot);
	}

	FreeExecutorState(estate);

	table_close(oldrel, NoLock);
	if (newrel)
	{
		FreeBulkInsertState(bistate);

		table_finish_bulk_insert(newrel, ti_options);

		table_close(newrel, NoLock);
	}
}

/*
 * ATGetQueueEntry: find or create an entry in the ALTER TABLE work queue
 */
static AlteredTableInfo *
ATGetQueueEntry(List **wqueue, Relation rel)
{
	Oid			relid = RelationGetRelid(rel);
	AlteredTableInfo *tab;
	ListCell   *ltab;

	foreach(ltab, *wqueue)
	{
		tab = (AlteredTableInfo *) lfirst(ltab);
		if (tab->relid == relid)
			return tab;
	}

	/*
	 * Not there, so add it.  Note that we make a copy of the relation's
	 * existing descriptor before anything interesting can happen to it.
	 */
	tab = (AlteredTableInfo *) palloc0(sizeof(AlteredTableInfo));
	tab->relid = relid;
	tab->rel = NULL;			/* set later */
	tab->relkind = rel->rd_rel->relkind;
	tab->oldDesc = CreateTupleDescCopyConstr(RelationGetDescr(rel));
	tab->newAccessMethod = InvalidOid;
	tab->chgAccessMethod = false;
	tab->newTableSpace = InvalidOid;
	tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
	tab->chgPersistence = false;

	*wqueue = lappend(*wqueue, tab);

	return tab;
}

static const char *
alter_table_type_to_string(AlterTableType cmdtype)
{
	switch (cmdtype)
	{
		case AT_AddColumn:
		case AT_AddColumnToView:
			return "ADD COLUMN";
		case AT_ColumnDefault:
		case AT_CookedColumnDefault:
			return "ALTER COLUMN ... SET DEFAULT";
		case AT_DropNotNull:
			return "ALTER COLUMN ... DROP NOT NULL";
		case AT_SetNotNull:
			return "ALTER COLUMN ... SET NOT NULL";
		case AT_SetExpression:
			return "ALTER COLUMN ... SET EXPRESSION";
		case AT_DropExpression:
			return "ALTER COLUMN ... DROP EXPRESSION";
		case AT_SetStatistics:
			return "ALTER COLUMN ... SET STATISTICS";
		case AT_SetOptions:
			return "ALTER COLUMN ... SET";
		case AT_ResetOptions:
			return "ALTER COLUMN ... RESET";
		case AT_SetStorage:
			return "ALTER COLUMN ... SET STORAGE";
		case AT_SetCompression:
			return "ALTER COLUMN ... SET COMPRESSION";
		case AT_DropColumn:
			return "DROP COLUMN";
		case AT_AddIndex:
		case AT_ReAddIndex:
			return NULL;		/* not real grammar */
		case AT_AddConstraint:
		case AT_ReAddConstraint:
		case AT_ReAddDomainConstraint:
		case AT_AddIndexConstraint:
			return "ADD CONSTRAINT";
		case AT_AlterConstraint:
			return "ALTER CONSTRAINT";
		case AT_ValidateConstraint:
			return "VALIDATE CONSTRAINT";
		case AT_DropConstraint:
			return "DROP CONSTRAINT";
		case AT_ReAddComment:
			return NULL;		/* not real grammar */
		case AT_AlterColumnType:
			return "ALTER COLUMN ... SET DATA TYPE";
		case AT_AlterColumnGenericOptions:
			return "ALTER COLUMN ... OPTIONS";
		case AT_ChangeOwner:
			return "OWNER TO";
		case AT_ClusterOn:
			return "CLUSTER ON";
		case AT_DropCluster:
			return "SET WITHOUT CLUSTER";
		case AT_SetAccessMethod:
			return "SET ACCESS METHOD";
		case AT_SetLogged:
			return "SET LOGGED";
		case AT_SetUnLogged:
			return "SET UNLOGGED";
		case AT_DropOids:
			return "SET WITHOUT OIDS";
		case AT_SetTableSpace:
			return "SET TABLESPACE";
		case AT_SetRelOptions:
			return "SET";
		case AT_ResetRelOptions:
			return "RESET";
		case AT_ReplaceRelOptions:
			return NULL;		/* not real grammar */
		case AT_EnableTrig:
			return "ENABLE TRIGGER";
		case AT_EnableAlwaysTrig:
			return "ENABLE ALWAYS TRIGGER";
		case AT_EnableReplicaTrig:
			return "ENABLE REPLICA TRIGGER";
		case AT_DisableTrig:
			return "DISABLE TRIGGER";
		case AT_EnableTrigAll:
			return "ENABLE TRIGGER ALL";
		case AT_DisableTrigAll:
			return "DISABLE TRIGGER ALL";
		case AT_EnableTrigUser:
			return "ENABLE TRIGGER USER";
		case AT_DisableTrigUser:
			return "DISABLE TRIGGER USER";
		case AT_EnableRule:
			return "ENABLE RULE";
		case AT_EnableAlwaysRule:
			return "ENABLE ALWAYS RULE";
		case AT_EnableReplicaRule:
			return "ENABLE REPLICA RULE";
		case AT_DisableRule:
			return "DISABLE RULE";
		case AT_AddInherit:
			return "INHERIT";
		case AT_DropInherit:
			return "NO INHERIT";
		case AT_AddOf:
			return "OF";
		case AT_DropOf:
			return "NOT OF";
		case AT_ReplicaIdentity:
			return "REPLICA IDENTITY";
		case AT_EnableRowSecurity:
			return "ENABLE ROW SECURITY";
		case AT_DisableRowSecurity:
			return "DISABLE ROW SECURITY";
		case AT_ForceRowSecurity:
			return "FORCE ROW SECURITY";
		case AT_NoForceRowSecurity:
			return "NO FORCE ROW SECURITY";
		case AT_GenericOptions:
			return "OPTIONS";
		case AT_AttachPartition:
			return "ATTACH PARTITION";
		case AT_DetachPartition:
			return "DETACH PARTITION";
		case AT_DetachPartitionFinalize:
			return "DETACH PARTITION ... FINALIZE";
		case AT_AddIdentity:
			return "ALTER COLUMN ... ADD IDENTITY";
		case AT_SetIdentity:
			return "ALTER COLUMN ... SET";
		case AT_DropIdentity:
			return "ALTER COLUMN ... DROP IDENTITY";
		case AT_ReAddStatistics:
			return NULL;		/* not real grammar */
	}

	return NULL;
}

/*
 * ATSimplePermissions
 *
 * - Ensure that it is a relation (or possibly a view)
 * - Ensure this user is the owner
 * - Ensure that it is not a system table
 */
static void
ATSimplePermissions(AlterTableType cmdtype, Relation rel, int allowed_targets)
{
	int			actual_target;

	switch (rel->rd_rel->relkind)
	{
		case RELKIND_RELATION:
			actual_target = ATT_TABLE;
			break;
		case RELKIND_PARTITIONED_TABLE:
			actual_target = ATT_PARTITIONED_TABLE;
			break;
		case RELKIND_VIEW:
			actual_target = ATT_VIEW;
			break;
		case RELKIND_MATVIEW:
			actual_target = ATT_MATVIEW;
			break;
		case RELKIND_INDEX:
			actual_target = ATT_INDEX;
			break;
		case RELKIND_PARTITIONED_INDEX:
			actual_target = ATT_PARTITIONED_INDEX;
			break;
		case RELKIND_COMPOSITE_TYPE:
			actual_target = ATT_COMPOSITE_TYPE;
			break;
		case RELKIND_FOREIGN_TABLE:
			actual_target = ATT_FOREIGN_TABLE;
			break;
		case RELKIND_SEQUENCE:
			actual_target = ATT_SEQUENCE;
			break;
		default:
			actual_target = 0;
			break;
	}

	/* Wrong target type? */
	if ((actual_target & allowed_targets) == 0)
	{
		const char *action_str = alter_table_type_to_string(cmdtype);

		if (action_str)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
			/* translator: %s is a group of some SQL keywords */
					 errmsg("ALTER action %s cannot be performed on relation \"%s\"",
							action_str, RelationGetRelationName(rel)),
					 errdetail_relkind_not_supported(rel->rd_rel->relkind)));
		else
			/* internal error? */
			elog(ERROR, "invalid ALTER action attempted on relation \"%s\"",
				 RelationGetRelationName(rel));
	}

	/* Permissions checks */
	if (!object_ownercheck(RelationRelationId, RelationGetRelid(rel), GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(rel->rd_rel->relkind),
					   RelationGetRelationName(rel));

	if (!allowSystemTableMods && IsSystemRelation(rel))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						RelationGetRelationName(rel))));
}

/*
 * ATSimpleRecursion
 *
 * Simple table recursion sufficient for most ALTER TABLE operations.
 * All direct and indirect children are processed in an unspecified order.
 * Note that if a child inherits from the original table via multiple
 * inheritance paths, it will be visited just once.
 */
static void
ATSimpleRecursion(List **wqueue, Relation rel,
				  AlterTableCmd *cmd, bool recurse, LOCKMODE lockmode,
				  AlterTableUtilityContext *context)
{
	/*
	 * Propagate to children, if desired and if there are (or might be) any
	 * children.
	 */
	if (recurse && rel->rd_rel->relhassubclass)
	{
		Oid			relid = RelationGetRelid(rel);
		ListCell   *child;
		List	   *children;

		children = find_all_inheritors(relid, lockmode, NULL);

		/*
		 * find_all_inheritors does the recursive search of the inheritance
		 * hierarchy, so all we have to do is process all of the relids in the
		 * list that it returns.
		 */
		foreach(child, children)
		{
			Oid			childrelid = lfirst_oid(child);
			Relation	childrel;

			if (childrelid == relid)
				continue;
			/* find_all_inheritors already got lock */
			childrel = relation_open(childrelid, NoLock);
			CheckAlterTableIsSafe(childrel);
			ATPrepCmd(wqueue, childrel, cmd, false, true, lockmode, context);
			relation_close(childrel, NoLock);
		}
	}
}

/*
 * Obtain list of partitions of the given table, locking them all at the given
 * lockmode and ensuring that they all pass CheckAlterTableIsSafe.
 *
 * This function is a no-op if the given relation is not a partitioned table;
 * in particular, nothing is done if it's a legacy inheritance parent.
 */
static void
ATCheckPartitionsNotInUse(Relation rel, LOCKMODE lockmode)
{
	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
	{
		List	   *inh;
		ListCell   *cell;

		inh = find_all_inheritors(RelationGetRelid(rel), lockmode, NULL);
		/* first element is the parent rel; must ignore it */
		for_each_from(cell, inh, 1)
		{
			Relation	childrel;

			/* find_all_inheritors already got lock */
			childrel = table_open(lfirst_oid(cell), NoLock);
			CheckAlterTableIsSafe(childrel);
			table_close(childrel, NoLock);
		}
		list_free(inh);
	}
}

/*
 * ATTypedTableRecursion
 *
 * Propagate ALTER TYPE operations to the typed tables of that type.
 * Also check the RESTRICT/CASCADE behavior.  Given CASCADE, also permit
 * recursion to inheritance children of the typed tables.
 */
static void
ATTypedTableRecursion(List **wqueue, Relation rel, AlterTableCmd *cmd,
					  LOCKMODE lockmode, AlterTableUtilityContext *context)
{
	ListCell   *child;
	List	   *children;

	Assert(rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE);

	children = find_typed_table_dependencies(rel->rd_rel->reltype,
											 RelationGetRelationName(rel),
											 cmd->behavior);

	foreach(child, children)
	{
		Oid			childrelid = lfirst_oid(child);
		Relation	childrel;

		childrel = relation_open(childrelid, lockmode);
		CheckAlterTableIsSafe(childrel);
		ATPrepCmd(wqueue, childrel, cmd, true, true, lockmode, context);
		relation_close(childrel, NoLock);
	}
}


/*
 * find_composite_type_dependencies
 *
 * Check to see if the type "typeOid" is being used as a column in some table
 * (possibly nested several levels deep in composite types, arrays, etc!).
 * Eventually, we'd like to propagate the check or rewrite operation
 * into such tables, but for now, just error out if we find any.
 *
 * Caller should provide either the associated relation of a rowtype,
 * or a type name (not both) for use in the error message, if any.
 *
 * Note that "typeOid" is not necessarily a composite type; it could also be
 * another container type such as an array or range, or a domain over one of
 * these things.  The name of this function is therefore somewhat historical,
 * but it's not worth changing.
 *
 * We assume that functions and views depending on the type are not reasons
 * to reject the ALTER.  (How safe is this really?)
 */
void
find_composite_type_dependencies(Oid typeOid, Relation origRelation,
								 const char *origTypeName)
{
	Relation	depRel;
	ScanKeyData key[2];
	SysScanDesc depScan;
	HeapTuple	depTup;

	/* since this function recurses, it could be driven to stack overflow */
	check_stack_depth();

	/*
	 * We scan pg_depend to find those things that depend on the given type.
	 * (We assume we can ignore refobjsubid for a type.)
	 */
	depRel = table_open(DependRelationId, AccessShareLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_refclassid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(TypeRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_refobjid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(typeOid));

	depScan = systable_beginscan(depRel, DependReferenceIndexId, true,
								 NULL, 2, key);

	while (HeapTupleIsValid(depTup = systable_getnext(depScan)))
	{
		Form_pg_depend pg_depend = (Form_pg_depend) GETSTRUCT(depTup);
		Relation	rel;
		TupleDesc	tupleDesc;
		Form_pg_attribute att;

		/* Check for directly dependent types */
		if (pg_depend->classid == TypeRelationId)
		{
			/*
			 * This must be an array, domain, or range containing the given
			 * type, so recursively check for uses of this type.  Note that
			 * any error message will mention the original type not the
			 * container; this is intentional.
			 */
			find_composite_type_dependencies(pg_depend->objid,
											 origRelation, origTypeName);
			continue;
		}

		/* Else, ignore dependees that aren't relations */
		if (pg_depend->classid != RelationRelationId)
			continue;

		rel = relation_open(pg_depend->objid, AccessShareLock);
		tupleDesc = RelationGetDescr(rel);

		/*
		 * If objsubid identifies a specific column, refer to that in error
		 * messages.  Otherwise, search to see if there's a user column of the
		 * type.  (We assume system columns are never of interesting types.)
		 * The search is needed because an index containing an expression
		 * column of the target type will just be recorded as a whole-relation
		 * dependency.  If we do not find a column of the type, the dependency
		 * must indicate that the type is transiently referenced in an index
		 * expression but not stored on disk, which we assume is OK, just as
		 * we do for references in views.  (It could also be that the target
		 * type is embedded in some container type that is stored in an index
		 * column, but the previous recursion should catch such cases.)
		 */
		if (pg_depend->objsubid > 0 && pg_depend->objsubid <= tupleDesc->natts)
			att = TupleDescAttr(tupleDesc, pg_depend->objsubid - 1);
		else
		{
			att = NULL;
			for (int attno = 1; attno <= tupleDesc->natts; attno++)
			{
				att = TupleDescAttr(tupleDesc, attno - 1);
				if (att->atttypid == typeOid && !att->attisdropped)
					break;
				att = NULL;
			}
			if (att == NULL)
			{
				/* No such column, so assume OK */
				relation_close(rel, AccessShareLock);
				continue;
			}
		}

		/*
		 * We definitely should reject if the relation has storage.  If it's
		 * partitioned, then perhaps we don't have to reject: if there are
		 * partitions then we'll fail when we find one, else there is no
		 * stored data to worry about.  However, it's possible that the type
		 * change would affect conclusions about whether the type is sortable
		 * or hashable and thus (if it's a partitioning column) break the
		 * partitioning rule.  For now, reject for partitioned rels too.
		 */
		if (RELKIND_HAS_STORAGE(rel->rd_rel->relkind) ||
			RELKIND_HAS_PARTITIONS(rel->rd_rel->relkind))
		{
			if (origTypeName)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot alter type \"%s\" because column \"%s.%s\" uses it",
								origTypeName,
								RelationGetRelationName(rel),
								NameStr(att->attname))));
			else if (origRelation->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot alter type \"%s\" because column \"%s.%s\" uses it",
								RelationGetRelationName(origRelation),
								RelationGetRelationName(rel),
								NameStr(att->attname))));
			else if (origRelation->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot alter foreign table \"%s\" because column \"%s.%s\" uses its row type",
								RelationGetRelationName(origRelation),
								RelationGetRelationName(rel),
								NameStr(att->attname))));
			else
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("cannot alter table \"%s\" because column \"%s.%s\" uses its row type",
								RelationGetRelationName(origRelation),
								RelationGetRelationName(rel),
								NameStr(att->attname))));
		}
		else if (OidIsValid(rel->rd_rel->reltype))
		{
			/*
			 * A view or composite type itself isn't a problem, but we must
			 * recursively check for indirect dependencies via its rowtype.
			 */
			find_composite_type_dependencies(rel->rd_rel->reltype,
											 origRelation, origTypeName);
		}

		relation_close(rel, AccessShareLock);
	}

	systable_endscan(depScan);

	relation_close(depRel, AccessShareLock);
}


/*
 * find_typed_table_dependencies
 *
 * Check to see if a composite type is being used as the type of a
 * typed table.  Abort if any are found and behavior is RESTRICT.
 * Else return the list of tables.
 */
static List *
find_typed_table_dependencies(Oid typeOid, const char *typeName, DropBehavior behavior)
{
	Relation	classRel;
	ScanKeyData key[1];
	TableScanDesc scan;
	HeapTuple	tuple;
	List	   *result = NIL;

	classRel = table_open(RelationRelationId, AccessShareLock);

	ScanKeyInit(&key[0],
				Anum_pg_class_reloftype,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(typeOid));

	scan = table_beginscan_catalog(classRel, 1, key);

	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
	{
		Form_pg_class classform = (Form_pg_class) GETSTRUCT(tuple);

		if (behavior == DROP_RESTRICT)
			ereport(ERROR,
					(errcode(ERRCODE_DEPENDENT_OBJECTS_STILL_EXIST),
					 errmsg("cannot alter type \"%s\" because it is the type of a typed table",
							typeName),
					 errhint("Use ALTER ... CASCADE to alter the typed tables too.")));
		else
			result = lappend_oid(result, classform->oid);
	}

	table_endscan(scan);
	table_close(classRel, AccessShareLock);

	return result;
}


/*
 * check_of_type
 *
 * Check whether a type is suitable for CREATE TABLE OF/ALTER TABLE OF.  If it
 * isn't suitable, throw an error.  Currently, we require that the type
 * originated with CREATE TYPE AS.  We could support any row type, but doing so
 * would require handling a number of extra corner cases in the DDL commands.
 * (Also, allowing domain-over-composite would open up a can of worms about
 * whether and how the domain's constraints should apply to derived tables.)
 */
void
check_of_type(HeapTuple typetuple)
{
	Form_pg_type typ = (Form_pg_type) GETSTRUCT(typetuple);
	bool		typeOk = false;

	if (typ->typtype == TYPTYPE_COMPOSITE)
	{
		Relation	typeRelation;

		Assert(OidIsValid(typ->typrelid));
		typeRelation = relation_open(typ->typrelid, AccessShareLock);
		typeOk = (typeRelation->rd_rel->relkind == RELKIND_COMPOSITE_TYPE);

		/*
		 * Close the parent rel, but keep our AccessShareLock on it until xact
		 * commit.  That will prevent someone else from deleting or ALTERing
		 * the type before the typed table creation/conversion commits.
		 */
		relation_close(typeRelation, NoLock);

		if (!typeOk)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("type %s is the row type of another table",
							format_type_be(typ->oid)),
					 errdetail("A typed table must use a stand-alone composite type created with CREATE TYPE.")));
	}
	else
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("type %s is not a composite type",
						format_type_be(typ->oid))));
}


/*
 * ALTER TABLE ADD COLUMN
 *
 * Adds an additional attribute to a relation making the assumption that
 * CHECK, NOT NULL, and FOREIGN KEY constraints will be removed from the
 * AT_AddColumn AlterTableCmd by parse_utilcmd.c and added as independent
 * AlterTableCmd's.
 *
 * ADD COLUMN cannot use the normal ALTER TABLE recursion mechanism, because we
 * have to decide at runtime whether to recurse or not depending on whether we
 * actually add a column or merely merge with an existing column.  (We can't
 * check this in a static pre-pass because it won't handle multiple inheritance
 * situations correctly.)
 */
static void
ATPrepAddColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
				bool is_view, AlterTableCmd *cmd, LOCKMODE lockmode,
				AlterTableUtilityContext *context)
{
	if (rel->rd_rel->reloftype && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot add column to typed table")));

	if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
		ATTypedTableRecursion(wqueue, rel, cmd, lockmode, context);

	if (recurse && !is_view)
		cmd->recurse = true;
}

/*
 * Add a column to a table.  The return value is the address of the
 * new column in the parent relation.
 *
 * cmd is pass-by-ref so that we can replace it with the parse-transformed
 * copy (but that happens only after we check for IF NOT EXISTS).
 */
static ObjectAddress
ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
				AlterTableCmd **cmd, bool recurse, bool recursing,
				LOCKMODE lockmode, AlterTablePass cur_pass,
				AlterTableUtilityContext *context)
{
	Oid			myrelid = RelationGetRelid(rel);
	ColumnDef  *colDef = castNode(ColumnDef, (*cmd)->def);
	bool		if_not_exists = (*cmd)->missing_ok;
	Relation	pgclass,
				attrdesc;
	HeapTuple	reltup;
	Form_pg_class relform;
	Form_pg_attribute attribute;
	int			newattnum;
	char		relkind;
	Expr	   *defval;
	List	   *children;
	ListCell   *child;
	AlterTableCmd *childcmd;
	ObjectAddress address;
	TupleDesc	tupdesc;

	/* since this function recurses, it could be driven to stack overflow */
	check_stack_depth();

	/* At top level, permission check was done in ATPrepCmd, else do it */
	if (recursing)
		ATSimplePermissions((*cmd)->subtype, rel,
							ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);

	if (rel->rd_rel->relispartition && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot add column to a partition")));

	attrdesc = table_open(AttributeRelationId, RowExclusiveLock);

	/*
	 * Are we adding the column to a recursion child?  If so, check whether to
	 * merge with an existing definition for the column.  If we do merge, we
	 * must not recurse.  Children will already have the column, and recursing
	 * into them would mess up attinhcount.
	 */
	if (colDef->inhcount > 0)
	{
		HeapTuple	tuple;

		/* Does child already have a column by this name? */
		tuple = SearchSysCacheCopyAttName(myrelid, colDef->colname);
		if (HeapTupleIsValid(tuple))
		{
			Form_pg_attribute childatt = (Form_pg_attribute) GETSTRUCT(tuple);
			Oid			ctypeId;
			int32		ctypmod;
			Oid			ccollid;

			/* Child column must match on type, typmod, and collation */
			typenameTypeIdAndMod(NULL, colDef->typeName, &ctypeId, &ctypmod);
			if (ctypeId != childatt->atttypid ||
				ctypmod != childatt->atttypmod)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("child table \"%s\" has different type for column \"%s\"",
								RelationGetRelationName(rel), colDef->colname)));
			ccollid = GetColumnDefCollation(NULL, colDef, ctypeId);
			if (ccollid != childatt->attcollation)
				ereport(ERROR,
						(errcode(ERRCODE_COLLATION_MISMATCH),
						 errmsg("child table \"%s\" has different collation for column \"%s\"",
								RelationGetRelationName(rel), colDef->colname),
						 errdetail("\"%s\" versus \"%s\"",
								   get_collation_name(ccollid),
								   get_collation_name(childatt->attcollation))));

			/* Bump the existing child att's inhcount */
			if (pg_add_s16_overflow(childatt->attinhcount, 1,
									&childatt->attinhcount))
				ereport(ERROR,
						errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
						errmsg("too many inheritance parents"));
			CatalogTupleUpdate(attrdesc, &tuple->t_self, tuple);

			heap_freetuple(tuple);

			/* Inform the user about the merge */
			ereport(NOTICE,
					(errmsg("merging definition of column \"%s\" for child \"%s\"",
							colDef->colname, RelationGetRelationName(rel))));

			table_close(attrdesc, RowExclusiveLock);

			/* Make the child column change visible */
			CommandCounterIncrement();

			return InvalidObjectAddress;
		}
	}

	/* skip if the name already exists and if_not_exists is true */
	if (!check_for_column_name_collision(rel, colDef->colname, if_not_exists))
	{
		table_close(attrdesc, RowExclusiveLock);
		return InvalidObjectAddress;
	}

	/*
	 * Okay, we need to add the column, so go ahead and do parse
	 * transformation.  This can result in queueing up, or even immediately
	 * executing, subsidiary operations (such as creation of unique indexes);
	 * so we mustn't do it until we have made the if_not_exists check.
	 *
	 * When recursing, the command was already transformed and we needn't do
	 * so again.  Also, if context isn't given we can't transform.  (That
	 * currently happens only for AT_AddColumnToView; we expect that view.c
	 * passed us a ColumnDef that doesn't need work.)
	 */
	if (context != NULL && !recursing)
	{
		*cmd = ATParseTransformCmd(wqueue, tab, rel, *cmd, recurse, lockmode,
								   cur_pass, context);
		Assert(*cmd != NULL);
		colDef = castNode(ColumnDef, (*cmd)->def);
	}

	/*
	 * Regular inheritance children are independent enough not to inherit the
	 * identity column from parent hence cannot recursively add identity
	 * column if the table has inheritance children.
	 *
	 * Partitions, on the other hand, are integral part of a partitioned table
	 * and inherit identity column.  Hence propagate identity column down the
	 * partition hierarchy.
	 */
	if (colDef->identity &&
		recurse &&
		rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE &&
		find_inheritance_children(myrelid, NoLock) != NIL)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot recursively add identity column to table that has child tables")));

	pgclass = table_open(RelationRelationId, RowExclusiveLock);

	reltup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(myrelid));
	if (!HeapTupleIsValid(reltup))
		elog(ERROR, "cache lookup failed for relation %u", myrelid);
	relform = (Form_pg_class) GETSTRUCT(reltup);
	relkind = relform->relkind;

	/* Determine the new attribute's number */
	newattnum = relform->relnatts + 1;
	if (newattnum > MaxHeapAttributeNumber)
		ereport(ERROR,
				(errcode(ERRCODE_TOO_MANY_COLUMNS),
				 errmsg("tables can have at most %d columns",
						MaxHeapAttributeNumber)));

	/*
	 * Construct new attribute's pg_attribute entry.
	 */
	tupdesc = BuildDescForRelation(list_make1(colDef));

	attribute = TupleDescAttr(tupdesc, 0);

	/* Fix up attribute number */
	attribute->attnum = newattnum;

	/* make sure datatype is legal for a column */
	CheckAttributeType(NameStr(attribute->attname), attribute->atttypid, attribute->attcollation,
					   list_make1_oid(rel->rd_rel->reltype),
					   (attribute->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL ? CHKATYPE_IS_VIRTUAL : 0));

	InsertPgAttributeTuples(attrdesc, tupdesc, myrelid, NULL, NULL);

	table_close(attrdesc, RowExclusiveLock);

	/*
	 * Update pg_class tuple as appropriate
	 */
	relform->relnatts = newattnum;

	CatalogTupleUpdate(pgclass, &reltup->t_self, reltup);

	heap_freetuple(reltup);

	/* Post creation hook for new attribute */
	InvokeObjectPostCreateHook(RelationRelationId, myrelid, newattnum);

	table_close(pgclass, RowExclusiveLock);

	/* Make the attribute's catalog entry visible */
	CommandCounterIncrement();

	/*
	 * Store the DEFAULT, if any, in the catalogs
	 */
	if (colDef->raw_default)
	{
		RawColumnDefault *rawEnt;

		rawEnt = (RawColumnDefault *) palloc(sizeof(RawColumnDefault));
		rawEnt->attnum = attribute->attnum;
		rawEnt->raw_default = copyObject(colDef->raw_default);
		rawEnt->generated = colDef->generated;

		/*
		 * This function is intended for CREATE TABLE, so it processes a
		 * _list_ of defaults, but we just do one.
		 */
		AddRelationNewConstraints(rel, list_make1(rawEnt), NIL,
								  false, true, false, NULL);

		/* Make the additional catalog changes visible */
		CommandCounterIncrement();
	}

	/*
	 * Tell Phase 3 to fill in the default expression, if there is one.
	 *
	 * If there is no default, Phase 3 doesn't have to do anything, because
	 * that effectively means that the default is NULL.  The heap tuple access
	 * routines always check for attnum > # of attributes in tuple, and return
	 * NULL if so, so without any modification of the tuple data we will get
	 * the effect of NULL values in the new column.
	 *
	 * An exception occurs when the new column is of a domain type: the domain
	 * might have a not-null constraint, or a check constraint that indirectly
	 * rejects nulls.  If there are any domain constraints then we construct
	 * an explicit NULL default value that will be passed through
	 * CoerceToDomain processing.  (This is a tad inefficient, since it causes
	 * rewriting the table which we really wouldn't have to do; but we do it
	 * to preserve the historical behavior that such a failure will be raised
	 * only if the table currently contains some rows.)
	 *
	 * Note: we use build_column_default, and not just the cooked default
	 * returned by AddRelationNewConstraints, so that the right thing happens
	 * when a datatype's default applies.
	 *
	 * Note: it might seem that this should happen at the end of Phase 2, so
	 * that the effects of subsequent subcommands can be taken into account.
	 * It's intentional that we do it now, though.  The new column should be
	 * filled according to what is said in the ADD COLUMN subcommand, so that
	 * the effects are the same as if this subcommand had been run by itself
	 * and the later subcommands had been issued in new ALTER TABLE commands.
	 *
	 * We can skip this entirely for relations without storage, since Phase 3
	 * is certainly not going to touch them.
	 */
	if (RELKIND_HAS_STORAGE(relkind))
	{
		bool		has_domain_constraints;
		bool		has_missing = false;

		/*
		 * For an identity column, we can't use build_column_default(),
		 * because the sequence ownership isn't set yet.  So do it manually.
		 */
		if (colDef->identity)
		{
			NextValueExpr *nve = makeNode(NextValueExpr);

			nve->seqid = RangeVarGetRelid(colDef->identitySequence, NoLock, false);
			nve->typeId = attribute->atttypid;

			defval = (Expr *) nve;
		}
		else
			defval = (Expr *) build_column_default(rel, attribute->attnum);

		/* Build CoerceToDomain(NULL) expression if needed */
		has_domain_constraints = DomainHasConstraints(attribute->atttypid);
		if (!defval && has_domain_constraints)
		{
			Oid			baseTypeId;
			int32		baseTypeMod;
			Oid			baseTypeColl;

			baseTypeMod = attribute->atttypmod;
			baseTypeId = getBaseTypeAndTypmod(attribute->atttypid, &baseTypeMod);
			baseTypeColl = get_typcollation(baseTypeId);
			defval = (Expr *) makeNullConst(baseTypeId, baseTypeMod, baseTypeColl);
			defval = (Expr *) coerce_to_target_type(NULL,
													(Node *) defval,
													baseTypeId,
													attribute->atttypid,
													attribute->atttypmod,
													COERCION_ASSIGNMENT,
													COERCE_IMPLICIT_CAST,
													-1);
			if (defval == NULL) /* should not happen */
				elog(ERROR, "failed to coerce base type to domain");
		}

		if (defval)
		{
			NewColumnValue *newval;

			/* Prepare defval for execution, either here or in Phase 3 */
			defval = expression_planner(defval);

			/* Add the new default to the newvals list */
			newval = (NewColumnValue *) palloc0(sizeof(NewColumnValue));
			newval->attnum = attribute->attnum;
			newval->expr = defval;
			newval->is_generated = (colDef->generated != '\0');

			tab->newvals = lappend(tab->newvals, newval);

			/*
			 * Attempt to skip a complete table rewrite by storing the
			 * specified DEFAULT value outside of the heap.  This is only
			 * allowed for plain relations and non-generated columns, and the
			 * default expression can't be volatile (stable is OK).  Note that
			 * contain_volatile_functions deems CoerceToDomain immutable, but
			 * here we consider that coercion to a domain with constraints is
			 * volatile; else it might fail even when the table is empty.
			 */
			if (rel->rd_rel->relkind == RELKIND_RELATION &&
				!colDef->generated &&
				!has_domain_constraints &&
				!contain_volatile_functions((Node *) defval))
			{
				EState	   *estate;
				ExprState  *exprState;
				Datum		missingval;
				bool		missingIsNull;

				/* Evaluate the default expression */
				estate = CreateExecutorState();
				exprState = ExecPrepareExpr(defval, estate);
				missingval = ExecEvalExpr(exprState,
										  GetPerTupleExprContext(estate),
										  &missingIsNull);
				/* If it turns out NULL, nothing to do; else store it */
				if (!missingIsNull)
				{
					StoreAttrMissingVal(rel, attribute->attnum, missingval);
					/* Make the additional catalog change visible */
					CommandCounterIncrement();
					has_missing = true;
				}
				FreeExecutorState(estate);
			}
			else
			{
				/*
				 * Failed to use missing mode.  We have to do a table rewrite
				 * to install the value --- unless it's a virtual generated
				 * column.
				 */
				if (colDef->generated != ATTRIBUTE_GENERATED_VIRTUAL)
					tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
			}
		}

		if (!has_missing)
		{
			/*
			 * If the new column is NOT NULL, and there is no missing value,
			 * tell Phase 3 it needs to check for NULLs.
			 */
			tab->verify_new_notnull |= colDef->is_not_null;
		}
	}

	/*
	 * Add needed dependency entries for the new column.
	 */
	add_column_datatype_dependency(myrelid, newattnum, attribute->atttypid);
	add_column_collation_dependency(myrelid, newattnum, attribute->attcollation);

	/*
	 * Propagate to children as appropriate.  Unlike most other ALTER
	 * routines, we have to do this one level of recursion at a time; we can't
	 * use find_all_inheritors to do it in one pass.
	 */
	children =
		find_inheritance_children(RelationGetRelid(rel), lockmode);

	/*
	 * If we are told not to recurse, there had better not be any child
	 * tables; else the addition would put them out of step.
	 */
	if (children && !recurse)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("column must be added to child tables too")));

	/* Children should see column as singly inherited */
	if (!recursing)
	{
		childcmd = copyObject(*cmd);
		colDef = castNode(ColumnDef, childcmd->def);
		colDef->inhcount = 1;
		colDef->is_local = false;
	}
	else
		childcmd = *cmd;		/* no need to copy again */

	foreach(child, children)
	{
		Oid			childrelid = lfirst_oid(child);
		Relation	childrel;
		AlteredTableInfo *childtab;

		/* find_inheritance_children already got lock */
		childrel = table_open(childrelid, NoLock);
		CheckAlterTableIsSafe(childrel);

		/* Find or create work queue entry for this table */
		childtab = ATGetQueueEntry(wqueue, childrel);

		/* Recurse to child; return value is ignored */
		ATExecAddColumn(wqueue, childtab, childrel,
						&childcmd, recurse, true,
						lockmode, cur_pass, context);

		table_close(childrel, NoLock);
	}

	ObjectAddressSubSet(address, RelationRelationId, myrelid, newattnum);
	return address;
}

/*
 * If a new or renamed column will collide with the name of an existing
 * column and if_not_exists is false then error out, else do nothing.
 */
static bool
check_for_column_name_collision(Relation rel, const char *colname,
								bool if_not_exists)
{
	HeapTuple	attTuple;
	int			attnum;

	/*
	 * this test is deliberately not attisdropped-aware, since if one tries to
	 * add a column matching a dropped column name, it's gonna fail anyway.
	 */
	attTuple = SearchSysCache2(ATTNAME,
							   ObjectIdGetDatum(RelationGetRelid(rel)),
							   PointerGetDatum(colname));
	if (!HeapTupleIsValid(attTuple))
		return true;

	attnum = ((Form_pg_attribute) GETSTRUCT(attTuple))->attnum;
	ReleaseSysCache(attTuple);

	/*
	 * We throw a different error message for conflicts with system column
	 * names, since they are normally not shown and the user might otherwise
	 * be confused about the reason for the conflict.
	 */
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_COLUMN),
				 errmsg("column name \"%s\" conflicts with a system column name",
						colname)));
	else
	{
		if (if_not_exists)
		{
			ereport(NOTICE,
					(errcode(ERRCODE_DUPLICATE_COLUMN),
					 errmsg("column \"%s\" of relation \"%s\" already exists, skipping",
							colname, RelationGetRelationName(rel))));
			return false;
		}

		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" already exists",
						colname, RelationGetRelationName(rel))));
	}

	return true;
}

/*
 * Install a column's dependency on its datatype.
 */
static void
add_column_datatype_dependency(Oid relid, int32 attnum, Oid typid)
{
	ObjectAddress myself,
				referenced;

	myself.classId = RelationRelationId;
	myself.objectId = relid;
	myself.objectSubId = attnum;
	referenced.classId = TypeRelationId;
	referenced.objectId = typid;
	referenced.objectSubId = 0;
	recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
}

/*
 * Install a column's dependency on its collation.
 */
static void
add_column_collation_dependency(Oid relid, int32 attnum, Oid collid)
{
	ObjectAddress myself,
				referenced;

	/* We know the default collation is pinned, so don't bother recording it */
	if (OidIsValid(collid) && collid != DEFAULT_COLLATION_OID)
	{
		myself.classId = RelationRelationId;
		myself.objectId = relid;
		myself.objectSubId = attnum;
		referenced.classId = CollationRelationId;
		referenced.objectId = collid;
		referenced.objectSubId = 0;
		recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
	}
}

/*
 * ALTER TABLE ALTER COLUMN DROP NOT NULL
 *
 * Return the address of the modified column.  If the column was already
 * nullable, InvalidObjectAddress is returned.
 */
static ObjectAddress
ATExecDropNotNull(Relation rel, const char *colName, bool recurse,
				  LOCKMODE lockmode)
{
	HeapTuple	tuple;
	HeapTuple	conTup;
	Form_pg_attribute attTup;
	AttrNumber	attnum;
	Relation	attr_rel;
	ObjectAddress address;

	/*
	 * lookup the attribute
	 */
	attr_rel = table_open(AttributeRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));
	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = attTup->attnum;
	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);

	/* If the column is already nullable there's nothing to do. */
	if (!attTup->attnotnull)
	{
		table_close(attr_rel, RowExclusiveLock);
		return InvalidObjectAddress;
	}

	/* Prevent them from altering a system attribute */
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	if (attTup->attidentity)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("column \"%s\" of relation \"%s\" is an identity column",
						colName, RelationGetRelationName(rel))));

	/*
	 * If rel is partition, shouldn't drop NOT NULL if parent has the same.
	 */
	if (rel->rd_rel->relispartition)
	{
		Oid			parentId = get_partition_parent(RelationGetRelid(rel), false);
		Relation	parent = table_open(parentId, AccessShareLock);
		TupleDesc	tupDesc = RelationGetDescr(parent);
		AttrNumber	parent_attnum;

		parent_attnum = get_attnum(parentId, colName);
		if (TupleDescAttr(tupDesc, parent_attnum - 1)->attnotnull)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("column \"%s\" is marked NOT NULL in parent table",
							colName)));
		table_close(parent, AccessShareLock);
	}

	/*
	 * Find the constraint that makes this column NOT NULL, and drop it.
	 * dropconstraint_internal() resets attnotnull.
	 */
	conTup = findNotNullConstraintAttnum(RelationGetRelid(rel), attnum);
	if (conTup == NULL)
		elog(ERROR, "cache lookup failed for not-null constraint on column \"%s\" of relation \"%s\"",
			 colName, RelationGetRelationName(rel));

	/* The normal case: we have a pg_constraint row, remove it */
	dropconstraint_internal(rel, conTup, DROP_RESTRICT, recurse, false,
							false, lockmode);
	heap_freetuple(conTup);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), attnum);

	table_close(attr_rel, RowExclusiveLock);

	return address;
}

/*
 * set_attnotnull
 *		Helper to update/validate the pg_attribute status of a not-null
 *		constraint
 *
 * pg_attribute.attnotnull is set true, if it isn't already.
 * If queue_validation is true, also set up wqueue to validate the constraint.
 * wqueue may be given as NULL when validation is not needed (e.g., on table
 * creation).
 */
static void
set_attnotnull(List **wqueue, Relation rel, AttrNumber attnum,
			   bool is_valid, bool queue_validation)
{
	Form_pg_attribute attr;
	CompactAttribute *thisatt;

	Assert(!queue_validation || wqueue);

	CheckAlterTableIsSafe(rel);

	/*
	 * Exit quickly by testing attnotnull from the tupledesc's copy of the
	 * attribute.
	 */
	attr = TupleDescAttr(RelationGetDescr(rel), attnum - 1);
	if (attr->attisdropped)
		return;

	if (!attr->attnotnull)
	{
		Relation	attr_rel;
		HeapTuple	tuple;

		attr_rel = table_open(AttributeRelationId, RowExclusiveLock);

		tuple = SearchSysCacheCopyAttNum(RelationGetRelid(rel), attnum);
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
				 attnum, RelationGetRelid(rel));

		thisatt = TupleDescCompactAttr(RelationGetDescr(rel), attnum - 1);
		thisatt->attnullability = ATTNULLABLE_VALID;

		attr = (Form_pg_attribute) GETSTRUCT(tuple);

		attr->attnotnull = true;
		CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);

		/*
		 * If the nullness isn't already proven by validated constraints, have
		 * ALTER TABLE phase 3 test for it.
		 */
		if (queue_validation && wqueue &&
			!NotNullImpliedByRelConstraints(rel, attr))
		{
			AlteredTableInfo *tab;

			tab = ATGetQueueEntry(wqueue, rel);
			tab->verify_new_notnull = true;
		}

		CommandCounterIncrement();

		table_close(attr_rel, RowExclusiveLock);
		heap_freetuple(tuple);
	}
	else
	{
		CacheInvalidateRelcache(rel);
	}
}

/*
 * ALTER TABLE ALTER COLUMN SET NOT NULL
 *
 * Add a not-null constraint to a single table and its children.  Returns
 * the address of the constraint added to the parent relation, if one gets
 * added, or InvalidObjectAddress otherwise.
 *
 * We must recurse to child tables during execution, rather than using
 * ALTER TABLE's normal prep-time recursion.
 */
static ObjectAddress
ATExecSetNotNull(List **wqueue, Relation rel, char *conName, char *colName,
				 bool recurse, bool recursing, LOCKMODE lockmode)
{
	HeapTuple	tuple;
	AttrNumber	attnum;
	ObjectAddress address;
	Constraint *constraint;
	CookedConstraint *ccon;
	List	   *cooked;
	bool		is_no_inherit = false;

	/* Guard against stack overflow due to overly deep inheritance tree. */
	check_stack_depth();

	/* At top level, permission check was done in ATPrepCmd, else do it */
	if (recursing)
	{
		ATSimplePermissions(AT_AddConstraint, rel,
							ATT_PARTITIONED_TABLE | ATT_TABLE | ATT_FOREIGN_TABLE);
		Assert(conName != NULL);
	}

	attnum = get_attnum(RelationGetRelid(rel), colName);
	if (attnum == InvalidAttrNumber)
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));

	/* Prevent them from altering a system attribute */
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	/* See if there's already a constraint */
	tuple = findNotNullConstraintAttnum(RelationGetRelid(rel), attnum);
	if (HeapTupleIsValid(tuple))
	{
		Form_pg_constraint conForm = (Form_pg_constraint) GETSTRUCT(tuple);
		bool		changed = false;

		/*
		 * Don't let a NO INHERIT constraint be changed into inherit.
		 */
		if (conForm->connoinherit && recurse)
			ereport(ERROR,
					errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					errmsg("cannot change NO INHERIT status of NOT NULL constraint \"%s\" on relation \"%s\"",
						   NameStr(conForm->conname),
						   RelationGetRelationName(rel)));

		/*
		 * If we find an appropriate constraint, we're almost done, but just
		 * need to change some properties on it: if we're recursing, increment
		 * coninhcount; if not, set conislocal if not already set.
		 */
		if (recursing)
		{
			if (pg_add_s16_overflow(conForm->coninhcount, 1,
									&conForm->coninhcount))
				ereport(ERROR,
						errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
						errmsg("too many inheritance parents"));
			changed = true;
		}
		else if (!conForm->conislocal)
		{
			conForm->conislocal = true;
			changed = true;
		}
		else if (!conForm->convalidated)
		{
			/*
			 * Flip attnotnull and convalidated, and also validate the
			 * constraint.
			 */
			return ATExecValidateConstraint(wqueue, rel, NameStr(conForm->conname),
											recurse, recursing, lockmode);
		}

		if (changed)
		{
			Relation	constr_rel;

			constr_rel = table_open(ConstraintRelationId, RowExclusiveLock);

			CatalogTupleUpdate(constr_rel, &tuple->t_self, tuple);
			ObjectAddressSet(address, ConstraintRelationId, conForm->oid);
			table_close(constr_rel, RowExclusiveLock);
		}

		if (changed)
			return address;
		else
			return InvalidObjectAddress;
	}

	/*
	 * If we're asked not to recurse, and children exist, raise an error for
	 * partitioned tables.  For inheritance, we act as if NO INHERIT had been
	 * specified.
	 */
	if (!recurse &&
		find_inheritance_children(RelationGetRelid(rel),
								  NoLock) != NIL)
	{
		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
			ereport(ERROR,
					errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					errmsg("constraint must be added to child tables too"),
					errhint("Do not specify the ONLY keyword."));
		else
			is_no_inherit = true;
	}

	/*
	 * No constraint exists; we must add one.  First determine a name to use,
	 * if we haven't already.
	 */
	if (!recursing)
	{
		Assert(conName == NULL);
		conName = ChooseConstraintName(RelationGetRelationName(rel),
									   colName, "not_null",
									   RelationGetNamespace(rel),
									   NIL);
	}

	constraint = makeNotNullConstraint(makeString(colName));
	constraint->is_no_inherit = is_no_inherit;
	constraint->conname = conName;

	/* and do it */
	cooked = AddRelationNewConstraints(rel, NIL, list_make1(constraint),
									   false, !recursing, false, NULL);
	ccon = linitial(cooked);
	ObjectAddressSet(address, ConstraintRelationId, ccon->conoid);

	/* Mark pg_attribute.attnotnull for the column and queue validation */
	set_attnotnull(wqueue, rel, attnum, true, true);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), attnum);

	/*
	 * Recurse to propagate the constraint to children that don't have one.
	 */
	if (recurse)
	{
		List	   *children;

		children = find_inheritance_children(RelationGetRelid(rel),
											 lockmode);

		foreach_oid(childoid, children)
		{
			Relation	childrel = table_open(childoid, NoLock);

			CommandCounterIncrement();

			ATExecSetNotNull(wqueue, childrel, conName, colName,
							 recurse, true, lockmode);
			table_close(childrel, NoLock);
		}
	}

	return address;
}

/*
 * NotNullImpliedByRelConstraints
 *		Does rel's existing constraints imply NOT NULL for the given attribute?
 */
static bool
NotNullImpliedByRelConstraints(Relation rel, Form_pg_attribute attr)
{
	NullTest   *nnulltest = makeNode(NullTest);

	nnulltest->arg = (Expr *) makeVar(1,
									  attr->attnum,
									  attr->atttypid,
									  attr->atttypmod,
									  attr->attcollation,
									  0);
	nnulltest->nulltesttype = IS_NOT_NULL;

	/*
	 * argisrow = false is correct even for a composite column, because
	 * attnotnull does not represent a SQL-spec IS NOT NULL test in such a
	 * case, just IS DISTINCT FROM NULL.
	 */
	nnulltest->argisrow = false;
	nnulltest->location = -1;

	if (ConstraintImpliedByRelConstraint(rel, list_make1(nnulltest), NIL))
	{
		ereport(DEBUG1,
				(errmsg_internal("existing constraints on column \"%s.%s\" are sufficient to prove that it does not contain nulls",
								 RelationGetRelationName(rel), NameStr(attr->attname))));
		return true;
	}

	return false;
}

/*
 * ALTER TABLE ALTER COLUMN SET/DROP DEFAULT
 *
 * Return the address of the affected column.
 */
static ObjectAddress
ATExecColumnDefault(Relation rel, const char *colName,
					Node *newDefault, LOCKMODE lockmode)
{
	TupleDesc	tupdesc = RelationGetDescr(rel);
	AttrNumber	attnum;
	ObjectAddress address;

	/*
	 * get the number of the attribute
	 */
	attnum = get_attnum(RelationGetRelid(rel), colName);
	if (attnum == InvalidAttrNumber)
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));

	/* Prevent them from altering a system attribute */
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	if (TupleDescAttr(tupdesc, attnum - 1)->attidentity)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("column \"%s\" of relation \"%s\" is an identity column",
						colName, RelationGetRelationName(rel)),
		/* translator: %s is an SQL ALTER command */
				 newDefault ? 0 : errhint("Use %s instead.",
										  "ALTER TABLE ... ALTER COLUMN ... DROP IDENTITY")));

	if (TupleDescAttr(tupdesc, attnum - 1)->attgenerated)
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("column \"%s\" of relation \"%s\" is a generated column",
						colName, RelationGetRelationName(rel)),
				 newDefault ?
		/* translator: %s is an SQL ALTER command */
				 errhint("Use %s instead.", "ALTER TABLE ... ALTER COLUMN ... SET EXPRESSION") :
				 (TupleDescAttr(tupdesc, attnum - 1)->attgenerated == ATTRIBUTE_GENERATED_STORED ?
				  errhint("Use %s instead.", "ALTER TABLE ... ALTER COLUMN ... DROP EXPRESSION") : 0)));

	/*
	 * Remove any old default for the column.  We use RESTRICT here for
	 * safety, but at present we do not expect anything to depend on the
	 * default.
	 *
	 * We treat removing the existing default as an internal operation when it
	 * is preparatory to adding a new default, but as a user-initiated
	 * operation when the user asked for a drop.
	 */
	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false,
					  newDefault != NULL);

	if (newDefault)
	{
		/* SET DEFAULT */
		RawColumnDefault *rawEnt;

		rawEnt = (RawColumnDefault *) palloc(sizeof(RawColumnDefault));
		rawEnt->attnum = attnum;
		rawEnt->raw_default = newDefault;
		rawEnt->generated = '\0';

		/*
		 * This function is intended for CREATE TABLE, so it processes a
		 * _list_ of defaults, but we just do one.
		 */
		AddRelationNewConstraints(rel, list_make1(rawEnt), NIL,
								  false, true, false, NULL);
	}

	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	return address;
}

/*
 * Add a pre-cooked default expression.
 *
 * Return the address of the affected column.
 */
static ObjectAddress
ATExecCookedColumnDefault(Relation rel, AttrNumber attnum,
						  Node *newDefault)
{
	ObjectAddress address;

	/* We assume no checking is required */

	/*
	 * Remove any old default for the column.  We use RESTRICT here for
	 * safety, but at present we do not expect anything to depend on the
	 * default.  (In ordinary cases, there could not be a default in place
	 * anyway, but it's possible when combining LIKE with inheritance.)
	 */
	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, false,
					  true);

	(void) StoreAttrDefault(rel, attnum, newDefault, true);

	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	return address;
}

/*
 * ALTER TABLE ALTER COLUMN ADD IDENTITY
 *
 * Return the address of the affected column.
 */
static ObjectAddress
ATExecAddIdentity(Relation rel, const char *colName,
				  Node *def, LOCKMODE lockmode, bool recurse, bool recursing)
{
	Relation	attrelation;
	HeapTuple	tuple;
	Form_pg_attribute attTup;
	AttrNumber	attnum;
	ObjectAddress address;
	ColumnDef  *cdef = castNode(ColumnDef, def);
	bool		ispartitioned;

	ispartitioned = (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
	if (ispartitioned && !recurse)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot add identity to a column of only the partitioned table"),
				 errhint("Do not specify the ONLY keyword.")));

	if (rel->rd_rel->relispartition && !recursing)
		ereport(ERROR,
				errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				errmsg("cannot add identity to a column of a partition"));

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));
	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = attTup->attnum;

	/* Can't alter a system attribute */
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	/*
	 * Creating a column as identity implies NOT NULL, so adding the identity
	 * to an existing column that is not NOT NULL would create a state that
	 * cannot be reproduced without contortions.
	 */
	if (!attTup->attnotnull)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("column \"%s\" of relation \"%s\" must be declared NOT NULL before identity can be added",
						colName, RelationGetRelationName(rel))));

	/*
	 * On the other hand, if a not-null constraint exists, then verify that
	 * it's compatible.
	 */
	if (attTup->attnotnull)
	{
		HeapTuple	contup;
		Form_pg_constraint conForm;

		contup = findNotNullConstraintAttnum(RelationGetRelid(rel),
											 attnum);
		if (!HeapTupleIsValid(contup))
			elog(ERROR, "cache lookup failed for not-null constraint on column \"%s\" of relation \"%s\"",
				 colName, RelationGetRelationName(rel));

		conForm = (Form_pg_constraint) GETSTRUCT(contup);
		if (!conForm->convalidated)
			ereport(ERROR,
					errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					errmsg("incompatible NOT VALID constraint \"%s\" on relation \"%s\"",
						   NameStr(conForm->conname), RelationGetRelationName(rel)),
					errhint("You might need to validate it using %s.",
							"ALTER TABLE ... VALIDATE CONSTRAINT"));
	}

	if (attTup->attidentity)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("column \"%s\" of relation \"%s\" is already an identity column",
						colName, RelationGetRelationName(rel))));

	if (attTup->atthasdef)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("column \"%s\" of relation \"%s\" already has a default value",
						colName, RelationGetRelationName(rel))));

	attTup->attidentity = cdef->identity;
	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  attTup->attnum);
	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	heap_freetuple(tuple);

	table_close(attrelation, RowExclusiveLock);

	/*
	 * Recurse to propagate the identity column to partitions.  Identity is
	 * not inherited in regular inheritance children.
	 */
	if (recurse && ispartitioned)
	{
		List	   *children;
		ListCell   *lc;

		children = find_inheritance_children(RelationGetRelid(rel), lockmode);

		foreach(lc, children)
		{
			Relation	childrel;

			childrel = table_open(lfirst_oid(lc), NoLock);
			ATExecAddIdentity(childrel, colName, def, lockmode, recurse, true);
			table_close(childrel, NoLock);
		}
	}

	return address;
}

/*
 * ALTER TABLE ALTER COLUMN SET { GENERATED or sequence options }
 *
 * Return the address of the affected column.
 */
static ObjectAddress
ATExecSetIdentity(Relation rel, const char *colName, Node *def,
				  LOCKMODE lockmode, bool recurse, bool recursing)
{
	ListCell   *option;
	DefElem    *generatedEl = NULL;
	HeapTuple	tuple;
	Form_pg_attribute attTup;
	AttrNumber	attnum;
	Relation	attrelation;
	ObjectAddress address;
	bool		ispartitioned;

	ispartitioned = (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
	if (ispartitioned && !recurse)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot change identity column of only the partitioned table"),
				 errhint("Do not specify the ONLY keyword.")));

	if (rel->rd_rel->relispartition && !recursing)
		ereport(ERROR,
				errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				errmsg("cannot change identity column of a partition"));

	foreach(option, castNode(List, def))
	{
		DefElem    *defel = lfirst_node(DefElem, option);

		if (strcmp(defel->defname, "generated") == 0)
		{
			if (generatedEl)
				ereport(ERROR,
						(errcode(ERRCODE_SYNTAX_ERROR),
						 errmsg("conflicting or redundant options")));
			generatedEl = defel;
		}
		else
			elog(ERROR, "option \"%s\" not recognized",
				 defel->defname);
	}

	/*
	 * Even if there is nothing to change here, we run all the checks.  There
	 * will be a subsequent ALTER SEQUENCE that relies on everything being
	 * there.
	 */

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);
	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));

	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = attTup->attnum;

	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	if (!attTup->attidentity)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("column \"%s\" of relation \"%s\" is not an identity column",
						colName, RelationGetRelationName(rel))));

	if (generatedEl)
	{
		attTup->attidentity = defGetInt32(generatedEl);
		CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);

		InvokeObjectPostAlterHook(RelationRelationId,
								  RelationGetRelid(rel),
								  attTup->attnum);
		ObjectAddressSubSet(address, RelationRelationId,
							RelationGetRelid(rel), attnum);
	}
	else
		address = InvalidObjectAddress;

	heap_freetuple(tuple);
	table_close(attrelation, RowExclusiveLock);

	/*
	 * Recurse to propagate the identity change to partitions. Identity is not
	 * inherited in regular inheritance children.
	 */
	if (generatedEl && recurse && ispartitioned)
	{
		List	   *children;
		ListCell   *lc;

		children = find_inheritance_children(RelationGetRelid(rel), lockmode);

		foreach(lc, children)
		{
			Relation	childrel;

			childrel = table_open(lfirst_oid(lc), NoLock);
			ATExecSetIdentity(childrel, colName, def, lockmode, recurse, true);
			table_close(childrel, NoLock);
		}
	}

	return address;
}

/*
 * ALTER TABLE ALTER COLUMN DROP IDENTITY
 *
 * Return the address of the affected column.
 */
static ObjectAddress
ATExecDropIdentity(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode,
				   bool recurse, bool recursing)
{
	HeapTuple	tuple;
	Form_pg_attribute attTup;
	AttrNumber	attnum;
	Relation	attrelation;
	ObjectAddress address;
	Oid			seqid;
	ObjectAddress seqaddress;
	bool		ispartitioned;

	ispartitioned = (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);
	if (ispartitioned && !recurse)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot drop identity from a column of only the partitioned table"),
				 errhint("Do not specify the ONLY keyword.")));

	if (rel->rd_rel->relispartition && !recursing)
		ereport(ERROR,
				errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				errmsg("cannot drop identity from a column of a partition"));

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);
	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));

	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = attTup->attnum;

	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	if (!attTup->attidentity)
	{
		if (!missing_ok)
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("column \"%s\" of relation \"%s\" is not an identity column",
							colName, RelationGetRelationName(rel))));
		else
		{
			ereport(NOTICE,
					(errmsg("column \"%s\" of relation \"%s\" is not an identity column, skipping",
							colName, RelationGetRelationName(rel))));
			heap_freetuple(tuple);
			table_close(attrelation, RowExclusiveLock);
			return InvalidObjectAddress;
		}
	}

	attTup->attidentity = '\0';
	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  attTup->attnum);
	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	heap_freetuple(tuple);

	table_close(attrelation, RowExclusiveLock);

	/*
	 * Recurse to drop the identity from column in partitions.  Identity is
	 * not inherited in regular inheritance children so ignore them.
	 */
	if (recurse && ispartitioned)
	{
		List	   *children;
		ListCell   *lc;

		children = find_inheritance_children(RelationGetRelid(rel), lockmode);

		foreach(lc, children)
		{
			Relation	childrel;

			childrel = table_open(lfirst_oid(lc), NoLock);
			ATExecDropIdentity(childrel, colName, false, lockmode, recurse, true);
			table_close(childrel, NoLock);
		}
	}

	if (!recursing)
	{
		/* drop the internal sequence */
		seqid = getIdentitySequence(rel, attnum, false);
		deleteDependencyRecordsForClass(RelationRelationId, seqid,
										RelationRelationId, DEPENDENCY_INTERNAL);
		CommandCounterIncrement();
		seqaddress.classId = RelationRelationId;
		seqaddress.objectId = seqid;
		seqaddress.objectSubId = 0;
		performDeletion(&seqaddress, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);
	}

	return address;
}

/*
 * ALTER TABLE ALTER COLUMN SET EXPRESSION
 *
 * Return the address of the affected column.
 */
static ObjectAddress
ATExecSetExpression(AlteredTableInfo *tab, Relation rel, const char *colName,
					Node *newExpr, LOCKMODE lockmode)
{
	HeapTuple	tuple;
	Form_pg_attribute attTup;
	AttrNumber	attnum;
	char		attgenerated;
	bool		rewrite;
	Oid			attrdefoid;
	ObjectAddress address;
	Expr	   *defval;
	NewColumnValue *newval;
	RawColumnDefault *rawEnt;

	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));

	attTup = (Form_pg_attribute) GETSTRUCT(tuple);

	attnum = attTup->attnum;
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	attgenerated = attTup->attgenerated;
	if (!attgenerated)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("column \"%s\" of relation \"%s\" is not a generated column",
						colName, RelationGetRelationName(rel))));

	/*
	 * TODO: This could be done, just need to recheck any constraints
	 * afterwards.
	 */
	if (attgenerated == ATTRIBUTE_GENERATED_VIRTUAL &&
		rel->rd_att->constr && rel->rd_att->constr->num_check > 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("ALTER TABLE / SET EXPRESSION is not supported for virtual generated columns in tables with check constraints"),
				 errdetail("Column \"%s\" of relation \"%s\" is a virtual generated column.",
						   colName, RelationGetRelationName(rel))));

	if (attgenerated == ATTRIBUTE_GENERATED_VIRTUAL && attTup->attnotnull)
		tab->verify_new_notnull = true;

	/*
	 * We need to prevent this because a change of expression could affect a
	 * row filter and inject expressions that are not permitted in a row
	 * filter.  XXX We could try to have a more precise check to catch only
	 * publications with row filters, or even re-verify the row filter
	 * expressions.
	 */
	if (attgenerated == ATTRIBUTE_GENERATED_VIRTUAL &&
		GetRelationPublications(RelationGetRelid(rel)) != NIL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("ALTER TABLE / SET EXPRESSION is not supported for virtual generated columns in tables that are part of a publication"),
				 errdetail("Column \"%s\" of relation \"%s\" is a virtual generated column.",
						   colName, RelationGetRelationName(rel))));

	rewrite = (attgenerated == ATTRIBUTE_GENERATED_STORED);

	ReleaseSysCache(tuple);

	if (rewrite)
	{
		/*
		 * Clear all the missing values if we're rewriting the table, since
		 * this renders them pointless.
		 */
		RelationClearMissing(rel);

		/* make sure we don't conflict with later attribute modifications */
		CommandCounterIncrement();

		/*
		 * Find everything that depends on the column (constraints, indexes,
		 * etc), and record enough information to let us recreate the objects
		 * after rewrite.
		 */
		RememberAllDependentForRebuilding(tab, AT_SetExpression, rel, attnum, colName);
	}

	/*
	 * Drop the dependency records of the GENERATED expression, in particular
	 * its INTERNAL dependency on the column, which would otherwise cause
	 * dependency.c to refuse to perform the deletion.
	 */
	attrdefoid = GetAttrDefaultOid(RelationGetRelid(rel), attnum);
	if (!OidIsValid(attrdefoid))
		elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
			 RelationGetRelid(rel), attnum);
	(void) deleteDependencyRecordsFor(AttrDefaultRelationId, attrdefoid, false);

	/* Make above changes visible */
	CommandCounterIncrement();

	/*
	 * Get rid of the GENERATED expression itself.  We use RESTRICT here for
	 * safety, but at present we do not expect anything to depend on the
	 * expression.
	 */
	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT,
					  false, false);

	/* Prepare to store the new expression, in the catalogs */
	rawEnt = (RawColumnDefault *) palloc(sizeof(RawColumnDefault));
	rawEnt->attnum = attnum;
	rawEnt->raw_default = newExpr;
	rawEnt->generated = attgenerated;

	/* Store the generated expression */
	AddRelationNewConstraints(rel, list_make1(rawEnt), NIL,
							  false, true, false, NULL);

	/* Make above new expression visible */
	CommandCounterIncrement();

	if (rewrite)
	{
		/* Prepare for table rewrite */
		defval = (Expr *) build_column_default(rel, attnum);

		newval = (NewColumnValue *) palloc0(sizeof(NewColumnValue));
		newval->attnum = attnum;
		newval->expr = expression_planner(defval);
		newval->is_generated = true;

		tab->newvals = lappend(tab->newvals, newval);
		tab->rewrite |= AT_REWRITE_DEFAULT_VAL;
	}

	/* Drop any pg_statistic entry for the column */
	RemoveStatistics(RelationGetRelid(rel), attnum);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), attnum);

	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	return address;
}

/*
 * ALTER TABLE ALTER COLUMN DROP EXPRESSION
 */
static void
ATPrepDropExpression(Relation rel, AlterTableCmd *cmd, bool recurse, bool recursing, LOCKMODE lockmode)
{
	/*
	 * Reject ONLY if there are child tables.  We could implement this, but it
	 * is a bit complicated.  GENERATED clauses must be attached to the column
	 * definition and cannot be added later like DEFAULT, so if a child table
	 * has a generation expression that the parent does not have, the child
	 * column will necessarily be an attislocal column.  So to implement ONLY
	 * here, we'd need extra code to update attislocal of the direct child
	 * tables, somewhat similar to how DROP COLUMN does it, so that the
	 * resulting state can be properly dumped and restored.
	 */
	if (!recurse &&
		find_inheritance_children(RelationGetRelid(rel), lockmode))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("ALTER TABLE / DROP EXPRESSION must be applied to child tables too")));

	/*
	 * Cannot drop generation expression from inherited columns.
	 */
	if (!recursing)
	{
		HeapTuple	tuple;
		Form_pg_attribute attTup;

		tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), cmd->name);
		if (!HeapTupleIsValid(tuple))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_COLUMN),
					 errmsg("column \"%s\" of relation \"%s\" does not exist",
							cmd->name, RelationGetRelationName(rel))));

		attTup = (Form_pg_attribute) GETSTRUCT(tuple);

		if (attTup->attinhcount > 0)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("cannot drop generation expression from inherited column")));
	}
}

/*
 * Return the address of the affected column.
 */
static ObjectAddress
ATExecDropExpression(Relation rel, const char *colName, bool missing_ok, LOCKMODE lockmode)
{
	HeapTuple	tuple;
	Form_pg_attribute attTup;
	AttrNumber	attnum;
	Relation	attrelation;
	Oid			attrdefoid;
	ObjectAddress address;

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);
	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));

	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = attTup->attnum;

	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	/*
	 * TODO: This could be done, but it would need a table rewrite to
	 * materialize the generated values.  Note that for the time being, we
	 * still error with missing_ok, so that we don't silently leave the column
	 * as generated.
	 */
	if (attTup->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("ALTER TABLE / DROP EXPRESSION is not supported for virtual generated columns"),
				 errdetail("Column \"%s\" of relation \"%s\" is a virtual generated column.",
						   colName, RelationGetRelationName(rel))));

	if (!attTup->attgenerated)
	{
		if (!missing_ok)
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("column \"%s\" of relation \"%s\" is not a generated column",
							colName, RelationGetRelationName(rel))));
		else
		{
			ereport(NOTICE,
					(errmsg("column \"%s\" of relation \"%s\" is not a generated column, skipping",
							colName, RelationGetRelationName(rel))));
			heap_freetuple(tuple);
			table_close(attrelation, RowExclusiveLock);
			return InvalidObjectAddress;
		}
	}

	/*
	 * Mark the column as no longer generated.  (The atthasdef flag needs to
	 * get cleared too, but RemoveAttrDefault will handle that.)
	 */
	attTup->attgenerated = '\0';
	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  attnum);
	heap_freetuple(tuple);

	table_close(attrelation, RowExclusiveLock);

	/*
	 * Drop the dependency records of the GENERATED expression, in particular
	 * its INTERNAL dependency on the column, which would otherwise cause
	 * dependency.c to refuse to perform the deletion.
	 */
	attrdefoid = GetAttrDefaultOid(RelationGetRelid(rel), attnum);
	if (!OidIsValid(attrdefoid))
		elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
			 RelationGetRelid(rel), attnum);
	(void) deleteDependencyRecordsFor(AttrDefaultRelationId, attrdefoid, false);

	/* Make above changes visible */
	CommandCounterIncrement();

	/*
	 * Get rid of the GENERATED expression itself.  We use RESTRICT here for
	 * safety, but at present we do not expect anything to depend on the
	 * default.
	 */
	RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT,
					  false, false);

	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	return address;
}

/*
 * ALTER TABLE ALTER COLUMN SET STATISTICS
 *
 * Return value is the address of the modified column
 */
static ObjectAddress
ATExecSetStatistics(Relation rel, const char *colName, int16 colNum, Node *newValue, LOCKMODE lockmode)
{
	int			newtarget = 0;
	bool		newtarget_default;
	Relation	attrelation;
	HeapTuple	tuple,
				newtuple;
	Form_pg_attribute attrtuple;
	AttrNumber	attnum;
	ObjectAddress address;
	Datum		repl_val[Natts_pg_attribute];
	bool		repl_null[Natts_pg_attribute];
	bool		repl_repl[Natts_pg_attribute];

	/*
	 * We allow referencing columns by numbers only for indexes, since table
	 * column numbers could contain gaps if columns are later dropped.
	 */
	if (rel->rd_rel->relkind != RELKIND_INDEX &&
		rel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX &&
		!colName)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot refer to non-index column by number")));

	/* -1 was used in previous versions for the default setting */
	if (newValue && intVal(newValue) != -1)
	{
		newtarget = intVal(newValue);
		newtarget_default = false;
	}
	else
		newtarget_default = true;

	if (!newtarget_default)
	{
		/*
		 * Limit target to a sane range
		 */
		if (newtarget < 0)
		{
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
					 errmsg("statistics target %d is too low",
							newtarget)));
		}
		else if (newtarget > MAX_STATISTICS_TARGET)
		{
			newtarget = MAX_STATISTICS_TARGET;
			ereport(WARNING,
					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
					 errmsg("lowering statistics target to %d",
							newtarget)));
		}
	}

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);

	if (colName)
	{
		tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);

		if (!HeapTupleIsValid(tuple))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_COLUMN),
					 errmsg("column \"%s\" of relation \"%s\" does not exist",
							colName, RelationGetRelationName(rel))));
	}
	else
	{
		tuple = SearchSysCacheAttNum(RelationGetRelid(rel), colNum);

		if (!HeapTupleIsValid(tuple))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_COLUMN),
					 errmsg("column number %d of relation \"%s\" does not exist",
							colNum, RelationGetRelationName(rel))));
	}

	attrtuple = (Form_pg_attribute) GETSTRUCT(tuple);

	attnum = attrtuple->attnum;
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	/*
	 * Prevent this as long as the ANALYZE code skips virtual generated
	 * columns.
	 */
	if (attrtuple->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter statistics on virtual generated column \"%s\"",
						colName)));

	if (rel->rd_rel->relkind == RELKIND_INDEX ||
		rel->rd_rel->relkind == RELKIND_PARTITIONED_INDEX)
	{
		if (attnum > rel->rd_index->indnkeyatts)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot alter statistics on included column \"%s\" of index \"%s\"",
							NameStr(attrtuple->attname), RelationGetRelationName(rel))));
		else if (rel->rd_index->indkey.values[attnum - 1] != 0)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot alter statistics on non-expression column \"%s\" of index \"%s\"",
							NameStr(attrtuple->attname), RelationGetRelationName(rel)),
					 errhint("Alter statistics on table column instead.")));
	}

	/* Build new tuple. */
	memset(repl_null, false, sizeof(repl_null));
	memset(repl_repl, false, sizeof(repl_repl));
	if (!newtarget_default)
		repl_val[Anum_pg_attribute_attstattarget - 1] = newtarget;
	else
		repl_null[Anum_pg_attribute_attstattarget - 1] = true;
	repl_repl[Anum_pg_attribute_attstattarget - 1] = true;
	newtuple = heap_modify_tuple(tuple, RelationGetDescr(attrelation),
								 repl_val, repl_null, repl_repl);
	CatalogTupleUpdate(attrelation, &tuple->t_self, newtuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  attrtuple->attnum);
	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);

	heap_freetuple(newtuple);

	ReleaseSysCache(tuple);

	table_close(attrelation, RowExclusiveLock);

	return address;
}

/*
 * Return value is the address of the modified column
 */
static ObjectAddress
ATExecSetOptions(Relation rel, const char *colName, Node *options,
				 bool isReset, LOCKMODE lockmode)
{
	Relation	attrelation;
	HeapTuple	tuple,
				newtuple;
	Form_pg_attribute attrtuple;
	AttrNumber	attnum;
	Datum		datum,
				newOptions;
	bool		isnull;
	ObjectAddress address;
	Datum		repl_val[Natts_pg_attribute];
	bool		repl_null[Natts_pg_attribute];
	bool		repl_repl[Natts_pg_attribute];

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);

	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);

	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));
	attrtuple = (Form_pg_attribute) GETSTRUCT(tuple);

	attnum = attrtuple->attnum;
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	/* Generate new proposed attoptions (text array) */
	datum = SysCacheGetAttr(ATTNAME, tuple, Anum_pg_attribute_attoptions,
							&isnull);
	newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
									 castNode(List, options), NULL, NULL,
									 false, isReset);
	/* Validate new options */
	(void) attribute_reloptions(newOptions, true);

	/* Build new tuple. */
	memset(repl_null, false, sizeof(repl_null));
	memset(repl_repl, false, sizeof(repl_repl));
	if (newOptions != (Datum) 0)
		repl_val[Anum_pg_attribute_attoptions - 1] = newOptions;
	else
		repl_null[Anum_pg_attribute_attoptions - 1] = true;
	repl_repl[Anum_pg_attribute_attoptions - 1] = true;
	newtuple = heap_modify_tuple(tuple, RelationGetDescr(attrelation),
								 repl_val, repl_null, repl_repl);

	/* Update system catalog. */
	CatalogTupleUpdate(attrelation, &newtuple->t_self, newtuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  attrtuple->attnum);
	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);

	heap_freetuple(newtuple);

	ReleaseSysCache(tuple);

	table_close(attrelation, RowExclusiveLock);

	return address;
}

/*
 * Helper function for ATExecSetStorage and ATExecSetCompression
 *
 * Set the attstorage and/or attcompression fields for index columns
 * associated with the specified table column.
 */
static void
SetIndexStorageProperties(Relation rel, Relation attrelation,
						  AttrNumber attnum,
						  bool setstorage, char newstorage,
						  bool setcompression, char newcompression,
						  LOCKMODE lockmode)
{
	ListCell   *lc;

	foreach(lc, RelationGetIndexList(rel))
	{
		Oid			indexoid = lfirst_oid(lc);
		Relation	indrel;
		AttrNumber	indattnum = 0;
		HeapTuple	tuple;

		indrel = index_open(indexoid, lockmode);

		for (int i = 0; i < indrel->rd_index->indnatts; i++)
		{
			if (indrel->rd_index->indkey.values[i] == attnum)
			{
				indattnum = i + 1;
				break;
			}
		}

		if (indattnum == 0)
		{
			index_close(indrel, lockmode);
			continue;
		}

		tuple = SearchSysCacheCopyAttNum(RelationGetRelid(indrel), indattnum);

		if (HeapTupleIsValid(tuple))
		{
			Form_pg_attribute attrtuple = (Form_pg_attribute) GETSTRUCT(tuple);

			if (setstorage)
				attrtuple->attstorage = newstorage;

			if (setcompression)
				attrtuple->attcompression = newcompression;

			CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);

			InvokeObjectPostAlterHook(RelationRelationId,
									  RelationGetRelid(rel),
									  attrtuple->attnum);

			heap_freetuple(tuple);
		}

		index_close(indrel, lockmode);
	}
}

/*
 * ALTER TABLE ALTER COLUMN SET STORAGE
 *
 * Return value is the address of the modified column
 */
static ObjectAddress
ATExecSetStorage(Relation rel, const char *colName, Node *newValue, LOCKMODE lockmode)
{
	Relation	attrelation;
	HeapTuple	tuple;
	Form_pg_attribute attrtuple;
	AttrNumber	attnum;
	ObjectAddress address;

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);

	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));
	attrtuple = (Form_pg_attribute) GETSTRUCT(tuple);

	attnum = attrtuple->attnum;
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"",
						colName)));

	attrtuple->attstorage = GetAttributeStorage(attrtuple->atttypid, strVal(newValue));

	CatalogTupleUpdate(attrelation, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  attrtuple->attnum);

	/*
	 * Apply the change to indexes as well (only for simple index columns,
	 * matching behavior of index.c ConstructTupleDescriptor()).
	 */
	SetIndexStorageProperties(rel, attrelation, attnum,
							  true, attrtuple->attstorage,
							  false, 0,
							  lockmode);

	heap_freetuple(tuple);

	table_close(attrelation, RowExclusiveLock);

	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	return address;
}


/*
 * ALTER TABLE DROP COLUMN
 *
 * DROP COLUMN cannot use the normal ALTER TABLE recursion mechanism,
 * because we have to decide at runtime whether to recurse or not depending
 * on whether attinhcount goes to zero or not.  (We can't check this in a
 * static pre-pass because it won't handle multiple inheritance situations
 * correctly.)
 */
static void
ATPrepDropColumn(List **wqueue, Relation rel, bool recurse, bool recursing,
				 AlterTableCmd *cmd, LOCKMODE lockmode,
				 AlterTableUtilityContext *context)
{
	if (rel->rd_rel->reloftype && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot drop column from typed table")));

	if (rel->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
		ATTypedTableRecursion(wqueue, rel, cmd, lockmode, context);

	if (recurse)
		cmd->recurse = true;
}

/*
 * Drops column 'colName' from relation 'rel' and returns the address of the
 * dropped column.  The column is also dropped (or marked as no longer
 * inherited from relation) from the relation's inheritance children, if any.
 *
 * In the recursive invocations for inheritance child relations, instead of
 * dropping the column directly (if to be dropped at all), its object address
 * is added to 'addrs', which must be non-NULL in such invocations.  All
 * columns are dropped at the same time after all the children have been
 * checked recursively.
 */
static ObjectAddress
ATExecDropColumn(List **wqueue, Relation rel, const char *colName,
				 DropBehavior behavior,
				 bool recurse, bool recursing,
				 bool missing_ok, LOCKMODE lockmode,
				 ObjectAddresses *addrs)
{
	HeapTuple	tuple;
	Form_pg_attribute targetatt;
	AttrNumber	attnum;
	List	   *children;
	ObjectAddress object;
	bool		is_expr;

	/* At top level, permission check was done in ATPrepCmd, else do it */
	if (recursing)
		ATSimplePermissions(AT_DropColumn, rel,
							ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);

	/* Initialize addrs on the first invocation */
	Assert(!recursing || addrs != NULL);

	/* since this function recurses, it could be driven to stack overflow */
	check_stack_depth();

	if (!recursing)
		addrs = new_object_addresses();

	/*
	 * get the number of the attribute
	 */
	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
	{
		if (!missing_ok)
		{
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_COLUMN),
					 errmsg("column \"%s\" of relation \"%s\" does not exist",
							colName, RelationGetRelationName(rel))));
		}
		else
		{
			ereport(NOTICE,
					(errmsg("column \"%s\" of relation \"%s\" does not exist, skipping",
							colName, RelationGetRelationName(rel))));
			return InvalidObjectAddress;
		}
	}
	targetatt = (Form_pg_attribute) GETSTRUCT(tuple);

	attnum = targetatt->attnum;

	/* Can't drop a system attribute */
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot drop system column \"%s\"",
						colName)));

	/*
	 * Don't drop inherited columns, unless recursing (presumably from a drop
	 * of the parent column)
	 */
	if (targetatt->attinhcount > 0 && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot drop inherited column \"%s\"",
						colName)));

	/*
	 * Don't drop columns used in the partition key, either.  (If we let this
	 * go through, the key column's dependencies would cause a cascaded drop
	 * of the whole table, which is surely not what the user expected.)
	 */
	if (has_partition_attrs(rel,
							bms_make_singleton(attnum - FirstLowInvalidHeapAttributeNumber),
							&is_expr))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot drop column \"%s\" because it is part of the partition key of relation \"%s\"",
						colName, RelationGetRelationName(rel))));

	ReleaseSysCache(tuple);

	/*
	 * Propagate to children as appropriate.  Unlike most other ALTER
	 * routines, we have to do this one level of recursion at a time; we can't
	 * use find_all_inheritors to do it in one pass.
	 */
	children =
		find_inheritance_children(RelationGetRelid(rel), lockmode);

	if (children)
	{
		Relation	attr_rel;
		ListCell   *child;

		/*
		 * In case of a partitioned table, the column must be dropped from the
		 * partitions as well.
		 */
		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE && !recurse)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("cannot drop column from only the partitioned table when partitions exist"),
					 errhint("Do not specify the ONLY keyword.")));

		attr_rel = table_open(AttributeRelationId, RowExclusiveLock);
		foreach(child, children)
		{
			Oid			childrelid = lfirst_oid(child);
			Relation	childrel;
			Form_pg_attribute childatt;

			/* find_inheritance_children already got lock */
			childrel = table_open(childrelid, NoLock);
			CheckAlterTableIsSafe(childrel);

			tuple = SearchSysCacheCopyAttName(childrelid, colName);
			if (!HeapTupleIsValid(tuple))	/* shouldn't happen */
				elog(ERROR, "cache lookup failed for attribute \"%s\" of relation %u",
					 colName, childrelid);
			childatt = (Form_pg_attribute) GETSTRUCT(tuple);

			if (childatt->attinhcount <= 0) /* shouldn't happen */
				elog(ERROR, "relation %u has non-inherited attribute \"%s\"",
					 childrelid, colName);

			if (recurse)
			{
				/*
				 * If the child column has other definition sources, just
				 * decrement its inheritance count; if not, recurse to delete
				 * it.
				 */
				if (childatt->attinhcount == 1 && !childatt->attislocal)
				{
					/* Time to delete this child column, too */
					ATExecDropColumn(wqueue, childrel, colName,
									 behavior, true, true,
									 false, lockmode, addrs);
				}
				else
				{
					/* Child column must survive my deletion */
					childatt->attinhcount--;

					CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);

					/* Make update visible */
					CommandCounterIncrement();
				}
			}
			else
			{
				/*
				 * If we were told to drop ONLY in this table (no recursion),
				 * we need to mark the inheritors' attributes as locally
				 * defined rather than inherited.
				 */
				childatt->attinhcount--;
				childatt->attislocal = true;

				CatalogTupleUpdate(attr_rel, &tuple->t_self, tuple);

				/* Make update visible */
				CommandCounterIncrement();
			}

			heap_freetuple(tuple);

			table_close(childrel, NoLock);
		}
		table_close(attr_rel, RowExclusiveLock);
	}

	/* Add object to delete */
	object.classId = RelationRelationId;
	object.objectId = RelationGetRelid(rel);
	object.objectSubId = attnum;
	add_exact_object_address(&object, addrs);

	if (!recursing)
	{
		/* Recursion has ended, drop everything that was collected */
		performMultipleDeletions(addrs, behavior, 0);
		free_object_addresses(addrs);
	}

	return object;
}

/*
 * Prepare to add a primary key on a table, by adding not-null constraints
 * on all columns.
 *
 * The not-null constraints for a primary key must cover the whole inheritance
 * hierarchy (failing to ensure that leads to funny corner cases).  For the
 * normal case where we're asked to recurse, this routine checks if the
 * not-null constraints exist already, and if not queues a requirement for
 * them to be created by phase 2.
 *
 * For the case where we're asked not to recurse, we verify that a not-null
 * constraint exists on each column of each (direct) child table, throwing an
 * error if not.  Not throwing an error would also work, because a not-null
 * constraint would be created anyway, but it'd cause a silent scan of the
 * child table to verify absence of nulls.  We prefer to let the user know so
 * that they can add the constraint manually without having to hold
 * AccessExclusiveLock while at it.
 *
 * However, it's also important that we do not acquire locks on children if
 * the not-null constraints already exist on the parent, to avoid risking
 * deadlocks during parallel pg_restore of PKs on partitioned tables.
 */
static void
ATPrepAddPrimaryKey(List **wqueue, Relation rel, AlterTableCmd *cmd,
					bool recurse, LOCKMODE lockmode,
					AlterTableUtilityContext *context)
{
	Constraint *pkconstr;
	List	   *children = NIL;
	bool		got_children = false;

	pkconstr = castNode(Constraint, cmd->def);
	if (pkconstr->contype != CONSTR_PRIMARY)
		return;

	/* Verify that columns are not-null, or request that they be made so */
	foreach_node(String, column, pkconstr->keys)
	{
		AlterTableCmd *newcmd;
		Constraint *nnconstr;
		HeapTuple	tuple;

		/*
		 * First check if a suitable constraint exists.  If it does, we don't
		 * need to request another one.  We do need to bail out if it's not
		 * valid, though.
		 */
		tuple = findNotNullConstraint(RelationGetRelid(rel), strVal(column));
		if (tuple != NULL)
		{
			verifyNotNullPKCompatible(tuple, strVal(column));

			/* All good with this one; don't request another */
			heap_freetuple(tuple);
			continue;
		}
		else if (!recurse)
		{
			/*
			 * No constraint on this column.  Asked not to recurse, we won't
			 * create one here, but verify that all children have one.
			 */
			if (!got_children)
			{
				children = find_inheritance_children(RelationGetRelid(rel),
													 lockmode);
				/* only search for children on the first time through */
				got_children = true;
			}

			foreach_oid(childrelid, children)
			{
				HeapTuple	tup;

				tup = findNotNullConstraint(childrelid, strVal(column));
				if (!tup)
					ereport(ERROR,
							errmsg("column \"%s\" of table \"%s\" is not marked NOT NULL",
								   strVal(column), get_rel_name(childrelid)));
				/* verify it's good enough */
				verifyNotNullPKCompatible(tup, strVal(column));
			}
		}

		/* This column is not already not-null, so add it to the queue */
		nnconstr = makeNotNullConstraint(column);

		newcmd = makeNode(AlterTableCmd);
		newcmd->subtype = AT_AddConstraint;
		/* note we force recurse=true here; see above */
		newcmd->recurse = true;
		newcmd->def = (Node *) nnconstr;

		ATPrepCmd(wqueue, rel, newcmd, true, false, lockmode, context);
	}
}

/*
 * Verify whether the given not-null constraint is compatible with a
 * primary key.  If not, an error is thrown.
 */
static void
verifyNotNullPKCompatible(HeapTuple tuple, const char *colname)
{
	Form_pg_constraint conForm = (Form_pg_constraint) GETSTRUCT(tuple);

	if (conForm->contype != CONSTRAINT_NOTNULL)
		elog(ERROR, "constraint %u is not a not-null constraint", conForm->oid);

	/* a NO INHERIT constraint is no good */
	if (conForm->connoinherit)
		ereport(ERROR,
				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				errmsg("cannot create primary key on column \"%s\"", colname),
		/*- translator: fourth %s is a constraint characteristic such as NOT VALID */
				errdetail("The constraint \"%s\" on column \"%s\" of table \"%s\", marked %s, is incompatible with a primary key.",
						  NameStr(conForm->conname), colname,
						  get_rel_name(conForm->conrelid), "NO INHERIT"),
				errhint("You might need to make the existing constraint inheritable using %s.",
						"ALTER TABLE ... ALTER CONSTRAINT ... INHERIT"));

	/* an unvalidated constraint is no good */
	if (!conForm->convalidated)
		ereport(ERROR,
				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				errmsg("cannot create primary key on column \"%s\"", colname),
		/*- translator: fourth %s is a constraint characteristic such as NOT VALID */
				errdetail("The constraint \"%s\" on column \"%s\" of table \"%s\", marked %s, is incompatible with a primary key.",
						  NameStr(conForm->conname), colname,
						  get_rel_name(conForm->conrelid), "NOT VALID"),
				errhint("You might need to validate it using %s.",
						"ALTER TABLE ... VALIDATE CONSTRAINT"));
}

/*
 * ALTER TABLE ADD INDEX
 *
 * There is no such command in the grammar, but parse_utilcmd.c converts
 * UNIQUE and PRIMARY KEY constraints into AT_AddIndex subcommands.  This lets
 * us schedule creation of the index at the appropriate time during ALTER.
 *
 * Return value is the address of the new index.
 */
static ObjectAddress
ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
			   IndexStmt *stmt, bool is_rebuild, LOCKMODE lockmode)
{
	bool		check_rights;
	bool		skip_build;
	bool		quiet;
	ObjectAddress address;

	Assert(IsA(stmt, IndexStmt));
	Assert(!stmt->concurrent);

	/* The IndexStmt has already been through transformIndexStmt */
	Assert(stmt->transformed);

	/* suppress schema rights check when rebuilding existing index */
	check_rights = !is_rebuild;
	/* skip index build if phase 3 will do it or we're reusing an old one */
	skip_build = tab->rewrite > 0 || RelFileNumberIsValid(stmt->oldNumber);
	/* suppress notices when rebuilding existing index */
	quiet = is_rebuild;

	address = DefineIndex(RelationGetRelid(rel),
						  stmt,
						  InvalidOid,	/* no predefined OID */
						  InvalidOid,	/* no parent index */
						  InvalidOid,	/* no parent constraint */
						  -1,	/* total_parts unknown */
						  true, /* is_alter_table */
						  check_rights,
						  false,	/* check_not_in_use - we did it already */
						  skip_build,
						  quiet);

	/*
	 * If TryReuseIndex() stashed a relfilenumber for us, we used it for the
	 * new index instead of building from scratch.  Restore associated fields.
	 * This may store InvalidSubTransactionId in both fields, in which case
	 * relcache.c will assume it can rebuild the relcache entry.  Hence, do
	 * this after the CCI that made catalog rows visible to any rebuild.  The
	 * DROP of the old edition of this index will have scheduled the storage
	 * for deletion at commit, so cancel that pending deletion.
	 */
	if (RelFileNumberIsValid(stmt->oldNumber))
	{
		Relation	irel = index_open(address.objectId, NoLock);

		irel->rd_createSubid = stmt->oldCreateSubid;
		irel->rd_firstRelfilelocatorSubid = stmt->oldFirstRelfilelocatorSubid;
		RelationPreserveStorage(irel->rd_locator, true);
		index_close(irel, NoLock);
	}

	return address;
}

/*
 * ALTER TABLE ADD STATISTICS
 *
 * This is no such command in the grammar, but we use this internally to add
 * AT_ReAddStatistics subcommands to rebuild extended statistics after a table
 * column type change.
 */
static ObjectAddress
ATExecAddStatistics(AlteredTableInfo *tab, Relation rel,
					CreateStatsStmt *stmt, bool is_rebuild, LOCKMODE lockmode)
{
	ObjectAddress address;

	Assert(IsA(stmt, CreateStatsStmt));

	/* The CreateStatsStmt has already been through transformStatsStmt */
	Assert(stmt->transformed);

	address = CreateStatistics(stmt, !is_rebuild);

	return address;
}

/*
 * ALTER TABLE ADD CONSTRAINT USING INDEX
 *
 * Returns the address of the new constraint.
 */
static ObjectAddress
ATExecAddIndexConstraint(AlteredTableInfo *tab, Relation rel,
						 IndexStmt *stmt, LOCKMODE lockmode)
{
	Oid			index_oid = stmt->indexOid;
	Relation	indexRel;
	char	   *indexName;
	IndexInfo  *indexInfo;
	char	   *constraintName;
	char		constraintType;
	ObjectAddress address;
	bits16		flags;

	Assert(IsA(stmt, IndexStmt));
	Assert(OidIsValid(index_oid));
	Assert(stmt->isconstraint);

	/*
	 * Doing this on partitioned tables is not a simple feature to implement,
	 * so let's punt for now.
	 */
	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("ALTER TABLE / ADD CONSTRAINT USING INDEX is not supported on partitioned tables")));

	indexRel = index_open(index_oid, AccessShareLock);

	indexName = pstrdup(RelationGetRelationName(indexRel));

	indexInfo = BuildIndexInfo(indexRel);

	/* this should have been checked at parse time */
	if (!indexInfo->ii_Unique)
		elog(ERROR, "index \"%s\" is not unique", indexName);

	/*
	 * Determine name to assign to constraint.  We require a constraint to
	 * have the same name as the underlying index; therefore, use the index's
	 * existing name as the default constraint name, and if the user
	 * explicitly gives some other name for the constraint, rename the index
	 * to match.
	 */
	constraintName = stmt->idxname;
	if (constraintName == NULL)
		constraintName = indexName;
	else if (strcmp(constraintName, indexName) != 0)
	{
		ereport(NOTICE,
				(errmsg("ALTER TABLE / ADD CONSTRAINT USING INDEX will rename index \"%s\" to \"%s\"",
						indexName, constraintName)));
		RenameRelationInternal(index_oid, constraintName, false, true);
	}

	/* Extra checks needed if making primary key */
	if (stmt->primary)
		index_check_primary_key(rel, indexInfo, true, stmt);

	/* Note we currently don't support EXCLUSION constraints here */
	if (stmt->primary)
		constraintType = CONSTRAINT_PRIMARY;
	else
		constraintType = CONSTRAINT_UNIQUE;

	/* Create the catalog entries for the constraint */
	flags = INDEX_CONSTR_CREATE_UPDATE_INDEX |
		INDEX_CONSTR_CREATE_REMOVE_OLD_DEPS |
		(stmt->initdeferred ? INDEX_CONSTR_CREATE_INIT_DEFERRED : 0) |
		(stmt->deferrable ? INDEX_CONSTR_CREATE_DEFERRABLE : 0) |
		(stmt->primary ? INDEX_CONSTR_CREATE_MARK_AS_PRIMARY : 0);

	address = index_constraint_create(rel,
									  index_oid,
									  InvalidOid,
									  indexInfo,
									  constraintName,
									  constraintType,
									  flags,
									  allowSystemTableMods,
									  false);	/* is_internal */

	index_close(indexRel, NoLock);

	return address;
}

/*
 * ALTER TABLE ADD CONSTRAINT
 *
 * Return value is the address of the new constraint; if no constraint was
 * added, InvalidObjectAddress is returned.
 */
static ObjectAddress
ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
					Constraint *newConstraint, bool recurse, bool is_readd,
					LOCKMODE lockmode)
{
	ObjectAddress address = InvalidObjectAddress;

	Assert(IsA(newConstraint, Constraint));

	/*
	 * Currently, we only expect to see CONSTR_CHECK, CONSTR_NOTNULL and
	 * CONSTR_FOREIGN nodes arriving here (see the preprocessing done in
	 * parse_utilcmd.c).
	 */
	switch (newConstraint->contype)
	{
		case CONSTR_CHECK:
		case CONSTR_NOTNULL:
			address =
				ATAddCheckNNConstraint(wqueue, tab, rel,
									   newConstraint, recurse, false, is_readd,
									   lockmode);
			break;

		case CONSTR_FOREIGN:

			/*
			 * Assign or validate constraint name
			 */
			if (newConstraint->conname)
			{
				if (ConstraintNameIsUsed(CONSTRAINT_RELATION,
										 RelationGetRelid(rel),
										 newConstraint->conname))
					ereport(ERROR,
							(errcode(ERRCODE_DUPLICATE_OBJECT),
							 errmsg("constraint \"%s\" for relation \"%s\" already exists",
									newConstraint->conname,
									RelationGetRelationName(rel))));
			}
			else
				newConstraint->conname =
					ChooseConstraintName(RelationGetRelationName(rel),
										 ChooseForeignKeyConstraintNameAddition(newConstraint->fk_attrs),
										 "fkey",
										 RelationGetNamespace(rel),
										 NIL);

			address = ATAddForeignKeyConstraint(wqueue, tab, rel,
												newConstraint,
												recurse, false,
												lockmode);
			break;

		default:
			elog(ERROR, "unrecognized constraint type: %d",
				 (int) newConstraint->contype);
	}

	return address;
}

/*
 * Generate the column-name portion of the constraint name for a new foreign
 * key given the list of column names that reference the referenced
 * table.  This will be passed to ChooseConstraintName along with the parent
 * table name and the "fkey" suffix.
 *
 * We know that less than NAMEDATALEN characters will actually be used, so we
 * can truncate the result once we've generated that many.
 *
 * XXX see also ChooseExtendedStatisticNameAddition and
 * ChooseIndexNameAddition.
 */
static char *
ChooseForeignKeyConstraintNameAddition(List *colnames)
{
	char		buf[NAMEDATALEN * 2];
	int			buflen = 0;
	ListCell   *lc;

	buf[0] = '\0';
	foreach(lc, colnames)
	{
		const char *name = strVal(lfirst(lc));

		if (buflen > 0)
			buf[buflen++] = '_';	/* insert _ between names */

		/*
		 * At this point we have buflen <= NAMEDATALEN.  name should be less
		 * than NAMEDATALEN already, but use strlcpy for paranoia.
		 */
		strlcpy(buf + buflen, name, NAMEDATALEN);
		buflen += strlen(buf + buflen);
		if (buflen >= NAMEDATALEN)
			break;
	}
	return pstrdup(buf);
}

/*
 * Add a check or not-null constraint to a single table and its children.
 * Returns the address of the constraint added to the parent relation,
 * if one gets added, or InvalidObjectAddress otherwise.
 *
 * Subroutine for ATExecAddConstraint.
 *
 * We must recurse to child tables during execution, rather than using
 * ALTER TABLE's normal prep-time recursion.  The reason is that all the
 * constraints *must* be given the same name, else they won't be seen as
 * related later.  If the user didn't explicitly specify a name, then
 * AddRelationNewConstraints would normally assign different names to the
 * child constraints.  To fix that, we must capture the name assigned at
 * the parent table and pass that down.
 */
static ObjectAddress
ATAddCheckNNConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
					   Constraint *constr, bool recurse, bool recursing,
					   bool is_readd, LOCKMODE lockmode)
{
	List	   *newcons;
	ListCell   *lcon;
	List	   *children;
	ListCell   *child;
	ObjectAddress address = InvalidObjectAddress;

	/* Guard against stack overflow due to overly deep inheritance tree. */
	check_stack_depth();

	/* At top level, permission check was done in ATPrepCmd, else do it */
	if (recursing)
		ATSimplePermissions(AT_AddConstraint, rel,
							ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);

	/*
	 * Call AddRelationNewConstraints to do the work, making sure it works on
	 * a copy of the Constraint so transformExpr can't modify the original. It
	 * returns a list of cooked constraints.
	 *
	 * If the constraint ends up getting merged with a pre-existing one, it's
	 * omitted from the returned list, which is what we want: we do not need
	 * to do any validation work.  That can only happen at child tables,
	 * though, since we disallow merging at the top level.
	 */
	newcons = AddRelationNewConstraints(rel, NIL,
										list_make1(copyObject(constr)),
										recursing || is_readd,	/* allow_merge */
										!recursing, /* is_local */
										is_readd,	/* is_internal */
										NULL);	/* queryString not available
												 * here */

	/* we don't expect more than one constraint here */
	Assert(list_length(newcons) <= 1);

	/* Add each to-be-validated constraint to Phase 3's queue */
	foreach(lcon, newcons)
	{
		CookedConstraint *ccon = (CookedConstraint *) lfirst(lcon);

		if (!ccon->skip_validation && ccon->contype != CONSTR_NOTNULL)
		{
			NewConstraint *newcon;

			newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
			newcon->name = ccon->name;
			newcon->contype = ccon->contype;
			newcon->qual = ccon->expr;

			tab->constraints = lappend(tab->constraints, newcon);
		}

		/* Save the actually assigned name if it was defaulted */
		if (constr->conname == NULL)
			constr->conname = ccon->name;

		/*
		 * If adding a valid not-null constraint, set the pg_attribute flag
		 * and tell phase 3 to verify existing rows, if needed.  For an
		 * invalid constraint, just set attnotnull, without queueing
		 * verification.
		 */
		if (constr->contype == CONSTR_NOTNULL)
			set_attnotnull(wqueue, rel, ccon->attnum,
						   !constr->skip_validation,
						   !constr->skip_validation);

		ObjectAddressSet(address, ConstraintRelationId, ccon->conoid);
	}

	/* At this point we must have a locked-down name to use */
	Assert(newcons == NIL || constr->conname != NULL);

	/* Advance command counter in case same table is visited multiple times */
	CommandCounterIncrement();

	/*
	 * If the constraint got merged with an existing constraint, we're done.
	 * We mustn't recurse to child tables in this case, because they've
	 * already got the constraint, and visiting them again would lead to an
	 * incorrect value for coninhcount.
	 */
	if (newcons == NIL)
		return address;

	/*
	 * If adding a NO INHERIT constraint, no need to find our children.
	 */
	if (constr->is_no_inherit)
		return address;

	/*
	 * Propagate to children as appropriate.  Unlike most other ALTER
	 * routines, we have to do this one level of recursion at a time; we can't
	 * use find_all_inheritors to do it in one pass.
	 */
	children =
		find_inheritance_children(RelationGetRelid(rel), lockmode);

	/*
	 * Check if ONLY was specified with ALTER TABLE.  If so, allow the
	 * constraint creation only if there are no children currently. Error out
	 * otherwise.
	 */
	if (!recurse && children != NIL)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("constraint must be added to child tables too")));

	/*
	 * Recurse to create the constraint on each child.
	 */
	foreach(child, children)
	{
		Oid			childrelid = lfirst_oid(child);
		Relation	childrel;
		AlteredTableInfo *childtab;

		/* find_inheritance_children already got lock */
		childrel = table_open(childrelid, NoLock);
		CheckAlterTableIsSafe(childrel);

		/* Find or create work queue entry for this table */
		childtab = ATGetQueueEntry(wqueue, childrel);

		/* Recurse to this child */
		ATAddCheckNNConstraint(wqueue, childtab, childrel,
							   constr, recurse, true, is_readd, lockmode);

		table_close(childrel, NoLock);
	}

	return address;
}

/*
 * Add a foreign-key constraint to a single table; return the new constraint's
 * address.
 *
 * Subroutine for ATExecAddConstraint.  Must already hold exclusive
 * lock on the rel, and have done appropriate validity checks for it.
 * We do permissions checks here, however.
 *
 * When the referenced or referencing tables (or both) are partitioned,
 * multiple pg_constraint rows are required -- one for each partitioned table
 * and each partition on each side (fortunately, not one for every combination
 * thereof).  We also need action triggers on each leaf partition on the
 * referenced side, and check triggers on each leaf partition on the
 * referencing side.
 */
static ObjectAddress
ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
						  Constraint *fkconstraint,
						  bool recurse, bool recursing, LOCKMODE lockmode)
{
	Relation	pkrel;
	int16		pkattnum[INDEX_MAX_KEYS] = {0};
	int16		fkattnum[INDEX_MAX_KEYS] = {0};
	Oid			pktypoid[INDEX_MAX_KEYS] = {0};
	Oid			fktypoid[INDEX_MAX_KEYS] = {0};
	Oid			pkcolloid[INDEX_MAX_KEYS] = {0};
	Oid			fkcolloid[INDEX_MAX_KEYS] = {0};
	Oid			opclasses[INDEX_MAX_KEYS] = {0};
	Oid			pfeqoperators[INDEX_MAX_KEYS] = {0};
	Oid			ppeqoperators[INDEX_MAX_KEYS] = {0};
	Oid			ffeqoperators[INDEX_MAX_KEYS] = {0};
	int16		fkdelsetcols[INDEX_MAX_KEYS] = {0};
	bool		with_period;
	bool		pk_has_without_overlaps;
	int			i;
	int			numfks,
				numpks,
				numfkdelsetcols;
	Oid			indexOid;
	bool		old_check_ok;
	ObjectAddress address;
	ListCell   *old_pfeqop_item = list_head(fkconstraint->old_conpfeqop);

	/*
	 * Grab ShareRowExclusiveLock on the pk table, so that someone doesn't
	 * delete rows out from under us.
	 */
	if (OidIsValid(fkconstraint->old_pktable_oid))
		pkrel = table_open(fkconstraint->old_pktable_oid, ShareRowExclusiveLock);
	else
		pkrel = table_openrv(fkconstraint->pktable, ShareRowExclusiveLock);

	/*
	 * Validity checks (permission checks wait till we have the column
	 * numbers)
	 */
	if (!recurse && rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				errcode(ERRCODE_WRONG_OBJECT_TYPE),
				errmsg("cannot use ONLY for foreign key on partitioned table \"%s\" referencing relation \"%s\"",
					   RelationGetRelationName(rel),
					   RelationGetRelationName(pkrel)));

	if (pkrel->rd_rel->relkind != RELKIND_RELATION &&
		pkrel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("referenced relation \"%s\" is not a table",
						RelationGetRelationName(pkrel))));

	if (!allowSystemTableMods && IsSystemRelation(pkrel))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						RelationGetRelationName(pkrel))));

	/*
	 * References from permanent or unlogged tables to temp tables, and from
	 * permanent tables to unlogged tables, are disallowed because the
	 * referenced data can vanish out from under us.  References from temp
	 * tables to any other table type are also disallowed, because other
	 * backends might need to run the RI triggers on the perm table, but they
	 * can't reliably see tuples in the local buffers of other backends.
	 */
	switch (rel->rd_rel->relpersistence)
	{
		case RELPERSISTENCE_PERMANENT:
			if (!RelationIsPermanent(pkrel))
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
						 errmsg("constraints on permanent tables may reference only permanent tables")));
			break;
		case RELPERSISTENCE_UNLOGGED:
			if (!RelationIsPermanent(pkrel)
				&& pkrel->rd_rel->relpersistence != RELPERSISTENCE_UNLOGGED)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
						 errmsg("constraints on unlogged tables may reference only permanent or unlogged tables")));
			break;
		case RELPERSISTENCE_TEMP:
			if (pkrel->rd_rel->relpersistence != RELPERSISTENCE_TEMP)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
						 errmsg("constraints on temporary tables may reference only temporary tables")));
			if (!pkrel->rd_islocaltemp || !rel->rd_islocaltemp)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
						 errmsg("constraints on temporary tables must involve temporary tables of this session")));
			break;
	}

	/*
	 * Look up the referencing attributes to make sure they exist, and record
	 * their attnums and type and collation OIDs.
	 */
	numfks = transformColumnNameList(RelationGetRelid(rel),
									 fkconstraint->fk_attrs,
									 fkattnum, fktypoid, fkcolloid);
	with_period = fkconstraint->fk_with_period || fkconstraint->pk_with_period;
	if (with_period && !fkconstraint->fk_with_period)
		ereport(ERROR,
				errcode(ERRCODE_INVALID_FOREIGN_KEY),
				errmsg("foreign key uses PERIOD on the referenced table but not the referencing table"));

	numfkdelsetcols = transformColumnNameList(RelationGetRelid(rel),
											  fkconstraint->fk_del_set_cols,
											  fkdelsetcols, NULL, NULL);
	numfkdelsetcols = validateFkOnDeleteSetColumns(numfks, fkattnum,
												   numfkdelsetcols,
												   fkdelsetcols,
												   fkconstraint->fk_del_set_cols);

	/*
	 * If the attribute list for the referenced table was omitted, lookup the
	 * definition of the primary key and use it.  Otherwise, validate the
	 * supplied attribute list.  In either case, discover the index OID and
	 * index opclasses, and the attnums and type and collation OIDs of the
	 * attributes.
	 */
	if (fkconstraint->pk_attrs == NIL)
	{
		numpks = transformFkeyGetPrimaryKey(pkrel, &indexOid,
											&fkconstraint->pk_attrs,
											pkattnum, pktypoid, pkcolloid,
											opclasses, &pk_has_without_overlaps);

		/* If the primary key uses WITHOUT OVERLAPS, the fk must use PERIOD */
		if (pk_has_without_overlaps && !fkconstraint->fk_with_period)
			ereport(ERROR,
					errcode(ERRCODE_INVALID_FOREIGN_KEY),
					errmsg("foreign key uses PERIOD on the referenced table but not the referencing table"));
	}
	else
	{
		numpks = transformColumnNameList(RelationGetRelid(pkrel),
										 fkconstraint->pk_attrs,
										 pkattnum, pktypoid, pkcolloid);

		/* Since we got pk_attrs, one should be a period. */
		if (with_period && !fkconstraint->pk_with_period)
			ereport(ERROR,
					errcode(ERRCODE_INVALID_FOREIGN_KEY),
					errmsg("foreign key uses PERIOD on the referencing table but not the referenced table"));

		/* Look for an index matching the column list */
		indexOid = transformFkeyCheckAttrs(pkrel, numpks, pkattnum,
										   with_period, opclasses, &pk_has_without_overlaps);
	}

	/*
	 * If the referenced primary key has WITHOUT OVERLAPS, the foreign key
	 * must use PERIOD.
	 */
	if (pk_has_without_overlaps && !with_period)
		ereport(ERROR,
				errcode(ERRCODE_INVALID_FOREIGN_KEY),
				errmsg("foreign key must use PERIOD when referencing a primary key using WITHOUT OVERLAPS"));

	/*
	 * Now we can check permissions.
	 */
	checkFkeyPermissions(pkrel, pkattnum, numpks);

	/*
	 * Check some things for generated columns.
	 */
	for (i = 0; i < numfks; i++)
	{
		char		attgenerated = TupleDescAttr(RelationGetDescr(rel), fkattnum[i] - 1)->attgenerated;

		if (attgenerated)
		{
			/*
			 * Check restrictions on UPDATE/DELETE actions, per SQL standard
			 */
			if (fkconstraint->fk_upd_action == FKCONSTR_ACTION_SETNULL ||
				fkconstraint->fk_upd_action == FKCONSTR_ACTION_SETDEFAULT ||
				fkconstraint->fk_upd_action == FKCONSTR_ACTION_CASCADE)
				ereport(ERROR,
						(errcode(ERRCODE_SYNTAX_ERROR),
						 errmsg("invalid %s action for foreign key constraint containing generated column",
								"ON UPDATE")));
			if (fkconstraint->fk_del_action == FKCONSTR_ACTION_SETNULL ||
				fkconstraint->fk_del_action == FKCONSTR_ACTION_SETDEFAULT)
				ereport(ERROR,
						(errcode(ERRCODE_SYNTAX_ERROR),
						 errmsg("invalid %s action for foreign key constraint containing generated column",
								"ON DELETE")));
		}

		/*
		 * FKs on virtual columns are not supported.  This would require
		 * various additional support in ri_triggers.c, including special
		 * handling in ri_NullCheck(), ri_KeysEqual(),
		 * RI_FKey_fk_upd_check_required() (since all virtual columns appear
		 * as NULL there).  Also not really practical as long as you can't
		 * index virtual columns.
		 */
		if (attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("foreign key constraints on virtual generated columns are not supported")));
	}

	/*
	 * Some actions are currently unsupported for foreign keys using PERIOD.
	 */
	if (fkconstraint->fk_with_period)
	{
		if (fkconstraint->fk_upd_action == FKCONSTR_ACTION_RESTRICT ||
			fkconstraint->fk_upd_action == FKCONSTR_ACTION_CASCADE ||
			fkconstraint->fk_upd_action == FKCONSTR_ACTION_SETNULL ||
			fkconstraint->fk_upd_action == FKCONSTR_ACTION_SETDEFAULT)
			ereport(ERROR,
					errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					errmsg("unsupported %s action for foreign key constraint using PERIOD",
						   "ON UPDATE"));

		if (fkconstraint->fk_del_action == FKCONSTR_ACTION_RESTRICT ||
			fkconstraint->fk_del_action == FKCONSTR_ACTION_CASCADE ||
			fkconstraint->fk_del_action == FKCONSTR_ACTION_SETNULL ||
			fkconstraint->fk_del_action == FKCONSTR_ACTION_SETDEFAULT)
			ereport(ERROR,
					errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					errmsg("unsupported %s action for foreign key constraint using PERIOD",
						   "ON DELETE"));
	}

	/*
	 * Look up the equality operators to use in the constraint.
	 *
	 * Note that we have to be careful about the difference between the actual
	 * PK column type and the opclass' declared input type, which might be
	 * only binary-compatible with it.  The declared opcintype is the right
	 * thing to probe pg_amop with.
	 */
	if (numfks != numpks)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_FOREIGN_KEY),
				 errmsg("number of referencing and referenced columns for foreign key disagree")));

	/*
	 * On the strength of a previous constraint, we might avoid scanning
	 * tables to validate this one.  See below.
	 */
	old_check_ok = (fkconstraint->old_conpfeqop != NIL);
	Assert(!old_check_ok || numfks == list_length(fkconstraint->old_conpfeqop));

	for (i = 0; i < numpks; i++)
	{
		Oid			pktype = pktypoid[i];
		Oid			fktype = fktypoid[i];
		Oid			fktyped;
		Oid			pkcoll = pkcolloid[i];
		Oid			fkcoll = fkcolloid[i];
		HeapTuple	cla_ht;
		Form_pg_opclass cla_tup;
		Oid			amid;
		Oid			opfamily;
		Oid			opcintype;
		bool		for_overlaps;
		CompareType cmptype;
		Oid			pfeqop;
		Oid			ppeqop;
		Oid			ffeqop;
		int16		eqstrategy;
		Oid			pfeqop_right;

		/* We need several fields out of the pg_opclass entry */
		cla_ht = SearchSysCache1(CLAOID, ObjectIdGetDatum(opclasses[i]));
		if (!HeapTupleIsValid(cla_ht))
			elog(ERROR, "cache lookup failed for opclass %u", opclasses[i]);
		cla_tup = (Form_pg_opclass) GETSTRUCT(cla_ht);
		amid = cla_tup->opcmethod;
		opfamily = cla_tup->opcfamily;
		opcintype = cla_tup->opcintype;
		ReleaseSysCache(cla_ht);

		/*
		 * Get strategy number from index AM.
		 *
		 * For a normal foreign-key constraint, this should not fail, since we
		 * already checked that the index is unique and should therefore have
		 * appropriate equal operators.  For a period foreign key, this could
		 * fail if we selected a non-matching exclusion constraint earlier.
		 * (XXX Maybe we should do these lookups earlier so we don't end up
		 * doing that.)
		 */
		for_overlaps = with_period && i == numpks - 1;
		cmptype = for_overlaps ? COMPARE_OVERLAP : COMPARE_EQ;
		eqstrategy = IndexAmTranslateCompareType(cmptype, amid, opfamily, true);
		if (eqstrategy == InvalidStrategy)
			ereport(ERROR,
					errcode(ERRCODE_UNDEFINED_OBJECT),
					for_overlaps
					? errmsg("could not identify an overlaps operator for foreign key")
					: errmsg("could not identify an equality operator for foreign key"),
					errdetail("Could not translate compare type %d for operator family \"%s\" of access method \"%s\".",
							  cmptype, get_opfamily_name(opfamily, false), get_am_name(amid)));

		/*
		 * There had better be a primary equality operator for the index.
		 * We'll use it for PK = PK comparisons.
		 */
		ppeqop = get_opfamily_member(opfamily, opcintype, opcintype,
									 eqstrategy);

		if (!OidIsValid(ppeqop))
			elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
				 eqstrategy, opcintype, opcintype, opfamily);

		/*
		 * Are there equality operators that take exactly the FK type? Assume
		 * we should look through any domain here.
		 */
		fktyped = getBaseType(fktype);

		pfeqop = get_opfamily_member(opfamily, opcintype, fktyped,
									 eqstrategy);
		if (OidIsValid(pfeqop))
		{
			pfeqop_right = fktyped;
			ffeqop = get_opfamily_member(opfamily, fktyped, fktyped,
										 eqstrategy);
		}
		else
		{
			/* keep compiler quiet */
			pfeqop_right = InvalidOid;
			ffeqop = InvalidOid;
		}

		if (!(OidIsValid(pfeqop) && OidIsValid(ffeqop)))
		{
			/*
			 * Otherwise, look for an implicit cast from the FK type to the
			 * opcintype, and if found, use the primary equality operator.
			 * This is a bit tricky because opcintype might be a polymorphic
			 * type such as ANYARRAY or ANYENUM; so what we have to test is
			 * whether the two actual column types can be concurrently cast to
			 * that type.  (Otherwise, we'd fail to reject combinations such
			 * as int[] and point[].)
			 */
			Oid			input_typeids[2];
			Oid			target_typeids[2];

			input_typeids[0] = pktype;
			input_typeids[1] = fktype;
			target_typeids[0] = opcintype;
			target_typeids[1] = opcintype;
			if (can_coerce_type(2, input_typeids, target_typeids,
								COERCION_IMPLICIT))
			{
				pfeqop = ffeqop = ppeqop;
				pfeqop_right = opcintype;
			}
		}

		if (!(OidIsValid(pfeqop) && OidIsValid(ffeqop)))
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("foreign key constraint \"%s\" cannot be implemented",
							fkconstraint->conname),
					 errdetail("Key columns \"%s\" of the referencing table and \"%s\" of the referenced table "
							   "are of incompatible types: %s and %s.",
							   strVal(list_nth(fkconstraint->fk_attrs, i)),
							   strVal(list_nth(fkconstraint->pk_attrs, i)),
							   format_type_be(fktype),
							   format_type_be(pktype))));

		/*
		 * This shouldn't be possible, but better check to make sure we have a
		 * consistent state for the check below.
		 */
		if ((OidIsValid(pkcoll) && !OidIsValid(fkcoll)) || (!OidIsValid(pkcoll) && OidIsValid(fkcoll)))
			elog(ERROR, "key columns are not both collatable");

		if (OidIsValid(pkcoll) && OidIsValid(fkcoll))
		{
			bool		pkcolldet;
			bool		fkcolldet;

			pkcolldet = get_collation_isdeterministic(pkcoll);
			fkcolldet = get_collation_isdeterministic(fkcoll);

			/*
			 * SQL requires that both collations are the same.  This is
			 * because we need a consistent notion of equality on both
			 * columns.  We relax this by allowing different collations if
			 * they are both deterministic.  (This is also for backward
			 * compatibility, because PostgreSQL has always allowed this.)
			 */
			if ((!pkcolldet || !fkcolldet) && pkcoll != fkcoll)
				ereport(ERROR,
						(errcode(ERRCODE_COLLATION_MISMATCH),
						 errmsg("foreign key constraint \"%s\" cannot be implemented", fkconstraint->conname),
						 errdetail("Key columns \"%s\" of the referencing table and \"%s\" of the referenced table "
								   "have incompatible collations: \"%s\" and \"%s\".  "
								   "If either collation is nondeterministic, then both collations have to be the same.",
								   strVal(list_nth(fkconstraint->fk_attrs, i)),
								   strVal(list_nth(fkconstraint->pk_attrs, i)),
								   get_collation_name(fkcoll),
								   get_collation_name(pkcoll))));
		}

		if (old_check_ok)
		{
			/*
			 * When a pfeqop changes, revalidate the constraint.  We could
			 * permit intra-opfamily changes, but that adds subtle complexity
			 * without any concrete benefit for core types.  We need not
			 * assess ppeqop or ffeqop, which RI_Initial_Check() does not use.
			 */
			old_check_ok = (pfeqop == lfirst_oid(old_pfeqop_item));
			old_pfeqop_item = lnext(fkconstraint->old_conpfeqop,
									old_pfeqop_item);
		}
		if (old_check_ok)
		{
			Oid			old_fktype;
			Oid			new_fktype;
			CoercionPathType old_pathtype;
			CoercionPathType new_pathtype;
			Oid			old_castfunc;
			Oid			new_castfunc;
			Oid			old_fkcoll;
			Oid			new_fkcoll;
			Form_pg_attribute attr = TupleDescAttr(tab->oldDesc,
												   fkattnum[i] - 1);

			/*
			 * Identify coercion pathways from each of the old and new FK-side
			 * column types to the right (foreign) operand type of the pfeqop.
			 * We may assume that pg_constraint.conkey is not changing.
			 */
			old_fktype = attr->atttypid;
			new_fktype = fktype;
			old_pathtype = findFkeyCast(pfeqop_right, old_fktype,
										&old_castfunc);
			new_pathtype = findFkeyCast(pfeqop_right, new_fktype,
										&new_castfunc);

			old_fkcoll = attr->attcollation;
			new_fkcoll = fkcoll;

			/*
			 * Upon a change to the cast from the FK column to its pfeqop
			 * operand, revalidate the constraint.  For this evaluation, a
			 * binary coercion cast is equivalent to no cast at all.  While
			 * type implementors should design implicit casts with an eye
			 * toward consistency of operations like equality, we cannot
			 * assume here that they have done so.
			 *
			 * A function with a polymorphic argument could change behavior
			 * arbitrarily in response to get_fn_expr_argtype().  Therefore,
			 * when the cast destination is polymorphic, we only avoid
			 * revalidation if the input type has not changed at all.  Given
			 * just the core data types and operator classes, this requirement
			 * prevents no would-be optimizations.
			 *
			 * If the cast converts from a base type to a domain thereon, then
			 * that domain type must be the opcintype of the unique index.
			 * Necessarily, the primary key column must then be of the domain
			 * type.  Since the constraint was previously valid, all values on
			 * the foreign side necessarily exist on the primary side and in
			 * turn conform to the domain.  Consequently, we need not treat
			 * domains specially here.
			 *
			 * If the collation changes, revalidation is required, unless both
			 * collations are deterministic, because those share the same
			 * notion of equality (because texteq reduces to bitwise
			 * equality).
			 *
			 * We need not directly consider the PK type.  It's necessarily
			 * binary coercible to the opcintype of the unique index column,
			 * and ri_triggers.c will only deal with PK datums in terms of
			 * that opcintype.  Changing the opcintype also changes pfeqop.
			 */
			old_check_ok = (new_pathtype == old_pathtype &&
							new_castfunc == old_castfunc &&
							(!IsPolymorphicType(pfeqop_right) ||
							 new_fktype == old_fktype) &&
							(new_fkcoll == old_fkcoll ||
							 (get_collation_isdeterministic(old_fkcoll) && get_collation_isdeterministic(new_fkcoll))));
		}

		pfeqoperators[i] = pfeqop;
		ppeqoperators[i] = ppeqop;
		ffeqoperators[i] = ffeqop;
	}

	/*
	 * For FKs with PERIOD we need additional operators to check whether the
	 * referencing row's range is contained by the aggregated ranges of the
	 * referenced row(s). For rangetypes and multirangetypes this is
	 * fk.periodatt <@ range_agg(pk.periodatt). Those are the only types we
	 * support for now. FKs will look these up at "runtime", but we should
	 * make sure the lookup works here, even if we don't use the values.
	 */
	if (with_period)
	{
		Oid			periodoperoid;
		Oid			aggedperiodoperoid;
		Oid			intersectoperoid;

		FindFKPeriodOpers(opclasses[numpks - 1], &periodoperoid, &aggedperiodoperoid,
						  &intersectoperoid);
	}

	/* First, create the constraint catalog entry itself. */
	address = addFkConstraint(addFkBothSides,
							  fkconstraint->conname, fkconstraint, rel, pkrel,
							  indexOid,
							  InvalidOid,	/* no parent constraint */
							  numfks,
							  pkattnum,
							  fkattnum,
							  pfeqoperators,
							  ppeqoperators,
							  ffeqoperators,
							  numfkdelsetcols,
							  fkdelsetcols,
							  false,
							  with_period);

	/* Next process the action triggers at the referenced side and recurse */
	addFkRecurseReferenced(fkconstraint, rel, pkrel,
						   indexOid,
						   address.objectId,
						   numfks,
						   pkattnum,
						   fkattnum,
						   pfeqoperators,
						   ppeqoperators,
						   ffeqoperators,
						   numfkdelsetcols,
						   fkdelsetcols,
						   old_check_ok,
						   InvalidOid, InvalidOid,
						   with_period);

	/* Lastly create the check triggers at the referencing side and recurse */
	addFkRecurseReferencing(wqueue, fkconstraint, rel, pkrel,
							indexOid,
							address.objectId,
							numfks,
							pkattnum,
							fkattnum,
							pfeqoperators,
							ppeqoperators,
							ffeqoperators,
							numfkdelsetcols,
							fkdelsetcols,
							old_check_ok,
							lockmode,
							InvalidOid, InvalidOid,
							with_period);

	/*
	 * Done.  Close pk table, but keep lock until we've committed.
	 */
	table_close(pkrel, NoLock);

	return address;
}

/*
 * validateFkOnDeleteSetColumns
 *		Verifies that columns used in ON DELETE SET NULL/DEFAULT (...)
 *		column lists are valid.
 *
 * If there are duplicates in the fksetcolsattnums[] array, this silently
 * removes the dups.  The new count of numfksetcols is returned.
 */
static int
validateFkOnDeleteSetColumns(int numfks, const int16 *fkattnums,
							 int numfksetcols, int16 *fksetcolsattnums,
							 List *fksetcols)
{
	int			numcolsout = 0;

	for (int i = 0; i < numfksetcols; i++)
	{
		int16		setcol_attnum = fksetcolsattnums[i];
		bool		seen = false;

		/* Make sure it's in fkattnums[] */
		for (int j = 0; j < numfks; j++)
		{
			if (fkattnums[j] == setcol_attnum)
			{
				seen = true;
				break;
			}
		}

		if (!seen)
		{
			char	   *col = strVal(list_nth(fksetcols, i));

			ereport(ERROR,
					(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
					 errmsg("column \"%s\" referenced in ON DELETE SET action must be part of foreign key", col)));
		}

		/* Now check for dups */
		seen = false;
		for (int j = 0; j < numcolsout; j++)
		{
			if (fksetcolsattnums[j] == setcol_attnum)
			{
				seen = true;
				break;
			}
		}
		if (!seen)
			fksetcolsattnums[numcolsout++] = setcol_attnum;
	}
	return numcolsout;
}

/*
 * addFkConstraint
 *		Install pg_constraint entries to implement a foreign key constraint.
 *		Caller must separately invoke addFkRecurseReferenced and
 *		addFkRecurseReferencing, as appropriate, to install pg_trigger entries
 *		and (for partitioned tables) recurse to partitions.
 *
 * fkside: the side of the FK (or both) to create.  Caller should
 *      call addFkRecurseReferenced if this is addFkReferencedSide,
 *      addFkRecurseReferencing if it's addFkReferencingSide, or both if it's
 *      addFkBothSides.
 * constraintname: the base name for the constraint being added,
 *      copied to fkconstraint->conname if the latter is not set
 * fkconstraint: the constraint being added
 * rel: the root referencing relation
 * pkrel: the referenced relation; might be a partition, if recursing
 * indexOid: the OID of the index (on pkrel) implementing this constraint
 * parentConstr: the OID of a parent constraint; InvalidOid if this is a
 *      top-level constraint
 * numfks: the number of columns in the foreign key
 * pkattnum: the attnum array of referenced attributes
 * fkattnum: the attnum array of referencing attributes
 * pf/pp/ffeqoperators: OID array of operators between columns
 * numfkdelsetcols: the number of columns in the ON DELETE SET NULL/DEFAULT
 *      (...) clause
 * fkdelsetcols: the attnum array of the columns in the ON DELETE SET
 *      NULL/DEFAULT clause
 * with_period: true if this is a temporal FK
 */
static ObjectAddress
addFkConstraint(addFkConstraintSides fkside,
				char *constraintname, Constraint *fkconstraint,
				Relation rel, Relation pkrel, Oid indexOid, Oid parentConstr,
				int numfks, int16 *pkattnum,
				int16 *fkattnum, Oid *pfeqoperators, Oid *ppeqoperators,
				Oid *ffeqoperators, int numfkdelsetcols, int16 *fkdelsetcols,
				bool is_internal, bool with_period)
{
	ObjectAddress address;
	Oid			constrOid;
	char	   *conname;
	bool		conislocal;
	int16		coninhcount;
	bool		connoinherit;

	/*
	 * Verify relkind for each referenced partition.  At the top level, this
	 * is redundant with a previous check, but we need it when recursing.
	 */
	if (pkrel->rd_rel->relkind != RELKIND_RELATION &&
		pkrel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("referenced relation \"%s\" is not a table",
						RelationGetRelationName(pkrel))));

	/*
	 * Caller supplies us with a constraint name; however, it may be used in
	 * this partition, so come up with a different one in that case.  Unless
	 * truncation to NAMEDATALEN dictates otherwise, the new name will be the
	 * supplied name with an underscore and digit(s) appended.
	 */
	if (ConstraintNameIsUsed(CONSTRAINT_RELATION,
							 RelationGetRelid(rel),
							 constraintname))
		conname = ChooseConstraintName(constraintname,
									   NULL,
									   "",
									   RelationGetNamespace(rel), NIL);
	else
		conname = constraintname;

	if (fkconstraint->conname == NULL)
		fkconstraint->conname = pstrdup(conname);

	if (OidIsValid(parentConstr))
	{
		conislocal = false;
		coninhcount = 1;
		connoinherit = false;
	}
	else
	{
		conislocal = true;
		coninhcount = 0;

		/*
		 * always inherit for partitioned tables, never for legacy inheritance
		 */
		connoinherit = rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE;
	}

	/*
	 * Record the FK constraint in pg_constraint.
	 */
	constrOid = CreateConstraintEntry(conname,
									  RelationGetNamespace(rel),
									  CONSTRAINT_FOREIGN,
									  fkconstraint->deferrable,
									  fkconstraint->initdeferred,
									  fkconstraint->is_enforced,
									  fkconstraint->initially_valid,
									  parentConstr,
									  RelationGetRelid(rel),
									  fkattnum,
									  numfks,
									  numfks,
									  InvalidOid,	/* not a domain constraint */
									  indexOid,
									  RelationGetRelid(pkrel),
									  pkattnum,
									  pfeqoperators,
									  ppeqoperators,
									  ffeqoperators,
									  numfks,
									  fkconstraint->fk_upd_action,
									  fkconstraint->fk_del_action,
									  fkdelsetcols,
									  numfkdelsetcols,
									  fkconstraint->fk_matchtype,
									  NULL, /* no exclusion constraint */
									  NULL, /* no check constraint */
									  NULL,
									  conislocal,	/* islocal */
									  coninhcount,	/* inhcount */
									  connoinherit, /* conNoInherit */
									  with_period,	/* conPeriod */
									  is_internal); /* is_internal */

	ObjectAddressSet(address, ConstraintRelationId, constrOid);

	/*
	 * In partitioning cases, create the dependency entries for this
	 * constraint.  (For non-partitioned cases, relevant entries were created
	 * by CreateConstraintEntry.)
	 *
	 * On the referenced side, we need the constraint to have an internal
	 * dependency on its parent constraint; this means that this constraint
	 * cannot be dropped on its own -- only through the parent constraint. It
	 * also means the containing partition cannot be dropped on its own, but
	 * it can be detached, at which point this dependency is removed (after
	 * verifying that no rows are referenced via this FK.)
	 *
	 * When processing the referencing side, we link the constraint via the
	 * special partitioning dependencies: the parent constraint is the primary
	 * dependent, and the partition on which the foreign key exists is the
	 * secondary dependency.  That way, this constraint is dropped if either
	 * of these objects is.
	 *
	 * Note that this is only necessary for the subsidiary pg_constraint rows
	 * in partitions; the topmost row doesn't need any of this.
	 */
	if (OidIsValid(parentConstr))
	{
		ObjectAddress referenced;

		ObjectAddressSet(referenced, ConstraintRelationId, parentConstr);

		Assert(fkside != addFkBothSides);
		if (fkside == addFkReferencedSide)
			recordDependencyOn(&address, &referenced, DEPENDENCY_INTERNAL);
		else
		{
			recordDependencyOn(&address, &referenced, DEPENDENCY_PARTITION_PRI);
			ObjectAddressSet(referenced, RelationRelationId, RelationGetRelid(rel));
			recordDependencyOn(&address, &referenced, DEPENDENCY_PARTITION_SEC);
		}
	}

	/* make new constraint visible, in case we add more */
	CommandCounterIncrement();

	return address;
}

/*
 * addFkRecurseReferenced
 *		Recursive helper for the referenced side of foreign key creation,
 *		which creates the action triggers and recurses
 *
 * If the referenced relation is a plain relation, create the necessary action
 * triggers that implement the constraint.  If the referenced relation is a
 * partitioned table, then we create a pg_constraint row referencing the parent
 * of the referencing side for it and recurse on this routine for each
 * partition.
 *
 * fkconstraint: the constraint being added
 * rel: the root referencing relation
 * pkrel: the referenced relation; might be a partition, if recursing
 * indexOid: the OID of the index (on pkrel) implementing this constraint
 * parentConstr: the OID of a parent constraint; InvalidOid if this is a
 *      top-level constraint
 * numfks: the number of columns in the foreign key
 * pkattnum: the attnum array of referenced attributes
 * fkattnum: the attnum array of referencing attributes
 * numfkdelsetcols: the number of columns in the ON DELETE SET
 *      NULL/DEFAULT (...) clause
 * fkdelsetcols: the attnum array of the columns in the ON DELETE SET
 *      NULL/DEFAULT clause
 * pf/pp/ffeqoperators: OID array of operators between columns
 * old_check_ok: true if this constraint replaces an existing one that
 *      was already validated (thus this one doesn't need validation)
 * parentDelTrigger and parentUpdTrigger: when recursively called on a
 *      partition, the OIDs of the parent action triggers for DELETE and
 *      UPDATE respectively.
 * with_period: true if this is a temporal FK
 */
static void
addFkRecurseReferenced(Constraint *fkconstraint, Relation rel,
					   Relation pkrel, Oid indexOid, Oid parentConstr,
					   int numfks,
					   int16 *pkattnum, int16 *fkattnum, Oid *pfeqoperators,
					   Oid *ppeqoperators, Oid *ffeqoperators,
					   int numfkdelsetcols, int16 *fkdelsetcols,
					   bool old_check_ok,
					   Oid parentDelTrigger, Oid parentUpdTrigger,
					   bool with_period)
{
	Oid			deleteTriggerOid = InvalidOid,
				updateTriggerOid = InvalidOid;

	Assert(CheckRelationLockedByMe(pkrel, ShareRowExclusiveLock, true));
	Assert(CheckRelationLockedByMe(rel, ShareRowExclusiveLock, true));

	/*
	 * Create action triggers to enforce the constraint, or skip them if the
	 * constraint is NOT ENFORCED.
	 */
	if (fkconstraint->is_enforced)
		createForeignKeyActionTriggers(RelationGetRelid(rel),
									   RelationGetRelid(pkrel),
									   fkconstraint,
									   parentConstr, indexOid,
									   parentDelTrigger, parentUpdTrigger,
									   &deleteTriggerOid, &updateTriggerOid);

	/*
	 * If the referenced table is partitioned, recurse on ourselves to handle
	 * each partition.  We need one pg_constraint row created for each
	 * partition in addition to the pg_constraint row for the parent table.
	 */
	if (pkrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
	{
		PartitionDesc pd = RelationGetPartitionDesc(pkrel, true);

		for (int i = 0; i < pd->nparts; i++)
		{
			Relation	partRel;
			AttrMap    *map;
			AttrNumber *mapped_pkattnum;
			Oid			partIndexId;
			ObjectAddress address;

			/* XXX would it be better to acquire these locks beforehand? */
			partRel = table_open(pd->oids[i], ShareRowExclusiveLock);

			/*
			 * Map the attribute numbers in the referenced side of the FK
			 * definition to match the partition's column layout.
			 */
			map = build_attrmap_by_name_if_req(RelationGetDescr(partRel),
											   RelationGetDescr(pkrel),
											   false);
			if (map)
			{
				mapped_pkattnum = palloc(sizeof(AttrNumber) * numfks);
				for (int j = 0; j < numfks; j++)
					mapped_pkattnum[j] = map->attnums[pkattnum[j] - 1];
			}
			else
				mapped_pkattnum = pkattnum;

			/* Determine the index to use at this level */
			partIndexId = index_get_partition(partRel, indexOid);
			if (!OidIsValid(partIndexId))
				elog(ERROR, "index for %u not found in partition %s",
					 indexOid, RelationGetRelationName(partRel));

			/* Create entry at this level ... */
			address = addFkConstraint(addFkReferencedSide,
									  fkconstraint->conname, fkconstraint, rel,
									  partRel, partIndexId, parentConstr,
									  numfks, mapped_pkattnum,
									  fkattnum, pfeqoperators, ppeqoperators,
									  ffeqoperators, numfkdelsetcols,
									  fkdelsetcols, true, with_period);
			/* ... and recurse to our children */
			addFkRecurseReferenced(fkconstraint, rel, partRel,
								   partIndexId, address.objectId, numfks,
								   mapped_pkattnum, fkattnum,
								   pfeqoperators, ppeqoperators, ffeqoperators,
								   numfkdelsetcols, fkdelsetcols,
								   old_check_ok,
								   deleteTriggerOid, updateTriggerOid,
								   with_period);

			/* Done -- clean up (but keep the lock) */
			table_close(partRel, NoLock);
			if (map)
			{
				pfree(mapped_pkattnum);
				free_attrmap(map);
			}
		}
	}
}

/*
 * addFkRecurseReferencing
 *		Recursive helper for the referencing side of foreign key creation,
 *		which creates the check triggers and recurses
 *
 * If the referencing relation is a plain relation, create the necessary check
 * triggers that implement the constraint, and set up for Phase 3 constraint
 * verification.  If the referencing relation is a partitioned table, then
 * we create a pg_constraint row for it and recurse on this routine for each
 * partition.
 *
 * We assume that the referenced relation is locked against concurrent
 * deletions.  If it's a partitioned relation, every partition must be so
 * locked.
 *
 * wqueue: the ALTER TABLE work queue; NULL when not running as part
 *      of an ALTER TABLE sequence.
 * fkconstraint: the constraint being added
 * rel: the referencing relation; might be a partition, if recursing
 * pkrel: the root referenced relation
 * indexOid: the OID of the index (on pkrel) implementing this constraint
 * parentConstr: the OID of the parent constraint (there is always one)
 * numfks: the number of columns in the foreign key
 * pkattnum: the attnum array of referenced attributes
 * fkattnum: the attnum array of referencing attributes
 * pf/pp/ffeqoperators: OID array of operators between columns
 * numfkdelsetcols: the number of columns in the ON DELETE SET NULL/DEFAULT
 *      (...) clause
 * fkdelsetcols: the attnum array of the columns in the ON DELETE SET
 *      NULL/DEFAULT clause
 * old_check_ok: true if this constraint replaces an existing one that
 *      was already validated (thus this one doesn't need validation)
 * lockmode: the lockmode to acquire on partitions when recursing
 * parentInsTrigger and parentUpdTrigger: when being recursively called on
 *      a partition, the OIDs of the parent check triggers for INSERT and
 *      UPDATE respectively.
 * with_period: true if this is a temporal FK
 */
static void
addFkRecurseReferencing(List **wqueue, Constraint *fkconstraint, Relation rel,
						Relation pkrel, Oid indexOid, Oid parentConstr,
						int numfks, int16 *pkattnum, int16 *fkattnum,
						Oid *pfeqoperators, Oid *ppeqoperators, Oid *ffeqoperators,
						int numfkdelsetcols, int16 *fkdelsetcols,
						bool old_check_ok, LOCKMODE lockmode,
						Oid parentInsTrigger, Oid parentUpdTrigger,
						bool with_period)
{
	Oid			insertTriggerOid = InvalidOid,
				updateTriggerOid = InvalidOid;

	Assert(OidIsValid(parentConstr));
	Assert(CheckRelationLockedByMe(rel, ShareRowExclusiveLock, true));
	Assert(CheckRelationLockedByMe(pkrel, ShareRowExclusiveLock, true));

	if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("foreign key constraints are not supported on foreign tables")));

	/*
	 * Add check triggers if the constraint is ENFORCED, and if needed,
	 * schedule them to be checked in Phase 3.
	 *
	 * If the relation is partitioned, drill down to do it to its partitions.
	 */
	if (fkconstraint->is_enforced)
		createForeignKeyCheckTriggers(RelationGetRelid(rel),
									  RelationGetRelid(pkrel),
									  fkconstraint,
									  parentConstr,
									  indexOid,
									  parentInsTrigger, parentUpdTrigger,
									  &insertTriggerOid, &updateTriggerOid);

	if (rel->rd_rel->relkind == RELKIND_RELATION)
	{
		/*
		 * Tell Phase 3 to check that the constraint is satisfied by existing
		 * rows. We can skip this during table creation, when constraint is
		 * specified as NOT ENFORCED, or when requested explicitly by
		 * specifying NOT VALID in an ADD FOREIGN KEY command, and when we're
		 * recreating a constraint following a SET DATA TYPE operation that
		 * did not impugn its validity.
		 */
		if (wqueue && !old_check_ok && !fkconstraint->skip_validation &&
			fkconstraint->is_enforced)
		{
			NewConstraint *newcon;
			AlteredTableInfo *tab;

			tab = ATGetQueueEntry(wqueue, rel);

			newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
			newcon->name = get_constraint_name(parentConstr);
			newcon->contype = CONSTR_FOREIGN;
			newcon->refrelid = RelationGetRelid(pkrel);
			newcon->refindid = indexOid;
			newcon->conid = parentConstr;
			newcon->conwithperiod = fkconstraint->fk_with_period;
			newcon->qual = (Node *) fkconstraint;

			tab->constraints = lappend(tab->constraints, newcon);
		}
	}
	else if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
	{
		PartitionDesc pd = RelationGetPartitionDesc(rel, true);
		Relation	trigrel;

		/*
		 * Triggers of the foreign keys will be manipulated a bunch of times
		 * in the loop below.  To avoid repeatedly opening/closing the trigger
		 * catalog relation, we open it here and pass it to the subroutines
		 * called below.
		 */
		trigrel = table_open(TriggerRelationId, RowExclusiveLock);

		/*
		 * Recurse to take appropriate action on each partition; either we
		 * find an existing constraint to reparent to ours, or we create a new
		 * one.
		 */
		for (int i = 0; i < pd->nparts; i++)
		{
			Relation	partition = table_open(pd->oids[i], lockmode);
			List	   *partFKs;
			AttrMap    *attmap;
			AttrNumber	mapped_fkattnum[INDEX_MAX_KEYS];
			bool		attached;
			ObjectAddress address;

			CheckAlterTableIsSafe(partition);

			attmap = build_attrmap_by_name(RelationGetDescr(partition),
										   RelationGetDescr(rel),
										   false);
			for (int j = 0; j < numfks; j++)
				mapped_fkattnum[j] = attmap->attnums[fkattnum[j] - 1];

			/* Check whether an existing constraint can be repurposed */
			partFKs = copyObject(RelationGetFKeyList(partition));
			attached = false;
			foreach_node(ForeignKeyCacheInfo, fk, partFKs)
			{
				if (tryAttachPartitionForeignKey(wqueue,
												 fk,
												 partition,
												 parentConstr,
												 numfks,
												 mapped_fkattnum,
												 pkattnum,
												 pfeqoperators,
												 insertTriggerOid,
												 updateTriggerOid,
												 trigrel))
				{
					attached = true;
					break;
				}
			}
			if (attached)
			{
				table_close(partition, NoLock);
				continue;
			}

			/*
			 * No luck finding a good constraint to reuse; create our own.
			 */
			address = addFkConstraint(addFkReferencingSide,
									  fkconstraint->conname, fkconstraint,
									  partition, pkrel, indexOid, parentConstr,
									  numfks, pkattnum,
									  mapped_fkattnum, pfeqoperators,
									  ppeqoperators, ffeqoperators,
									  numfkdelsetcols, fkdelsetcols, true,
									  with_period);

			/* call ourselves to finalize the creation and we're done */
			addFkRecurseReferencing(wqueue, fkconstraint, partition, pkrel,
									indexOid,
									address.objectId,
									numfks,
									pkattnum,
									mapped_fkattnum,
									pfeqoperators,
									ppeqoperators,
									ffeqoperators,
									numfkdelsetcols,
									fkdelsetcols,
									old_check_ok,
									lockmode,
									insertTriggerOid,
									updateTriggerOid,
									with_period);

			table_close(partition, NoLock);
		}

		table_close(trigrel, RowExclusiveLock);
	}
}

/*
 * CloneForeignKeyConstraints
 *		Clone foreign keys from a partitioned table to a newly acquired
 *		partition.
 *
 * partitionRel is a partition of parentRel, so we can be certain that it has
 * the same columns with the same datatypes.  The columns may be in different
 * order, though.
 *
 * wqueue must be passed to set up phase 3 constraint checking, unless the
 * referencing-side partition is known to be empty (such as in CREATE TABLE /
 * PARTITION OF).
 */
static void
CloneForeignKeyConstraints(List **wqueue, Relation parentRel,
						   Relation partitionRel)
{
	/* This only works for declarative partitioning */
	Assert(parentRel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);

	/*
	 * First, clone constraints where the parent is on the referencing side.
	 */
	CloneFkReferencing(wqueue, parentRel, partitionRel);

	/*
	 * Clone constraints for which the parent is on the referenced side.
	 */
	CloneFkReferenced(parentRel, partitionRel);
}

/*
 * CloneFkReferenced
 *		Subroutine for CloneForeignKeyConstraints
 *
 * Find all the FKs that have the parent relation on the referenced side;
 * clone those constraints to the given partition.  This is to be called
 * when the partition is being created or attached.
 *
 * This recurses to partitions, if the relation being attached is partitioned.
 * Recursion is done by calling addFkRecurseReferenced.
 */
static void
CloneFkReferenced(Relation parentRel, Relation partitionRel)
{
	Relation	pg_constraint;
	AttrMap    *attmap;
	ListCell   *cell;
	SysScanDesc scan;
	ScanKeyData key[2];
	HeapTuple	tuple;
	List	   *clone = NIL;
	Relation	trigrel;

	/*
	 * Search for any constraints where this partition's parent is in the
	 * referenced side.  However, we must not clone any constraint whose
	 * parent constraint is also going to be cloned, to avoid duplicates.  So
	 * do it in two steps: first construct the list of constraints to clone,
	 * then go over that list cloning those whose parents are not in the list.
	 * (We must not rely on the parent being seen first, since the catalog
	 * scan could return children first.)
	 */
	pg_constraint = table_open(ConstraintRelationId, RowShareLock);
	ScanKeyInit(&key[0],
				Anum_pg_constraint_confrelid, BTEqualStrategyNumber,
				F_OIDEQ, ObjectIdGetDatum(RelationGetRelid(parentRel)));
	ScanKeyInit(&key[1],
				Anum_pg_constraint_contype, BTEqualStrategyNumber,
				F_CHAREQ, CharGetDatum(CONSTRAINT_FOREIGN));
	/* This is a seqscan, as we don't have a usable index ... */
	scan = systable_beginscan(pg_constraint, InvalidOid, true,
							  NULL, 2, key);
	while ((tuple = systable_getnext(scan)) != NULL)
	{
		Form_pg_constraint constrForm = (Form_pg_constraint) GETSTRUCT(tuple);

		clone = lappend_oid(clone, constrForm->oid);
	}
	systable_endscan(scan);
	table_close(pg_constraint, RowShareLock);

	/*
	 * Triggers of the foreign keys will be manipulated a bunch of times in
	 * the loop below.  To avoid repeatedly opening/closing the trigger
	 * catalog relation, we open it here and pass it to the subroutines called
	 * below.
	 */
	trigrel = table_open(TriggerRelationId, RowExclusiveLock);

	attmap = build_attrmap_by_name(RelationGetDescr(partitionRel),
								   RelationGetDescr(parentRel),
								   false);
	foreach(cell, clone)
	{
		Oid			constrOid = lfirst_oid(cell);
		Form_pg_constraint constrForm;
		Relation	fkRel;
		Oid			indexOid;
		Oid			partIndexId;
		int			numfks;
		AttrNumber	conkey[INDEX_MAX_KEYS];
		AttrNumber	mapped_confkey[INDEX_MAX_KEYS];
		AttrNumber	confkey[INDEX_MAX_KEYS];
		Oid			conpfeqop[INDEX_MAX_KEYS];
		Oid			conppeqop[INDEX_MAX_KEYS];
		Oid			conffeqop[INDEX_MAX_KEYS];
		int			numfkdelsetcols;
		AttrNumber	confdelsetcols[INDEX_MAX_KEYS];
		Constraint *fkconstraint;
		ObjectAddress address;
		Oid			deleteTriggerOid = InvalidOid,
					updateTriggerOid = InvalidOid;

		tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constrOid));
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for constraint %u", constrOid);
		constrForm = (Form_pg_constraint) GETSTRUCT(tuple);

		/*
		 * As explained above: don't try to clone a constraint for which we're
		 * going to clone the parent.
		 */
		if (list_member_oid(clone, constrForm->conparentid))
		{
			ReleaseSysCache(tuple);
			continue;
		}

		/* We need the same lock level that CreateTrigger will acquire */
		fkRel = table_open(constrForm->conrelid, ShareRowExclusiveLock);

		indexOid = constrForm->conindid;
		DeconstructFkConstraintRow(tuple,
								   &numfks,
								   conkey,
								   confkey,
								   conpfeqop,
								   conppeqop,
								   conffeqop,
								   &numfkdelsetcols,
								   confdelsetcols);

		for (int i = 0; i < numfks; i++)
			mapped_confkey[i] = attmap->attnums[confkey[i] - 1];

		fkconstraint = makeNode(Constraint);
		fkconstraint->contype = CONSTRAINT_FOREIGN;
		fkconstraint->conname = NameStr(constrForm->conname);
		fkconstraint->deferrable = constrForm->condeferrable;
		fkconstraint->initdeferred = constrForm->condeferred;
		fkconstraint->location = -1;
		fkconstraint->pktable = NULL;
		/* ->fk_attrs determined below */
		fkconstraint->pk_attrs = NIL;
		fkconstraint->fk_matchtype = constrForm->confmatchtype;
		fkconstraint->fk_upd_action = constrForm->confupdtype;
		fkconstraint->fk_del_action = constrForm->confdeltype;
		fkconstraint->fk_del_set_cols = NIL;
		fkconstraint->old_conpfeqop = NIL;
		fkconstraint->old_pktable_oid = InvalidOid;
		fkconstraint->is_enforced = constrForm->conenforced;
		fkconstraint->skip_validation = false;
		fkconstraint->initially_valid = constrForm->convalidated;

		/* set up colnames that are used to generate the constraint name */
		for (int i = 0; i < numfks; i++)
		{
			Form_pg_attribute att;

			att = TupleDescAttr(RelationGetDescr(fkRel),
								conkey[i] - 1);
			fkconstraint->fk_attrs = lappend(fkconstraint->fk_attrs,
											 makeString(NameStr(att->attname)));
		}

		/*
		 * Add the new foreign key constraint pointing to the new partition.
		 * Because this new partition appears in the referenced side of the
		 * constraint, we don't need to set up for Phase 3 check.
		 */
		partIndexId = index_get_partition(partitionRel, indexOid);
		if (!OidIsValid(partIndexId))
			elog(ERROR, "index for %u not found in partition %s",
				 indexOid, RelationGetRelationName(partitionRel));

		/*
		 * Get the "action" triggers belonging to the constraint to pass as
		 * parent OIDs for similar triggers that will be created on the
		 * partition in addFkRecurseReferenced().
		 */
		if (constrForm->conenforced)
			GetForeignKeyActionTriggers(trigrel, constrOid,
										constrForm->confrelid, constrForm->conrelid,
										&deleteTriggerOid, &updateTriggerOid);

		/* Add this constraint ... */
		address = addFkConstraint(addFkReferencedSide,
								  fkconstraint->conname, fkconstraint, fkRel,
								  partitionRel, partIndexId, constrOid,
								  numfks, mapped_confkey,
								  conkey, conpfeqop, conppeqop, conffeqop,
								  numfkdelsetcols, confdelsetcols, false,
								  constrForm->conperiod);
		/* ... and recurse */
		addFkRecurseReferenced(fkconstraint,
							   fkRel,
							   partitionRel,
							   partIndexId,
							   address.objectId,
							   numfks,
							   mapped_confkey,
							   conkey,
							   conpfeqop,
							   conppeqop,
							   conffeqop,
							   numfkdelsetcols,
							   confdelsetcols,
							   true,
							   deleteTriggerOid,
							   updateTriggerOid,
							   constrForm->conperiod);

		table_close(fkRel, NoLock);
		ReleaseSysCache(tuple);
	}

	table_close(trigrel, RowExclusiveLock);
}

/*
 * CloneFkReferencing
 *		Subroutine for CloneForeignKeyConstraints
 *
 * For each FK constraint of the parent relation in the given list, find an
 * equivalent constraint in its partition relation that can be reparented;
 * if one cannot be found, create a new constraint in the partition as its
 * child.
 *
 * If wqueue is given, it is used to set up phase-3 verification for each
 * cloned constraint; omit it if such verification is not needed
 * (example: the partition is being created anew).
 */
static void
CloneFkReferencing(List **wqueue, Relation parentRel, Relation partRel)
{
	AttrMap    *attmap;
	List	   *partFKs;
	List	   *clone = NIL;
	ListCell   *cell;
	Relation	trigrel;

	/* obtain a list of constraints that we need to clone */
	foreach(cell, RelationGetFKeyList(parentRel))
	{
		ForeignKeyCacheInfo *fk = lfirst(cell);

		/*
		 * Refuse to attach a table as partition that this partitioned table
		 * already has a foreign key to.  This isn't useful schema, which is
		 * proven by the fact that there have been no user complaints that
		 * it's already impossible to achieve this in the opposite direction,
		 * i.e., creating a foreign key that references a partition.  This
		 * restriction allows us to dodge some complexities around
		 * pg_constraint and pg_trigger row creations that would be needed
		 * during ATTACH/DETACH for this kind of relationship.
		 */
		if (fk->confrelid == RelationGetRelid(partRel))
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot attach table \"%s\" as a partition because it is referenced by foreign key \"%s\"",
							RelationGetRelationName(partRel),
							get_constraint_name(fk->conoid))));

		clone = lappend_oid(clone, fk->conoid);
	}

	/*
	 * Silently do nothing if there's nothing to do.  In particular, this
	 * avoids throwing a spurious error for foreign tables.
	 */
	if (clone == NIL)
		return;

	if (partRel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("foreign key constraints are not supported on foreign tables")));

	/*
	 * Triggers of the foreign keys will be manipulated a bunch of times in
	 * the loop below.  To avoid repeatedly opening/closing the trigger
	 * catalog relation, we open it here and pass it to the subroutines called
	 * below.
	 */
	trigrel = table_open(TriggerRelationId, RowExclusiveLock);

	/*
	 * The constraint key may differ, if the columns in the partition are
	 * different.  This map is used to convert them.
	 */
	attmap = build_attrmap_by_name(RelationGetDescr(partRel),
								   RelationGetDescr(parentRel),
								   false);

	partFKs = copyObject(RelationGetFKeyList(partRel));

	foreach(cell, clone)
	{
		Oid			parentConstrOid = lfirst_oid(cell);
		Form_pg_constraint constrForm;
		Relation	pkrel;
		HeapTuple	tuple;
		int			numfks;
		AttrNumber	conkey[INDEX_MAX_KEYS];
		AttrNumber	mapped_conkey[INDEX_MAX_KEYS];
		AttrNumber	confkey[INDEX_MAX_KEYS];
		Oid			conpfeqop[INDEX_MAX_KEYS];
		Oid			conppeqop[INDEX_MAX_KEYS];
		Oid			conffeqop[INDEX_MAX_KEYS];
		int			numfkdelsetcols;
		AttrNumber	confdelsetcols[INDEX_MAX_KEYS];
		Constraint *fkconstraint;
		bool		attached;
		Oid			indexOid;
		ObjectAddress address;
		ListCell   *lc;
		Oid			insertTriggerOid = InvalidOid,
					updateTriggerOid = InvalidOid;
		bool		with_period;

		tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(parentConstrOid));
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for constraint %u",
				 parentConstrOid);
		constrForm = (Form_pg_constraint) GETSTRUCT(tuple);

		/* Don't clone constraints whose parents are being cloned */
		if (list_member_oid(clone, constrForm->conparentid))
		{
			ReleaseSysCache(tuple);
			continue;
		}

		/*
		 * Need to prevent concurrent deletions.  If pkrel is a partitioned
		 * relation, that means to lock all partitions.
		 */
		pkrel = table_open(constrForm->confrelid, ShareRowExclusiveLock);
		if (pkrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
			(void) find_all_inheritors(RelationGetRelid(pkrel),
									   ShareRowExclusiveLock, NULL);

		DeconstructFkConstraintRow(tuple, &numfks, conkey, confkey,
								   conpfeqop, conppeqop, conffeqop,
								   &numfkdelsetcols, confdelsetcols);
		for (int i = 0; i < numfks; i++)
			mapped_conkey[i] = attmap->attnums[conkey[i] - 1];

		/*
		 * Get the "check" triggers belonging to the constraint, if it is
		 * ENFORCED, to pass as parent OIDs for similar triggers that will be
		 * created on the partition in addFkRecurseReferencing().  They are
		 * also passed to tryAttachPartitionForeignKey() below to simply
		 * assign as parents to the partition's existing "check" triggers,
		 * that is, if the corresponding constraints is deemed attachable to
		 * the parent constraint.
		 */
		if (constrForm->conenforced)
			GetForeignKeyCheckTriggers(trigrel, constrForm->oid,
									   constrForm->confrelid, constrForm->conrelid,
									   &insertTriggerOid, &updateTriggerOid);

		/*
		 * Before creating a new constraint, see whether any existing FKs are
		 * fit for the purpose.  If one is, attach the parent constraint to
		 * it, and don't clone anything.  This way we avoid the expensive
		 * verification step and don't end up with a duplicate FK, and we
		 * don't need to recurse to partitions for this constraint.
		 */
		attached = false;
		foreach(lc, partFKs)
		{
			ForeignKeyCacheInfo *fk = lfirst_node(ForeignKeyCacheInfo, lc);

			if (tryAttachPartitionForeignKey(wqueue,
											 fk,
											 partRel,
											 parentConstrOid,
											 numfks,
											 mapped_conkey,
											 confkey,
											 conpfeqop,
											 insertTriggerOid,
											 updateTriggerOid,
											 trigrel))
			{
				attached = true;
				table_close(pkrel, NoLock);
				break;
			}
		}
		if (attached)
		{
			ReleaseSysCache(tuple);
			continue;
		}

		/* No dice.  Set up to create our own constraint */
		fkconstraint = makeNode(Constraint);
		fkconstraint->contype = CONSTRAINT_FOREIGN;
		/* ->conname determined below */
		fkconstraint->deferrable = constrForm->condeferrable;
		fkconstraint->initdeferred = constrForm->condeferred;
		fkconstraint->location = -1;
		fkconstraint->pktable = NULL;
		/* ->fk_attrs determined below */
		fkconstraint->pk_attrs = NIL;
		fkconstraint->fk_matchtype = constrForm->confmatchtype;
		fkconstraint->fk_upd_action = constrForm->confupdtype;
		fkconstraint->fk_del_action = constrForm->confdeltype;
		fkconstraint->fk_del_set_cols = NIL;
		fkconstraint->old_conpfeqop = NIL;
		fkconstraint->old_pktable_oid = InvalidOid;
		fkconstraint->is_enforced = constrForm->conenforced;
		fkconstraint->skip_validation = false;
		fkconstraint->initially_valid = constrForm->convalidated;
		for (int i = 0; i < numfks; i++)
		{
			Form_pg_attribute att;

			att = TupleDescAttr(RelationGetDescr(partRel),
								mapped_conkey[i] - 1);
			fkconstraint->fk_attrs = lappend(fkconstraint->fk_attrs,
											 makeString(NameStr(att->attname)));
		}

		indexOid = constrForm->conindid;
		with_period = constrForm->conperiod;

		/* Create the pg_constraint entry at this level */
		address = addFkConstraint(addFkReferencingSide,
								  NameStr(constrForm->conname), fkconstraint,
								  partRel, pkrel, indexOid, parentConstrOid,
								  numfks, confkey,
								  mapped_conkey, conpfeqop,
								  conppeqop, conffeqop,
								  numfkdelsetcols, confdelsetcols,
								  false, with_period);

		/* Done with the cloned constraint's tuple */
		ReleaseSysCache(tuple);

		/* Create the check triggers, and recurse to partitions, if any */
		addFkRecurseReferencing(wqueue,
								fkconstraint,
								partRel,
								pkrel,
								indexOid,
								address.objectId,
								numfks,
								confkey,
								mapped_conkey,
								conpfeqop,
								conppeqop,
								conffeqop,
								numfkdelsetcols,
								confdelsetcols,
								false,	/* no old check exists */
								AccessExclusiveLock,
								insertTriggerOid,
								updateTriggerOid,
								with_period);
		table_close(pkrel, NoLock);
	}

	table_close(trigrel, RowExclusiveLock);
}

/*
 * When the parent of a partition receives [the referencing side of] a foreign
 * key, we must propagate that foreign key to the partition.  However, the
 * partition might already have an equivalent foreign key; this routine
 * compares the given ForeignKeyCacheInfo (in the partition) to the FK defined
 * by the other parameters.  If they are equivalent, create the link between
 * the two constraints and return true.
 *
 * If the given FK does not match the one defined by rest of the params,
 * return false.
 */
static bool
tryAttachPartitionForeignKey(List **wqueue,
							 ForeignKeyCacheInfo *fk,
							 Relation partition,
							 Oid parentConstrOid,
							 int numfks,
							 AttrNumber *mapped_conkey,
							 AttrNumber *confkey,
							 Oid *conpfeqop,
							 Oid parentInsTrigger,
							 Oid parentUpdTrigger,
							 Relation trigrel)
{
	HeapTuple	parentConstrTup;
	Form_pg_constraint parentConstr;
	HeapTuple	partcontup;
	Form_pg_constraint partConstr;

	parentConstrTup = SearchSysCache1(CONSTROID,
									  ObjectIdGetDatum(parentConstrOid));
	if (!HeapTupleIsValid(parentConstrTup))
		elog(ERROR, "cache lookup failed for constraint %u", parentConstrOid);
	parentConstr = (Form_pg_constraint) GETSTRUCT(parentConstrTup);

	/*
	 * Do some quick & easy initial checks.  If any of these fail, we cannot
	 * use this constraint.
	 */
	if (fk->confrelid != parentConstr->confrelid || fk->nkeys != numfks)
	{
		ReleaseSysCache(parentConstrTup);
		return false;
	}
	for (int i = 0; i < numfks; i++)
	{
		if (fk->conkey[i] != mapped_conkey[i] ||
			fk->confkey[i] != confkey[i] ||
			fk->conpfeqop[i] != conpfeqop[i])
		{
			ReleaseSysCache(parentConstrTup);
			return false;
		}
	}

	/* Looks good so far; perform more extensive checks. */
	partcontup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fk->conoid));
	if (!HeapTupleIsValid(partcontup))
		elog(ERROR, "cache lookup failed for constraint %u", fk->conoid);
	partConstr = (Form_pg_constraint) GETSTRUCT(partcontup);

	/*
	 * An error should be raised if the constraint enforceability is
	 * different. Returning false without raising an error, as we do for other
	 * attributes, could lead to a duplicate constraint with the same
	 * enforceability as the parent. While this may be acceptable, it may not
	 * be ideal. Therefore, it's better to raise an error and allow the user
	 * to correct the enforceability before proceeding.
	 */
	if (partConstr->conenforced != parentConstr->conenforced)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
				 errmsg("constraint \"%s\" enforceability conflicts with constraint \"%s\" on relation \"%s\"",
						NameStr(parentConstr->conname),
						NameStr(partConstr->conname),
						RelationGetRelationName(partition))));

	if (OidIsValid(partConstr->conparentid) ||
		partConstr->condeferrable != parentConstr->condeferrable ||
		partConstr->condeferred != parentConstr->condeferred ||
		partConstr->confupdtype != parentConstr->confupdtype ||
		partConstr->confdeltype != parentConstr->confdeltype ||
		partConstr->confmatchtype != parentConstr->confmatchtype)
	{
		ReleaseSysCache(parentConstrTup);
		ReleaseSysCache(partcontup);
		return false;
	}

	ReleaseSysCache(parentConstrTup);
	ReleaseSysCache(partcontup);

	/* Looks good!  Attach this constraint. */
	AttachPartitionForeignKey(wqueue, partition, fk->conoid,
							  parentConstrOid, parentInsTrigger,
							  parentUpdTrigger, trigrel);

	return true;
}

/*
 * AttachPartitionForeignKey
 *
 * The subroutine for tryAttachPartitionForeignKey performs the final tasks of
 * attaching the constraint, removing redundant triggers and entries from
 * pg_constraint, and setting the constraint's parent.
 */
static void
AttachPartitionForeignKey(List **wqueue,
						  Relation partition,
						  Oid partConstrOid,
						  Oid parentConstrOid,
						  Oid parentInsTrigger,
						  Oid parentUpdTrigger,
						  Relation trigrel)
{
	HeapTuple	parentConstrTup;
	Form_pg_constraint parentConstr;
	HeapTuple	partcontup;
	Form_pg_constraint partConstr;
	bool		queueValidation;
	Oid			partConstrFrelid;
	Oid			partConstrRelid;
	bool		parentConstrIsEnforced;

	/* Fetch the parent constraint tuple */
	parentConstrTup = SearchSysCache1(CONSTROID,
									  ObjectIdGetDatum(parentConstrOid));
	if (!HeapTupleIsValid(parentConstrTup))
		elog(ERROR, "cache lookup failed for constraint %u", parentConstrOid);
	parentConstr = (Form_pg_constraint) GETSTRUCT(parentConstrTup);
	parentConstrIsEnforced = parentConstr->conenforced;

	/* Fetch the child constraint tuple */
	partcontup = SearchSysCache1(CONSTROID,
								 ObjectIdGetDatum(partConstrOid));
	if (!HeapTupleIsValid(partcontup))
		elog(ERROR, "cache lookup failed for constraint %u", partConstrOid);
	partConstr = (Form_pg_constraint) GETSTRUCT(partcontup);
	partConstrFrelid = partConstr->confrelid;
	partConstrRelid = partConstr->conrelid;

	/*
	 * If the referenced table is partitioned, then the partition we're
	 * attaching now has extra pg_constraint rows and action triggers that are
	 * no longer needed.  Remove those.
	 */
	if (get_rel_relkind(partConstrFrelid) == RELKIND_PARTITIONED_TABLE)
	{
		Relation	pg_constraint = table_open(ConstraintRelationId, RowShareLock);

		RemoveInheritedConstraint(pg_constraint, trigrel, partConstrOid,
								  partConstrRelid);

		table_close(pg_constraint, RowShareLock);
	}

	/*
	 * Will we need to validate this constraint?   A valid parent constraint
	 * implies that all child constraints have been validated, so if this one
	 * isn't, we must trigger phase 3 validation.
	 */
	queueValidation = parentConstr->convalidated && !partConstr->convalidated;

	ReleaseSysCache(partcontup);
	ReleaseSysCache(parentConstrTup);

	/*
	 * The action triggers in the new partition become redundant -- the parent
	 * table already has equivalent ones, and those will be able to reach the
	 * partition.  Remove the ones in the partition.  We identify them because
	 * they have our constraint OID, as well as being on the referenced rel.
	 */
	DropForeignKeyConstraintTriggers(trigrel, partConstrOid, partConstrFrelid,
									 partConstrRelid);

	ConstraintSetParentConstraint(partConstrOid, parentConstrOid,
								  RelationGetRelid(partition));

	/*
	 * Like the constraint, attach partition's "check" triggers to the
	 * corresponding parent triggers if the constraint is ENFORCED. NOT
	 * ENFORCED constraints do not have these triggers.
	 */
	if (parentConstrIsEnforced)
	{
		Oid			insertTriggerOid,
					updateTriggerOid;

		GetForeignKeyCheckTriggers(trigrel,
								   partConstrOid, partConstrFrelid, partConstrRelid,
								   &insertTriggerOid, &updateTriggerOid);
		Assert(OidIsValid(insertTriggerOid) && OidIsValid(parentInsTrigger));
		TriggerSetParentTrigger(trigrel, insertTriggerOid, parentInsTrigger,
								RelationGetRelid(partition));
		Assert(OidIsValid(updateTriggerOid) && OidIsValid(parentUpdTrigger));
		TriggerSetParentTrigger(trigrel, updateTriggerOid, parentUpdTrigger,
								RelationGetRelid(partition));
	}

	/*
	 * We updated this pg_constraint row above to set its parent; validating
	 * it will cause its convalidated flag to change, so we need CCI here.  In
	 * addition, we need it unconditionally for the rare case where the parent
	 * table has *two* identical constraints; when reaching this function for
	 * the second one, we must have made our changes visible, otherwise we
	 * would try to attach both to this one.
	 */
	CommandCounterIncrement();

	/* If validation is needed, put it in the queue now. */
	if (queueValidation)
	{
		Relation	conrel;
		Oid			confrelid;

		conrel = table_open(ConstraintRelationId, RowExclusiveLock);

		partcontup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(partConstrOid));
		if (!HeapTupleIsValid(partcontup))
			elog(ERROR, "cache lookup failed for constraint %u", partConstrOid);

		confrelid = ((Form_pg_constraint) GETSTRUCT(partcontup))->confrelid;

		/* Use the same lock as for AT_ValidateConstraint */
		QueueFKConstraintValidation(wqueue, conrel, partition, confrelid,
									partcontup, ShareUpdateExclusiveLock);
		ReleaseSysCache(partcontup);
		table_close(conrel, RowExclusiveLock);
	}
}

/*
 * RemoveInheritedConstraint
 *
 * Removes the constraint and its associated trigger from the specified
 * relation, which inherited the given constraint.
 */
static void
RemoveInheritedConstraint(Relation conrel, Relation trigrel, Oid conoid,
						  Oid conrelid)
{
	ObjectAddresses *objs;
	HeapTuple	consttup;
	ScanKeyData key;
	SysScanDesc scan;
	HeapTuple	trigtup;

	ScanKeyInit(&key,
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(conrelid));

	scan = systable_beginscan(conrel,
							  ConstraintRelidTypidNameIndexId,
							  true, NULL, 1, &key);
	objs = new_object_addresses();
	while ((consttup = systable_getnext(scan)) != NULL)
	{
		Form_pg_constraint conform = (Form_pg_constraint) GETSTRUCT(consttup);

		if (conform->conparentid != conoid)
			continue;
		else
		{
			ObjectAddress addr;
			SysScanDesc scan2;
			ScanKeyData key2;
			int			n PG_USED_FOR_ASSERTS_ONLY;

			ObjectAddressSet(addr, ConstraintRelationId, conform->oid);
			add_exact_object_address(&addr, objs);

			/*
			 * First we must delete the dependency record that binds the
			 * constraint records together.
			 */
			n = deleteDependencyRecordsForSpecific(ConstraintRelationId,
												   conform->oid,
												   DEPENDENCY_INTERNAL,
												   ConstraintRelationId,
												   conoid);
			Assert(n == 1);		/* actually only one is expected */

			/*
			 * Now search for the triggers for this constraint and set them up
			 * for deletion too
			 */
			ScanKeyInit(&key2,
						Anum_pg_trigger_tgconstraint,
						BTEqualStrategyNumber, F_OIDEQ,
						ObjectIdGetDatum(conform->oid));
			scan2 = systable_beginscan(trigrel, TriggerConstraintIndexId,
									   true, NULL, 1, &key2);
			while ((trigtup = systable_getnext(scan2)) != NULL)
			{
				ObjectAddressSet(addr, TriggerRelationId,
								 ((Form_pg_trigger) GETSTRUCT(trigtup))->oid);
				add_exact_object_address(&addr, objs);
			}
			systable_endscan(scan2);
		}
	}
	/* make the dependency deletions visible */
	CommandCounterIncrement();
	performMultipleDeletions(objs, DROP_RESTRICT,
							 PERFORM_DELETION_INTERNAL);
	systable_endscan(scan);
}

/*
 * DropForeignKeyConstraintTriggers
 *
 * The subroutine for tryAttachPartitionForeignKey handles the deletion of
 * action triggers for the foreign key constraint.
 *
 * If valid confrelid and conrelid values are not provided, the respective
 * trigger check will be skipped, and the trigger will be considered for
 * removal.
 */
static void
DropForeignKeyConstraintTriggers(Relation trigrel, Oid conoid, Oid confrelid,
								 Oid conrelid)
{
	ScanKeyData key;
	SysScanDesc scan;
	HeapTuple	trigtup;

	ScanKeyInit(&key,
				Anum_pg_trigger_tgconstraint,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(conoid));
	scan = systable_beginscan(trigrel, TriggerConstraintIndexId, true,
							  NULL, 1, &key);
	while ((trigtup = systable_getnext(scan)) != NULL)
	{
		Form_pg_trigger trgform = (Form_pg_trigger) GETSTRUCT(trigtup);
		ObjectAddress trigger;

		/* Invalid if trigger is not for a referential integrity constraint */
		if (!OidIsValid(trgform->tgconstrrelid))
			continue;
		if (OidIsValid(conrelid) && trgform->tgconstrrelid != conrelid)
			continue;
		if (OidIsValid(confrelid) && trgform->tgrelid != confrelid)
			continue;

		/* We should be dropping trigger related to foreign key constraint */
		Assert(trgform->tgfoid == F_RI_FKEY_CHECK_INS ||
			   trgform->tgfoid == F_RI_FKEY_CHECK_UPD ||
			   trgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
			   trgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
			   trgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
			   trgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
			   trgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
			   trgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
			   trgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL ||
			   trgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD ||
			   trgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
			   trgform->tgfoid == F_RI_FKEY_NOACTION_UPD);

		/*
		 * The constraint is originally set up to contain this trigger as an
		 * implementation object, so there's a dependency record that links
		 * the two; however, since the trigger is no longer needed, we remove
		 * the dependency link in order to be able to drop the trigger while
		 * keeping the constraint intact.
		 */
		deleteDependencyRecordsFor(TriggerRelationId,
								   trgform->oid,
								   false);
		/* make dependency deletion visible to performDeletion */
		CommandCounterIncrement();
		ObjectAddressSet(trigger, TriggerRelationId,
						 trgform->oid);
		performDeletion(&trigger, DROP_RESTRICT, 0);
		/* make trigger drop visible, in case the loop iterates */
		CommandCounterIncrement();
	}

	systable_endscan(scan);
}

/*
 * GetForeignKeyActionTriggers
 * 		Returns delete and update "action" triggers of the given relation
 * 		belonging to the given constraint
 */
static void
GetForeignKeyActionTriggers(Relation trigrel,
							Oid conoid, Oid confrelid, Oid conrelid,
							Oid *deleteTriggerOid,
							Oid *updateTriggerOid)
{
	ScanKeyData key;
	SysScanDesc scan;
	HeapTuple	trigtup;

	*deleteTriggerOid = *updateTriggerOid = InvalidOid;
	ScanKeyInit(&key,
				Anum_pg_trigger_tgconstraint,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(conoid));

	scan = systable_beginscan(trigrel, TriggerConstraintIndexId, true,
							  NULL, 1, &key);
	while ((trigtup = systable_getnext(scan)) != NULL)
	{
		Form_pg_trigger trgform = (Form_pg_trigger) GETSTRUCT(trigtup);

		if (trgform->tgconstrrelid != conrelid)
			continue;
		if (trgform->tgrelid != confrelid)
			continue;
		/* Only ever look at "action" triggers on the PK side. */
		if (RI_FKey_trigger_type(trgform->tgfoid) != RI_TRIGGER_PK)
			continue;
		if (TRIGGER_FOR_DELETE(trgform->tgtype))
		{
			Assert(*deleteTriggerOid == InvalidOid);
			*deleteTriggerOid = trgform->oid;
		}
		else if (TRIGGER_FOR_UPDATE(trgform->tgtype))
		{
			Assert(*updateTriggerOid == InvalidOid);
			*updateTriggerOid = trgform->oid;
		}
#ifndef USE_ASSERT_CHECKING
		/* In an assert-enabled build, continue looking to find duplicates */
		if (OidIsValid(*deleteTriggerOid) && OidIsValid(*updateTriggerOid))
			break;
#endif
	}

	if (!OidIsValid(*deleteTriggerOid))
		elog(ERROR, "could not find ON DELETE action trigger of foreign key constraint %u",
			 conoid);
	if (!OidIsValid(*updateTriggerOid))
		elog(ERROR, "could not find ON UPDATE action trigger of foreign key constraint %u",
			 conoid);

	systable_endscan(scan);
}

/*
 * GetForeignKeyCheckTriggers
 * 		Returns insert and update "check" triggers of the given relation
 * 		belonging to the given constraint
 */
static void
GetForeignKeyCheckTriggers(Relation trigrel,
						   Oid conoid, Oid confrelid, Oid conrelid,
						   Oid *insertTriggerOid,
						   Oid *updateTriggerOid)
{
	ScanKeyData key;
	SysScanDesc scan;
	HeapTuple	trigtup;

	*insertTriggerOid = *updateTriggerOid = InvalidOid;
	ScanKeyInit(&key,
				Anum_pg_trigger_tgconstraint,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(conoid));

	scan = systable_beginscan(trigrel, TriggerConstraintIndexId, true,
							  NULL, 1, &key);
	while ((trigtup = systable_getnext(scan)) != NULL)
	{
		Form_pg_trigger trgform = (Form_pg_trigger) GETSTRUCT(trigtup);

		if (trgform->tgconstrrelid != confrelid)
			continue;
		if (trgform->tgrelid != conrelid)
			continue;
		/* Only ever look at "check" triggers on the FK side. */
		if (RI_FKey_trigger_type(trgform->tgfoid) != RI_TRIGGER_FK)
			continue;
		if (TRIGGER_FOR_INSERT(trgform->tgtype))
		{
			Assert(*insertTriggerOid == InvalidOid);
			*insertTriggerOid = trgform->oid;
		}
		else if (TRIGGER_FOR_UPDATE(trgform->tgtype))
		{
			Assert(*updateTriggerOid == InvalidOid);
			*updateTriggerOid = trgform->oid;
		}
#ifndef USE_ASSERT_CHECKING
		/* In an assert-enabled build, continue looking to find duplicates. */
		if (OidIsValid(*insertTriggerOid) && OidIsValid(*updateTriggerOid))
			break;
#endif
	}

	if (!OidIsValid(*insertTriggerOid))
		elog(ERROR, "could not find ON INSERT check triggers of foreign key constraint %u",
			 conoid);
	if (!OidIsValid(*updateTriggerOid))
		elog(ERROR, "could not find ON UPDATE check triggers of foreign key constraint %u",
			 conoid);

	systable_endscan(scan);
}

/*
 * ALTER TABLE ALTER CONSTRAINT
 *
 * Update the attributes of a constraint.
 *
 * Currently only works for Foreign Key and not null constraints.
 *
 * If the constraint is modified, returns its address; otherwise, return
 * InvalidObjectAddress.
 */
static ObjectAddress
ATExecAlterConstraint(List **wqueue, Relation rel, ATAlterConstraint *cmdcon,
					  bool recurse, LOCKMODE lockmode)
{
	Relation	conrel;
	Relation	tgrel;
	SysScanDesc scan;
	ScanKeyData skey[3];
	HeapTuple	contuple;
	Form_pg_constraint currcon;
	ObjectAddress address;

	/*
	 * Disallow altering ONLY a partitioned table, as it would make no sense.
	 * This is okay for legacy inheritance.
	 */
	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE && !recurse)
		ereport(ERROR,
				errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				errmsg("constraint must be altered in child tables too"),
				errhint("Do not specify the ONLY keyword."));


	conrel = table_open(ConstraintRelationId, RowExclusiveLock);
	tgrel = table_open(TriggerRelationId, RowExclusiveLock);

	/*
	 * Find and check the target constraint
	 */
	ScanKeyInit(&skey[0],
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	ScanKeyInit(&skey[1],
				Anum_pg_constraint_contypid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(InvalidOid));
	ScanKeyInit(&skey[2],
				Anum_pg_constraint_conname,
				BTEqualStrategyNumber, F_NAMEEQ,
				CStringGetDatum(cmdcon->conname));
	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
							  true, NULL, 3, skey);

	/* There can be at most one matching row */
	if (!HeapTupleIsValid(contuple = systable_getnext(scan)))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
						cmdcon->conname, RelationGetRelationName(rel))));

	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
	if (cmdcon->alterDeferrability && currcon->contype != CONSTRAINT_FOREIGN)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
						cmdcon->conname, RelationGetRelationName(rel))));
	if (cmdcon->alterEnforceability && currcon->contype != CONSTRAINT_FOREIGN)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot alter enforceability of constraint \"%s\" of relation \"%s\"",
						cmdcon->conname, RelationGetRelationName(rel))));
	if (cmdcon->alterInheritability &&
		currcon->contype != CONSTRAINT_NOTNULL)
		ereport(ERROR,
				errcode(ERRCODE_WRONG_OBJECT_TYPE),
				errmsg("constraint \"%s\" of relation \"%s\" is not a not-null constraint",
					   cmdcon->conname, RelationGetRelationName(rel)));

	/* Refuse to modify inheritability of inherited constraints */
	if (cmdcon->alterInheritability &&
		cmdcon->noinherit && currcon->coninhcount > 0)
		ereport(ERROR,
				errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				errmsg("cannot alter inherited constraint \"%s\" on relation \"%s\"",
					   NameStr(currcon->conname),
					   RelationGetRelationName(rel)));

	/*
	 * If it's not the topmost constraint, raise an error.
	 *
	 * Altering a non-topmost constraint leaves some triggers untouched, since
	 * they are not directly connected to this constraint; also, pg_dump would
	 * ignore the deferrability status of the individual constraint, since it
	 * only dumps topmost constraints.  Avoid these problems by refusing this
	 * operation and telling the user to alter the parent constraint instead.
	 */
	if (OidIsValid(currcon->conparentid))
	{
		HeapTuple	tp;
		Oid			parent = currcon->conparentid;
		char	   *ancestorname = NULL;
		char	   *ancestortable = NULL;

		/* Loop to find the topmost constraint */
		while (HeapTupleIsValid(tp = SearchSysCache1(CONSTROID, ObjectIdGetDatum(parent))))
		{
			Form_pg_constraint contup = (Form_pg_constraint) GETSTRUCT(tp);

			/* If no parent, this is the constraint we want */
			if (!OidIsValid(contup->conparentid))
			{
				ancestorname = pstrdup(NameStr(contup->conname));
				ancestortable = get_rel_name(contup->conrelid);
				ReleaseSysCache(tp);
				break;
			}

			parent = contup->conparentid;
			ReleaseSysCache(tp);
		}

		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("cannot alter constraint \"%s\" on relation \"%s\"",
						cmdcon->conname, RelationGetRelationName(rel)),
				 ancestorname && ancestortable ?
				 errdetail("Constraint \"%s\" is derived from constraint \"%s\" of relation \"%s\".",
						   cmdcon->conname, ancestorname, ancestortable) : 0,
				 errhint("You may alter the constraint it derives from instead.")));
	}

	address = InvalidObjectAddress;

	/*
	 * Do the actual catalog work, and recurse if necessary.
	 */
	if (ATExecAlterConstraintInternal(wqueue, cmdcon, conrel, tgrel, rel,
									  contuple, recurse, lockmode))
		ObjectAddressSet(address, ConstraintRelationId, currcon->oid);

	systable_endscan(scan);

	table_close(tgrel, RowExclusiveLock);
	table_close(conrel, RowExclusiveLock);

	return address;
}

/*
 * A subroutine of ATExecAlterConstraint that calls the respective routines for
 * altering constraint's enforceability, deferrability or inheritability.
 */
static bool
ATExecAlterConstraintInternal(List **wqueue, ATAlterConstraint *cmdcon,
							  Relation conrel, Relation tgrel, Relation rel,
							  HeapTuple contuple, bool recurse,
							  LOCKMODE lockmode)
{
	Form_pg_constraint currcon;
	bool		changed = false;
	List	   *otherrelids = NIL;

	currcon = (Form_pg_constraint) GETSTRUCT(contuple);

	/*
	 * Do the catalog work for the enforceability or deferrability change,
	 * recurse if necessary.
	 *
	 * Note that even if deferrability is requested to be altered along with
	 * enforceability, we don't need to explicitly update multiple entries in
	 * pg_trigger related to deferrability.
	 *
	 * Modifying enforceability involves either creating or dropping the
	 * trigger, during which the deferrability setting will be adjusted
	 * automatically.
	 */
	if (cmdcon->alterEnforceability &&
		ATExecAlterConstrEnforceability(wqueue, cmdcon, conrel, tgrel,
										currcon->conrelid, currcon->confrelid,
										contuple, lockmode, InvalidOid,
										InvalidOid, InvalidOid, InvalidOid))
		changed = true;

	else if (cmdcon->alterDeferrability &&
			 ATExecAlterConstrDeferrability(wqueue, cmdcon, conrel, tgrel, rel,
											contuple, recurse, &otherrelids,
											lockmode))
	{
		/*
		 * AlterConstrUpdateConstraintEntry already invalidated relcache for
		 * the relations having the constraint itself; here we also invalidate
		 * for relations that have any triggers that are part of the
		 * constraint.
		 */
		foreach_oid(relid, otherrelids)
			CacheInvalidateRelcacheByRelid(relid);

		changed = true;
	}

	/*
	 * Do the catalog work for the inheritability change.
	 */
	if (cmdcon->alterInheritability &&
		ATExecAlterConstrInheritability(wqueue, cmdcon, conrel, rel, contuple,
										lockmode))
		changed = true;

	return changed;
}

/*
 * Returns true if the constraint's enforceability is altered.
 *
 * Depending on whether the constraint is being set to ENFORCED or NOT
 * ENFORCED, it creates or drops the trigger accordingly.
 *
 * Note that we must recurse even when trying to change a constraint to not
 * enforced if it is already not enforced, in case descendant constraints
 * might be enforced and need to be changed to not enforced. Conversely, we
 * should do nothing if a constraint is being set to enforced and is already
 * enforced, as descendant constraints cannot be different in that case.
 */
static bool
ATExecAlterConstrEnforceability(List **wqueue, ATAlterConstraint *cmdcon,
								Relation conrel, Relation tgrel,
								Oid fkrelid, Oid pkrelid,
								HeapTuple contuple, LOCKMODE lockmode,
								Oid ReferencedParentDelTrigger,
								Oid ReferencedParentUpdTrigger,
								Oid ReferencingParentInsTrigger,
								Oid ReferencingParentUpdTrigger)
{
	Form_pg_constraint currcon;
	Oid			conoid;
	Relation	rel;
	bool		changed = false;

	/* Since this function recurses, it could be driven to stack overflow */
	check_stack_depth();

	Assert(cmdcon->alterEnforceability);

	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
	conoid = currcon->oid;

	/* Should be foreign key constraint */
	Assert(currcon->contype == CONSTRAINT_FOREIGN);

	rel = table_open(currcon->conrelid, lockmode);

	if (currcon->conenforced != cmdcon->is_enforced)
	{
		AlterConstrUpdateConstraintEntry(cmdcon, conrel, contuple);
		changed = true;
	}

	/* Drop triggers */
	if (!cmdcon->is_enforced)
	{
		/*
		 * When setting a constraint to NOT ENFORCED, the constraint triggers
		 * need to be dropped. Therefore, we must process the child relations
		 * first, followed by the parent, to account for dependencies.
		 */
		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
			get_rel_relkind(currcon->confrelid) == RELKIND_PARTITIONED_TABLE)
			AlterConstrEnforceabilityRecurse(wqueue, cmdcon, conrel, tgrel,
											 fkrelid, pkrelid, contuple,
											 lockmode, InvalidOid, InvalidOid,
											 InvalidOid, InvalidOid);

		/* Drop all the triggers */
		DropForeignKeyConstraintTriggers(tgrel, conoid, InvalidOid, InvalidOid);
	}
	else if (changed)			/* Create triggers */
	{
		Oid			ReferencedDelTriggerOid = InvalidOid,
					ReferencedUpdTriggerOid = InvalidOid,
					ReferencingInsTriggerOid = InvalidOid,
					ReferencingUpdTriggerOid = InvalidOid;

		/* Prepare the minimal information required for trigger creation. */
		Constraint *fkconstraint = makeNode(Constraint);

		fkconstraint->conname = pstrdup(NameStr(currcon->conname));
		fkconstraint->fk_matchtype = currcon->confmatchtype;
		fkconstraint->fk_upd_action = currcon->confupdtype;
		fkconstraint->fk_del_action = currcon->confdeltype;
		fkconstraint->deferrable = currcon->condeferrable;
		fkconstraint->initdeferred = currcon->condeferred;

		/* Create referenced triggers */
		if (currcon->conrelid == fkrelid)
			createForeignKeyActionTriggers(currcon->conrelid,
										   currcon->confrelid,
										   fkconstraint,
										   conoid,
										   currcon->conindid,
										   ReferencedParentDelTrigger,
										   ReferencedParentUpdTrigger,
										   &ReferencedDelTriggerOid,
										   &ReferencedUpdTriggerOid);

		/* Create referencing triggers */
		if (currcon->confrelid == pkrelid)
			createForeignKeyCheckTriggers(currcon->conrelid,
										  pkrelid,
										  fkconstraint,
										  conoid,
										  currcon->conindid,
										  ReferencingParentInsTrigger,
										  ReferencingParentUpdTrigger,
										  &ReferencingInsTriggerOid,
										  &ReferencingUpdTriggerOid);

		/*
		 * Tell Phase 3 to check that the constraint is satisfied by existing
		 * rows.  Only applies to leaf partitions, and (for constraints that
		 * reference a partitioned table) only if this is not one of the
		 * pg_constraint rows that exist solely to support action triggers.
		 */
		if (rel->rd_rel->relkind == RELKIND_RELATION &&
			currcon->confrelid == pkrelid)
		{
			AlteredTableInfo *tab;
			NewConstraint *newcon;

			newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
			newcon->name = fkconstraint->conname;
			newcon->contype = CONSTR_FOREIGN;
			newcon->refrelid = currcon->confrelid;
			newcon->refindid = currcon->conindid;
			newcon->conid = currcon->oid;
			newcon->qual = (Node *) fkconstraint;

			/* Find or create work queue entry for this table */
			tab = ATGetQueueEntry(wqueue, rel);
			tab->constraints = lappend(tab->constraints, newcon);
		}

		/*
		 * If the table at either end of the constraint is partitioned, we
		 * need to recurse and create triggers for each constraint that is a
		 * child of this one.
		 */
		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
			get_rel_relkind(currcon->confrelid) == RELKIND_PARTITIONED_TABLE)
			AlterConstrEnforceabilityRecurse(wqueue, cmdcon, conrel, tgrel,
											 fkrelid, pkrelid, contuple,
											 lockmode, ReferencedDelTriggerOid,
											 ReferencedUpdTriggerOid,
											 ReferencingInsTriggerOid,
											 ReferencingUpdTriggerOid);
	}

	table_close(rel, NoLock);

	return changed;
}

/*
 * Returns true if the constraint's deferrability is altered.
 *
 * *otherrelids is appended OIDs of relations containing affected triggers.
 *
 * Note that we must recurse even when the values are correct, in case
 * indirect descendants have had their constraints altered locally.
 * (This could be avoided if we forbade altering constraints in partitions
 * but existing releases don't do that.)
 */
static bool
ATExecAlterConstrDeferrability(List **wqueue, ATAlterConstraint *cmdcon,
							   Relation conrel, Relation tgrel, Relation rel,
							   HeapTuple contuple, bool recurse,
							   List **otherrelids, LOCKMODE lockmode)
{
	Form_pg_constraint currcon;
	Oid			refrelid;
	bool		changed = false;

	/* since this function recurses, it could be driven to stack overflow */
	check_stack_depth();

	Assert(cmdcon->alterDeferrability);

	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
	refrelid = currcon->confrelid;

	/* Should be foreign key constraint */
	Assert(currcon->contype == CONSTRAINT_FOREIGN);

	/*
	 * If called to modify a constraint that's already in the desired state,
	 * silently do nothing.
	 */
	if (currcon->condeferrable != cmdcon->deferrable ||
		currcon->condeferred != cmdcon->initdeferred)
	{
		AlterConstrUpdateConstraintEntry(cmdcon, conrel, contuple);
		changed = true;

		/*
		 * Now we need to update the multiple entries in pg_trigger that
		 * implement the constraint.
		 */
		AlterConstrTriggerDeferrability(currcon->oid, tgrel, rel,
										cmdcon->deferrable,
										cmdcon->initdeferred, otherrelids);
	}

	/*
	 * If the table at either end of the constraint is partitioned, we need to
	 * handle every constraint that is a child of this one.
	 */
	if (recurse && changed &&
		(rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
		 get_rel_relkind(refrelid) == RELKIND_PARTITIONED_TABLE))
		AlterConstrDeferrabilityRecurse(wqueue, cmdcon, conrel, tgrel, rel,
										contuple, recurse, otherrelids,
										lockmode);

	return changed;
}

/*
 * Returns true if the constraint's inheritability is altered.
 */
static bool
ATExecAlterConstrInheritability(List **wqueue, ATAlterConstraint *cmdcon,
								Relation conrel, Relation rel,
								HeapTuple contuple, LOCKMODE lockmode)
{
	Form_pg_constraint currcon;
	AttrNumber	colNum;
	char	   *colName;
	List	   *children;

	Assert(cmdcon->alterInheritability);

	currcon = (Form_pg_constraint) GETSTRUCT(contuple);

	/* The current implementation only works for NOT NULL constraints */
	Assert(currcon->contype == CONSTRAINT_NOTNULL);

	/*
	 * If called to modify a constraint that's already in the desired state,
	 * silently do nothing.
	 */
	if (cmdcon->noinherit == currcon->connoinherit)
		return false;

	AlterConstrUpdateConstraintEntry(cmdcon, conrel, contuple);
	CommandCounterIncrement();

	/* Fetch the column number and name */
	colNum = extractNotNullColumn(contuple);
	colName = get_attname(currcon->conrelid, colNum, false);

	/*
	 * Propagate the change to children.  For this subcommand type we don't
	 * recursively affect children, just the immediate level.
	 */
	children = find_inheritance_children(RelationGetRelid(rel),
										 lockmode);
	foreach_oid(childoid, children)
	{
		ObjectAddress addr;

		if (cmdcon->noinherit)
		{
			HeapTuple	childtup;
			Form_pg_constraint childcon;

			childtup = findNotNullConstraint(childoid, colName);
			if (!childtup)
				elog(ERROR, "cache lookup failed for not-null constraint on column \"%s\" of relation %u",
					 colName, childoid);
			childcon = (Form_pg_constraint) GETSTRUCT(childtup);
			Assert(childcon->coninhcount > 0);
			childcon->coninhcount--;
			childcon->conislocal = true;
			CatalogTupleUpdate(conrel, &childtup->t_self, childtup);
			heap_freetuple(childtup);
		}
		else
		{
			Relation	childrel = table_open(childoid, NoLock);

			addr = ATExecSetNotNull(wqueue, childrel, NameStr(currcon->conname),
									colName, true, true, lockmode);
			if (OidIsValid(addr.objectId))
				CommandCounterIncrement();
			table_close(childrel, NoLock);
		}
	}

	return true;
}

/*
 * A subroutine of ATExecAlterConstrDeferrability that updated constraint
 * trigger's deferrability.
 *
 * The arguments to this function have the same meaning as the arguments to
 * ATExecAlterConstrDeferrability.
 */
static void
AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Relation rel,
								bool deferrable, bool initdeferred,
								List **otherrelids)
{
	HeapTuple	tgtuple;
	ScanKeyData tgkey;
	SysScanDesc tgscan;

	ScanKeyInit(&tgkey,
				Anum_pg_trigger_tgconstraint,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(conoid));
	tgscan = systable_beginscan(tgrel, TriggerConstraintIndexId, true,
								NULL, 1, &tgkey);
	while (HeapTupleIsValid(tgtuple = systable_getnext(tgscan)))
	{
		Form_pg_trigger tgform = (Form_pg_trigger) GETSTRUCT(tgtuple);
		Form_pg_trigger copy_tg;
		HeapTuple	tgCopyTuple;

		/*
		 * Remember OIDs of other relation(s) involved in FK constraint.
		 * (Note: it's likely that we could skip forcing a relcache inval for
		 * other rels that don't have a trigger whose properties change, but
		 * let's be conservative.)
		 */
		if (tgform->tgrelid != RelationGetRelid(rel))
			*otherrelids = list_append_unique_oid(*otherrelids,
												  tgform->tgrelid);

		/*
		 * Update enable status and deferrability of RI_FKey_noaction_del,
		 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
		 * triggers, but not others; see createForeignKeyActionTriggers and
		 * CreateFKCheckTrigger.
		 */
		if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
			tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
			tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
			tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
			continue;

		tgCopyTuple = heap_copytuple(tgtuple);
		copy_tg = (Form_pg_trigger) GETSTRUCT(tgCopyTuple);

		copy_tg->tgdeferrable = deferrable;
		copy_tg->tginitdeferred = initdeferred;
		CatalogTupleUpdate(tgrel, &tgCopyTuple->t_self, tgCopyTuple);

		InvokeObjectPostAlterHook(TriggerRelationId, tgform->oid, 0);

		heap_freetuple(tgCopyTuple);
	}

	systable_endscan(tgscan);
}

/*
 * Invokes ATExecAlterConstrEnforceability for each constraint that is a child of
 * the specified constraint.
 *
 * Note that this doesn't handle recursion the normal way, viz. by scanning the
 * list of child relations and recursing; instead it uses the conparentid
 * relationships.  This may need to be reconsidered.
 *
 * The arguments to this function have the same meaning as the arguments to
 * ATExecAlterConstrEnforceability.
 */
static void
AlterConstrEnforceabilityRecurse(List **wqueue, ATAlterConstraint *cmdcon,
								 Relation conrel, Relation tgrel,
								 Oid fkrelid, Oid pkrelid,
								 HeapTuple contuple, LOCKMODE lockmode,
								 Oid ReferencedParentDelTrigger,
								 Oid ReferencedParentUpdTrigger,
								 Oid ReferencingParentInsTrigger,
								 Oid ReferencingParentUpdTrigger)
{
	Form_pg_constraint currcon;
	Oid			conoid;
	ScanKeyData pkey;
	SysScanDesc pscan;
	HeapTuple	childtup;

	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
	conoid = currcon->oid;

	ScanKeyInit(&pkey,
				Anum_pg_constraint_conparentid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(conoid));

	pscan = systable_beginscan(conrel, ConstraintParentIndexId,
							   true, NULL, 1, &pkey);

	while (HeapTupleIsValid(childtup = systable_getnext(pscan)))
		ATExecAlterConstrEnforceability(wqueue, cmdcon, conrel, tgrel, fkrelid,
										pkrelid, childtup, lockmode,
										ReferencedParentDelTrigger,
										ReferencedParentUpdTrigger,
										ReferencingParentInsTrigger,
										ReferencingParentUpdTrigger);

	systable_endscan(pscan);
}

/*
 * Invokes ATExecAlterConstrDeferrability for each constraint that is a child of
 * the specified constraint.
 *
 * Note that this doesn't handle recursion the normal way, viz. by scanning the
 * list of child relations and recursing; instead it uses the conparentid
 * relationships.  This may need to be reconsidered.
 *
 * The arguments to this function have the same meaning as the arguments to
 * ATExecAlterConstrDeferrability.
 */
static void
AlterConstrDeferrabilityRecurse(List **wqueue, ATAlterConstraint *cmdcon,
								Relation conrel, Relation tgrel, Relation rel,
								HeapTuple contuple, bool recurse,
								List **otherrelids, LOCKMODE lockmode)
{
	Form_pg_constraint currcon;
	Oid			conoid;
	ScanKeyData pkey;
	SysScanDesc pscan;
	HeapTuple	childtup;

	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
	conoid = currcon->oid;

	ScanKeyInit(&pkey,
				Anum_pg_constraint_conparentid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(conoid));

	pscan = systable_beginscan(conrel, ConstraintParentIndexId,
							   true, NULL, 1, &pkey);

	while (HeapTupleIsValid(childtup = systable_getnext(pscan)))
	{
		Form_pg_constraint childcon = (Form_pg_constraint) GETSTRUCT(childtup);
		Relation	childrel;

		childrel = table_open(childcon->conrelid, lockmode);

		ATExecAlterConstrDeferrability(wqueue, cmdcon, conrel, tgrel, childrel,
									   childtup, recurse, otherrelids, lockmode);
		table_close(childrel, NoLock);
	}

	systable_endscan(pscan);
}

/*
 * Update the constraint entry for the given ATAlterConstraint command, and
 * invoke the appropriate hooks.
 */
static void
AlterConstrUpdateConstraintEntry(ATAlterConstraint *cmdcon, Relation conrel,
								 HeapTuple contuple)
{
	HeapTuple	copyTuple;
	Form_pg_constraint copy_con;

	Assert(cmdcon->alterEnforceability || cmdcon->alterDeferrability ||
		   cmdcon->alterInheritability);

	copyTuple = heap_copytuple(contuple);
	copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);

	if (cmdcon->alterEnforceability)
	{
		copy_con->conenforced = cmdcon->is_enforced;

		/*
		 * NB: The convalidated status is irrelevant when the constraint is
		 * set to NOT ENFORCED, but for consistency, it should still be set
		 * appropriately. Similarly, if the constraint is later changed to
		 * ENFORCED, validation will be performed during phase 3, so it makes
		 * sense to mark it as valid in that case.
		 */
		copy_con->convalidated = cmdcon->is_enforced;
	}
	if (cmdcon->alterDeferrability)
	{
		copy_con->condeferrable = cmdcon->deferrable;
		copy_con->condeferred = cmdcon->initdeferred;
	}
	if (cmdcon->alterInheritability)
		copy_con->connoinherit = cmdcon->noinherit;

	CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
	InvokeObjectPostAlterHook(ConstraintRelationId, copy_con->oid, 0);

	/* Make new constraint flags visible to others */
	CacheInvalidateRelcacheByRelid(copy_con->conrelid);

	heap_freetuple(copyTuple);
}

/*
 * ALTER TABLE VALIDATE CONSTRAINT
 *
 * XXX The reason we handle recursion here rather than at Phase 1 is because
 * there's no good way to skip recursing when handling foreign keys: there is
 * no need to lock children in that case, yet we wouldn't be able to avoid
 * doing so at that level.
 *
 * Return value is the address of the validated constraint.  If the constraint
 * was already validated, InvalidObjectAddress is returned.
 */
static ObjectAddress
ATExecValidateConstraint(List **wqueue, Relation rel, char *constrName,
						 bool recurse, bool recursing, LOCKMODE lockmode)
{
	Relation	conrel;
	SysScanDesc scan;
	ScanKeyData skey[3];
	HeapTuple	tuple;
	Form_pg_constraint con;
	ObjectAddress address;

	conrel = table_open(ConstraintRelationId, RowExclusiveLock);

	/*
	 * Find and check the target constraint
	 */
	ScanKeyInit(&skey[0],
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	ScanKeyInit(&skey[1],
				Anum_pg_constraint_contypid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(InvalidOid));
	ScanKeyInit(&skey[2],
				Anum_pg_constraint_conname,
				BTEqualStrategyNumber, F_NAMEEQ,
				CStringGetDatum(constrName));
	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
							  true, NULL, 3, skey);

	/* There can be at most one matching row */
	if (!HeapTupleIsValid(tuple = systable_getnext(scan)))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
						constrName, RelationGetRelationName(rel))));

	con = (Form_pg_constraint) GETSTRUCT(tuple);
	if (con->contype != CONSTRAINT_FOREIGN &&
		con->contype != CONSTRAINT_CHECK &&
		con->contype != CONSTRAINT_NOTNULL)
		ereport(ERROR,
				errcode(ERRCODE_WRONG_OBJECT_TYPE),
				errmsg("cannot validate constraint \"%s\" of relation \"%s\"",
					   constrName, RelationGetRelationName(rel)),
				errdetail("This operation is not supported for this type of constraint."));

	if (!con->conenforced)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("cannot validate NOT ENFORCED constraint")));

	if (!con->convalidated)
	{
		if (con->contype == CONSTRAINT_FOREIGN)
		{
			QueueFKConstraintValidation(wqueue, conrel, rel, con->confrelid,
										tuple, lockmode);
		}
		else if (con->contype == CONSTRAINT_CHECK)
		{
			QueueCheckConstraintValidation(wqueue, conrel, rel, constrName,
										   tuple, recurse, recursing, lockmode);
		}
		else if (con->contype == CONSTRAINT_NOTNULL)
		{
			QueueNNConstraintValidation(wqueue, conrel, rel,
										tuple, recurse, recursing, lockmode);
		}

		ObjectAddressSet(address, ConstraintRelationId, con->oid);
	}
	else
		address = InvalidObjectAddress; /* already validated */

	systable_endscan(scan);

	table_close(conrel, RowExclusiveLock);

	return address;
}

/*
 * QueueFKConstraintValidation
 *
 * Add an entry to the wqueue to validate the given foreign key constraint in
 * Phase 3 and update the convalidated field in the pg_constraint catalog
 * for the specified relation and all its children.
 */
static void
QueueFKConstraintValidation(List **wqueue, Relation conrel, Relation fkrel,
							Oid pkrelid, HeapTuple contuple, LOCKMODE lockmode)
{
	Form_pg_constraint con;
	AlteredTableInfo *tab;
	HeapTuple	copyTuple;
	Form_pg_constraint copy_con;

	con = (Form_pg_constraint) GETSTRUCT(contuple);
	Assert(con->contype == CONSTRAINT_FOREIGN);
	Assert(!con->convalidated);

	/*
	 * Add the validation to phase 3's queue; not needed for partitioned
	 * tables themselves, only for their partitions.
	 *
	 * When the referenced table (pkrelid) is partitioned, the referencing
	 * table (fkrel) has one pg_constraint row pointing to each partition
	 * thereof.  These rows are there only to support action triggers and no
	 * table scan is needed, therefore skip this for them as well.
	 */
	if (fkrel->rd_rel->relkind == RELKIND_RELATION &&
		con->confrelid == pkrelid)
	{
		NewConstraint *newcon;
		Constraint *fkconstraint;

		/* Queue validation for phase 3 */
		fkconstraint = makeNode(Constraint);
		/* for now this is all we need */
		fkconstraint->conname = pstrdup(NameStr(con->conname));

		newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
		newcon->name = fkconstraint->conname;
		newcon->contype = CONSTR_FOREIGN;
		newcon->refrelid = con->confrelid;
		newcon->refindid = con->conindid;
		newcon->conid = con->oid;
		newcon->qual = (Node *) fkconstraint;

		/* Find or create work queue entry for this table */
		tab = ATGetQueueEntry(wqueue, fkrel);
		tab->constraints = lappend(tab->constraints, newcon);
	}

	/*
	 * If the table at either end of the constraint is partitioned, we need to
	 * recurse and handle every unvalidate constraint that is a child of this
	 * constraint.
	 */
	if (fkrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
		get_rel_relkind(con->confrelid) == RELKIND_PARTITIONED_TABLE)
	{
		ScanKeyData pkey;
		SysScanDesc pscan;
		HeapTuple	childtup;

		ScanKeyInit(&pkey,
					Anum_pg_constraint_conparentid,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(con->oid));

		pscan = systable_beginscan(conrel, ConstraintParentIndexId,
								   true, NULL, 1, &pkey);

		while (HeapTupleIsValid(childtup = systable_getnext(pscan)))
		{
			Form_pg_constraint childcon;
			Relation	childrel;

			childcon = (Form_pg_constraint) GETSTRUCT(childtup);

			/*
			 * If the child constraint has already been validated, no further
			 * action is required for it or its descendants, as they are all
			 * valid.
			 */
			if (childcon->convalidated)
				continue;

			childrel = table_open(childcon->conrelid, lockmode);

			/*
			 * NB: Note that pkrelid should be passed as-is during recursion,
			 * as it is required to identify the root referenced table.
			 */
			QueueFKConstraintValidation(wqueue, conrel, childrel, pkrelid,
										childtup, lockmode);
			table_close(childrel, NoLock);
		}

		systable_endscan(pscan);
	}

	/*
	 * Now mark the pg_constraint row as validated (even if we didn't check,
	 * notably the ones for partitions on the referenced side).
	 *
	 * We rely on transaction abort to roll back this change if phase 3
	 * ultimately finds violating rows.  This is a bit ugly.
	 */
	copyTuple = heap_copytuple(contuple);
	copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
	copy_con->convalidated = true;
	CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);

	InvokeObjectPostAlterHook(ConstraintRelationId, con->oid, 0);

	heap_freetuple(copyTuple);
}

/*
 * QueueCheckConstraintValidation
 *
 * Add an entry to the wqueue to validate the given check constraint in Phase 3
 * and update the convalidated field in the pg_constraint catalog for the
 * specified relation and all its inheriting children.
 */
static void
QueueCheckConstraintValidation(List **wqueue, Relation conrel, Relation rel,
							   char *constrName, HeapTuple contuple,
							   bool recurse, bool recursing, LOCKMODE lockmode)
{
	Form_pg_constraint con;
	AlteredTableInfo *tab;
	HeapTuple	copyTuple;
	Form_pg_constraint copy_con;

	List	   *children = NIL;
	ListCell   *child;
	NewConstraint *newcon;
	Datum		val;
	char	   *conbin;

	con = (Form_pg_constraint) GETSTRUCT(contuple);
	Assert(con->contype == CONSTRAINT_CHECK);

	/*
	 * If we're recursing, the parent has already done this, so skip it. Also,
	 * if the constraint is a NO INHERIT constraint, we shouldn't try to look
	 * for it in the children.
	 */
	if (!recursing && !con->connoinherit)
		children = find_all_inheritors(RelationGetRelid(rel),
									   lockmode, NULL);

	/*
	 * For CHECK constraints, we must ensure that we only mark the constraint
	 * as validated on the parent if it's already validated on the children.
	 *
	 * We recurse before validating on the parent, to reduce risk of
	 * deadlocks.
	 */
	foreach(child, children)
	{
		Oid			childoid = lfirst_oid(child);
		Relation	childrel;

		if (childoid == RelationGetRelid(rel))
			continue;

		/*
		 * If we are told not to recurse, there had better not be any child
		 * tables, because we can't mark the constraint on the parent valid
		 * unless it is valid for all child tables.
		 */
		if (!recurse)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("constraint must be validated on child tables too")));

		/* find_all_inheritors already got lock */
		childrel = table_open(childoid, NoLock);

		ATExecValidateConstraint(wqueue, childrel, constrName, false,
								 true, lockmode);
		table_close(childrel, NoLock);
	}

	/* Queue validation for phase 3 */
	newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
	newcon->name = constrName;
	newcon->contype = CONSTR_CHECK;
	newcon->refrelid = InvalidOid;
	newcon->refindid = InvalidOid;
	newcon->conid = con->oid;

	val = SysCacheGetAttrNotNull(CONSTROID, contuple,
								 Anum_pg_constraint_conbin);
	conbin = TextDatumGetCString(val);
	newcon->qual = expand_generated_columns_in_expr(stringToNode(conbin), rel, 1);

	/* Find or create work queue entry for this table */
	tab = ATGetQueueEntry(wqueue, rel);
	tab->constraints = lappend(tab->constraints, newcon);

	/*
	 * Invalidate relcache so that others see the new validated constraint.
	 */
	CacheInvalidateRelcache(rel);

	/*
	 * Now update the catalog, while we have the door open.
	 */
	copyTuple = heap_copytuple(contuple);
	copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
	copy_con->convalidated = true;
	CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);

	InvokeObjectPostAlterHook(ConstraintRelationId, con->oid, 0);

	heap_freetuple(copyTuple);
}

/*
 * QueueNNConstraintValidation
 *
 * Add an entry to the wqueue to validate the given not-null constraint in
 * Phase 3 and update the convalidated field in the pg_constraint catalog for
 * the specified relation and all its inheriting children.
 */
static void
QueueNNConstraintValidation(List **wqueue, Relation conrel, Relation rel,
							HeapTuple contuple, bool recurse, bool recursing,
							LOCKMODE lockmode)
{
	Form_pg_constraint con;
	AlteredTableInfo *tab;
	HeapTuple	copyTuple;
	Form_pg_constraint copy_con;
	List	   *children = NIL;
	AttrNumber	attnum;
	char	   *colname;

	con = (Form_pg_constraint) GETSTRUCT(contuple);
	Assert(con->contype == CONSTRAINT_NOTNULL);

	attnum = extractNotNullColumn(contuple);

	/*
	 * If we're recursing, we've already done this for parent, so skip it.
	 * Also, if the constraint is a NO INHERIT constraint, we shouldn't try to
	 * look for it in the children.
	 *
	 * We recurse before validating on the parent, to reduce risk of
	 * deadlocks.
	 */
	if (!recursing && !con->connoinherit)
		children = find_all_inheritors(RelationGetRelid(rel), lockmode, NULL);

	colname = get_attname(RelationGetRelid(rel), attnum, false);
	foreach_oid(childoid, children)
	{
		Relation	childrel;
		HeapTuple	contup;
		Form_pg_constraint childcon;
		char	   *conname;

		if (childoid == RelationGetRelid(rel))
			continue;

		/*
		 * If we are told not to recurse, there had better not be any child
		 * tables, because we can't mark the constraint on the parent valid
		 * unless it is valid for all child tables.
		 */
		if (!recurse)
			ereport(ERROR,
					errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					errmsg("constraint must be validated on child tables too"));

		/*
		 * The column on child might have a different attnum, so search by
		 * column name.
		 */
		contup = findNotNullConstraint(childoid, colname);
		if (!contup)
			elog(ERROR, "cache lookup failed for not-null constraint on column \"%s\" of relation \"%s\"",
				 colname, get_rel_name(childoid));
		childcon = (Form_pg_constraint) GETSTRUCT(contup);
		if (childcon->convalidated)
			continue;

		/* find_all_inheritors already got lock */
		childrel = table_open(childoid, NoLock);
		conname = pstrdup(NameStr(childcon->conname));

		/* XXX improve ATExecValidateConstraint API to avoid double search */
		ATExecValidateConstraint(wqueue, childrel, conname,
								 false, true, lockmode);
		table_close(childrel, NoLock);
	}

	/* Set attnotnull appropriately without queueing another validation */
	set_attnotnull(NULL, rel, attnum, true, false);

	tab = ATGetQueueEntry(wqueue, rel);
	tab->verify_new_notnull = true;

	/*
	 * Invalidate relcache so that others see the new validated constraint.
	 */
	CacheInvalidateRelcache(rel);

	/*
	 * Now update the catalogs, while we have the door open.
	 */
	copyTuple = heap_copytuple(contuple);
	copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
	copy_con->convalidated = true;
	CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);

	InvokeObjectPostAlterHook(ConstraintRelationId, con->oid, 0);

	heap_freetuple(copyTuple);
}

/*
 * transformColumnNameList - transform list of column names
 *
 * Lookup each name and return its attnum and, optionally, type and collation
 * OIDs
 *
 * Note: the name of this function suggests that it's general-purpose,
 * but actually it's only used to look up names appearing in foreign-key
 * clauses.  The error messages would need work to use it in other cases,
 * and perhaps the validity checks as well.
 */
static int
transformColumnNameList(Oid relId, List *colList,
						int16 *attnums, Oid *atttypids, Oid *attcollids)
{
	ListCell   *l;
	int			attnum;

	attnum = 0;
	foreach(l, colList)
	{
		char	   *attname = strVal(lfirst(l));
		HeapTuple	atttuple;
		Form_pg_attribute attform;

		atttuple = SearchSysCacheAttName(relId, attname);
		if (!HeapTupleIsValid(atttuple))
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_COLUMN),
					 errmsg("column \"%s\" referenced in foreign key constraint does not exist",
							attname)));
		attform = (Form_pg_attribute) GETSTRUCT(atttuple);
		if (attform->attnum < 0)
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("system columns cannot be used in foreign keys")));
		if (attnum >= INDEX_MAX_KEYS)
			ereport(ERROR,
					(errcode(ERRCODE_TOO_MANY_COLUMNS),
					 errmsg("cannot have more than %d keys in a foreign key",
							INDEX_MAX_KEYS)));
		attnums[attnum] = attform->attnum;
		if (atttypids != NULL)
			atttypids[attnum] = attform->atttypid;
		if (attcollids != NULL)
			attcollids[attnum] = attform->attcollation;
		ReleaseSysCache(atttuple);
		attnum++;
	}

	return attnum;
}

/*
 * transformFkeyGetPrimaryKey -
 *
 *	Look up the names, attnums, types, and collations of the primary key attributes
 *	for the pkrel.  Also return the index OID and index opclasses of the
 *	index supporting the primary key.  Also return whether the index has
 *	WITHOUT OVERLAPS.
 *
 *	All parameters except pkrel are output parameters.  Also, the function
 *	return value is the number of attributes in the primary key.
 *
 *	Used when the column list in the REFERENCES specification is omitted.
 */
static int
transformFkeyGetPrimaryKey(Relation pkrel, Oid *indexOid,
						   List **attnamelist,
						   int16 *attnums, Oid *atttypids, Oid *attcollids,
						   Oid *opclasses, bool *pk_has_without_overlaps)
{
	List	   *indexoidlist;
	ListCell   *indexoidscan;
	HeapTuple	indexTuple = NULL;
	Form_pg_index indexStruct = NULL;
	Datum		indclassDatum;
	oidvector  *indclass;
	int			i;

	/*
	 * Get the list of index OIDs for the table from the relcache, and look up
	 * each one in the pg_index syscache until we find one marked primary key
	 * (hopefully there isn't more than one such).  Insist it's valid, too.
	 */
	*indexOid = InvalidOid;

	indexoidlist = RelationGetIndexList(pkrel);

	foreach(indexoidscan, indexoidlist)
	{
		Oid			indexoid = lfirst_oid(indexoidscan);

		indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
		if (!HeapTupleIsValid(indexTuple))
			elog(ERROR, "cache lookup failed for index %u", indexoid);
		indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
		if (indexStruct->indisprimary && indexStruct->indisvalid)
		{
			/*
			 * Refuse to use a deferrable primary key.  This is per SQL spec,
			 * and there would be a lot of interesting semantic problems if we
			 * tried to allow it.
			 */
			if (!indexStruct->indimmediate)
				ereport(ERROR,
						(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
						 errmsg("cannot use a deferrable primary key for referenced table \"%s\"",
								RelationGetRelationName(pkrel))));

			*indexOid = indexoid;
			break;
		}
		ReleaseSysCache(indexTuple);
	}

	list_free(indexoidlist);

	/*
	 * Check that we found it
	 */
	if (!OidIsValid(*indexOid))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("there is no primary key for referenced table \"%s\"",
						RelationGetRelationName(pkrel))));

	/* Must get indclass the hard way */
	indclassDatum = SysCacheGetAttrNotNull(INDEXRELID, indexTuple,
										   Anum_pg_index_indclass);
	indclass = (oidvector *) DatumGetPointer(indclassDatum);

	/*
	 * Now build the list of PK attributes from the indkey definition (we
	 * assume a primary key cannot have expressional elements)
	 */
	*attnamelist = NIL;
	for (i = 0; i < indexStruct->indnkeyatts; i++)
	{
		int			pkattno = indexStruct->indkey.values[i];

		attnums[i] = pkattno;
		atttypids[i] = attnumTypeId(pkrel, pkattno);
		attcollids[i] = attnumCollationId(pkrel, pkattno);
		opclasses[i] = indclass->values[i];
		*attnamelist = lappend(*attnamelist,
							   makeString(pstrdup(NameStr(*attnumAttName(pkrel, pkattno)))));
	}

	*pk_has_without_overlaps = indexStruct->indisexclusion;

	ReleaseSysCache(indexTuple);

	return i;
}

/*
 * transformFkeyCheckAttrs -
 *
 *	Validate that the 'attnums' columns in the 'pkrel' relation are valid to
 *	reference as part of a foreign key constraint.
 *
 *	Returns the OID of the unique index supporting the constraint and
 *	populates the caller-provided 'opclasses' array with the opclasses
 *	associated with the index columns.  Also sets whether the index
 *	uses WITHOUT OVERLAPS.
 *
 *	Raises an ERROR on validation failure.
 */
static Oid
transformFkeyCheckAttrs(Relation pkrel,
						int numattrs, int16 *attnums,
						bool with_period, Oid *opclasses,
						bool *pk_has_without_overlaps)
{
	Oid			indexoid = InvalidOid;
	bool		found = false;
	bool		found_deferrable = false;
	List	   *indexoidlist;
	ListCell   *indexoidscan;
	int			i,
				j;

	/*
	 * Reject duplicate appearances of columns in the referenced-columns list.
	 * Such a case is forbidden by the SQL standard, and even if we thought it
	 * useful to allow it, there would be ambiguity about how to match the
	 * list to unique indexes (in particular, it'd be unclear which index
	 * opclass goes with which FK column).
	 */
	for (i = 0; i < numattrs; i++)
	{
		for (j = i + 1; j < numattrs; j++)
		{
			if (attnums[i] == attnums[j])
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_FOREIGN_KEY),
						 errmsg("foreign key referenced-columns list must not contain duplicates")));
		}
	}

	/*
	 * Get the list of index OIDs for the table from the relcache, and look up
	 * each one in the pg_index syscache, and match unique indexes to the list
	 * of attnums we are given.
	 */
	indexoidlist = RelationGetIndexList(pkrel);

	foreach(indexoidscan, indexoidlist)
	{
		HeapTuple	indexTuple;
		Form_pg_index indexStruct;

		indexoid = lfirst_oid(indexoidscan);
		indexTuple = SearchSysCache1(INDEXRELID, ObjectIdGetDatum(indexoid));
		if (!HeapTupleIsValid(indexTuple))
			elog(ERROR, "cache lookup failed for index %u", indexoid);
		indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);

		/*
		 * Must have the right number of columns; must be unique (or if
		 * temporal then exclusion instead) and not a partial index; forget it
		 * if there are any expressions, too. Invalid indexes are out as well.
		 */
		if (indexStruct->indnkeyatts == numattrs &&
			(with_period ? indexStruct->indisexclusion : indexStruct->indisunique) &&
			indexStruct->indisvalid &&
			heap_attisnull(indexTuple, Anum_pg_index_indpred, NULL) &&
			heap_attisnull(indexTuple, Anum_pg_index_indexprs, NULL))
		{
			Datum		indclassDatum;
			oidvector  *indclass;

			/* Must get indclass the hard way */
			indclassDatum = SysCacheGetAttrNotNull(INDEXRELID, indexTuple,
												   Anum_pg_index_indclass);
			indclass = (oidvector *) DatumGetPointer(indclassDatum);

			/*
			 * The given attnum list may match the index columns in any order.
			 * Check for a match, and extract the appropriate opclasses while
			 * we're at it.
			 *
			 * We know that attnums[] is duplicate-free per the test at the
			 * start of this function, and we checked above that the number of
			 * index columns agrees, so if we find a match for each attnums[]
			 * entry then we must have a one-to-one match in some order.
			 */
			for (i = 0; i < numattrs; i++)
			{
				found = false;
				for (j = 0; j < numattrs; j++)
				{
					if (attnums[i] == indexStruct->indkey.values[j])
					{
						opclasses[i] = indclass->values[j];
						found = true;
						break;
					}
				}
				if (!found)
					break;
			}
			/* The last attribute in the index must be the PERIOD FK part */
			if (found && with_period)
			{
				int16		periodattnum = attnums[numattrs - 1];

				found = (periodattnum == indexStruct->indkey.values[numattrs - 1]);
			}

			/*
			 * Refuse to use a deferrable unique/primary key.  This is per SQL
			 * spec, and there would be a lot of interesting semantic problems
			 * if we tried to allow it.
			 */
			if (found && !indexStruct->indimmediate)
			{
				/*
				 * Remember that we found an otherwise matching index, so that
				 * we can generate a more appropriate error message.
				 */
				found_deferrable = true;
				found = false;
			}

			/* We need to know whether the index has WITHOUT OVERLAPS */
			if (found)
				*pk_has_without_overlaps = indexStruct->indisexclusion;
		}
		ReleaseSysCache(indexTuple);
		if (found)
			break;
	}

	if (!found)
	{
		if (found_deferrable)
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("cannot use a deferrable unique constraint for referenced table \"%s\"",
							RelationGetRelationName(pkrel))));
		else
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_FOREIGN_KEY),
					 errmsg("there is no unique constraint matching given keys for referenced table \"%s\"",
							RelationGetRelationName(pkrel))));
	}

	list_free(indexoidlist);

	return indexoid;
}

/*
 * findFkeyCast -
 *
 *	Wrapper around find_coercion_pathway() for ATAddForeignKeyConstraint().
 *	Caller has equal regard for binary coercibility and for an exact match.
*/
static CoercionPathType
findFkeyCast(Oid targetTypeId, Oid sourceTypeId, Oid *funcid)
{
	CoercionPathType ret;

	if (targetTypeId == sourceTypeId)
	{
		ret = COERCION_PATH_RELABELTYPE;
		*funcid = InvalidOid;
	}
	else
	{
		ret = find_coercion_pathway(targetTypeId, sourceTypeId,
									COERCION_IMPLICIT, funcid);
		if (ret == COERCION_PATH_NONE)
			/* A previously-relied-upon cast is now gone. */
			elog(ERROR, "could not find cast from %u to %u",
				 sourceTypeId, targetTypeId);
	}

	return ret;
}

/*
 * Permissions checks on the referenced table for ADD FOREIGN KEY
 *
 * Note: we have already checked that the user owns the referencing table,
 * else we'd have failed much earlier; no additional checks are needed for it.
 */
static void
checkFkeyPermissions(Relation rel, int16 *attnums, int natts)
{
	Oid			roleid = GetUserId();
	AclResult	aclresult;
	int			i;

	/* Okay if we have relation-level REFERENCES permission */
	aclresult = pg_class_aclcheck(RelationGetRelid(rel), roleid,
								  ACL_REFERENCES);
	if (aclresult == ACLCHECK_OK)
		return;
	/* Else we must have REFERENCES on each column */
	for (i = 0; i < natts; i++)
	{
		aclresult = pg_attribute_aclcheck(RelationGetRelid(rel), attnums[i],
										  roleid, ACL_REFERENCES);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error(aclresult, get_relkind_objtype(rel->rd_rel->relkind),
						   RelationGetRelationName(rel));
	}
}

/*
 * Scan the existing rows in a table to verify they meet a proposed FK
 * constraint.
 *
 * Caller must have opened and locked both relations appropriately.
 */
static void
validateForeignKeyConstraint(char *conname,
							 Relation rel,
							 Relation pkrel,
							 Oid pkindOid,
							 Oid constraintOid,
							 bool hasperiod)
{
	TupleTableSlot *slot;
	TableScanDesc scan;
	Trigger		trig = {0};
	Snapshot	snapshot;
	MemoryContext oldcxt;
	MemoryContext perTupCxt;

	ereport(DEBUG1,
			(errmsg_internal("validating foreign key constraint \"%s\"", conname)));

	/*
	 * Build a trigger call structure; we'll need it either way.
	 */
	trig.tgoid = InvalidOid;
	trig.tgname = conname;
	trig.tgenabled = TRIGGER_FIRES_ON_ORIGIN;
	trig.tgisinternal = true;
	trig.tgconstrrelid = RelationGetRelid(pkrel);
	trig.tgconstrindid = pkindOid;
	trig.tgconstraint = constraintOid;
	trig.tgdeferrable = false;
	trig.tginitdeferred = false;
	/* we needn't fill in remaining fields */

	/*
	 * See if we can do it with a single LEFT JOIN query.  A false result
	 * indicates we must proceed with the fire-the-trigger method. We can't do
	 * a LEFT JOIN for temporal FKs yet, but we can once we support temporal
	 * left joins.
	 */
	if (!hasperiod && RI_Initial_Check(&trig, rel, pkrel))
		return;

	/*
	 * Scan through each tuple, calling RI_FKey_check_ins (insert trigger) as
	 * if that tuple had just been inserted.  If any of those fail, it should
	 * ereport(ERROR) and that's that.
	 */
	snapshot = RegisterSnapshot(GetLatestSnapshot());
	slot = table_slot_create(rel, NULL);
	scan = table_beginscan(rel, snapshot, 0, NULL);

	perTupCxt = AllocSetContextCreate(CurrentMemoryContext,
									  "validateForeignKeyConstraint",
									  ALLOCSET_SMALL_SIZES);
	oldcxt = MemoryContextSwitchTo(perTupCxt);

	while (table_scan_getnextslot(scan, ForwardScanDirection, slot))
	{
		LOCAL_FCINFO(fcinfo, 0);
		TriggerData trigdata = {0};

		CHECK_FOR_INTERRUPTS();

		/*
		 * Make a call to the trigger function
		 *
		 * No parameters are passed, but we do set a context
		 */
		MemSet(fcinfo, 0, SizeForFunctionCallInfo(0));

		/*
		 * We assume RI_FKey_check_ins won't look at flinfo...
		 */
		trigdata.type = T_TriggerData;
		trigdata.tg_event = TRIGGER_EVENT_INSERT | TRIGGER_EVENT_ROW;
		trigdata.tg_relation = rel;
		trigdata.tg_trigtuple = ExecFetchSlotHeapTuple(slot, false, NULL);
		trigdata.tg_trigslot = slot;
		trigdata.tg_trigger = &trig;

		fcinfo->context = (Node *) &trigdata;

		RI_FKey_check_ins(fcinfo);

		MemoryContextReset(perTupCxt);
	}

	MemoryContextSwitchTo(oldcxt);
	MemoryContextDelete(perTupCxt);
	table_endscan(scan);
	UnregisterSnapshot(snapshot);
	ExecDropSingleTupleTableSlot(slot);
}

/*
 * CreateFKCheckTrigger
 *		Creates the insert (on_insert=true) or update "check" trigger that
 *		implements a given foreign key
 *
 * Returns the OID of the so created trigger.
 */
static Oid
CreateFKCheckTrigger(Oid myRelOid, Oid refRelOid, Constraint *fkconstraint,
					 Oid constraintOid, Oid indexOid, Oid parentTrigOid,
					 bool on_insert)
{
	ObjectAddress trigAddress;
	CreateTrigStmt *fk_trigger;

	/*
	 * Note: for a self-referential FK (referencing and referenced tables are
	 * the same), it is important that the ON UPDATE action fires before the
	 * CHECK action, since both triggers will fire on the same row during an
	 * UPDATE event; otherwise the CHECK trigger will be checking a non-final
	 * state of the row.  Triggers fire in name order, so we ensure this by
	 * using names like "RI_ConstraintTrigger_a_NNNN" for the action triggers
	 * and "RI_ConstraintTrigger_c_NNNN" for the check triggers.
	 */
	fk_trigger = makeNode(CreateTrigStmt);
	fk_trigger->replace = false;
	fk_trigger->isconstraint = true;
	fk_trigger->trigname = "RI_ConstraintTrigger_c";
	fk_trigger->relation = NULL;

	/* Either ON INSERT or ON UPDATE */
	if (on_insert)
	{
		fk_trigger->funcname = SystemFuncName("RI_FKey_check_ins");
		fk_trigger->events = TRIGGER_TYPE_INSERT;
	}
	else
	{
		fk_trigger->funcname = SystemFuncName("RI_FKey_check_upd");
		fk_trigger->events = TRIGGER_TYPE_UPDATE;
	}

	fk_trigger->args = NIL;
	fk_trigger->row = true;
	fk_trigger->timing = TRIGGER_TYPE_AFTER;
	fk_trigger->columns = NIL;
	fk_trigger->whenClause = NULL;
	fk_trigger->transitionRels = NIL;
	fk_trigger->deferrable = fkconstraint->deferrable;
	fk_trigger->initdeferred = fkconstraint->initdeferred;
	fk_trigger->constrrel = NULL;

	trigAddress = CreateTrigger(fk_trigger, NULL, myRelOid, refRelOid,
								constraintOid, indexOid, InvalidOid,
								parentTrigOid, NULL, true, false);

	/* Make changes-so-far visible */
	CommandCounterIncrement();

	return trigAddress.objectId;
}

/*
 * createForeignKeyActionTriggers
 *		Create the referenced-side "action" triggers that implement a foreign
 *		key.
 *
 * Returns the OIDs of the so created triggers in *deleteTrigOid and
 * *updateTrigOid.
 */
static void
createForeignKeyActionTriggers(Oid myRelOid, Oid refRelOid, Constraint *fkconstraint,
							   Oid constraintOid, Oid indexOid,
							   Oid parentDelTrigger, Oid parentUpdTrigger,
							   Oid *deleteTrigOid, Oid *updateTrigOid)
{
	CreateTrigStmt *fk_trigger;
	ObjectAddress trigAddress;

	/*
	 * Build and execute a CREATE CONSTRAINT TRIGGER statement for the ON
	 * DELETE action on the referenced table.
	 */
	fk_trigger = makeNode(CreateTrigStmt);
	fk_trigger->replace = false;
	fk_trigger->isconstraint = true;
	fk_trigger->trigname = "RI_ConstraintTrigger_a";
	fk_trigger->relation = NULL;
	fk_trigger->args = NIL;
	fk_trigger->row = true;
	fk_trigger->timing = TRIGGER_TYPE_AFTER;
	fk_trigger->events = TRIGGER_TYPE_DELETE;
	fk_trigger->columns = NIL;
	fk_trigger->whenClause = NULL;
	fk_trigger->transitionRels = NIL;
	fk_trigger->constrrel = NULL;

	switch (fkconstraint->fk_del_action)
	{
		case FKCONSTR_ACTION_NOACTION:
			fk_trigger->deferrable = fkconstraint->deferrable;
			fk_trigger->initdeferred = fkconstraint->initdeferred;
			fk_trigger->funcname = SystemFuncName("RI_FKey_noaction_del");
			break;
		case FKCONSTR_ACTION_RESTRICT:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_restrict_del");
			break;
		case FKCONSTR_ACTION_CASCADE:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_cascade_del");
			break;
		case FKCONSTR_ACTION_SETNULL:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_setnull_del");
			break;
		case FKCONSTR_ACTION_SETDEFAULT:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_setdefault_del");
			break;
		default:
			elog(ERROR, "unrecognized FK action type: %d",
				 (int) fkconstraint->fk_del_action);
			break;
	}

	trigAddress = CreateTrigger(fk_trigger, NULL, refRelOid, myRelOid,
								constraintOid, indexOid, InvalidOid,
								parentDelTrigger, NULL, true, false);
	if (deleteTrigOid)
		*deleteTrigOid = trigAddress.objectId;

	/* Make changes-so-far visible */
	CommandCounterIncrement();

	/*
	 * Build and execute a CREATE CONSTRAINT TRIGGER statement for the ON
	 * UPDATE action on the referenced table.
	 */
	fk_trigger = makeNode(CreateTrigStmt);
	fk_trigger->replace = false;
	fk_trigger->isconstraint = true;
	fk_trigger->trigname = "RI_ConstraintTrigger_a";
	fk_trigger->relation = NULL;
	fk_trigger->args = NIL;
	fk_trigger->row = true;
	fk_trigger->timing = TRIGGER_TYPE_AFTER;
	fk_trigger->events = TRIGGER_TYPE_UPDATE;
	fk_trigger->columns = NIL;
	fk_trigger->whenClause = NULL;
	fk_trigger->transitionRels = NIL;
	fk_trigger->constrrel = NULL;

	switch (fkconstraint->fk_upd_action)
	{
		case FKCONSTR_ACTION_NOACTION:
			fk_trigger->deferrable = fkconstraint->deferrable;
			fk_trigger->initdeferred = fkconstraint->initdeferred;
			fk_trigger->funcname = SystemFuncName("RI_FKey_noaction_upd");
			break;
		case FKCONSTR_ACTION_RESTRICT:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_restrict_upd");
			break;
		case FKCONSTR_ACTION_CASCADE:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_cascade_upd");
			break;
		case FKCONSTR_ACTION_SETNULL:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_setnull_upd");
			break;
		case FKCONSTR_ACTION_SETDEFAULT:
			fk_trigger->deferrable = false;
			fk_trigger->initdeferred = false;
			fk_trigger->funcname = SystemFuncName("RI_FKey_setdefault_upd");
			break;
		default:
			elog(ERROR, "unrecognized FK action type: %d",
				 (int) fkconstraint->fk_upd_action);
			break;
	}

	trigAddress = CreateTrigger(fk_trigger, NULL, refRelOid, myRelOid,
								constraintOid, indexOid, InvalidOid,
								parentUpdTrigger, NULL, true, false);
	if (updateTrigOid)
		*updateTrigOid = trigAddress.objectId;
}

/*
 * createForeignKeyCheckTriggers
 *		Create the referencing-side "check" triggers that implement a foreign
 *		key.
 *
 * Returns the OIDs of the so created triggers in *insertTrigOid and
 * *updateTrigOid.
 */
static void
createForeignKeyCheckTriggers(Oid myRelOid, Oid refRelOid,
							  Constraint *fkconstraint, Oid constraintOid,
							  Oid indexOid,
							  Oid parentInsTrigger, Oid parentUpdTrigger,
							  Oid *insertTrigOid, Oid *updateTrigOid)
{
	*insertTrigOid = CreateFKCheckTrigger(myRelOid, refRelOid, fkconstraint,
										  constraintOid, indexOid,
										  parentInsTrigger, true);
	*updateTrigOid = CreateFKCheckTrigger(myRelOid, refRelOid, fkconstraint,
										  constraintOid, indexOid,
										  parentUpdTrigger, false);
}

/*
 * ALTER TABLE DROP CONSTRAINT
 *
 * Like DROP COLUMN, we can't use the normal ALTER TABLE recursion mechanism.
 */
static void
ATExecDropConstraint(Relation rel, const char *constrName,
					 DropBehavior behavior, bool recurse,
					 bool missing_ok, LOCKMODE lockmode)
{
	Relation	conrel;
	SysScanDesc scan;
	ScanKeyData skey[3];
	HeapTuple	tuple;
	bool		found = false;

	conrel = table_open(ConstraintRelationId, RowExclusiveLock);

	/*
	 * Find and drop the target constraint
	 */
	ScanKeyInit(&skey[0],
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	ScanKeyInit(&skey[1],
				Anum_pg_constraint_contypid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(InvalidOid));
	ScanKeyInit(&skey[2],
				Anum_pg_constraint_conname,
				BTEqualStrategyNumber, F_NAMEEQ,
				CStringGetDatum(constrName));
	scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
							  true, NULL, 3, skey);

	/* There can be at most one matching row */
	if (HeapTupleIsValid(tuple = systable_getnext(scan)))
	{
		dropconstraint_internal(rel, tuple, behavior, recurse, false,
								missing_ok, lockmode);
		found = true;
	}

	systable_endscan(scan);

	if (!found)
	{
		if (!missing_ok)
			ereport(ERROR,
					errcode(ERRCODE_UNDEFINED_OBJECT),
					errmsg("constraint \"%s\" of relation \"%s\" does not exist",
						   constrName, RelationGetRelationName(rel)));
		else
			ereport(NOTICE,
					errmsg("constraint \"%s\" of relation \"%s\" does not exist, skipping",
						   constrName, RelationGetRelationName(rel)));
	}

	table_close(conrel, RowExclusiveLock);
}

/*
 * Remove a constraint, using its pg_constraint tuple
 *
 * Implementation for ALTER TABLE DROP CONSTRAINT and ALTER TABLE ALTER COLUMN
 * DROP NOT NULL.
 *
 * Returns the address of the constraint being removed.
 */
static ObjectAddress
dropconstraint_internal(Relation rel, HeapTuple constraintTup, DropBehavior behavior,
						bool recurse, bool recursing, bool missing_ok,
						LOCKMODE lockmode)
{
	Relation	conrel;
	Form_pg_constraint con;
	ObjectAddress conobj;
	List	   *children;
	bool		is_no_inherit_constraint = false;
	char	   *constrName;
	char	   *colname = NULL;

	/* Guard against stack overflow due to overly deep inheritance tree. */
	check_stack_depth();

	/* At top level, permission check was done in ATPrepCmd, else do it */
	if (recursing)
		ATSimplePermissions(AT_DropConstraint, rel,
							ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);

	conrel = table_open(ConstraintRelationId, RowExclusiveLock);

	con = (Form_pg_constraint) GETSTRUCT(constraintTup);
	constrName = NameStr(con->conname);

	/* Don't allow drop of inherited constraints */
	if (con->coninhcount > 0 && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot drop inherited constraint \"%s\" of relation \"%s\"",
						constrName, RelationGetRelationName(rel))));

	/*
	 * Reset pg_constraint.attnotnull, if this is a not-null constraint.
	 *
	 * While doing that, we're in a good position to disallow dropping a not-
	 * null constraint underneath a primary key, a replica identity index, or
	 * a generated identity column.
	 */
	if (con->contype == CONSTRAINT_NOTNULL)
	{
		Relation	attrel = table_open(AttributeRelationId, RowExclusiveLock);
		AttrNumber	attnum = extractNotNullColumn(constraintTup);
		Bitmapset  *pkattrs;
		Bitmapset  *irattrs;
		HeapTuple	atttup;
		Form_pg_attribute attForm;

		/* save column name for recursion step */
		colname = get_attname(RelationGetRelid(rel), attnum, false);

		/*
		 * Disallow if it's in the primary key.  For partitioned tables we
		 * cannot rely solely on RelationGetIndexAttrBitmap, because it'll
		 * return NULL if the primary key is invalid; but we still need to
		 * protect not-null constraints under such a constraint, so check the
		 * slow way.
		 */
		pkattrs = RelationGetIndexAttrBitmap(rel, INDEX_ATTR_BITMAP_PRIMARY_KEY);

		if (pkattrs == NULL &&
			rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
		{
			Oid			pkindex = RelationGetPrimaryKeyIndex(rel, true);

			if (OidIsValid(pkindex))
			{
				Relation	pk = relation_open(pkindex, AccessShareLock);

				pkattrs = NULL;
				for (int i = 0; i < pk->rd_index->indnkeyatts; i++)
					pkattrs = bms_add_member(pkattrs, pk->rd_index->indkey.values[i]);

				relation_close(pk, AccessShareLock);
			}
		}

		if (pkattrs &&
			bms_is_member(attnum - FirstLowInvalidHeapAttributeNumber, pkattrs))
			ereport(ERROR,
					errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					errmsg("column \"%s\" is in a primary key",
						   get_attname(RelationGetRelid(rel), attnum, false)));

		/* Disallow if it's in the replica identity */
		irattrs = RelationGetIndexAttrBitmap(rel, INDEX_ATTR_BITMAP_IDENTITY_KEY);
		if (bms_is_member(attnum - FirstLowInvalidHeapAttributeNumber, irattrs))
			ereport(ERROR,
					errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					errmsg("column \"%s\" is in index used as replica identity",
						   get_attname(RelationGetRelid(rel), attnum, false)));

		/* Disallow if it's a GENERATED AS IDENTITY column */
		atttup = SearchSysCacheCopyAttNum(RelationGetRelid(rel), attnum);
		if (!HeapTupleIsValid(atttup))
			elog(ERROR, "cache lookup failed for attribute %d of relation %u",
				 attnum, RelationGetRelid(rel));
		attForm = (Form_pg_attribute) GETSTRUCT(atttup);
		if (attForm->attidentity != '\0')
			ereport(ERROR,
					errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					errmsg("column \"%s\" of relation \"%s\" is an identity column",
						   get_attname(RelationGetRelid(rel), attnum,
									   false),
						   RelationGetRelationName(rel)));

		/* All good -- reset attnotnull if needed */
		if (attForm->attnotnull)
		{
			attForm->attnotnull = false;
			CatalogTupleUpdate(attrel, &atttup->t_self, atttup);
		}

		table_close(attrel, RowExclusiveLock);
	}

	is_no_inherit_constraint = con->connoinherit;

	/*
	 * If it's a foreign-key constraint, we'd better lock the referenced table
	 * and check that that's not in use, just as we've already done for the
	 * constrained table (else we might, eg, be dropping a trigger that has
	 * unfired events).  But we can/must skip that in the self-referential
	 * case.
	 */
	if (con->contype == CONSTRAINT_FOREIGN &&
		con->confrelid != RelationGetRelid(rel))
	{
		Relation	frel;

		/* Must match lock taken by RemoveTriggerById: */
		frel = table_open(con->confrelid, AccessExclusiveLock);
		CheckAlterTableIsSafe(frel);
		table_close(frel, NoLock);
	}

	/*
	 * Perform the actual constraint deletion
	 */
	ObjectAddressSet(conobj, ConstraintRelationId, con->oid);
	performDeletion(&conobj, behavior, 0);

	/*
	 * For partitioned tables, non-CHECK, non-NOT-NULL inherited constraints
	 * are dropped via the dependency mechanism, so we're done here.
	 */
	if (con->contype != CONSTRAINT_CHECK &&
		con->contype != CONSTRAINT_NOTNULL &&
		rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
	{
		table_close(conrel, RowExclusiveLock);
		return conobj;
	}

	/*
	 * Propagate to children as appropriate.  Unlike most other ALTER
	 * routines, we have to do this one level of recursion at a time; we can't
	 * use find_all_inheritors to do it in one pass.
	 */
	if (!is_no_inherit_constraint)
		children = find_inheritance_children(RelationGetRelid(rel), lockmode);
	else
		children = NIL;

	foreach_oid(childrelid, children)
	{
		Relation	childrel;
		HeapTuple	tuple;
		Form_pg_constraint childcon;

		/* find_inheritance_children already got lock */
		childrel = table_open(childrelid, NoLock);
		CheckAlterTableIsSafe(childrel);

		/*
		 * We search for not-null constraints by column name, and others by
		 * constraint name.
		 */
		if (con->contype == CONSTRAINT_NOTNULL)
		{
			tuple = findNotNullConstraint(childrelid, colname);
			if (!HeapTupleIsValid(tuple))
				elog(ERROR, "cache lookup failed for not-null constraint on column \"%s\" of relation %u",
					 colname, RelationGetRelid(childrel));
		}
		else
		{
			SysScanDesc scan;
			ScanKeyData skey[3];

			ScanKeyInit(&skey[0],
						Anum_pg_constraint_conrelid,
						BTEqualStrategyNumber, F_OIDEQ,
						ObjectIdGetDatum(childrelid));
			ScanKeyInit(&skey[1],
						Anum_pg_constraint_contypid,
						BTEqualStrategyNumber, F_OIDEQ,
						ObjectIdGetDatum(InvalidOid));
			ScanKeyInit(&skey[2],
						Anum_pg_constraint_conname,
						BTEqualStrategyNumber, F_NAMEEQ,
						CStringGetDatum(constrName));
			scan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId,
									  true, NULL, 3, skey);
			/* There can only be one, so no need to loop */
			tuple = systable_getnext(scan);
			if (!HeapTupleIsValid(tuple))
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_OBJECT),
						 errmsg("constraint \"%s\" of relation \"%s\" does not exist",
								constrName,
								RelationGetRelationName(childrel))));
			tuple = heap_copytuple(tuple);
			systable_endscan(scan);
		}

		childcon = (Form_pg_constraint) GETSTRUCT(tuple);

		/* Right now only CHECK and not-null constraints can be inherited */
		if (childcon->contype != CONSTRAINT_CHECK &&
			childcon->contype != CONSTRAINT_NOTNULL)
			elog(ERROR, "inherited constraint is not a CHECK or not-null constraint");

		if (childcon->coninhcount <= 0) /* shouldn't happen */
			elog(ERROR, "relation %u has non-inherited constraint \"%s\"",
				 childrelid, NameStr(childcon->conname));

		if (recurse)
		{
			/*
			 * If the child constraint has other definition sources, just
			 * decrement its inheritance count; if not, recurse to delete it.
			 */
			if (childcon->coninhcount == 1 && !childcon->conislocal)
			{
				/* Time to delete this child constraint, too */
				dropconstraint_internal(childrel, tuple, behavior,
										recurse, true, missing_ok,
										lockmode);
			}
			else
			{
				/* Child constraint must survive my deletion */
				childcon->coninhcount--;
				CatalogTupleUpdate(conrel, &tuple->t_self, tuple);

				/* Make update visible */
				CommandCounterIncrement();
			}
		}
		else
		{
			/*
			 * If we were told to drop ONLY in this table (no recursion) and
			 * there are no further parents for this constraint, we need to
			 * mark the inheritors' constraints as locally defined rather than
			 * inherited.
			 */
			childcon->coninhcount--;
			if (childcon->coninhcount == 0)
				childcon->conislocal = true;

			CatalogTupleUpdate(conrel, &tuple->t_self, tuple);

			/* Make update visible */
			CommandCounterIncrement();
		}

		heap_freetuple(tuple);

		table_close(childrel, NoLock);
	}

	table_close(conrel, RowExclusiveLock);

	return conobj;
}

/*
 * ALTER COLUMN TYPE
 *
 * Unlike other subcommand types, we do parse transformation for ALTER COLUMN
 * TYPE during phase 1 --- the AlterTableCmd passed in here is already
 * transformed (and must be, because we rely on some transformed fields).
 *
 * The point of this is that the execution of all ALTER COLUMN TYPEs for a
 * table will be done "in parallel" during phase 3, so all the USING
 * expressions should be parsed assuming the original column types.  Also,
 * this allows a USING expression to refer to a field that will be dropped.
 *
 * To make this work safely, AT_PASS_DROP then AT_PASS_ALTER_TYPE must be
 * the first two execution steps in phase 2; they must not see the effects
 * of any other subcommand types, since the USING expressions are parsed
 * against the unmodified table's state.
 */
static void
ATPrepAlterColumnType(List **wqueue,
					  AlteredTableInfo *tab, Relation rel,
					  bool recurse, bool recursing,
					  AlterTableCmd *cmd, LOCKMODE lockmode,
					  AlterTableUtilityContext *context)
{
	char	   *colName = cmd->name;
	ColumnDef  *def = (ColumnDef *) cmd->def;
	TypeName   *typeName = def->typeName;
	Node	   *transform = def->cooked_default;
	HeapTuple	tuple;
	Form_pg_attribute attTup;
	AttrNumber	attnum;
	Oid			targettype;
	int32		targettypmod;
	Oid			targetcollid;
	NewColumnValue *newval;
	ParseState *pstate = make_parsestate(NULL);
	AclResult	aclresult;
	bool		is_expr;

	pstate->p_sourcetext = context->queryString;

	if (rel->rd_rel->reloftype && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot alter column type of typed table"),
				 parser_errposition(pstate, def->location)));

	/* lookup the attribute so we can check inheritance status */
	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel)),
				 parser_errposition(pstate, def->location)));
	attTup = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = attTup->attnum;

	/* Can't alter a system attribute */
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"", colName),
				 parser_errposition(pstate, def->location)));

	/*
	 * Cannot specify USING when altering type of a generated column, because
	 * that would violate the generation expression.
	 */
	if (attTup->attgenerated && def->cooked_default)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_COLUMN_DEFINITION),
				 errmsg("cannot specify USING when altering type of generated column"),
				 errdetail("Column \"%s\" is a generated column.", colName),
				 parser_errposition(pstate, def->location)));

	/*
	 * Don't alter inherited columns.  At outer level, there had better not be
	 * any inherited definition; when recursing, we assume this was checked at
	 * the parent level (see below).
	 */
	if (attTup->attinhcount > 0 && !recursing)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot alter inherited column \"%s\"", colName),
				 parser_errposition(pstate, def->location)));

	/* Don't alter columns used in the partition key */
	if (has_partition_attrs(rel,
							bms_make_singleton(attnum - FirstLowInvalidHeapAttributeNumber),
							&is_expr))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("cannot alter column \"%s\" because it is part of the partition key of relation \"%s\"",
						colName, RelationGetRelationName(rel)),
				 parser_errposition(pstate, def->location)));

	/* Look up the target type */
	typenameTypeIdAndMod(pstate, typeName, &targettype, &targettypmod);

	aclresult = object_aclcheck(TypeRelationId, targettype, GetUserId(), ACL_USAGE);
	if (aclresult != ACLCHECK_OK)
		aclcheck_error_type(aclresult, targettype);

	/* And the collation */
	targetcollid = GetColumnDefCollation(pstate, def, targettype);

	/* make sure datatype is legal for a column */
	CheckAttributeType(colName, targettype, targetcollid,
					   list_make1_oid(rel->rd_rel->reltype),
					   (attTup->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL ? CHKATYPE_IS_VIRTUAL : 0));

	if (attTup->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
	{
		/* do nothing */
	}
	else if (tab->relkind == RELKIND_RELATION ||
			 tab->relkind == RELKIND_PARTITIONED_TABLE)
	{
		/*
		 * Set up an expression to transform the old data value to the new
		 * type. If a USING option was given, use the expression as
		 * transformed by transformAlterTableStmt, else just take the old
		 * value and try to coerce it.  We do this first so that type
		 * incompatibility can be detected before we waste effort, and because
		 * we need the expression to be parsed against the original table row
		 * type.
		 */
		if (!transform)
		{
			transform = (Node *) makeVar(1, attnum,
										 attTup->atttypid, attTup->atttypmod,
										 attTup->attcollation,
										 0);
		}

		transform = coerce_to_target_type(pstate,
										  transform, exprType(transform),
										  targettype, targettypmod,
										  COERCION_ASSIGNMENT,
										  COERCE_IMPLICIT_CAST,
										  -1);
		if (transform == NULL)
		{
			/* error text depends on whether USING was specified or not */
			if (def->cooked_default != NULL)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("result of USING clause for column \"%s\""
								" cannot be cast automatically to type %s",
								colName, format_type_be(targettype)),
						 errhint("You might need to add an explicit cast.")));
			else
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("column \"%s\" cannot be cast automatically to type %s",
								colName, format_type_be(targettype)),
						 !attTup->attgenerated ?
				/* translator: USING is SQL, don't translate it */
						 errhint("You might need to specify \"USING %s::%s\".",
								 quote_identifier(colName),
								 format_type_with_typemod(targettype,
														  targettypmod)) : 0));
		}

		/* Fix collations after all else */
		assign_expr_collations(pstate, transform);

		/* Expand virtual generated columns in the expr. */
		transform = expand_generated_columns_in_expr(transform, rel, 1);

		/* Plan the expr now so we can accurately assess the need to rewrite. */
		transform = (Node *) expression_planner((Expr *) transform);

		/*
		 * Add a work queue item to make ATRewriteTable update the column
		 * contents.
		 */
		newval = (NewColumnValue *) palloc0(sizeof(NewColumnValue));
		newval->attnum = attnum;
		newval->expr = (Expr *) transform;
		newval->is_generated = false;

		tab->newvals = lappend(tab->newvals, newval);
		if (ATColumnChangeRequiresRewrite(transform, attnum))
			tab->rewrite |= AT_REWRITE_COLUMN_REWRITE;
	}
	else if (transform)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a table",
						RelationGetRelationName(rel))));

	if (!RELKIND_HAS_STORAGE(tab->relkind) || attTup->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
	{
		/*
		 * For relations or columns without storage, do this check now.
		 * Regular tables will check it later when the table is being
		 * rewritten.
		 */
		find_composite_type_dependencies(rel->rd_rel->reltype, rel, NULL);
	}

	ReleaseSysCache(tuple);

	/*
	 * Recurse manually by queueing a new command for each child, if
	 * necessary. We cannot apply ATSimpleRecursion here because we need to
	 * remap attribute numbers in the USING expression, if any.
	 *
	 * If we are told not to recurse, there had better not be any child
	 * tables; else the alter would put them out of step.
	 */
	if (recurse)
	{
		Oid			relid = RelationGetRelid(rel);
		List	   *child_oids,
				   *child_numparents;
		ListCell   *lo,
				   *li;

		child_oids = find_all_inheritors(relid, lockmode,
										 &child_numparents);

		/*
		 * find_all_inheritors does the recursive search of the inheritance
		 * hierarchy, so all we have to do is process all of the relids in the
		 * list that it returns.
		 */
		forboth(lo, child_oids, li, child_numparents)
		{
			Oid			childrelid = lfirst_oid(lo);
			int			numparents = lfirst_int(li);
			Relation	childrel;
			HeapTuple	childtuple;
			Form_pg_attribute childattTup;

			if (childrelid == relid)
				continue;

			/* find_all_inheritors already got lock */
			childrel = relation_open(childrelid, NoLock);
			CheckAlterTableIsSafe(childrel);

			/*
			 * Verify that the child doesn't have any inherited definitions of
			 * this column that came from outside this inheritance hierarchy.
			 * (renameatt makes a similar test, though in a different way
			 * because of its different recursion mechanism.)
			 */
			childtuple = SearchSysCacheAttName(RelationGetRelid(childrel),
											   colName);
			if (!HeapTupleIsValid(childtuple))
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_COLUMN),
						 errmsg("column \"%s\" of relation \"%s\" does not exist",
								colName, RelationGetRelationName(childrel))));
			childattTup = (Form_pg_attribute) GETSTRUCT(childtuple);

			if (childattTup->attinhcount > numparents)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
						 errmsg("cannot alter inherited column \"%s\" of relation \"%s\"",
								colName, RelationGetRelationName(childrel))));

			ReleaseSysCache(childtuple);

			/*
			 * Remap the attribute numbers.  If no USING expression was
			 * specified, there is no need for this step.
			 */
			if (def->cooked_default)
			{
				AttrMap    *attmap;
				bool		found_whole_row;

				/* create a copy to scribble on */
				cmd = copyObject(cmd);

				attmap = build_attrmap_by_name(RelationGetDescr(childrel),
											   RelationGetDescr(rel),
											   false);
				((ColumnDef *) cmd->def)->cooked_default =
					map_variable_attnos(def->cooked_default,
										1, 0,
										attmap,
										InvalidOid, &found_whole_row);
				if (found_whole_row)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot convert whole-row table reference"),
							 errdetail("USING expression contains a whole-row table reference.")));
				pfree(attmap);
			}
			ATPrepCmd(wqueue, childrel, cmd, false, true, lockmode, context);
			relation_close(childrel, NoLock);
		}
	}
	else if (!recursing &&
			 find_inheritance_children(RelationGetRelid(rel), NoLock) != NIL)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
				 errmsg("type of inherited column \"%s\" must be changed in child tables too",
						colName)));

	if (tab->relkind == RELKIND_COMPOSITE_TYPE)
		ATTypedTableRecursion(wqueue, rel, cmd, lockmode, context);
}

/*
 * When the data type of a column is changed, a rewrite might not be required
 * if the new type is sufficiently identical to the old one, and the USING
 * clause isn't trying to insert some other value.  It's safe to skip the
 * rewrite in these cases:
 *
 * - the old type is binary coercible to the new type
 * - the new type is an unconstrained domain over the old type
 * - {NEW,OLD} or {OLD,NEW} is {timestamptz,timestamp} and the timezone is UTC
 *
 * In the case of a constrained domain, we could get by with scanning the
 * table and checking the constraint rather than actually rewriting it, but we
 * don't currently try to do that.
 */
static bool
ATColumnChangeRequiresRewrite(Node *expr, AttrNumber varattno)
{
	Assert(expr != NULL);

	for (;;)
	{
		/* only one varno, so no need to check that */
		if (IsA(expr, Var) && ((Var *) expr)->varattno == varattno)
			return false;
		else if (IsA(expr, RelabelType))
			expr = (Node *) ((RelabelType *) expr)->arg;
		else if (IsA(expr, CoerceToDomain))
		{
			CoerceToDomain *d = (CoerceToDomain *) expr;

			if (DomainHasConstraints(d->resulttype))
				return true;
			expr = (Node *) d->arg;
		}
		else if (IsA(expr, FuncExpr))
		{
			FuncExpr   *f = (FuncExpr *) expr;

			switch (f->funcid)
			{
				case F_TIMESTAMPTZ_TIMESTAMP:
				case F_TIMESTAMP_TIMESTAMPTZ:
					if (TimestampTimestampTzRequiresRewrite())
						return true;
					else
						expr = linitial(f->args);
					break;
				default:
					return true;
			}
		}
		else
			return true;
	}
}

/*
 * ALTER COLUMN .. SET DATA TYPE
 *
 * Return the address of the modified column.
 */
static ObjectAddress
ATExecAlterColumnType(AlteredTableInfo *tab, Relation rel,
					  AlterTableCmd *cmd, LOCKMODE lockmode)
{
	char	   *colName = cmd->name;
	ColumnDef  *def = (ColumnDef *) cmd->def;
	TypeName   *typeName = def->typeName;
	HeapTuple	heapTup;
	Form_pg_attribute attTup,
				attOldTup;
	AttrNumber	attnum;
	HeapTuple	typeTuple;
	Form_pg_type tform;
	Oid			targettype;
	int32		targettypmod;
	Oid			targetcollid;
	Node	   *defaultexpr;
	Relation	attrelation;
	Relation	depRel;
	ScanKeyData key[3];
	SysScanDesc scan;
	HeapTuple	depTup;
	ObjectAddress address;

	/*
	 * Clear all the missing values if we're rewriting the table, since this
	 * renders them pointless.
	 */
	if (tab->rewrite)
	{
		Relation	newrel;

		newrel = table_open(RelationGetRelid(rel), NoLock);
		RelationClearMissing(newrel);
		relation_close(newrel, NoLock);
		/* make sure we don't conflict with later attribute modifications */
		CommandCounterIncrement();
	}

	attrelation = table_open(AttributeRelationId, RowExclusiveLock);

	/* Look up the target column */
	heapTup = SearchSysCacheCopyAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(heapTup)) /* shouldn't happen */
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));
	attTup = (Form_pg_attribute) GETSTRUCT(heapTup);
	attnum = attTup->attnum;
	attOldTup = TupleDescAttr(tab->oldDesc, attnum - 1);

	/* Check for multiple ALTER TYPE on same column --- can't cope */
	if (attTup->atttypid != attOldTup->atttypid ||
		attTup->atttypmod != attOldTup->atttypmod)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter type of column \"%s\" twice",
						colName)));

	/* Look up the target type (should not fail, since prep found it) */
	typeTuple = typenameType(NULL, typeName, &targettypmod);
	tform = (Form_pg_type) GETSTRUCT(typeTuple);
	targettype = tform->oid;
	/* And the collation */
	targetcollid = GetColumnDefCollation(NULL, def, targettype);

	/*
	 * If there is a default expression for the column, get it and ensure we
	 * can coerce it to the new datatype.  (We must do this before changing
	 * the column type, because build_column_default itself will try to
	 * coerce, and will not issue the error message we want if it fails.)
	 *
	 * We remove any implicit coercion steps at the top level of the old
	 * default expression; this has been agreed to satisfy the principle of
	 * least surprise.  (The conversion to the new column type should act like
	 * it started from what the user sees as the stored expression, and the
	 * implicit coercions aren't going to be shown.)
	 */
	if (attTup->atthasdef)
	{
		defaultexpr = build_column_default(rel, attnum);
		Assert(defaultexpr);
		defaultexpr = strip_implicit_coercions(defaultexpr);
		defaultexpr = coerce_to_target_type(NULL,	/* no UNKNOWN params */
											defaultexpr, exprType(defaultexpr),
											targettype, targettypmod,
											COERCION_ASSIGNMENT,
											COERCE_IMPLICIT_CAST,
											-1);
		if (defaultexpr == NULL)
		{
			if (attTup->attgenerated)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("generation expression for column \"%s\" cannot be cast automatically to type %s",
								colName, format_type_be(targettype))));
			else
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("default for column \"%s\" cannot be cast automatically to type %s",
								colName, format_type_be(targettype))));
		}
	}
	else
		defaultexpr = NULL;

	/*
	 * Find everything that depends on the column (constraints, indexes, etc),
	 * and record enough information to let us recreate the objects.
	 *
	 * The actual recreation does not happen here, but only after we have
	 * performed all the individual ALTER TYPE operations.  We have to save
	 * the info before executing ALTER TYPE, though, else the deparser will
	 * get confused.
	 */
	RememberAllDependentForRebuilding(tab, AT_AlterColumnType, rel, attnum, colName);

	/*
	 * Now scan for dependencies of this column on other things.  The only
	 * things we should find are the dependency on the column datatype and
	 * possibly a collation dependency.  Those can be removed.
	 */
	depRel = table_open(DependRelationId, RowExclusiveLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_classid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_objid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	ScanKeyInit(&key[2],
				Anum_pg_depend_objsubid,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum((int32) attnum));

	scan = systable_beginscan(depRel, DependDependerIndexId, true,
							  NULL, 3, key);

	while (HeapTupleIsValid(depTup = systable_getnext(scan)))
	{
		Form_pg_depend foundDep = (Form_pg_depend) GETSTRUCT(depTup);
		ObjectAddress foundObject;

		foundObject.classId = foundDep->refclassid;
		foundObject.objectId = foundDep->refobjid;
		foundObject.objectSubId = foundDep->refobjsubid;

		if (foundDep->deptype != DEPENDENCY_NORMAL)
			elog(ERROR, "found unexpected dependency type '%c'",
				 foundDep->deptype);
		if (!(foundDep->refclassid == TypeRelationId &&
			  foundDep->refobjid == attTup->atttypid) &&
			!(foundDep->refclassid == CollationRelationId &&
			  foundDep->refobjid == attTup->attcollation))
			elog(ERROR, "found unexpected dependency for column: %s",
				 getObjectDescription(&foundObject, false));

		CatalogTupleDelete(depRel, &depTup->t_self);
	}

	systable_endscan(scan);

	table_close(depRel, RowExclusiveLock);

	/*
	 * Here we go --- change the recorded column type and collation.  (Note
	 * heapTup is a copy of the syscache entry, so okay to scribble on.) First
	 * fix up the missing value if any.
	 */
	if (attTup->atthasmissing)
	{
		Datum		missingval;
		bool		missingNull;

		/* if rewrite is true the missing value should already be cleared */
		Assert(tab->rewrite == 0);

		/* Get the missing value datum */
		missingval = heap_getattr(heapTup,
								  Anum_pg_attribute_attmissingval,
								  attrelation->rd_att,
								  &missingNull);

		/* if it's a null array there is nothing to do */

		if (!missingNull)
		{
			/*
			 * Get the datum out of the array and repack it in a new array
			 * built with the new type data. We assume that since the table
			 * doesn't need rewriting, the actual Datum doesn't need to be
			 * changed, only the array metadata.
			 */

			int			one = 1;
			bool		isNull;
			Datum		valuesAtt[Natts_pg_attribute] = {0};
			bool		nullsAtt[Natts_pg_attribute] = {0};
			bool		replacesAtt[Natts_pg_attribute] = {0};
			HeapTuple	newTup;

			missingval = array_get_element(missingval,
										   1,
										   &one,
										   0,
										   attTup->attlen,
										   attTup->attbyval,
										   attTup->attalign,
										   &isNull);
			missingval = PointerGetDatum(construct_array(&missingval,
														 1,
														 targettype,
														 tform->typlen,
														 tform->typbyval,
														 tform->typalign));

			valuesAtt[Anum_pg_attribute_attmissingval - 1] = missingval;
			replacesAtt[Anum_pg_attribute_attmissingval - 1] = true;
			nullsAtt[Anum_pg_attribute_attmissingval - 1] = false;

			newTup = heap_modify_tuple(heapTup, RelationGetDescr(attrelation),
									   valuesAtt, nullsAtt, replacesAtt);
			heap_freetuple(heapTup);
			heapTup = newTup;
			attTup = (Form_pg_attribute) GETSTRUCT(heapTup);
		}
	}

	attTup->atttypid = targettype;
	attTup->atttypmod = targettypmod;
	attTup->attcollation = targetcollid;
	if (list_length(typeName->arrayBounds) > PG_INT16_MAX)
		ereport(ERROR,
				errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
				errmsg("too many array dimensions"));
	attTup->attndims = list_length(typeName->arrayBounds);
	attTup->attlen = tform->typlen;
	attTup->attbyval = tform->typbyval;
	attTup->attalign = tform->typalign;
	attTup->attstorage = tform->typstorage;
	attTup->attcompression = InvalidCompressionMethod;

	ReleaseSysCache(typeTuple);

	CatalogTupleUpdate(attrelation, &heapTup->t_self, heapTup);

	table_close(attrelation, RowExclusiveLock);

	/* Install dependencies on new datatype and collation */
	add_column_datatype_dependency(RelationGetRelid(rel), attnum, targettype);
	add_column_collation_dependency(RelationGetRelid(rel), attnum, targetcollid);

	/*
	 * Drop any pg_statistic entry for the column, since it's now wrong type
	 */
	RemoveStatistics(RelationGetRelid(rel), attnum);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), attnum);

	/*
	 * Update the default, if present, by brute force --- remove and re-add
	 * the default.  Probably unsafe to take shortcuts, since the new version
	 * may well have additional dependencies.  (It's okay to do this now,
	 * rather than after other ALTER TYPE commands, since the default won't
	 * depend on other column types.)
	 */
	if (defaultexpr)
	{
		/*
		 * If it's a GENERATED default, drop its dependency records, in
		 * particular its INTERNAL dependency on the column, which would
		 * otherwise cause dependency.c to refuse to perform the deletion.
		 */
		if (attTup->attgenerated)
		{
			Oid			attrdefoid = GetAttrDefaultOid(RelationGetRelid(rel), attnum);

			if (!OidIsValid(attrdefoid))
				elog(ERROR, "could not find attrdef tuple for relation %u attnum %d",
					 RelationGetRelid(rel), attnum);
			(void) deleteDependencyRecordsFor(AttrDefaultRelationId, attrdefoid, false);
		}

		/*
		 * Make updates-so-far visible, particularly the new pg_attribute row
		 * which will be updated again.
		 */
		CommandCounterIncrement();

		/*
		 * We use RESTRICT here for safety, but at present we do not expect
		 * anything to depend on the default.
		 */
		RemoveAttrDefault(RelationGetRelid(rel), attnum, DROP_RESTRICT, true,
						  true);

		(void) StoreAttrDefault(rel, attnum, defaultexpr, true);
	}

	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);

	/* Cleanup */
	heap_freetuple(heapTup);

	return address;
}

/*
 * Subroutine for ATExecAlterColumnType and ATExecSetExpression: Find everything
 * that depends on the column (constraints, indexes, etc), and record enough
 * information to let us recreate the objects.
 */
static void
RememberAllDependentForRebuilding(AlteredTableInfo *tab, AlterTableType subtype,
								  Relation rel, AttrNumber attnum, const char *colName)
{
	Relation	depRel;
	ScanKeyData key[3];
	SysScanDesc scan;
	HeapTuple	depTup;

	Assert(subtype == AT_AlterColumnType || subtype == AT_SetExpression);

	depRel = table_open(DependRelationId, RowExclusiveLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_refclassid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_refobjid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	ScanKeyInit(&key[2],
				Anum_pg_depend_refobjsubid,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum((int32) attnum));

	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
							  NULL, 3, key);

	while (HeapTupleIsValid(depTup = systable_getnext(scan)))
	{
		Form_pg_depend foundDep = (Form_pg_depend) GETSTRUCT(depTup);
		ObjectAddress foundObject;

		foundObject.classId = foundDep->classid;
		foundObject.objectId = foundDep->objid;
		foundObject.objectSubId = foundDep->objsubid;

		switch (foundObject.classId)
		{
			case RelationRelationId:
				{
					char		relKind = get_rel_relkind(foundObject.objectId);

					if (relKind == RELKIND_INDEX ||
						relKind == RELKIND_PARTITIONED_INDEX)
					{
						Assert(foundObject.objectSubId == 0);
						RememberIndexForRebuilding(foundObject.objectId, tab);
					}
					else if (relKind == RELKIND_SEQUENCE)
					{
						/*
						 * This must be a SERIAL column's sequence.  We need
						 * not do anything to it.
						 */
						Assert(foundObject.objectSubId == 0);
					}
					else
					{
						/* Not expecting any other direct dependencies... */
						elog(ERROR, "unexpected object depending on column: %s",
							 getObjectDescription(&foundObject, false));
					}
					break;
				}

			case ConstraintRelationId:
				Assert(foundObject.objectSubId == 0);
				RememberConstraintForRebuilding(foundObject.objectId, tab);
				break;

			case ProcedureRelationId:

				/*
				 * A new-style SQL function can depend on a column, if that
				 * column is referenced in the parsed function body.  Ideally
				 * we'd automatically update the function by deparsing and
				 * reparsing it, but that's risky and might well fail anyhow.
				 * FIXME someday.
				 *
				 * This is only a problem for AT_AlterColumnType, not
				 * AT_SetExpression.
				 */
				if (subtype == AT_AlterColumnType)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot alter type of a column used by a function or procedure"),
							 errdetail("%s depends on column \"%s\"",
									   getObjectDescription(&foundObject, false),
									   colName)));
				break;

			case RewriteRelationId:

				/*
				 * View/rule bodies have pretty much the same issues as
				 * function bodies.  FIXME someday.
				 */
				if (subtype == AT_AlterColumnType)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot alter type of a column used by a view or rule"),
							 errdetail("%s depends on column \"%s\"",
									   getObjectDescription(&foundObject, false),
									   colName)));
				break;

			case TriggerRelationId:

				/*
				 * A trigger can depend on a column because the column is
				 * specified as an update target, or because the column is
				 * used in the trigger's WHEN condition.  The first case would
				 * not require any extra work, but the second case would
				 * require updating the WHEN expression, which has the same
				 * issues as above.  Since we can't easily tell which case
				 * applies, we punt for both.  FIXME someday.
				 */
				if (subtype == AT_AlterColumnType)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot alter type of a column used in a trigger definition"),
							 errdetail("%s depends on column \"%s\"",
									   getObjectDescription(&foundObject, false),
									   colName)));
				break;

			case PolicyRelationId:

				/*
				 * A policy can depend on a column because the column is
				 * specified in the policy's USING or WITH CHECK qual
				 * expressions.  It might be possible to rewrite and recheck
				 * the policy expression, but punt for now.  It's certainly
				 * easy enough to remove and recreate the policy; still, FIXME
				 * someday.
				 */
				if (subtype == AT_AlterColumnType)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot alter type of a column used in a policy definition"),
							 errdetail("%s depends on column \"%s\"",
									   getObjectDescription(&foundObject, false),
									   colName)));
				break;

			case AttrDefaultRelationId:
				{
					ObjectAddress col = GetAttrDefaultColumnAddress(foundObject.objectId);

					if (col.objectId == RelationGetRelid(rel) &&
						col.objectSubId == attnum)
					{
						/*
						 * Ignore the column's own default expression.  The
						 * caller deals with it.
						 */
					}
					else
					{
						/*
						 * This must be a reference from the expression of a
						 * generated column elsewhere in the same table.
						 * Changing the type/generated expression of a column
						 * that is used by a generated column is not allowed
						 * by SQL standard, so just punt for now.  It might be
						 * doable with some thinking and effort.
						 */
						if (subtype == AT_AlterColumnType)
							ereport(ERROR,
									(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
									 errmsg("cannot alter type of a column used by a generated column"),
									 errdetail("Column \"%s\" is used by generated column \"%s\".",
											   colName,
											   get_attname(col.objectId,
														   col.objectSubId,
														   false))));
					}
					break;
				}

			case StatisticExtRelationId:

				/*
				 * Give the extended-stats machinery a chance to fix anything
				 * that this column type change would break.
				 */
				RememberStatisticsForRebuilding(foundObject.objectId, tab);
				break;

			case PublicationRelRelationId:

				/*
				 * Column reference in a PUBLICATION ... FOR TABLE ... WHERE
				 * clause.  Same issues as above.  FIXME someday.
				 */
				if (subtype == AT_AlterColumnType)
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot alter type of a column used by a publication WHERE clause"),
							 errdetail("%s depends on column \"%s\"",
									   getObjectDescription(&foundObject, false),
									   colName)));
				break;

			default:

				/*
				 * We don't expect any other sorts of objects to depend on a
				 * column.
				 */
				elog(ERROR, "unexpected object depending on column: %s",
					 getObjectDescription(&foundObject, false));
				break;
		}
	}

	systable_endscan(scan);
	table_close(depRel, NoLock);
}

/*
 * Subroutine for ATExecAlterColumnType: remember that a replica identity
 * needs to be reset.
 */
static void
RememberReplicaIdentityForRebuilding(Oid indoid, AlteredTableInfo *tab)
{
	if (!get_index_isreplident(indoid))
		return;

	if (tab->replicaIdentityIndex)
		elog(ERROR, "relation %u has multiple indexes marked as replica identity", tab->relid);

	tab->replicaIdentityIndex = get_rel_name(indoid);
}

/*
 * Subroutine for ATExecAlterColumnType: remember any clustered index.
 */
static void
RememberClusterOnForRebuilding(Oid indoid, AlteredTableInfo *tab)
{
	if (!get_index_isclustered(indoid))
		return;

	if (tab->clusterOnIndex)
		elog(ERROR, "relation %u has multiple clustered indexes", tab->relid);

	tab->clusterOnIndex = get_rel_name(indoid);
}

/*
 * Subroutine for ATExecAlterColumnType: remember that a constraint needs
 * to be rebuilt (which we might already know).
 */
static void
RememberConstraintForRebuilding(Oid conoid, AlteredTableInfo *tab)
{
	/*
	 * This de-duplication check is critical for two independent reasons: we
	 * mustn't try to recreate the same constraint twice, and if a constraint
	 * depends on more than one column whose type is to be altered, we must
	 * capture its definition string before applying any of the column type
	 * changes.  ruleutils.c will get confused if we ask again later.
	 */
	if (!list_member_oid(tab->changedConstraintOids, conoid))
	{
		/* OK, capture the constraint's existing definition string */
		char	   *defstring = pg_get_constraintdef_command(conoid);
		Oid			indoid;

		/*
		 * It is critical to create not-null constraints ahead of primary key
		 * indexes; otherwise, the not-null constraint would be created by the
		 * primary key, and the constraint name would be wrong.
		 */
		if (get_constraint_type(conoid) == CONSTRAINT_NOTNULL)
		{
			tab->changedConstraintOids = lcons_oid(conoid,
												   tab->changedConstraintOids);
			tab->changedConstraintDefs = lcons(defstring,
											   tab->changedConstraintDefs);
		}
		else
		{

			tab->changedConstraintOids = lappend_oid(tab->changedConstraintOids,
													 conoid);
			tab->changedConstraintDefs = lappend(tab->changedConstraintDefs,
												 defstring);
		}

		/*
		 * For the index of a constraint, if any, remember if it is used for
		 * the table's replica identity or if it is a clustered index, so that
		 * ATPostAlterTypeCleanup() can queue up commands necessary to restore
		 * those properties.
		 */
		indoid = get_constraint_index(conoid);
		if (OidIsValid(indoid))
		{
			RememberReplicaIdentityForRebuilding(indoid, tab);
			RememberClusterOnForRebuilding(indoid, tab);
		}
	}
}

/*
 * Subroutine for ATExecAlterColumnType: remember that an index needs
 * to be rebuilt (which we might already know).
 */
static void
RememberIndexForRebuilding(Oid indoid, AlteredTableInfo *tab)
{
	/*
	 * This de-duplication check is critical for two independent reasons: we
	 * mustn't try to recreate the same index twice, and if an index depends
	 * on more than one column whose type is to be altered, we must capture
	 * its definition string before applying any of the column type changes.
	 * ruleutils.c will get confused if we ask again later.
	 */
	if (!list_member_oid(tab->changedIndexOids, indoid))
	{
		/*
		 * Before adding it as an index-to-rebuild, we'd better see if it
		 * belongs to a constraint, and if so rebuild the constraint instead.
		 * Typically this check fails, because constraint indexes normally
		 * have only dependencies on their constraint.  But it's possible for
		 * such an index to also have direct dependencies on table columns,
		 * for example with a partial exclusion constraint.
		 */
		Oid			conoid = get_index_constraint(indoid);

		if (OidIsValid(conoid))
		{
			RememberConstraintForRebuilding(conoid, tab);
		}
		else
		{
			/* OK, capture the index's existing definition string */
			char	   *defstring = pg_get_indexdef_string(indoid);

			tab->changedIndexOids = lappend_oid(tab->changedIndexOids,
												indoid);
			tab->changedIndexDefs = lappend(tab->changedIndexDefs,
											defstring);

			/*
			 * Remember if this index is used for the table's replica identity
			 * or if it is a clustered index, so that ATPostAlterTypeCleanup()
			 * can queue up commands necessary to restore those properties.
			 */
			RememberReplicaIdentityForRebuilding(indoid, tab);
			RememberClusterOnForRebuilding(indoid, tab);
		}
	}
}

/*
 * Subroutine for ATExecAlterColumnType: remember that a statistics object
 * needs to be rebuilt (which we might already know).
 */
static void
RememberStatisticsForRebuilding(Oid stxoid, AlteredTableInfo *tab)
{
	/*
	 * This de-duplication check is critical for two independent reasons: we
	 * mustn't try to recreate the same statistics object twice, and if the
	 * statistics object depends on more than one column whose type is to be
	 * altered, we must capture its definition string before applying any of
	 * the type changes. ruleutils.c will get confused if we ask again later.
	 */
	if (!list_member_oid(tab->changedStatisticsOids, stxoid))
	{
		/* OK, capture the statistics object's existing definition string */
		char	   *defstring = pg_get_statisticsobjdef_string(stxoid);

		tab->changedStatisticsOids = lappend_oid(tab->changedStatisticsOids,
												 stxoid);
		tab->changedStatisticsDefs = lappend(tab->changedStatisticsDefs,
											 defstring);
	}
}

/*
 * Cleanup after we've finished all the ALTER TYPE or SET EXPRESSION
 * operations for a particular relation.  We have to drop and recreate all the
 * indexes and constraints that depend on the altered columns.  We do the
 * actual dropping here, but re-creation is managed by adding work queue
 * entries to do those steps later.
 */
static void
ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode)
{
	ObjectAddress obj;
	ObjectAddresses *objects;
	ListCell   *def_item;
	ListCell   *oid_item;

	/*
	 * Collect all the constraints and indexes to drop so we can process them
	 * in a single call.  That way we don't have to worry about dependencies
	 * among them.
	 */
	objects = new_object_addresses();

	/*
	 * Re-parse the index and constraint definitions, and attach them to the
	 * appropriate work queue entries.  We do this before dropping because in
	 * the case of a constraint on another table, we might not yet have
	 * exclusive lock on the table the constraint is attached to, and we need
	 * to get that before reparsing/dropping.  (That's possible at least for
	 * FOREIGN KEY, CHECK, and EXCLUSION constraints; in non-FK cases it
	 * requires a dependency on the target table's composite type in the other
	 * table's constraint expressions.)
	 *
	 * We can't rely on the output of deparsing to tell us which relation to
	 * operate on, because concurrent activity might have made the name
	 * resolve differently.  Instead, we've got to use the OID of the
	 * constraint or index we're processing to figure out which relation to
	 * operate on.
	 */
	forboth(oid_item, tab->changedConstraintOids,
			def_item, tab->changedConstraintDefs)
	{
		Oid			oldId = lfirst_oid(oid_item);
		HeapTuple	tup;
		Form_pg_constraint con;
		Oid			relid;
		Oid			confrelid;
		bool		conislocal;

		tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(oldId));
		if (!HeapTupleIsValid(tup)) /* should not happen */
			elog(ERROR, "cache lookup failed for constraint %u", oldId);
		con = (Form_pg_constraint) GETSTRUCT(tup);
		if (OidIsValid(con->conrelid))
			relid = con->conrelid;
		else
		{
			/* must be a domain constraint */
			relid = get_typ_typrelid(getBaseType(con->contypid));
			if (!OidIsValid(relid))
				elog(ERROR, "could not identify relation associated with constraint %u", oldId);
		}
		confrelid = con->confrelid;
		conislocal = con->conislocal;
		ReleaseSysCache(tup);

		ObjectAddressSet(obj, ConstraintRelationId, oldId);
		add_exact_object_address(&obj, objects);

		/*
		 * If the constraint is inherited (only), we don't want to inject a
		 * new definition here; it'll get recreated when
		 * ATAddCheckNNConstraint recurses from adding the parent table's
		 * constraint.  But we had to carry the info this far so that we can
		 * drop the constraint below.
		 */
		if (!conislocal)
			continue;

		/*
		 * When rebuilding another table's constraint that references the
		 * table we're modifying, we might not yet have any lock on the other
		 * table, so get one now.  We'll need AccessExclusiveLock for the DROP
		 * CONSTRAINT step, so there's no value in asking for anything weaker.
		 */
		if (relid != tab->relid)
			LockRelationOid(relid, AccessExclusiveLock);

		ATPostAlterTypeParse(oldId, relid, confrelid,
							 (char *) lfirst(def_item),
							 wqueue, lockmode, tab->rewrite);
	}
	forboth(oid_item, tab->changedIndexOids,
			def_item, tab->changedIndexDefs)
	{
		Oid			oldId = lfirst_oid(oid_item);
		Oid			relid;

		relid = IndexGetRelation(oldId, false);

		/*
		 * As above, make sure we have lock on the index's table if it's not
		 * the same table.
		 */
		if (relid != tab->relid)
			LockRelationOid(relid, AccessExclusiveLock);

		ATPostAlterTypeParse(oldId, relid, InvalidOid,
							 (char *) lfirst(def_item),
							 wqueue, lockmode, tab->rewrite);

		ObjectAddressSet(obj, RelationRelationId, oldId);
		add_exact_object_address(&obj, objects);
	}

	/* add dependencies for new statistics */
	forboth(oid_item, tab->changedStatisticsOids,
			def_item, tab->changedStatisticsDefs)
	{
		Oid			oldId = lfirst_oid(oid_item);
		Oid			relid;

		relid = StatisticsGetRelation(oldId, false);

		/*
		 * As above, make sure we have lock on the statistics object's table
		 * if it's not the same table.  However, we take
		 * ShareUpdateExclusiveLock here, aligning with the lock level used in
		 * CreateStatistics and RemoveStatisticsById.
		 *
		 * CAUTION: this should be done after all cases that grab
		 * AccessExclusiveLock, else we risk causing deadlock due to needing
		 * to promote our table lock.
		 */
		if (relid != tab->relid)
			LockRelationOid(relid, ShareUpdateExclusiveLock);

		ATPostAlterTypeParse(oldId, relid, InvalidOid,
							 (char *) lfirst(def_item),
							 wqueue, lockmode, tab->rewrite);

		ObjectAddressSet(obj, StatisticExtRelationId, oldId);
		add_exact_object_address(&obj, objects);
	}

	/*
	 * Queue up command to restore replica identity index marking
	 */
	if (tab->replicaIdentityIndex)
	{
		AlterTableCmd *cmd = makeNode(AlterTableCmd);
		ReplicaIdentityStmt *subcmd = makeNode(ReplicaIdentityStmt);

		subcmd->identity_type = REPLICA_IDENTITY_INDEX;
		subcmd->name = tab->replicaIdentityIndex;
		cmd->subtype = AT_ReplicaIdentity;
		cmd->def = (Node *) subcmd;

		/* do it after indexes and constraints */
		tab->subcmds[AT_PASS_OLD_CONSTR] =
			lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
	}

	/*
	 * Queue up command to restore marking of index used for cluster.
	 */
	if (tab->clusterOnIndex)
	{
		AlterTableCmd *cmd = makeNode(AlterTableCmd);

		cmd->subtype = AT_ClusterOn;
		cmd->name = tab->clusterOnIndex;

		/* do it after indexes and constraints */
		tab->subcmds[AT_PASS_OLD_CONSTR] =
			lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
	}

	/*
	 * It should be okay to use DROP_RESTRICT here, since nothing else should
	 * be depending on these objects.
	 */
	performMultipleDeletions(objects, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);

	free_object_addresses(objects);

	/*
	 * The objects will get recreated during subsequent passes over the work
	 * queue.
	 */
}

/*
 * Parse the previously-saved definition string for a constraint, index or
 * statistics object against the newly-established column data type(s), and
 * queue up the resulting command parsetrees for execution.
 *
 * This might fail if, for example, you have a WHERE clause that uses an
 * operator that's not available for the new column type.
 */
static void
ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
					 List **wqueue, LOCKMODE lockmode, bool rewrite)
{
	List	   *raw_parsetree_list;
	List	   *querytree_list;
	ListCell   *list_item;
	Relation	rel;

	/*
	 * We expect that we will get only ALTER TABLE and CREATE INDEX
	 * statements. Hence, there is no need to pass them through
	 * parse_analyze_*() or the rewriter, but instead we need to pass them
	 * through parse_utilcmd.c to make them ready for execution.
	 */
	raw_parsetree_list = raw_parser(cmd, RAW_PARSE_DEFAULT);
	querytree_list = NIL;
	foreach(list_item, raw_parsetree_list)
	{
		RawStmt    *rs = lfirst_node(RawStmt, list_item);
		Node	   *stmt = rs->stmt;

		if (IsA(stmt, IndexStmt))
			querytree_list = lappend(querytree_list,
									 transformIndexStmt(oldRelId,
														(IndexStmt *) stmt,
														cmd));
		else if (IsA(stmt, AlterTableStmt))
		{
			List	   *beforeStmts;
			List	   *afterStmts;

			stmt = (Node *) transformAlterTableStmt(oldRelId,
													(AlterTableStmt *) stmt,
													cmd,
													&beforeStmts,
													&afterStmts);
			querytree_list = list_concat(querytree_list, beforeStmts);
			querytree_list = lappend(querytree_list, stmt);
			querytree_list = list_concat(querytree_list, afterStmts);
		}
		else if (IsA(stmt, CreateStatsStmt))
			querytree_list = lappend(querytree_list,
									 transformStatsStmt(oldRelId,
														(CreateStatsStmt *) stmt,
														cmd));
		else
			querytree_list = lappend(querytree_list, stmt);
	}

	/* Caller should already have acquired whatever lock we need. */
	rel = relation_open(oldRelId, NoLock);

	/*
	 * Attach each generated command to the proper place in the work queue.
	 * Note this could result in creation of entirely new work-queue entries.
	 *
	 * Also note that we have to tweak the command subtypes, because it turns
	 * out that re-creation of indexes and constraints has to act a bit
	 * differently from initial creation.
	 */
	foreach(list_item, querytree_list)
	{
		Node	   *stm = (Node *) lfirst(list_item);
		AlteredTableInfo *tab;

		tab = ATGetQueueEntry(wqueue, rel);

		if (IsA(stm, IndexStmt))
		{
			IndexStmt  *stmt = (IndexStmt *) stm;
			AlterTableCmd *newcmd;

			if (!rewrite)
				TryReuseIndex(oldId, stmt);
			stmt->reset_default_tblspc = true;
			/* keep the index's comment */
			stmt->idxcomment = GetComment(oldId, RelationRelationId, 0);

			newcmd = makeNode(AlterTableCmd);
			newcmd->subtype = AT_ReAddIndex;
			newcmd->def = (Node *) stmt;
			tab->subcmds[AT_PASS_OLD_INDEX] =
				lappend(tab->subcmds[AT_PASS_OLD_INDEX], newcmd);
		}
		else if (IsA(stm, AlterTableStmt))
		{
			AlterTableStmt *stmt = (AlterTableStmt *) stm;
			ListCell   *lcmd;

			foreach(lcmd, stmt->cmds)
			{
				AlterTableCmd *cmd = lfirst_node(AlterTableCmd, lcmd);

				if (cmd->subtype == AT_AddIndex)
				{
					IndexStmt  *indstmt;
					Oid			indoid;

					indstmt = castNode(IndexStmt, cmd->def);
					indoid = get_constraint_index(oldId);

					if (!rewrite)
						TryReuseIndex(indoid, indstmt);
					/* keep any comment on the index */
					indstmt->idxcomment = GetComment(indoid,
													 RelationRelationId, 0);
					indstmt->reset_default_tblspc = true;

					cmd->subtype = AT_ReAddIndex;
					tab->subcmds[AT_PASS_OLD_INDEX] =
						lappend(tab->subcmds[AT_PASS_OLD_INDEX], cmd);

					/* recreate any comment on the constraint */
					RebuildConstraintComment(tab,
											 AT_PASS_OLD_INDEX,
											 oldId,
											 rel,
											 NIL,
											 indstmt->idxname);
				}
				else if (cmd->subtype == AT_AddConstraint)
				{
					Constraint *con = castNode(Constraint, cmd->def);

					con->old_pktable_oid = refRelId;
					/* rewriting neither side of a FK */
					if (con->contype == CONSTR_FOREIGN &&
						!rewrite && tab->rewrite == 0)
						TryReuseForeignKey(oldId, con);
					con->reset_default_tblspc = true;
					cmd->subtype = AT_ReAddConstraint;
					tab->subcmds[AT_PASS_OLD_CONSTR] =
						lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);

					/*
					 * Recreate any comment on the constraint.  If we have
					 * recreated a primary key, then transformTableConstraint
					 * has added an unnamed not-null constraint here; skip
					 * this in that case.
					 */
					if (con->conname)
						RebuildConstraintComment(tab,
												 AT_PASS_OLD_CONSTR,
												 oldId,
												 rel,
												 NIL,
												 con->conname);
					else
						Assert(con->contype == CONSTR_NOTNULL);
				}
				else
					elog(ERROR, "unexpected statement subtype: %d",
						 (int) cmd->subtype);
			}
		}
		else if (IsA(stm, AlterDomainStmt))
		{
			AlterDomainStmt *stmt = (AlterDomainStmt *) stm;

			if (stmt->subtype == 'C')	/* ADD CONSTRAINT */
			{
				Constraint *con = castNode(Constraint, stmt->def);
				AlterTableCmd *cmd = makeNode(AlterTableCmd);

				cmd->subtype = AT_ReAddDomainConstraint;
				cmd->def = (Node *) stmt;
				tab->subcmds[AT_PASS_OLD_CONSTR] =
					lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);

				/* recreate any comment on the constraint */
				RebuildConstraintComment(tab,
										 AT_PASS_OLD_CONSTR,
										 oldId,
										 NULL,
										 stmt->typeName,
										 con->conname);
			}
			else
				elog(ERROR, "unexpected statement subtype: %d",
					 (int) stmt->subtype);
		}
		else if (IsA(stm, CreateStatsStmt))
		{
			CreateStatsStmt *stmt = (CreateStatsStmt *) stm;
			AlterTableCmd *newcmd;

			/* keep the statistics object's comment */
			stmt->stxcomment = GetComment(oldId, StatisticExtRelationId, 0);

			newcmd = makeNode(AlterTableCmd);
			newcmd->subtype = AT_ReAddStatistics;
			newcmd->def = (Node *) stmt;
			tab->subcmds[AT_PASS_MISC] =
				lappend(tab->subcmds[AT_PASS_MISC], newcmd);
		}
		else
			elog(ERROR, "unexpected statement type: %d",
				 (int) nodeTag(stm));
	}

	relation_close(rel, NoLock);
}

/*
 * Subroutine for ATPostAlterTypeParse() to recreate any existing comment
 * for a table or domain constraint that is being rebuilt.
 *
 * objid is the OID of the constraint.
 * Pass "rel" for a table constraint, or "domname" (domain's qualified name
 * as a string list) for a domain constraint.
 * (We could dig that info, as well as the conname, out of the pg_constraint
 * entry; but callers already have them so might as well pass them.)
 */
static void
RebuildConstraintComment(AlteredTableInfo *tab, AlterTablePass pass, Oid objid,
						 Relation rel, List *domname,
						 const char *conname)
{
	CommentStmt *cmd;
	char	   *comment_str;
	AlterTableCmd *newcmd;

	/* Look for comment for object wanted, and leave if none */
	comment_str = GetComment(objid, ConstraintRelationId, 0);
	if (comment_str == NULL)
		return;

	/* Build CommentStmt node, copying all input data for safety */
	cmd = makeNode(CommentStmt);
	if (rel)
	{
		cmd->objtype = OBJECT_TABCONSTRAINT;
		cmd->object = (Node *)
			list_make3(makeString(get_namespace_name(RelationGetNamespace(rel))),
					   makeString(pstrdup(RelationGetRelationName(rel))),
					   makeString(pstrdup(conname)));
	}
	else
	{
		cmd->objtype = OBJECT_DOMCONSTRAINT;
		cmd->object = (Node *)
			list_make2(makeTypeNameFromNameList(copyObject(domname)),
					   makeString(pstrdup(conname)));
	}
	cmd->comment = comment_str;

	/* Append it to list of commands */
	newcmd = makeNode(AlterTableCmd);
	newcmd->subtype = AT_ReAddComment;
	newcmd->def = (Node *) cmd;
	tab->subcmds[pass] = lappend(tab->subcmds[pass], newcmd);
}

/*
 * Subroutine for ATPostAlterTypeParse().  Calls out to CheckIndexCompatible()
 * for the real analysis, then mutates the IndexStmt based on that verdict.
 */
static void
TryReuseIndex(Oid oldId, IndexStmt *stmt)
{
	if (CheckIndexCompatible(oldId,
							 stmt->accessMethod,
							 stmt->indexParams,
							 stmt->excludeOpNames,
							 stmt->iswithoutoverlaps))
	{
		Relation	irel = index_open(oldId, NoLock);

		/* If it's a partitioned index, there is no storage to share. */
		if (irel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
		{
			stmt->oldNumber = irel->rd_locator.relNumber;
			stmt->oldCreateSubid = irel->rd_createSubid;
			stmt->oldFirstRelfilelocatorSubid = irel->rd_firstRelfilelocatorSubid;
		}
		index_close(irel, NoLock);
	}
}

/*
 * Subroutine for ATPostAlterTypeParse().
 *
 * Stash the old P-F equality operator into the Constraint node, for possible
 * use by ATAddForeignKeyConstraint() in determining whether revalidation of
 * this constraint can be skipped.
 */
static void
TryReuseForeignKey(Oid oldId, Constraint *con)
{
	HeapTuple	tup;
	Datum		adatum;
	ArrayType  *arr;
	Oid		   *rawarr;
	int			numkeys;
	int			i;

	Assert(con->contype == CONSTR_FOREIGN);
	Assert(con->old_conpfeqop == NIL);	/* already prepared this node */

	tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(oldId));
	if (!HeapTupleIsValid(tup)) /* should not happen */
		elog(ERROR, "cache lookup failed for constraint %u", oldId);

	adatum = SysCacheGetAttrNotNull(CONSTROID, tup,
									Anum_pg_constraint_conpfeqop);
	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
	numkeys = ARR_DIMS(arr)[0];
	/* test follows the one in ri_FetchConstraintInfo() */
	if (ARR_NDIM(arr) != 1 ||
		ARR_HASNULL(arr) ||
		ARR_ELEMTYPE(arr) != OIDOID)
		elog(ERROR, "conpfeqop is not a 1-D Oid array");
	rawarr = (Oid *) ARR_DATA_PTR(arr);

	/* stash a List of the operator Oids in our Constraint node */
	for (i = 0; i < numkeys; i++)
		con->old_conpfeqop = lappend_oid(con->old_conpfeqop, rawarr[i]);

	ReleaseSysCache(tup);
}

/*
 * ALTER COLUMN .. OPTIONS ( ... )
 *
 * Returns the address of the modified column
 */
static ObjectAddress
ATExecAlterColumnGenericOptions(Relation rel,
								const char *colName,
								List *options,
								LOCKMODE lockmode)
{
	Relation	ftrel;
	Relation	attrel;
	ForeignServer *server;
	ForeignDataWrapper *fdw;
	HeapTuple	tuple;
	HeapTuple	newtuple;
	bool		isnull;
	Datum		repl_val[Natts_pg_attribute];
	bool		repl_null[Natts_pg_attribute];
	bool		repl_repl[Natts_pg_attribute];
	Datum		datum;
	Form_pg_foreign_table fttableform;
	Form_pg_attribute atttableform;
	AttrNumber	attnum;
	ObjectAddress address;

	if (options == NIL)
		return InvalidObjectAddress;

	/* First, determine FDW validator associated to the foreign table. */
	ftrel = table_open(ForeignTableRelationId, AccessShareLock);
	tuple = SearchSysCache1(FOREIGNTABLEREL, ObjectIdGetDatum(rel->rd_id));
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("foreign table \"%s\" does not exist",
						RelationGetRelationName(rel))));
	fttableform = (Form_pg_foreign_table) GETSTRUCT(tuple);
	server = GetForeignServer(fttableform->ftserver);
	fdw = GetForeignDataWrapper(server->fdwid);

	table_close(ftrel, AccessShareLock);
	ReleaseSysCache(tuple);

	attrel = table_open(AttributeRelationId, RowExclusiveLock);
	tuple = SearchSysCacheAttName(RelationGetRelid(rel), colName);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						colName, RelationGetRelationName(rel))));

	/* Prevent them from altering a system attribute */
	atttableform = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = atttableform->attnum;
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"", colName)));


	/* Initialize buffers for new tuple values */
	memset(repl_val, 0, sizeof(repl_val));
	memset(repl_null, false, sizeof(repl_null));
	memset(repl_repl, false, sizeof(repl_repl));

	/* Extract the current options */
	datum = SysCacheGetAttr(ATTNAME,
							tuple,
							Anum_pg_attribute_attfdwoptions,
							&isnull);
	if (isnull)
		datum = PointerGetDatum(NULL);

	/* Transform the options */
	datum = transformGenericOptions(AttributeRelationId,
									datum,
									options,
									fdw->fdwvalidator);

	if (PointerIsValid(DatumGetPointer(datum)))
		repl_val[Anum_pg_attribute_attfdwoptions - 1] = datum;
	else
		repl_null[Anum_pg_attribute_attfdwoptions - 1] = true;

	repl_repl[Anum_pg_attribute_attfdwoptions - 1] = true;

	/* Everything looks good - update the tuple */

	newtuple = heap_modify_tuple(tuple, RelationGetDescr(attrel),
								 repl_val, repl_null, repl_repl);

	CatalogTupleUpdate(attrel, &newtuple->t_self, newtuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  atttableform->attnum);
	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);

	ReleaseSysCache(tuple);

	table_close(attrel, RowExclusiveLock);

	heap_freetuple(newtuple);

	return address;
}

/*
 * ALTER TABLE OWNER
 *
 * recursing is true if we are recursing from a table to its indexes,
 * sequences, or toast table.  We don't allow the ownership of those things to
 * be changed separately from the parent table.  Also, we can skip permission
 * checks (this is necessary not just an optimization, else we'd fail to
 * handle toast tables properly).
 *
 * recursing is also true if ALTER TYPE OWNER is calling us to fix up a
 * free-standing composite type.
 */
void
ATExecChangeOwner(Oid relationOid, Oid newOwnerId, bool recursing, LOCKMODE lockmode)
{
	Relation	target_rel;
	Relation	class_rel;
	HeapTuple	tuple;
	Form_pg_class tuple_class;

	/*
	 * Get exclusive lock till end of transaction on the target table. Use
	 * relation_open so that we can work on indexes and sequences.
	 */
	target_rel = relation_open(relationOid, lockmode);

	/* Get its pg_class tuple, too */
	class_rel = table_open(RelationRelationId, RowExclusiveLock);

	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relationOid));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", relationOid);
	tuple_class = (Form_pg_class) GETSTRUCT(tuple);

	/* Can we change the ownership of this tuple? */
	switch (tuple_class->relkind)
	{
		case RELKIND_RELATION:
		case RELKIND_VIEW:
		case RELKIND_MATVIEW:
		case RELKIND_FOREIGN_TABLE:
		case RELKIND_PARTITIONED_TABLE:
			/* ok to change owner */
			break;
		case RELKIND_INDEX:
			if (!recursing)
			{
				/*
				 * Because ALTER INDEX OWNER used to be allowed, and in fact
				 * is generated by old versions of pg_dump, we give a warning
				 * and do nothing rather than erroring out.  Also, to avoid
				 * unnecessary chatter while restoring those old dumps, say
				 * nothing at all if the command would be a no-op anyway.
				 */
				if (tuple_class->relowner != newOwnerId)
					ereport(WARNING,
							(errcode(ERRCODE_WRONG_OBJECT_TYPE),
							 errmsg("cannot change owner of index \"%s\"",
									NameStr(tuple_class->relname)),
							 errhint("Change the ownership of the index's table instead.")));
				/* quick hack to exit via the no-op path */
				newOwnerId = tuple_class->relowner;
			}
			break;
		case RELKIND_PARTITIONED_INDEX:
			if (recursing)
				break;
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot change owner of index \"%s\"",
							NameStr(tuple_class->relname)),
					 errhint("Change the ownership of the index's table instead.")));
			break;
		case RELKIND_SEQUENCE:
			if (!recursing &&
				tuple_class->relowner != newOwnerId)
			{
				/* if it's an owned sequence, disallow changing it by itself */
				Oid			tableId;
				int32		colId;

				if (sequenceIsOwned(relationOid, DEPENDENCY_AUTO, &tableId, &colId) ||
					sequenceIsOwned(relationOid, DEPENDENCY_INTERNAL, &tableId, &colId))
					ereport(ERROR,
							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
							 errmsg("cannot change owner of sequence \"%s\"",
									NameStr(tuple_class->relname)),
							 errdetail("Sequence \"%s\" is linked to table \"%s\".",
									   NameStr(tuple_class->relname),
									   get_rel_name(tableId))));
			}
			break;
		case RELKIND_COMPOSITE_TYPE:
			if (recursing)
				break;
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("\"%s\" is a composite type",
							NameStr(tuple_class->relname)),
			/* translator: %s is an SQL ALTER command */
					 errhint("Use %s instead.",
							 "ALTER TYPE")));
			break;
		case RELKIND_TOASTVALUE:
			if (recursing)
				break;
			/* FALL THRU */
		default:
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot change owner of relation \"%s\"",
							NameStr(tuple_class->relname)),
					 errdetail_relkind_not_supported(tuple_class->relkind)));
	}

	/*
	 * If the new owner is the same as the existing owner, consider the
	 * command to have succeeded.  This is for dump restoration purposes.
	 */
	if (tuple_class->relowner != newOwnerId)
	{
		Datum		repl_val[Natts_pg_class];
		bool		repl_null[Natts_pg_class];
		bool		repl_repl[Natts_pg_class];
		Acl		   *newAcl;
		Datum		aclDatum;
		bool		isNull;
		HeapTuple	newtuple;

		/* skip permission checks when recursing to index or toast table */
		if (!recursing)
		{
			/* Superusers can always do it */
			if (!superuser())
			{
				Oid			namespaceOid = tuple_class->relnamespace;
				AclResult	aclresult;

				/* Otherwise, must be owner of the existing object */
				if (!object_ownercheck(RelationRelationId, relationOid, GetUserId()))
					aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relationOid)),
								   RelationGetRelationName(target_rel));

				/* Must be able to become new owner */
				check_can_set_role(GetUserId(), newOwnerId);

				/* New owner must have CREATE privilege on namespace */
				aclresult = object_aclcheck(NamespaceRelationId, namespaceOid, newOwnerId,
											ACL_CREATE);
				if (aclresult != ACLCHECK_OK)
					aclcheck_error(aclresult, OBJECT_SCHEMA,
								   get_namespace_name(namespaceOid));
			}
		}

		memset(repl_null, false, sizeof(repl_null));
		memset(repl_repl, false, sizeof(repl_repl));

		repl_repl[Anum_pg_class_relowner - 1] = true;
		repl_val[Anum_pg_class_relowner - 1] = ObjectIdGetDatum(newOwnerId);

		/*
		 * Determine the modified ACL for the new owner.  This is only
		 * necessary when the ACL is non-null.
		 */
		aclDatum = SysCacheGetAttr(RELOID, tuple,
								   Anum_pg_class_relacl,
								   &isNull);
		if (!isNull)
		{
			newAcl = aclnewowner(DatumGetAclP(aclDatum),
								 tuple_class->relowner, newOwnerId);
			repl_repl[Anum_pg_class_relacl - 1] = true;
			repl_val[Anum_pg_class_relacl - 1] = PointerGetDatum(newAcl);
		}

		newtuple = heap_modify_tuple(tuple, RelationGetDescr(class_rel), repl_val, repl_null, repl_repl);

		CatalogTupleUpdate(class_rel, &newtuple->t_self, newtuple);

		heap_freetuple(newtuple);

		/*
		 * We must similarly update any per-column ACLs to reflect the new
		 * owner; for neatness reasons that's split out as a subroutine.
		 */
		change_owner_fix_column_acls(relationOid,
									 tuple_class->relowner,
									 newOwnerId);

		/*
		 * Update owner dependency reference, if any.  A composite type has
		 * none, because it's tracked for the pg_type entry instead of here;
		 * indexes and TOAST tables don't have their own entries either.
		 */
		if (tuple_class->relkind != RELKIND_COMPOSITE_TYPE &&
			tuple_class->relkind != RELKIND_INDEX &&
			tuple_class->relkind != RELKIND_PARTITIONED_INDEX &&
			tuple_class->relkind != RELKIND_TOASTVALUE)
			changeDependencyOnOwner(RelationRelationId, relationOid,
									newOwnerId);

		/*
		 * Also change the ownership of the table's row type, if it has one
		 */
		if (OidIsValid(tuple_class->reltype))
			AlterTypeOwnerInternal(tuple_class->reltype, newOwnerId);

		/*
		 * If we are operating on a table or materialized view, also change
		 * the ownership of any indexes and sequences that belong to the
		 * relation, as well as its toast table (if it has one).
		 */
		if (tuple_class->relkind == RELKIND_RELATION ||
			tuple_class->relkind == RELKIND_PARTITIONED_TABLE ||
			tuple_class->relkind == RELKIND_MATVIEW ||
			tuple_class->relkind == RELKIND_TOASTVALUE)
		{
			List	   *index_oid_list;
			ListCell   *i;

			/* Find all the indexes belonging to this relation */
			index_oid_list = RelationGetIndexList(target_rel);

			/* For each index, recursively change its ownership */
			foreach(i, index_oid_list)
				ATExecChangeOwner(lfirst_oid(i), newOwnerId, true, lockmode);

			list_free(index_oid_list);
		}

		/* If it has a toast table, recurse to change its ownership */
		if (tuple_class->reltoastrelid != InvalidOid)
			ATExecChangeOwner(tuple_class->reltoastrelid, newOwnerId,
							  true, lockmode);

		/* If it has dependent sequences, recurse to change them too */
		change_owner_recurse_to_sequences(relationOid, newOwnerId, lockmode);
	}

	InvokeObjectPostAlterHook(RelationRelationId, relationOid, 0);

	ReleaseSysCache(tuple);
	table_close(class_rel, RowExclusiveLock);
	relation_close(target_rel, NoLock);
}

/*
 * change_owner_fix_column_acls
 *
 * Helper function for ATExecChangeOwner.  Scan the columns of the table
 * and fix any non-null column ACLs to reflect the new owner.
 */
static void
change_owner_fix_column_acls(Oid relationOid, Oid oldOwnerId, Oid newOwnerId)
{
	Relation	attRelation;
	SysScanDesc scan;
	ScanKeyData key[1];
	HeapTuple	attributeTuple;

	attRelation = table_open(AttributeRelationId, RowExclusiveLock);
	ScanKeyInit(&key[0],
				Anum_pg_attribute_attrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relationOid));
	scan = systable_beginscan(attRelation, AttributeRelidNumIndexId,
							  true, NULL, 1, key);
	while (HeapTupleIsValid(attributeTuple = systable_getnext(scan)))
	{
		Form_pg_attribute att = (Form_pg_attribute) GETSTRUCT(attributeTuple);
		Datum		repl_val[Natts_pg_attribute];
		bool		repl_null[Natts_pg_attribute];
		bool		repl_repl[Natts_pg_attribute];
		Acl		   *newAcl;
		Datum		aclDatum;
		bool		isNull;
		HeapTuple	newtuple;

		/* Ignore dropped columns */
		if (att->attisdropped)
			continue;

		aclDatum = heap_getattr(attributeTuple,
								Anum_pg_attribute_attacl,
								RelationGetDescr(attRelation),
								&isNull);
		/* Null ACLs do not require changes */
		if (isNull)
			continue;

		memset(repl_null, false, sizeof(repl_null));
		memset(repl_repl, false, sizeof(repl_repl));

		newAcl = aclnewowner(DatumGetAclP(aclDatum),
							 oldOwnerId, newOwnerId);
		repl_repl[Anum_pg_attribute_attacl - 1] = true;
		repl_val[Anum_pg_attribute_attacl - 1] = PointerGetDatum(newAcl);

		newtuple = heap_modify_tuple(attributeTuple,
									 RelationGetDescr(attRelation),
									 repl_val, repl_null, repl_repl);

		CatalogTupleUpdate(attRelation, &newtuple->t_self, newtuple);

		heap_freetuple(newtuple);
	}
	systable_endscan(scan);
	table_close(attRelation, RowExclusiveLock);
}

/*
 * change_owner_recurse_to_sequences
 *
 * Helper function for ATExecChangeOwner.  Examines pg_depend searching
 * for sequences that are dependent on serial columns, and changes their
 * ownership.
 */
static void
change_owner_recurse_to_sequences(Oid relationOid, Oid newOwnerId, LOCKMODE lockmode)
{
	Relation	depRel;
	SysScanDesc scan;
	ScanKeyData key[2];
	HeapTuple	tup;

	/*
	 * SERIAL sequences are those having an auto dependency on one of the
	 * table's columns (we don't care *which* column, exactly).
	 */
	depRel = table_open(DependRelationId, AccessShareLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_refclassid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_refobjid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relationOid));
	/* we leave refobjsubid unspecified */

	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
							  NULL, 2, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		Form_pg_depend depForm = (Form_pg_depend) GETSTRUCT(tup);
		Relation	seqRel;

		/* skip dependencies other than auto dependencies on columns */
		if (depForm->refobjsubid == 0 ||
			depForm->classid != RelationRelationId ||
			depForm->objsubid != 0 ||
			!(depForm->deptype == DEPENDENCY_AUTO || depForm->deptype == DEPENDENCY_INTERNAL))
			continue;

		/* Use relation_open just in case it's an index */
		seqRel = relation_open(depForm->objid, lockmode);

		/* skip non-sequence relations */
		if (RelationGetForm(seqRel)->relkind != RELKIND_SEQUENCE)
		{
			/* No need to keep the lock */
			relation_close(seqRel, lockmode);
			continue;
		}

		/* We don't need to close the sequence while we alter it. */
		ATExecChangeOwner(depForm->objid, newOwnerId, true, lockmode);

		/* Now we can close it.  Keep the lock till end of transaction. */
		relation_close(seqRel, NoLock);
	}

	systable_endscan(scan);

	relation_close(depRel, AccessShareLock);
}

/*
 * ALTER TABLE CLUSTER ON
 *
 * The only thing we have to do is to change the indisclustered bits.
 *
 * Return the address of the new clustering index.
 */
static ObjectAddress
ATExecClusterOn(Relation rel, const char *indexName, LOCKMODE lockmode)
{
	Oid			indexOid;
	ObjectAddress address;

	indexOid = get_relname_relid(indexName, rel->rd_rel->relnamespace);

	if (!OidIsValid(indexOid))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("index \"%s\" for table \"%s\" does not exist",
						indexName, RelationGetRelationName(rel))));

	/* Check index is valid to cluster on */
	check_index_is_clusterable(rel, indexOid, lockmode);

	/* And do the work */
	mark_index_clustered(rel, indexOid, false);

	ObjectAddressSet(address,
					 RelationRelationId, indexOid);

	return address;
}

/*
 * ALTER TABLE SET WITHOUT CLUSTER
 *
 * We have to find any indexes on the table that have indisclustered bit
 * set and turn it off.
 */
static void
ATExecDropCluster(Relation rel, LOCKMODE lockmode)
{
	mark_index_clustered(rel, InvalidOid, false);
}

/*
 * Preparation phase for SET ACCESS METHOD
 *
 * Check that the access method exists and determine whether a change is
 * actually needed.
 */
static void
ATPrepSetAccessMethod(AlteredTableInfo *tab, Relation rel, const char *amname)
{
	Oid			amoid;

	/*
	 * Look up the access method name and check that it differs from the
	 * table's current AM.  If DEFAULT was specified for a partitioned table
	 * (amname is NULL), set it to InvalidOid to reset the catalogued AM.
	 */
	if (amname != NULL)
		amoid = get_table_am_oid(amname, false);
	else if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
		amoid = InvalidOid;
	else
		amoid = get_table_am_oid(default_table_access_method, false);

	/* if it's a match, phase 3 doesn't need to do anything */
	if (rel->rd_rel->relam == amoid)
		return;

	/* Save info for Phase 3 to do the real work */
	tab->rewrite |= AT_REWRITE_ACCESS_METHOD;
	tab->newAccessMethod = amoid;
	tab->chgAccessMethod = true;
}

/*
 * Special handling of ALTER TABLE SET ACCESS METHOD for relations with no
 * storage that have an interest in preserving AM.
 *
 * Since these have no storage, setting the access method is a catalog only
 * operation.
 */
static void
ATExecSetAccessMethodNoStorage(Relation rel, Oid newAccessMethodId)
{
	Relation	pg_class;
	Oid			oldAccessMethodId;
	HeapTuple	tuple;
	Form_pg_class rd_rel;
	Oid			reloid = RelationGetRelid(rel);

	/*
	 * Shouldn't be called on relations having storage; these are processed in
	 * phase 3.
	 */
	Assert(!RELKIND_HAS_STORAGE(rel->rd_rel->relkind));

	/* Get a modifiable copy of the relation's pg_class row. */
	pg_class = table_open(RelationRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(reloid));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", reloid);
	rd_rel = (Form_pg_class) GETSTRUCT(tuple);

	/* Update the pg_class row. */
	oldAccessMethodId = rd_rel->relam;
	rd_rel->relam = newAccessMethodId;

	/* Leave if no update required */
	if (rd_rel->relam == oldAccessMethodId)
	{
		heap_freetuple(tuple);
		table_close(pg_class, RowExclusiveLock);
		return;
	}

	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);

	/*
	 * Update the dependency on the new access method.  No dependency is added
	 * if the new access method is InvalidOid (default case).  Be very careful
	 * that this has to compare the previous value stored in pg_class with the
	 * new one.
	 */
	if (!OidIsValid(oldAccessMethodId) && OidIsValid(rd_rel->relam))
	{
		ObjectAddress relobj,
					referenced;

		/*
		 * New access method is defined and there was no dependency
		 * previously, so record a new one.
		 */
		ObjectAddressSet(relobj, RelationRelationId, reloid);
		ObjectAddressSet(referenced, AccessMethodRelationId, rd_rel->relam);
		recordDependencyOn(&relobj, &referenced, DEPENDENCY_NORMAL);
	}
	else if (OidIsValid(oldAccessMethodId) &&
			 !OidIsValid(rd_rel->relam))
	{
		/*
		 * There was an access method defined, and no new one, so just remove
		 * the existing dependency.
		 */
		deleteDependencyRecordsForClass(RelationRelationId, reloid,
										AccessMethodRelationId,
										DEPENDENCY_NORMAL);
	}
	else
	{
		Assert(OidIsValid(oldAccessMethodId) &&
			   OidIsValid(rd_rel->relam));

		/* Both are valid, so update the dependency */
		changeDependencyFor(RelationRelationId, reloid,
							AccessMethodRelationId,
							oldAccessMethodId, rd_rel->relam);
	}

	/* make the relam and dependency changes visible */
	CommandCounterIncrement();

	InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);

	heap_freetuple(tuple);
	table_close(pg_class, RowExclusiveLock);
}

/*
 * ALTER TABLE SET TABLESPACE
 */
static void
ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel, const char *tablespacename, LOCKMODE lockmode)
{
	Oid			tablespaceId;

	/* Check that the tablespace exists */
	tablespaceId = get_tablespace_oid(tablespacename, false);

	/* Check permissions except when moving to database's default */
	if (OidIsValid(tablespaceId) && tablespaceId != MyDatabaseTableSpace)
	{
		AclResult	aclresult;

		aclresult = object_aclcheck(TableSpaceRelationId, tablespaceId, GetUserId(), ACL_CREATE);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error(aclresult, OBJECT_TABLESPACE, tablespacename);
	}

	/* Save info for Phase 3 to do the real work */
	if (OidIsValid(tab->newTableSpace))
		ereport(ERROR,
				(errcode(ERRCODE_SYNTAX_ERROR),
				 errmsg("cannot have multiple SET TABLESPACE subcommands")));

	tab->newTableSpace = tablespaceId;
}

/*
 * Set, reset, or replace reloptions.
 */
static void
ATExecSetRelOptions(Relation rel, List *defList, AlterTableType operation,
					LOCKMODE lockmode)
{
	Oid			relid;
	Relation	pgclass;
	HeapTuple	tuple;
	HeapTuple	newtuple;
	Datum		datum;
	Datum		newOptions;
	Datum		repl_val[Natts_pg_class];
	bool		repl_null[Natts_pg_class];
	bool		repl_repl[Natts_pg_class];
	const char *const validnsps[] = HEAP_RELOPT_NAMESPACES;

	if (defList == NIL && operation != AT_ReplaceRelOptions)
		return;					/* nothing to do */

	pgclass = table_open(RelationRelationId, RowExclusiveLock);

	/* Fetch heap tuple */
	relid = RelationGetRelid(rel);
	tuple = SearchSysCacheLocked1(RELOID, ObjectIdGetDatum(relid));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", relid);

	if (operation == AT_ReplaceRelOptions)
	{
		/*
		 * If we're supposed to replace the reloptions list, we just pretend
		 * there were none before.
		 */
		datum = (Datum) 0;
	}
	else
	{
		bool		isnull;

		/* Get the old reloptions */
		datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
								&isnull);
		if (isnull)
			datum = (Datum) 0;
	}

	/* Generate new proposed reloptions (text array) */
	newOptions = transformRelOptions(datum, defList, NULL, validnsps, false,
									 operation == AT_ResetRelOptions);

	/* Validate */
	switch (rel->rd_rel->relkind)
	{
		case RELKIND_RELATION:
		case RELKIND_MATVIEW:
			(void) heap_reloptions(rel->rd_rel->relkind, newOptions, true);
			break;
		case RELKIND_PARTITIONED_TABLE:
			(void) partitioned_table_reloptions(newOptions, true);
			break;
		case RELKIND_VIEW:
			(void) view_reloptions(newOptions, true);
			break;
		case RELKIND_INDEX:
		case RELKIND_PARTITIONED_INDEX:
			(void) index_reloptions(rel->rd_indam->amoptions, newOptions, true);
			break;
		case RELKIND_TOASTVALUE:
			/* fall through to error -- shouldn't ever get here */
		default:
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot set options for relation \"%s\"",
							RelationGetRelationName(rel)),
					 errdetail_relkind_not_supported(rel->rd_rel->relkind)));
			break;
	}

	/* Special-case validation of view options */
	if (rel->rd_rel->relkind == RELKIND_VIEW)
	{
		Query	   *view_query = get_view_query(rel);
		List	   *view_options = untransformRelOptions(newOptions);
		ListCell   *cell;
		bool		check_option = false;

		foreach(cell, view_options)
		{
			DefElem    *defel = (DefElem *) lfirst(cell);

			if (strcmp(defel->defname, "check_option") == 0)
				check_option = true;
		}

		/*
		 * If the check option is specified, look to see if the view is
		 * actually auto-updatable or not.
		 */
		if (check_option)
		{
			const char *view_updatable_error =
				view_query_is_auto_updatable(view_query, true);

			if (view_updatable_error)
				ereport(ERROR,
						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
						 errmsg("WITH CHECK OPTION is supported only on automatically updatable views"),
						 errhint("%s", _(view_updatable_error))));
		}
	}

	/*
	 * All we need do here is update the pg_class row; the new options will be
	 * propagated into relcaches during post-commit cache inval.
	 */
	memset(repl_val, 0, sizeof(repl_val));
	memset(repl_null, false, sizeof(repl_null));
	memset(repl_repl, false, sizeof(repl_repl));

	if (newOptions != (Datum) 0)
		repl_val[Anum_pg_class_reloptions - 1] = newOptions;
	else
		repl_null[Anum_pg_class_reloptions - 1] = true;

	repl_repl[Anum_pg_class_reloptions - 1] = true;

	newtuple = heap_modify_tuple(tuple, RelationGetDescr(pgclass),
								 repl_val, repl_null, repl_repl);

	CatalogTupleUpdate(pgclass, &newtuple->t_self, newtuple);
	UnlockTuple(pgclass, &tuple->t_self, InplaceUpdateTupleLock);

	InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);

	heap_freetuple(newtuple);

	ReleaseSysCache(tuple);

	/* repeat the whole exercise for the toast table, if there's one */
	if (OidIsValid(rel->rd_rel->reltoastrelid))
	{
		Relation	toastrel;
		Oid			toastid = rel->rd_rel->reltoastrelid;

		toastrel = table_open(toastid, lockmode);

		/* Fetch heap tuple */
		tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(toastid));
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for relation %u", toastid);

		if (operation == AT_ReplaceRelOptions)
		{
			/*
			 * If we're supposed to replace the reloptions list, we just
			 * pretend there were none before.
			 */
			datum = (Datum) 0;
		}
		else
		{
			bool		isnull;

			/* Get the old reloptions */
			datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
									&isnull);
			if (isnull)
				datum = (Datum) 0;
		}

		newOptions = transformRelOptions(datum, defList, "toast", validnsps,
										 false, operation == AT_ResetRelOptions);

		(void) heap_reloptions(RELKIND_TOASTVALUE, newOptions, true);

		memset(repl_val, 0, sizeof(repl_val));
		memset(repl_null, false, sizeof(repl_null));
		memset(repl_repl, false, sizeof(repl_repl));

		if (newOptions != (Datum) 0)
			repl_val[Anum_pg_class_reloptions - 1] = newOptions;
		else
			repl_null[Anum_pg_class_reloptions - 1] = true;

		repl_repl[Anum_pg_class_reloptions - 1] = true;

		newtuple = heap_modify_tuple(tuple, RelationGetDescr(pgclass),
									 repl_val, repl_null, repl_repl);

		CatalogTupleUpdate(pgclass, &newtuple->t_self, newtuple);

		InvokeObjectPostAlterHookArg(RelationRelationId,
									 RelationGetRelid(toastrel), 0,
									 InvalidOid, true);

		heap_freetuple(newtuple);

		ReleaseSysCache(tuple);

		table_close(toastrel, NoLock);
	}

	table_close(pgclass, RowExclusiveLock);
}

/*
 * Execute ALTER TABLE SET TABLESPACE for cases where there is no tuple
 * rewriting to be done, so we just want to copy the data as fast as possible.
 */
static void
ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
{
	Relation	rel;
	Oid			reltoastrelid;
	RelFileNumber newrelfilenumber;
	RelFileLocator newrlocator;
	List	   *reltoastidxids = NIL;
	ListCell   *lc;

	/*
	 * Need lock here in case we are recursing to toast table or index
	 */
	rel = relation_open(tableOid, lockmode);

	/* Check first if relation can be moved to new tablespace */
	if (!CheckRelationTableSpaceMove(rel, newTableSpace))
	{
		InvokeObjectPostAlterHook(RelationRelationId,
								  RelationGetRelid(rel), 0);
		relation_close(rel, NoLock);
		return;
	}

	reltoastrelid = rel->rd_rel->reltoastrelid;
	/* Fetch the list of indexes on toast relation if necessary */
	if (OidIsValid(reltoastrelid))
	{
		Relation	toastRel = relation_open(reltoastrelid, lockmode);

		reltoastidxids = RelationGetIndexList(toastRel);
		relation_close(toastRel, lockmode);
	}

	/*
	 * Relfilenumbers are not unique in databases across tablespaces, so we
	 * need to allocate a new one in the new tablespace.
	 */
	newrelfilenumber = GetNewRelFileNumber(newTableSpace, NULL,
										   rel->rd_rel->relpersistence);

	/* Open old and new relation */
	newrlocator = rel->rd_locator;
	newrlocator.relNumber = newrelfilenumber;
	newrlocator.spcOid = newTableSpace;

	/* hand off to AM to actually create new rel storage and copy the data */
	if (rel->rd_rel->relkind == RELKIND_INDEX)
	{
		index_copy_data(rel, newrlocator);
	}
	else
	{
		Assert(RELKIND_HAS_TABLE_AM(rel->rd_rel->relkind));
		table_relation_copy_data(rel, &newrlocator);
	}

	/*
	 * Update the pg_class row.
	 *
	 * NB: This wouldn't work if ATExecSetTableSpace() were allowed to be
	 * executed on pg_class or its indexes (the above copy wouldn't contain
	 * the updated pg_class entry), but that's forbidden with
	 * CheckRelationTableSpaceMove().
	 */
	SetRelationTableSpace(rel, newTableSpace, newrelfilenumber);

	InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);

	RelationAssumeNewRelfilelocator(rel);

	relation_close(rel, NoLock);

	/* Make sure the reltablespace change is visible */
	CommandCounterIncrement();

	/* Move associated toast relation and/or indexes, too */
	if (OidIsValid(reltoastrelid))
		ATExecSetTableSpace(reltoastrelid, newTableSpace, lockmode);
	foreach(lc, reltoastidxids)
		ATExecSetTableSpace(lfirst_oid(lc), newTableSpace, lockmode);

	/* Clean up */
	list_free(reltoastidxids);
}

/*
 * Special handling of ALTER TABLE SET TABLESPACE for relations with no
 * storage that have an interest in preserving tablespace.
 *
 * Since these have no storage the tablespace can be updated with a simple
 * metadata only operation to update the tablespace.
 */
static void
ATExecSetTableSpaceNoStorage(Relation rel, Oid newTableSpace)
{
	/*
	 * Shouldn't be called on relations having storage; these are processed in
	 * phase 3.
	 */
	Assert(!RELKIND_HAS_STORAGE(rel->rd_rel->relkind));

	/* check if relation can be moved to its new tablespace */
	if (!CheckRelationTableSpaceMove(rel, newTableSpace))
	{
		InvokeObjectPostAlterHook(RelationRelationId,
								  RelationGetRelid(rel),
								  0);
		return;
	}

	/* Update can be done, so change reltablespace */
	SetRelationTableSpace(rel, newTableSpace, InvalidOid);

	InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);

	/* Make sure the reltablespace change is visible */
	CommandCounterIncrement();
}

/*
 * Alter Table ALL ... SET TABLESPACE
 *
 * Allows a user to move all objects of some type in a given tablespace in the
 * current database to another tablespace.  Objects can be chosen based on the
 * owner of the object also, to allow users to move only their objects.
 * The user must have CREATE rights on the new tablespace, as usual.   The main
 * permissions handling is done by the lower-level table move function.
 *
 * All to-be-moved objects are locked first. If NOWAIT is specified and the
 * lock can't be acquired then we ereport(ERROR).
 */
Oid
AlterTableMoveAll(AlterTableMoveAllStmt *stmt)
{
	List	   *relations = NIL;
	ListCell   *l;
	ScanKeyData key[1];
	Relation	rel;
	TableScanDesc scan;
	HeapTuple	tuple;
	Oid			orig_tablespaceoid;
	Oid			new_tablespaceoid;
	List	   *role_oids = roleSpecsToIds(stmt->roles);

	/* Ensure we were not asked to move something we can't */
	if (stmt->objtype != OBJECT_TABLE && stmt->objtype != OBJECT_INDEX &&
		stmt->objtype != OBJECT_MATVIEW)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("only tables, indexes, and materialized views exist in tablespaces")));

	/* Get the orig and new tablespace OIDs */
	orig_tablespaceoid = get_tablespace_oid(stmt->orig_tablespacename, false);
	new_tablespaceoid = get_tablespace_oid(stmt->new_tablespacename, false);

	/* Can't move shared relations in to or out of pg_global */
	/* This is also checked by ATExecSetTableSpace, but nice to stop earlier */
	if (orig_tablespaceoid == GLOBALTABLESPACE_OID ||
		new_tablespaceoid == GLOBALTABLESPACE_OID)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("cannot move relations in to or out of pg_global tablespace")));

	/*
	 * Must have CREATE rights on the new tablespace, unless it is the
	 * database default tablespace (which all users implicitly have CREATE
	 * rights on).
	 */
	if (OidIsValid(new_tablespaceoid) && new_tablespaceoid != MyDatabaseTableSpace)
	{
		AclResult	aclresult;

		aclresult = object_aclcheck(TableSpaceRelationId, new_tablespaceoid, GetUserId(),
									ACL_CREATE);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error(aclresult, OBJECT_TABLESPACE,
						   get_tablespace_name(new_tablespaceoid));
	}

	/*
	 * Now that the checks are done, check if we should set either to
	 * InvalidOid because it is our database's default tablespace.
	 */
	if (orig_tablespaceoid == MyDatabaseTableSpace)
		orig_tablespaceoid = InvalidOid;

	if (new_tablespaceoid == MyDatabaseTableSpace)
		new_tablespaceoid = InvalidOid;

	/* no-op */
	if (orig_tablespaceoid == new_tablespaceoid)
		return new_tablespaceoid;

	/*
	 * Walk the list of objects in the tablespace and move them. This will
	 * only find objects in our database, of course.
	 */
	ScanKeyInit(&key[0],
				Anum_pg_class_reltablespace,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(orig_tablespaceoid));

	rel = table_open(RelationRelationId, AccessShareLock);
	scan = table_beginscan_catalog(rel, 1, key);
	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
	{
		Form_pg_class relForm = (Form_pg_class) GETSTRUCT(tuple);
		Oid			relOid = relForm->oid;

		/*
		 * Do not move objects in pg_catalog as part of this, if an admin
		 * really wishes to do so, they can issue the individual ALTER
		 * commands directly.
		 *
		 * Also, explicitly avoid any shared tables, temp tables, or TOAST
		 * (TOAST will be moved with the main table).
		 */
		if (IsCatalogNamespace(relForm->relnamespace) ||
			relForm->relisshared ||
			isAnyTempNamespace(relForm->relnamespace) ||
			IsToastNamespace(relForm->relnamespace))
			continue;

		/* Only move the object type requested */
		if ((stmt->objtype == OBJECT_TABLE &&
			 relForm->relkind != RELKIND_RELATION &&
			 relForm->relkind != RELKIND_PARTITIONED_TABLE) ||
			(stmt->objtype == OBJECT_INDEX &&
			 relForm->relkind != RELKIND_INDEX &&
			 relForm->relkind != RELKIND_PARTITIONED_INDEX) ||
			(stmt->objtype == OBJECT_MATVIEW &&
			 relForm->relkind != RELKIND_MATVIEW))
			continue;

		/* Check if we are only moving objects owned by certain roles */
		if (role_oids != NIL && !list_member_oid(role_oids, relForm->relowner))
			continue;

		/*
		 * Handle permissions-checking here since we are locking the tables
		 * and also to avoid doing a bunch of work only to fail part-way. Note
		 * that permissions will also be checked by AlterTableInternal().
		 *
		 * Caller must be considered an owner on the table to move it.
		 */
		if (!object_ownercheck(RelationRelationId, relOid, GetUserId()))
			aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relOid)),
						   NameStr(relForm->relname));

		if (stmt->nowait &&
			!ConditionalLockRelationOid(relOid, AccessExclusiveLock))
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_IN_USE),
					 errmsg("aborting because lock on relation \"%s.%s\" is not available",
							get_namespace_name(relForm->relnamespace),
							NameStr(relForm->relname))));
		else
			LockRelationOid(relOid, AccessExclusiveLock);

		/* Add to our list of objects to move */
		relations = lappend_oid(relations, relOid);
	}

	table_endscan(scan);
	table_close(rel, AccessShareLock);

	if (relations == NIL)
		ereport(NOTICE,
				(errcode(ERRCODE_NO_DATA_FOUND),
				 errmsg("no matching relations in tablespace \"%s\" found",
						orig_tablespaceoid == InvalidOid ? "(database default)" :
						get_tablespace_name(orig_tablespaceoid))));

	/* Everything is locked, loop through and move all of the relations. */
	foreach(l, relations)
	{
		List	   *cmds = NIL;
		AlterTableCmd *cmd = makeNode(AlterTableCmd);

		cmd->subtype = AT_SetTableSpace;
		cmd->name = stmt->new_tablespacename;

		cmds = lappend(cmds, cmd);

		EventTriggerAlterTableStart((Node *) stmt);
		/* OID is set by AlterTableInternal */
		AlterTableInternal(lfirst_oid(l), cmds, false);
		EventTriggerAlterTableEnd();
	}

	return new_tablespaceoid;
}

static void
index_copy_data(Relation rel, RelFileLocator newrlocator)
{
	SMgrRelation dstrel;

	/*
	 * Since we copy the file directly without looking at the shared buffers,
	 * we'd better first flush out any pages of the source relation that are
	 * in shared buffers.  We assume no new changes will be made while we are
	 * holding exclusive lock on the rel.
	 */
	FlushRelationBuffers(rel);

	/*
	 * Create and copy all forks of the relation, and schedule unlinking of
	 * old physical files.
	 *
	 * NOTE: any conflict in relfilenumber value will be caught in
	 * RelationCreateStorage().
	 */
	dstrel = RelationCreateStorage(rel->rd_locator, newrlocator, rel->rd_rel->relpersistence, true);

	/* copy main fork */
	RelationCopyStorage(RelationGetSmgr(rel), dstrel, MAIN_FORKNUM,
						rel->rd_rel->relpersistence);

	/* copy those extra forks that exist */
	for (ForkNumber forkNum = MAIN_FORKNUM + 1;
		 forkNum <= MAX_FORKNUM; forkNum++)
	{
		if (smgrexists(RelationGetSmgr(rel), forkNum))
		{
			smgrcreate(rel->rd_locator, dstrel, forkNum, false);

			/*
			 * WAL log creation if the relation is persistent, or this is the
			 * init fork of an unlogged relation.
			 */
			if (RelationIsPermanent(rel) ||
				(rel->rd_rel->relpersistence == RELPERSISTENCE_UNLOGGED &&
				 forkNum == INIT_FORKNUM))
				log_smgrcreate(&newrlocator, forkNum);
			RelationCopyStorage(RelationGetSmgr(rel), dstrel, forkNum,
								rel->rd_rel->relpersistence);
		}
	}

	/* drop old relation, and close new one */
	RelationDropStorage(rel);
	smgrclose(dstrel);
}

/*
 * ALTER TABLE ENABLE/DISABLE TRIGGER
 *
 * We just pass this off to trigger.c.
 */
static void
ATExecEnableDisableTrigger(Relation rel, const char *trigname,
						   char fires_when, bool skip_system, bool recurse,
						   LOCKMODE lockmode)
{
	EnableDisableTrigger(rel, trigname, InvalidOid,
						 fires_when, skip_system, recurse,
						 lockmode);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), 0);
}

/*
 * ALTER TABLE ENABLE/DISABLE RULE
 *
 * We just pass this off to rewriteDefine.c.
 */
static void
ATExecEnableDisableRule(Relation rel, const char *rulename,
						char fires_when, LOCKMODE lockmode)
{
	EnableDisableRule(rel, rulename, fires_when);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), 0);
}

/*
 * ALTER TABLE INHERIT
 *
 * Add a parent to the child's parents. This verifies that all the columns and
 * check constraints of the parent appear in the child and that they have the
 * same data types and expressions.
 */
static void
ATPrepAddInherit(Relation child_rel)
{
	if (child_rel->rd_rel->reloftype)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot change inheritance of typed table")));

	if (child_rel->rd_rel->relispartition)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot change inheritance of a partition")));

	if (child_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot change inheritance of partitioned table")));
}

/*
 * Return the address of the new parent relation.
 */
static ObjectAddress
ATExecAddInherit(Relation child_rel, RangeVar *parent, LOCKMODE lockmode)
{
	Relation	parent_rel;
	List	   *children;
	ObjectAddress address;
	const char *trigger_name;

	/*
	 * A self-exclusive lock is needed here.  See the similar case in
	 * MergeAttributes() for a full explanation.
	 */
	parent_rel = table_openrv(parent, ShareUpdateExclusiveLock);

	/*
	 * Must be owner of both parent and child -- child was checked by
	 * ATSimplePermissions call in ATPrepCmd
	 */
	ATSimplePermissions(AT_AddInherit, parent_rel,
						ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);

	/* Permanent rels cannot inherit from temporary ones */
	if (parent_rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
		child_rel->rd_rel->relpersistence != RELPERSISTENCE_TEMP)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot inherit from temporary relation \"%s\"",
						RelationGetRelationName(parent_rel))));

	/* If parent rel is temp, it must belong to this session */
	if (parent_rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
		!parent_rel->rd_islocaltemp)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot inherit from temporary relation of another session")));

	/* Ditto for the child */
	if (child_rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
		!child_rel->rd_islocaltemp)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot inherit to temporary relation of another session")));

	/* Prevent partitioned tables from becoming inheritance parents */
	if (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot inherit from partitioned table \"%s\"",
						parent->relname)));

	/* Likewise for partitions */
	if (parent_rel->rd_rel->relispartition)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot inherit from a partition")));

	/*
	 * Prevent circularity by seeing if proposed parent inherits from child.
	 * (In particular, this disallows making a rel inherit from itself.)
	 *
	 * This is not completely bulletproof because of race conditions: in
	 * multi-level inheritance trees, someone else could concurrently be
	 * making another inheritance link that closes the loop but does not join
	 * either of the rels we have locked.  Preventing that seems to require
	 * exclusive locks on the entire inheritance tree, which is a cure worse
	 * than the disease.  find_all_inheritors() will cope with circularity
	 * anyway, so don't sweat it too much.
	 *
	 * We use weakest lock we can on child's children, namely AccessShareLock.
	 */
	children = find_all_inheritors(RelationGetRelid(child_rel),
								   AccessShareLock, NULL);

	if (list_member_oid(children, RelationGetRelid(parent_rel)))
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_TABLE),
				 errmsg("circular inheritance not allowed"),
				 errdetail("\"%s\" is already a child of \"%s\".",
						   parent->relname,
						   RelationGetRelationName(child_rel))));

	/*
	 * If child_rel has row-level triggers with transition tables, we
	 * currently don't allow it to become an inheritance child.  See also
	 * prohibitions in ATExecAttachPartition() and CreateTrigger().
	 */
	trigger_name = FindTriggerIncompatibleWithInheritance(child_rel->trigdesc);
	if (trigger_name != NULL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("trigger \"%s\" prevents table \"%s\" from becoming an inheritance child",
						trigger_name, RelationGetRelationName(child_rel)),
				 errdetail("ROW triggers with transition tables are not supported in inheritance hierarchies.")));

	/* OK to create inheritance */
	CreateInheritance(child_rel, parent_rel, false);

	ObjectAddressSet(address, RelationRelationId,
					 RelationGetRelid(parent_rel));

	/* keep our lock on the parent relation until commit */
	table_close(parent_rel, NoLock);

	return address;
}

/*
 * CreateInheritance
 *		Catalog manipulation portion of creating inheritance between a child
 *		table and a parent table.
 *
 * Common to ATExecAddInherit() and ATExecAttachPartition().
 */
static void
CreateInheritance(Relation child_rel, Relation parent_rel, bool ispartition)
{
	Relation	catalogRelation;
	SysScanDesc scan;
	ScanKeyData key;
	HeapTuple	inheritsTuple;
	int32		inhseqno;

	/* Note: get RowExclusiveLock because we will write pg_inherits below. */
	catalogRelation = table_open(InheritsRelationId, RowExclusiveLock);

	/*
	 * Check for duplicates in the list of parents, and determine the highest
	 * inhseqno already present; we'll use the next one for the new parent.
	 * Also, if proposed child is a partition, it cannot already be
	 * inheriting.
	 *
	 * Note: we do not reject the case where the child already inherits from
	 * the parent indirectly; CREATE TABLE doesn't reject comparable cases.
	 */
	ScanKeyInit(&key,
				Anum_pg_inherits_inhrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(child_rel)));
	scan = systable_beginscan(catalogRelation, InheritsRelidSeqnoIndexId,
							  true, NULL, 1, &key);

	/* inhseqno sequences start at 1 */
	inhseqno = 0;
	while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
	{
		Form_pg_inherits inh = (Form_pg_inherits) GETSTRUCT(inheritsTuple);

		if (inh->inhparent == RelationGetRelid(parent_rel))
			ereport(ERROR,
					(errcode(ERRCODE_DUPLICATE_TABLE),
					 errmsg("relation \"%s\" would be inherited from more than once",
							RelationGetRelationName(parent_rel))));

		if (inh->inhseqno > inhseqno)
			inhseqno = inh->inhseqno;
	}
	systable_endscan(scan);

	/* Match up the columns and bump attinhcount as needed */
	MergeAttributesIntoExisting(child_rel, parent_rel, ispartition);

	/* Match up the constraints and bump coninhcount as needed */
	MergeConstraintsIntoExisting(child_rel, parent_rel);

	/*
	 * OK, it looks valid.  Make the catalog entries that show inheritance.
	 */
	StoreCatalogInheritance1(RelationGetRelid(child_rel),
							 RelationGetRelid(parent_rel),
							 inhseqno + 1,
							 catalogRelation,
							 parent_rel->rd_rel->relkind ==
							 RELKIND_PARTITIONED_TABLE);

	/* Now we're done with pg_inherits */
	table_close(catalogRelation, RowExclusiveLock);
}

/*
 * Obtain the source-text form of the constraint expression for a check
 * constraint, given its pg_constraint tuple
 */
static char *
decompile_conbin(HeapTuple contup, TupleDesc tupdesc)
{
	Form_pg_constraint con;
	bool		isnull;
	Datum		attr;
	Datum		expr;

	con = (Form_pg_constraint) GETSTRUCT(contup);
	attr = heap_getattr(contup, Anum_pg_constraint_conbin, tupdesc, &isnull);
	if (isnull)
		elog(ERROR, "null conbin for constraint %u", con->oid);

	expr = DirectFunctionCall2(pg_get_expr, attr,
							   ObjectIdGetDatum(con->conrelid));
	return TextDatumGetCString(expr);
}

/*
 * Determine whether two check constraints are functionally equivalent
 *
 * The test we apply is to see whether they reverse-compile to the same
 * source string.  This insulates us from issues like whether attributes
 * have the same physical column numbers in parent and child relations.
 *
 * Note that we ignore enforceability as there are cases where constraints
 * with differing enforceability are allowed.
 */
static bool
constraints_equivalent(HeapTuple a, HeapTuple b, TupleDesc tupleDesc)
{
	Form_pg_constraint acon = (Form_pg_constraint) GETSTRUCT(a);
	Form_pg_constraint bcon = (Form_pg_constraint) GETSTRUCT(b);

	if (acon->condeferrable != bcon->condeferrable ||
		acon->condeferred != bcon->condeferred ||
		strcmp(decompile_conbin(a, tupleDesc),
			   decompile_conbin(b, tupleDesc)) != 0)
		return false;
	else
		return true;
}

/*
 * Check columns in child table match up with columns in parent, and increment
 * their attinhcount.
 *
 * Called by CreateInheritance
 *
 * Currently all parent columns must be found in child. Missing columns are an
 * error.  One day we might consider creating new columns like CREATE TABLE
 * does.  However, that is widely unpopular --- in the common use case of
 * partitioned tables it's a foot-gun.
 *
 * The data type must match exactly. If the parent column is NOT NULL then
 * the child must be as well. Defaults are not compared, however.
 */
static void
MergeAttributesIntoExisting(Relation child_rel, Relation parent_rel, bool ispartition)
{
	Relation	attrrel;
	TupleDesc	parent_desc;

	attrrel = table_open(AttributeRelationId, RowExclusiveLock);
	parent_desc = RelationGetDescr(parent_rel);

	for (AttrNumber parent_attno = 1; parent_attno <= parent_desc->natts; parent_attno++)
	{
		Form_pg_attribute parent_att = TupleDescAttr(parent_desc, parent_attno - 1);
		char	   *parent_attname = NameStr(parent_att->attname);
		HeapTuple	tuple;

		/* Ignore dropped columns in the parent. */
		if (parent_att->attisdropped)
			continue;

		/* Find same column in child (matching on column name). */
		tuple = SearchSysCacheCopyAttName(RelationGetRelid(child_rel), parent_attname);
		if (HeapTupleIsValid(tuple))
		{
			Form_pg_attribute child_att = (Form_pg_attribute) GETSTRUCT(tuple);

			if (parent_att->atttypid != child_att->atttypid ||
				parent_att->atttypmod != child_att->atttypmod)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("child table \"%s\" has different type for column \"%s\"",
								RelationGetRelationName(child_rel), parent_attname)));

			if (parent_att->attcollation != child_att->attcollation)
				ereport(ERROR,
						(errcode(ERRCODE_COLLATION_MISMATCH),
						 errmsg("child table \"%s\" has different collation for column \"%s\"",
								RelationGetRelationName(child_rel), parent_attname)));

			/*
			 * If the parent has a not-null constraint that's not NO INHERIT,
			 * make sure the child has one too.
			 *
			 * Other constraints are checked elsewhere.
			 */
			if (parent_att->attnotnull && !child_att->attnotnull)
			{
				HeapTuple	contup;

				contup = findNotNullConstraintAttnum(RelationGetRelid(parent_rel),
													 parent_att->attnum);
				if (HeapTupleIsValid(contup) &&
					!((Form_pg_constraint) GETSTRUCT(contup))->connoinherit)
					ereport(ERROR,
							errcode(ERRCODE_DATATYPE_MISMATCH),
							errmsg("column \"%s\" in child table \"%s\" must be marked NOT NULL",
								   parent_attname, RelationGetRelationName(child_rel)));
			}

			/*
			 * Child column must be generated if and only if parent column is.
			 */
			if (parent_att->attgenerated && !child_att->attgenerated)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("column \"%s\" in child table must be a generated column", parent_attname)));
			if (child_att->attgenerated && !parent_att->attgenerated)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("column \"%s\" in child table must not be a generated column", parent_attname)));

			if (parent_att->attgenerated && child_att->attgenerated && child_att->attgenerated != parent_att->attgenerated)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("column \"%s\" inherits from generated column of different kind", parent_attname),
						 errdetail("Parent column is %s, child column is %s.",
								   parent_att->attgenerated == ATTRIBUTE_GENERATED_STORED ? "STORED" : "VIRTUAL",
								   child_att->attgenerated == ATTRIBUTE_GENERATED_STORED ? "STORED" : "VIRTUAL")));

			/*
			 * Regular inheritance children are independent enough not to
			 * inherit identity columns.  But partitions are integral part of
			 * a partitioned table and inherit identity column.
			 */
			if (ispartition)
				child_att->attidentity = parent_att->attidentity;

			/*
			 * OK, bump the child column's inheritance count.  (If we fail
			 * later on, this change will just roll back.)
			 */
			if (pg_add_s16_overflow(child_att->attinhcount, 1,
									&child_att->attinhcount))
				ereport(ERROR,
						errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
						errmsg("too many inheritance parents"));

			/*
			 * In case of partitions, we must enforce that value of attislocal
			 * is same in all partitions. (Note: there are only inherited
			 * attributes in partitions)
			 */
			if (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
			{
				Assert(child_att->attinhcount == 1);
				child_att->attislocal = false;
			}

			CatalogTupleUpdate(attrrel, &tuple->t_self, tuple);
			heap_freetuple(tuple);
		}
		else
		{
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("child table is missing column \"%s\"", parent_attname)));
		}
	}

	table_close(attrrel, RowExclusiveLock);
}

/*
 * Check constraints in child table match up with constraints in parent,
 * and increment their coninhcount.
 *
 * Constraints that are marked ONLY in the parent are ignored.
 *
 * Called by CreateInheritance
 *
 * Currently all constraints in parent must be present in the child. One day we
 * may consider adding new constraints like CREATE TABLE does.
 *
 * XXX This is O(N^2) which may be an issue with tables with hundreds of
 * constraints. As long as tables have more like 10 constraints it shouldn't be
 * a problem though. Even 100 constraints ought not be the end of the world.
 *
 * XXX See MergeWithExistingConstraint too if you change this code.
 */
static void
MergeConstraintsIntoExisting(Relation child_rel, Relation parent_rel)
{
	Relation	constraintrel;
	SysScanDesc parent_scan;
	ScanKeyData parent_key;
	HeapTuple	parent_tuple;
	Oid			parent_relid = RelationGetRelid(parent_rel);
	AttrMap    *attmap;

	constraintrel = table_open(ConstraintRelationId, RowExclusiveLock);

	/* Outer loop scans through the parent's constraint definitions */
	ScanKeyInit(&parent_key,
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(parent_relid));
	parent_scan = systable_beginscan(constraintrel, ConstraintRelidTypidNameIndexId,
									 true, NULL, 1, &parent_key);

	attmap = build_attrmap_by_name(RelationGetDescr(parent_rel),
								   RelationGetDescr(child_rel),
								   true);

	while (HeapTupleIsValid(parent_tuple = systable_getnext(parent_scan)))
	{
		Form_pg_constraint parent_con = (Form_pg_constraint) GETSTRUCT(parent_tuple);
		SysScanDesc child_scan;
		ScanKeyData child_key;
		HeapTuple	child_tuple;
		AttrNumber	parent_attno;
		bool		found = false;

		if (parent_con->contype != CONSTRAINT_CHECK &&
			parent_con->contype != CONSTRAINT_NOTNULL)
			continue;

		/* if the parent's constraint is marked NO INHERIT, it's not inherited */
		if (parent_con->connoinherit)
			continue;

		if (parent_con->contype == CONSTRAINT_NOTNULL)
			parent_attno = extractNotNullColumn(parent_tuple);
		else
			parent_attno = InvalidAttrNumber;

		/* Search for a child constraint matching this one */
		ScanKeyInit(&child_key,
					Anum_pg_constraint_conrelid,
					BTEqualStrategyNumber, F_OIDEQ,
					ObjectIdGetDatum(RelationGetRelid(child_rel)));
		child_scan = systable_beginscan(constraintrel, ConstraintRelidTypidNameIndexId,
										true, NULL, 1, &child_key);

		while (HeapTupleIsValid(child_tuple = systable_getnext(child_scan)))
		{
			Form_pg_constraint child_con = (Form_pg_constraint) GETSTRUCT(child_tuple);
			HeapTuple	child_copy;

			if (child_con->contype != parent_con->contype)
				continue;

			/*
			 * CHECK constraint are matched by constraint name, NOT NULL ones
			 * by attribute number.
			 */
			if (child_con->contype == CONSTRAINT_CHECK)
			{
				if (strcmp(NameStr(parent_con->conname),
						   NameStr(child_con->conname)) != 0)
					continue;
			}
			else if (child_con->contype == CONSTRAINT_NOTNULL)
			{
				Form_pg_attribute parent_attr;
				Form_pg_attribute child_attr;
				AttrNumber	child_attno;

				parent_attr = TupleDescAttr(parent_rel->rd_att, parent_attno - 1);
				child_attno = extractNotNullColumn(child_tuple);
				if (parent_attno != attmap->attnums[child_attno - 1])
					continue;

				child_attr = TupleDescAttr(child_rel->rd_att, child_attno - 1);
				/* there shouldn't be constraints on dropped columns */
				if (parent_attr->attisdropped || child_attr->attisdropped)
					elog(ERROR, "found not-null constraint on dropped columns");
			}

			if (child_con->contype == CONSTRAINT_CHECK &&
				!constraints_equivalent(parent_tuple, child_tuple, RelationGetDescr(constraintrel)))
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("child table \"%s\" has different definition for check constraint \"%s\"",
								RelationGetRelationName(child_rel), NameStr(parent_con->conname))));

			/*
			 * If the child constraint is "no inherit" then cannot merge
			 */
			if (child_con->connoinherit)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("constraint \"%s\" conflicts with non-inherited constraint on child table \"%s\"",
								NameStr(child_con->conname), RelationGetRelationName(child_rel))));

			/*
			 * If the child constraint is "not valid" then cannot merge with a
			 * valid parent constraint
			 */
			if (parent_con->convalidated && child_con->conenforced &&
				!child_con->convalidated)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("constraint \"%s\" conflicts with NOT VALID constraint on child table \"%s\"",
								NameStr(child_con->conname), RelationGetRelationName(child_rel))));

			/*
			 * A NOT ENFORCED child constraint cannot be merged with an
			 * ENFORCED parent constraint. However, the reverse is allowed,
			 * where the child constraint is ENFORCED.
			 */
			if (parent_con->conenforced && !child_con->conenforced)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("constraint \"%s\" conflicts with NOT ENFORCED constraint on child table \"%s\"",
								NameStr(child_con->conname), RelationGetRelationName(child_rel))));

			/*
			 * OK, bump the child constraint's inheritance count.  (If we fail
			 * later on, this change will just roll back.)
			 */
			child_copy = heap_copytuple(child_tuple);
			child_con = (Form_pg_constraint) GETSTRUCT(child_copy);

			if (pg_add_s16_overflow(child_con->coninhcount, 1,
									&child_con->coninhcount))
				ereport(ERROR,
						errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
						errmsg("too many inheritance parents"));

			/*
			 * In case of partitions, an inherited constraint must be
			 * inherited only once since it cannot have multiple parents and
			 * it is never considered local.
			 */
			if (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
			{
				Assert(child_con->coninhcount == 1);
				child_con->conislocal = false;
			}

			CatalogTupleUpdate(constraintrel, &child_copy->t_self, child_copy);
			heap_freetuple(child_copy);

			found = true;
			break;
		}

		systable_endscan(child_scan);

		if (!found)
		{
			if (parent_con->contype == CONSTRAINT_NOTNULL)
				ereport(ERROR,
						errcode(ERRCODE_DATATYPE_MISMATCH),
						errmsg("column \"%s\" in child table \"%s\" must be marked NOT NULL",
							   get_attname(parent_relid,
										   extractNotNullColumn(parent_tuple),
										   false),
							   RelationGetRelationName(child_rel)));

			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("child table is missing constraint \"%s\"",
							NameStr(parent_con->conname))));
		}
	}

	systable_endscan(parent_scan);
	table_close(constraintrel, RowExclusiveLock);
}

/*
 * ALTER TABLE NO INHERIT
 *
 * Return value is the address of the relation that is no longer parent.
 */
static ObjectAddress
ATExecDropInherit(Relation rel, RangeVar *parent, LOCKMODE lockmode)
{
	ObjectAddress address;
	Relation	parent_rel;

	if (rel->rd_rel->relispartition)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot change inheritance of a partition")));

	/*
	 * AccessShareLock on the parent is probably enough, seeing that DROP
	 * TABLE doesn't lock parent tables at all.  We need some lock since we'll
	 * be inspecting the parent's schema.
	 */
	parent_rel = table_openrv(parent, AccessShareLock);

	/*
	 * We don't bother to check ownership of the parent table --- ownership of
	 * the child is presumed enough rights.
	 */

	/* Off to RemoveInheritance() where most of the work happens */
	RemoveInheritance(rel, parent_rel, false);

	ObjectAddressSet(address, RelationRelationId,
					 RelationGetRelid(parent_rel));

	/* keep our lock on the parent relation until commit */
	table_close(parent_rel, NoLock);

	return address;
}

/*
 * MarkInheritDetached
 *
 * Set inhdetachpending for a partition, for ATExecDetachPartition
 * in concurrent mode.  While at it, verify that no other partition is
 * already pending detach.
 */
static void
MarkInheritDetached(Relation child_rel, Relation parent_rel)
{
	Relation	catalogRelation;
	SysScanDesc scan;
	ScanKeyData key;
	HeapTuple	inheritsTuple;
	bool		found = false;

	Assert(parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);

	/*
	 * Find pg_inherits entries by inhparent.  (We need to scan them all in
	 * order to verify that no other partition is pending detach.)
	 */
	catalogRelation = table_open(InheritsRelationId, RowExclusiveLock);
	ScanKeyInit(&key,
				Anum_pg_inherits_inhparent,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
	scan = systable_beginscan(catalogRelation, InheritsParentIndexId,
							  true, NULL, 1, &key);

	while (HeapTupleIsValid(inheritsTuple = systable_getnext(scan)))
	{
		Form_pg_inherits inhForm;

		inhForm = (Form_pg_inherits) GETSTRUCT(inheritsTuple);
		if (inhForm->inhdetachpending)
			ereport(ERROR,
					errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					errmsg("partition \"%s\" already pending detach in partitioned table \"%s.%s\"",
						   get_rel_name(inhForm->inhrelid),
						   get_namespace_name(parent_rel->rd_rel->relnamespace),
						   RelationGetRelationName(parent_rel)),
					errhint("Use ALTER TABLE ... DETACH PARTITION ... FINALIZE to complete the pending detach operation."));

		if (inhForm->inhrelid == RelationGetRelid(child_rel))
		{
			HeapTuple	newtup;

			newtup = heap_copytuple(inheritsTuple);
			((Form_pg_inherits) GETSTRUCT(newtup))->inhdetachpending = true;

			CatalogTupleUpdate(catalogRelation,
							   &inheritsTuple->t_self,
							   newtup);
			found = true;
			heap_freetuple(newtup);
			/* keep looking, to ensure we catch others pending detach */
		}
	}

	/* Done */
	systable_endscan(scan);
	table_close(catalogRelation, RowExclusiveLock);

	if (!found)
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_TABLE),
				 errmsg("relation \"%s\" is not a partition of relation \"%s\"",
						RelationGetRelationName(child_rel),
						RelationGetRelationName(parent_rel))));
}

/*
 * RemoveInheritance
 *
 * Drop a parent from the child's parents. This just adjusts the attinhcount
 * and attislocal of the columns and removes the pg_inherit and pg_depend
 * entries.  expect_detached is passed down to DeleteInheritsTuple, q.v..
 *
 * If attinhcount goes to 0 then attislocal gets set to true. If it goes back
 * up attislocal stays true, which means if a child is ever removed from a
 * parent then its columns will never be automatically dropped which may
 * surprise. But at least we'll never surprise by dropping columns someone
 * isn't expecting to be dropped which would actually mean data loss.
 *
 * coninhcount and conislocal for inherited constraints are adjusted in
 * exactly the same way.
 *
 * Common to ATExecDropInherit() and ATExecDetachPartition().
 */
static void
RemoveInheritance(Relation child_rel, Relation parent_rel, bool expect_detached)
{
	Relation	catalogRelation;
	SysScanDesc scan;
	ScanKeyData key[3];
	HeapTuple	attributeTuple,
				constraintTuple;
	AttrMap    *attmap;
	List	   *connames;
	List	   *nncolumns;
	bool		found;
	bool		is_partitioning;

	is_partitioning = (parent_rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE);

	found = DeleteInheritsTuple(RelationGetRelid(child_rel),
								RelationGetRelid(parent_rel),
								expect_detached,
								RelationGetRelationName(child_rel));
	if (!found)
	{
		if (is_partitioning)
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_TABLE),
					 errmsg("relation \"%s\" is not a partition of relation \"%s\"",
							RelationGetRelationName(child_rel),
							RelationGetRelationName(parent_rel))));
		else
			ereport(ERROR,
					(errcode(ERRCODE_UNDEFINED_TABLE),
					 errmsg("relation \"%s\" is not a parent of relation \"%s\"",
							RelationGetRelationName(parent_rel),
							RelationGetRelationName(child_rel))));
	}

	/*
	 * Search through child columns looking for ones matching parent rel
	 */
	catalogRelation = table_open(AttributeRelationId, RowExclusiveLock);
	ScanKeyInit(&key[0],
				Anum_pg_attribute_attrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(child_rel)));
	scan = systable_beginscan(catalogRelation, AttributeRelidNumIndexId,
							  true, NULL, 1, key);
	while (HeapTupleIsValid(attributeTuple = systable_getnext(scan)))
	{
		Form_pg_attribute att = (Form_pg_attribute) GETSTRUCT(attributeTuple);

		/* Ignore if dropped or not inherited */
		if (att->attisdropped)
			continue;
		if (att->attinhcount <= 0)
			continue;

		if (SearchSysCacheExistsAttName(RelationGetRelid(parent_rel),
										NameStr(att->attname)))
		{
			/* Decrement inhcount and possibly set islocal to true */
			HeapTuple	copyTuple = heap_copytuple(attributeTuple);
			Form_pg_attribute copy_att = (Form_pg_attribute) GETSTRUCT(copyTuple);

			copy_att->attinhcount--;
			if (copy_att->attinhcount == 0)
				copy_att->attislocal = true;

			CatalogTupleUpdate(catalogRelation, &copyTuple->t_self, copyTuple);
			heap_freetuple(copyTuple);
		}
	}
	systable_endscan(scan);
	table_close(catalogRelation, RowExclusiveLock);

	/*
	 * Likewise, find inherited check and not-null constraints and disinherit
	 * them. To do this, we first need a list of the names of the parent's
	 * check constraints.  (We cheat a bit by only checking for name matches,
	 * assuming that the expressions will match.)
	 *
	 * For NOT NULL columns, we store column numbers to match, mapping them in
	 * to the child rel's attribute numbers.
	 */
	attmap = build_attrmap_by_name(RelationGetDescr(child_rel),
								   RelationGetDescr(parent_rel),
								   false);

	catalogRelation = table_open(ConstraintRelationId, RowExclusiveLock);
	ScanKeyInit(&key[0],
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(parent_rel)));
	scan = systable_beginscan(catalogRelation, ConstraintRelidTypidNameIndexId,
							  true, NULL, 1, key);

	connames = NIL;
	nncolumns = NIL;

	while (HeapTupleIsValid(constraintTuple = systable_getnext(scan)))
	{
		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(constraintTuple);

		if (con->connoinherit)
			continue;

		if (con->contype == CONSTRAINT_CHECK)
			connames = lappend(connames, pstrdup(NameStr(con->conname)));
		if (con->contype == CONSTRAINT_NOTNULL)
		{
			AttrNumber	parent_attno = extractNotNullColumn(constraintTuple);

			nncolumns = lappend_int(nncolumns, attmap->attnums[parent_attno - 1]);
		}
	}

	systable_endscan(scan);

	/* Now scan the child's constraints to find matches */
	ScanKeyInit(&key[0],
				Anum_pg_constraint_conrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(child_rel)));
	scan = systable_beginscan(catalogRelation, ConstraintRelidTypidNameIndexId,
							  true, NULL, 1, key);

	while (HeapTupleIsValid(constraintTuple = systable_getnext(scan)))
	{
		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(constraintTuple);
		bool		match = false;

		/*
		 * Match CHECK constraints by name, not-null constraints by column
		 * number, and ignore all others.
		 */
		if (con->contype == CONSTRAINT_CHECK)
		{
			foreach_ptr(char, chkname, connames)
			{
				if (con->contype == CONSTRAINT_CHECK &&
					strcmp(NameStr(con->conname), chkname) == 0)
				{
					match = true;
					connames = foreach_delete_current(connames, chkname);
					break;
				}
			}
		}
		else if (con->contype == CONSTRAINT_NOTNULL)
		{
			AttrNumber	child_attno = extractNotNullColumn(constraintTuple);

			foreach_int(prevattno, nncolumns)
			{
				if (prevattno == child_attno)
				{
					match = true;
					nncolumns = foreach_delete_current(nncolumns, prevattno);
					break;
				}
			}
		}
		else
			continue;

		if (match)
		{
			/* Decrement inhcount and possibly set islocal to true */
			HeapTuple	copyTuple = heap_copytuple(constraintTuple);
			Form_pg_constraint copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);

			if (copy_con->coninhcount <= 0) /* shouldn't happen */
				elog(ERROR, "relation %u has non-inherited constraint \"%s\"",
					 RelationGetRelid(child_rel), NameStr(copy_con->conname));

			copy_con->coninhcount--;
			if (copy_con->coninhcount == 0)
				copy_con->conislocal = true;

			CatalogTupleUpdate(catalogRelation, &copyTuple->t_self, copyTuple);
			heap_freetuple(copyTuple);
		}
	}

	/* We should have matched all constraints */
	if (connames != NIL || nncolumns != NIL)
		elog(ERROR, "%d unmatched constraints while removing inheritance from \"%s\" to \"%s\"",
			 list_length(connames) + list_length(nncolumns),
			 RelationGetRelationName(child_rel), RelationGetRelationName(parent_rel));

	systable_endscan(scan);
	table_close(catalogRelation, RowExclusiveLock);

	drop_parent_dependency(RelationGetRelid(child_rel),
						   RelationRelationId,
						   RelationGetRelid(parent_rel),
						   child_dependency_type(is_partitioning));

	/*
	 * Post alter hook of this inherits. Since object_access_hook doesn't take
	 * multiple object identifiers, we relay oid of parent relation using
	 * auxiliary_id argument.
	 */
	InvokeObjectPostAlterHookArg(InheritsRelationId,
								 RelationGetRelid(child_rel), 0,
								 RelationGetRelid(parent_rel), false);
}

/*
 * Drop the dependency created by StoreCatalogInheritance1 (CREATE TABLE
 * INHERITS/ALTER TABLE INHERIT -- refclassid will be RelationRelationId) or
 * heap_create_with_catalog (CREATE TABLE OF/ALTER TABLE OF -- refclassid will
 * be TypeRelationId).  There's no convenient way to do this, so go trawling
 * through pg_depend.
 */
static void
drop_parent_dependency(Oid relid, Oid refclassid, Oid refobjid,
					   DependencyType deptype)
{
	Relation	catalogRelation;
	SysScanDesc scan;
	ScanKeyData key[3];
	HeapTuple	depTuple;

	catalogRelation = table_open(DependRelationId, RowExclusiveLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_classid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_objid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relid));
	ScanKeyInit(&key[2],
				Anum_pg_depend_objsubid,
				BTEqualStrategyNumber, F_INT4EQ,
				Int32GetDatum(0));

	scan = systable_beginscan(catalogRelation, DependDependerIndexId, true,
							  NULL, 3, key);

	while (HeapTupleIsValid(depTuple = systable_getnext(scan)))
	{
		Form_pg_depend dep = (Form_pg_depend) GETSTRUCT(depTuple);

		if (dep->refclassid == refclassid &&
			dep->refobjid == refobjid &&
			dep->refobjsubid == 0 &&
			dep->deptype == deptype)
			CatalogTupleDelete(catalogRelation, &depTuple->t_self);
	}

	systable_endscan(scan);
	table_close(catalogRelation, RowExclusiveLock);
}

/*
 * ALTER TABLE OF
 *
 * Attach a table to a composite type, as though it had been created with CREATE
 * TABLE OF.  All attname, atttypid, atttypmod and attcollation must match.  The
 * subject table must not have inheritance parents.  These restrictions ensure
 * that you cannot create a configuration impossible with CREATE TABLE OF alone.
 *
 * The address of the type is returned.
 */
static ObjectAddress
ATExecAddOf(Relation rel, const TypeName *ofTypename, LOCKMODE lockmode)
{
	Oid			relid = RelationGetRelid(rel);
	Type		typetuple;
	Form_pg_type typeform;
	Oid			typeid;
	Relation	inheritsRelation,
				relationRelation;
	SysScanDesc scan;
	ScanKeyData key;
	AttrNumber	table_attno,
				type_attno;
	TupleDesc	typeTupleDesc,
				tableTupleDesc;
	ObjectAddress tableobj,
				typeobj;
	HeapTuple	classtuple;

	/* Validate the type. */
	typetuple = typenameType(NULL, ofTypename, NULL);
	check_of_type(typetuple);
	typeform = (Form_pg_type) GETSTRUCT(typetuple);
	typeid = typeform->oid;

	/* Fail if the table has any inheritance parents. */
	inheritsRelation = table_open(InheritsRelationId, AccessShareLock);
	ScanKeyInit(&key,
				Anum_pg_inherits_inhrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(relid));
	scan = systable_beginscan(inheritsRelation, InheritsRelidSeqnoIndexId,
							  true, NULL, 1, &key);
	if (HeapTupleIsValid(systable_getnext(scan)))
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("typed tables cannot inherit")));
	systable_endscan(scan);
	table_close(inheritsRelation, AccessShareLock);

	/*
	 * Check the tuple descriptors for compatibility.  Unlike inheritance, we
	 * require that the order also match.  However, attnotnull need not match.
	 */
	typeTupleDesc = lookup_rowtype_tupdesc(typeid, -1);
	tableTupleDesc = RelationGetDescr(rel);
	table_attno = 1;
	for (type_attno = 1; type_attno <= typeTupleDesc->natts; type_attno++)
	{
		Form_pg_attribute type_attr,
					table_attr;
		const char *type_attname,
				   *table_attname;

		/* Get the next non-dropped type attribute. */
		type_attr = TupleDescAttr(typeTupleDesc, type_attno - 1);
		if (type_attr->attisdropped)
			continue;
		type_attname = NameStr(type_attr->attname);

		/* Get the next non-dropped table attribute. */
		do
		{
			if (table_attno > tableTupleDesc->natts)
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("table is missing column \"%s\"",
								type_attname)));
			table_attr = TupleDescAttr(tableTupleDesc, table_attno - 1);
			table_attno++;
		} while (table_attr->attisdropped);
		table_attname = NameStr(table_attr->attname);

		/* Compare name. */
		if (strncmp(table_attname, type_attname, NAMEDATALEN) != 0)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("table has column \"%s\" where type requires \"%s\"",
							table_attname, type_attname)));

		/* Compare type. */
		if (table_attr->atttypid != type_attr->atttypid ||
			table_attr->atttypmod != type_attr->atttypmod ||
			table_attr->attcollation != type_attr->attcollation)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("table \"%s\" has different type for column \"%s\"",
							RelationGetRelationName(rel), type_attname)));
	}
	ReleaseTupleDesc(typeTupleDesc);

	/* Any remaining columns at the end of the table had better be dropped. */
	for (; table_attno <= tableTupleDesc->natts; table_attno++)
	{
		Form_pg_attribute table_attr = TupleDescAttr(tableTupleDesc,
													 table_attno - 1);

		if (!table_attr->attisdropped)
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("table has extra column \"%s\"",
							NameStr(table_attr->attname))));
	}

	/* If the table was already typed, drop the existing dependency. */
	if (rel->rd_rel->reloftype)
		drop_parent_dependency(relid, TypeRelationId, rel->rd_rel->reloftype,
							   DEPENDENCY_NORMAL);

	/* Record a dependency on the new type. */
	tableobj.classId = RelationRelationId;
	tableobj.objectId = relid;
	tableobj.objectSubId = 0;
	typeobj.classId = TypeRelationId;
	typeobj.objectId = typeid;
	typeobj.objectSubId = 0;
	recordDependencyOn(&tableobj, &typeobj, DEPENDENCY_NORMAL);

	/* Update pg_class.reloftype */
	relationRelation = table_open(RelationRelationId, RowExclusiveLock);
	classtuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
	if (!HeapTupleIsValid(classtuple))
		elog(ERROR, "cache lookup failed for relation %u", relid);
	((Form_pg_class) GETSTRUCT(classtuple))->reloftype = typeid;
	CatalogTupleUpdate(relationRelation, &classtuple->t_self, classtuple);

	InvokeObjectPostAlterHook(RelationRelationId, relid, 0);

	heap_freetuple(classtuple);
	table_close(relationRelation, RowExclusiveLock);

	ReleaseSysCache(typetuple);

	return typeobj;
}

/*
 * ALTER TABLE NOT OF
 *
 * Detach a typed table from its originating type.  Just clear reloftype and
 * remove the dependency.
 */
static void
ATExecDropOf(Relation rel, LOCKMODE lockmode)
{
	Oid			relid = RelationGetRelid(rel);
	Relation	relationRelation;
	HeapTuple	tuple;

	if (!OidIsValid(rel->rd_rel->reloftype))
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a typed table",
						RelationGetRelationName(rel))));

	/*
	 * We don't bother to check ownership of the type --- ownership of the
	 * table is presumed enough rights.  No lock required on the type, either.
	 */

	drop_parent_dependency(relid, TypeRelationId, rel->rd_rel->reloftype,
						   DEPENDENCY_NORMAL);

	/* Clear pg_class.reloftype */
	relationRelation = table_open(RelationRelationId, RowExclusiveLock);
	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", relid);
	((Form_pg_class) GETSTRUCT(tuple))->reloftype = InvalidOid;
	CatalogTupleUpdate(relationRelation, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId, relid, 0);

	heap_freetuple(tuple);
	table_close(relationRelation, RowExclusiveLock);
}

/*
 * relation_mark_replica_identity: Update a table's replica identity
 *
 * Iff ri_type = REPLICA_IDENTITY_INDEX, indexOid must be the Oid of a suitable
 * index. Otherwise, it must be InvalidOid.
 *
 * Caller had better hold an exclusive lock on the relation, as the results
 * of running two of these concurrently wouldn't be pretty.
 */
static void
relation_mark_replica_identity(Relation rel, char ri_type, Oid indexOid,
							   bool is_internal)
{
	Relation	pg_index;
	Relation	pg_class;
	HeapTuple	pg_class_tuple;
	HeapTuple	pg_index_tuple;
	Form_pg_class pg_class_form;
	Form_pg_index pg_index_form;
	ListCell   *index;

	/*
	 * Check whether relreplident has changed, and update it if so.
	 */
	pg_class = table_open(RelationRelationId, RowExclusiveLock);
	pg_class_tuple = SearchSysCacheCopy1(RELOID,
										 ObjectIdGetDatum(RelationGetRelid(rel)));
	if (!HeapTupleIsValid(pg_class_tuple))
		elog(ERROR, "cache lookup failed for relation \"%s\"",
			 RelationGetRelationName(rel));
	pg_class_form = (Form_pg_class) GETSTRUCT(pg_class_tuple);
	if (pg_class_form->relreplident != ri_type)
	{
		pg_class_form->relreplident = ri_type;
		CatalogTupleUpdate(pg_class, &pg_class_tuple->t_self, pg_class_tuple);
	}
	table_close(pg_class, RowExclusiveLock);
	heap_freetuple(pg_class_tuple);

	/*
	 * Update the per-index indisreplident flags correctly.
	 */
	pg_index = table_open(IndexRelationId, RowExclusiveLock);
	foreach(index, RelationGetIndexList(rel))
	{
		Oid			thisIndexOid = lfirst_oid(index);
		bool		dirty = false;

		pg_index_tuple = SearchSysCacheCopy1(INDEXRELID,
											 ObjectIdGetDatum(thisIndexOid));
		if (!HeapTupleIsValid(pg_index_tuple))
			elog(ERROR, "cache lookup failed for index %u", thisIndexOid);
		pg_index_form = (Form_pg_index) GETSTRUCT(pg_index_tuple);

		if (thisIndexOid == indexOid)
		{
			/* Set the bit if not already set. */
			if (!pg_index_form->indisreplident)
			{
				dirty = true;
				pg_index_form->indisreplident = true;
			}
		}
		else
		{
			/* Unset the bit if set. */
			if (pg_index_form->indisreplident)
			{
				dirty = true;
				pg_index_form->indisreplident = false;
			}
		}

		if (dirty)
		{
			CatalogTupleUpdate(pg_index, &pg_index_tuple->t_self, pg_index_tuple);
			InvokeObjectPostAlterHookArg(IndexRelationId, thisIndexOid, 0,
										 InvalidOid, is_internal);

			/*
			 * Invalidate the relcache for the table, so that after we commit
			 * all sessions will refresh the table's replica identity index
			 * before attempting any UPDATE or DELETE on the table.  (If we
			 * changed the table's pg_class row above, then a relcache inval
			 * is already queued due to that; but we might not have.)
			 */
			CacheInvalidateRelcache(rel);
		}
		heap_freetuple(pg_index_tuple);
	}

	table_close(pg_index, RowExclusiveLock);
}

/*
 * ALTER TABLE <name> REPLICA IDENTITY ...
 */
static void
ATExecReplicaIdentity(Relation rel, ReplicaIdentityStmt *stmt, LOCKMODE lockmode)
{
	Oid			indexOid;
	Relation	indexRel;
	int			key;

	if (stmt->identity_type == REPLICA_IDENTITY_DEFAULT)
	{
		relation_mark_replica_identity(rel, stmt->identity_type, InvalidOid, true);
		return;
	}
	else if (stmt->identity_type == REPLICA_IDENTITY_FULL)
	{
		relation_mark_replica_identity(rel, stmt->identity_type, InvalidOid, true);
		return;
	}
	else if (stmt->identity_type == REPLICA_IDENTITY_NOTHING)
	{
		relation_mark_replica_identity(rel, stmt->identity_type, InvalidOid, true);
		return;
	}
	else if (stmt->identity_type == REPLICA_IDENTITY_INDEX)
	{
		 /* fallthrough */ ;
	}
	else
		elog(ERROR, "unexpected identity type %u", stmt->identity_type);

	/* Check that the index exists */
	indexOid = get_relname_relid(stmt->name, rel->rd_rel->relnamespace);
	if (!OidIsValid(indexOid))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("index \"%s\" for table \"%s\" does not exist",
						stmt->name, RelationGetRelationName(rel))));

	indexRel = index_open(indexOid, ShareLock);

	/* Check that the index is on the relation we're altering. */
	if (indexRel->rd_index == NULL ||
		indexRel->rd_index->indrelid != RelationGetRelid(rel))
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not an index for table \"%s\"",
						RelationGetRelationName(indexRel),
						RelationGetRelationName(rel))));

	/*
	 * The AM must support uniqueness, and the index must in fact be unique.
	 * If we have a WITHOUT OVERLAPS constraint (identified by uniqueness +
	 * exclusion), we can use that too.
	 */
	if ((!indexRel->rd_indam->amcanunique ||
		 !indexRel->rd_index->indisunique) &&
		!(indexRel->rd_index->indisunique && indexRel->rd_index->indisexclusion))
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot use non-unique index \"%s\" as replica identity",
						RelationGetRelationName(indexRel))));
	/* Deferred indexes are not guaranteed to be always unique. */
	if (!indexRel->rd_index->indimmediate)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot use non-immediate index \"%s\" as replica identity",
						RelationGetRelationName(indexRel))));
	/* Expression indexes aren't supported. */
	if (RelationGetIndexExpressions(indexRel) != NIL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot use expression index \"%s\" as replica identity",
						RelationGetRelationName(indexRel))));
	/* Predicate indexes aren't supported. */
	if (RelationGetIndexPredicate(indexRel) != NIL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot use partial index \"%s\" as replica identity",
						RelationGetRelationName(indexRel))));

	/* Check index for nullable columns. */
	for (key = 0; key < IndexRelationGetNumberOfKeyAttributes(indexRel); key++)
	{
		int16		attno = indexRel->rd_index->indkey.values[key];
		Form_pg_attribute attr;

		/*
		 * Reject any other system columns.  (Going forward, we'll disallow
		 * indexes containing such columns in the first place, but they might
		 * exist in older branches.)
		 */
		if (attno <= 0)
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
					 errmsg("index \"%s\" cannot be used as replica identity because column %d is a system column",
							RelationGetRelationName(indexRel), attno)));

		attr = TupleDescAttr(rel->rd_att, attno - 1);
		if (!attr->attnotnull)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("index \"%s\" cannot be used as replica identity because column \"%s\" is nullable",
							RelationGetRelationName(indexRel),
							NameStr(attr->attname))));
	}

	/* This index is suitable for use as a replica identity. Mark it. */
	relation_mark_replica_identity(rel, stmt->identity_type, indexOid, true);

	index_close(indexRel, NoLock);
}

/*
 * ALTER TABLE ENABLE/DISABLE ROW LEVEL SECURITY
 */
static void
ATExecSetRowSecurity(Relation rel, bool rls)
{
	Relation	pg_class;
	Oid			relid;
	HeapTuple	tuple;

	relid = RelationGetRelid(rel);

	/* Pull the record for this relation and update it */
	pg_class = table_open(RelationRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));

	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", relid);

	((Form_pg_class) GETSTRUCT(tuple))->relrowsecurity = rls;
	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), 0);

	table_close(pg_class, RowExclusiveLock);
	heap_freetuple(tuple);
}

/*
 * ALTER TABLE FORCE/NO FORCE ROW LEVEL SECURITY
 */
static void
ATExecForceNoForceRowSecurity(Relation rel, bool force_rls)
{
	Relation	pg_class;
	Oid			relid;
	HeapTuple	tuple;

	relid = RelationGetRelid(rel);

	pg_class = table_open(RelationRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(relid));

	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u", relid);

	((Form_pg_class) GETSTRUCT(tuple))->relforcerowsecurity = force_rls;
	CatalogTupleUpdate(pg_class, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel), 0);

	table_close(pg_class, RowExclusiveLock);
	heap_freetuple(tuple);
}

/*
 * ALTER FOREIGN TABLE <name> OPTIONS (...)
 */
static void
ATExecGenericOptions(Relation rel, List *options)
{
	Relation	ftrel;
	ForeignServer *server;
	ForeignDataWrapper *fdw;
	HeapTuple	tuple;
	bool		isnull;
	Datum		repl_val[Natts_pg_foreign_table];
	bool		repl_null[Natts_pg_foreign_table];
	bool		repl_repl[Natts_pg_foreign_table];
	Datum		datum;
	Form_pg_foreign_table tableform;

	if (options == NIL)
		return;

	ftrel = table_open(ForeignTableRelationId, RowExclusiveLock);

	tuple = SearchSysCacheCopy1(FOREIGNTABLEREL,
								ObjectIdGetDatum(rel->rd_id));
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("foreign table \"%s\" does not exist",
						RelationGetRelationName(rel))));
	tableform = (Form_pg_foreign_table) GETSTRUCT(tuple);
	server = GetForeignServer(tableform->ftserver);
	fdw = GetForeignDataWrapper(server->fdwid);

	memset(repl_val, 0, sizeof(repl_val));
	memset(repl_null, false, sizeof(repl_null));
	memset(repl_repl, false, sizeof(repl_repl));

	/* Extract the current options */
	datum = SysCacheGetAttr(FOREIGNTABLEREL,
							tuple,
							Anum_pg_foreign_table_ftoptions,
							&isnull);
	if (isnull)
		datum = PointerGetDatum(NULL);

	/* Transform the options */
	datum = transformGenericOptions(ForeignTableRelationId,
									datum,
									options,
									fdw->fdwvalidator);

	if (PointerIsValid(DatumGetPointer(datum)))
		repl_val[Anum_pg_foreign_table_ftoptions - 1] = datum;
	else
		repl_null[Anum_pg_foreign_table_ftoptions - 1] = true;

	repl_repl[Anum_pg_foreign_table_ftoptions - 1] = true;

	/* Everything looks good - update the tuple */

	tuple = heap_modify_tuple(tuple, RelationGetDescr(ftrel),
							  repl_val, repl_null, repl_repl);

	CatalogTupleUpdate(ftrel, &tuple->t_self, tuple);

	/*
	 * Invalidate relcache so that all sessions will refresh any cached plans
	 * that might depend on the old options.
	 */
	CacheInvalidateRelcache(rel);

	InvokeObjectPostAlterHook(ForeignTableRelationId,
							  RelationGetRelid(rel), 0);

	table_close(ftrel, RowExclusiveLock);

	heap_freetuple(tuple);
}

/*
 * ALTER TABLE ALTER COLUMN SET COMPRESSION
 *
 * Return value is the address of the modified column
 */
static ObjectAddress
ATExecSetCompression(Relation rel,
					 const char *column,
					 Node *newValue,
					 LOCKMODE lockmode)
{
	Relation	attrel;
	HeapTuple	tuple;
	Form_pg_attribute atttableform;
	AttrNumber	attnum;
	char	   *compression;
	char		cmethod;
	ObjectAddress address;

	compression = strVal(newValue);

	attrel = table_open(AttributeRelationId, RowExclusiveLock);

	/* copy the cache entry so we can scribble on it below */
	tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), column);
	if (!HeapTupleIsValid(tuple))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_COLUMN),
				 errmsg("column \"%s\" of relation \"%s\" does not exist",
						column, RelationGetRelationName(rel))));

	/* prevent them from altering a system attribute */
	atttableform = (Form_pg_attribute) GETSTRUCT(tuple);
	attnum = atttableform->attnum;
	if (attnum <= 0)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("cannot alter system column \"%s\"", column)));

	/*
	 * Check that column type is compressible, then get the attribute
	 * compression method code
	 */
	cmethod = GetAttributeCompression(atttableform->atttypid, compression);

	/* update pg_attribute entry */
	atttableform->attcompression = cmethod;
	CatalogTupleUpdate(attrel, &tuple->t_self, tuple);

	InvokeObjectPostAlterHook(RelationRelationId,
							  RelationGetRelid(rel),
							  attnum);

	/*
	 * Apply the change to indexes as well (only for simple index columns,
	 * matching behavior of index.c ConstructTupleDescriptor()).
	 */
	SetIndexStorageProperties(rel, attrel, attnum,
							  false, 0,
							  true, cmethod,
							  lockmode);

	heap_freetuple(tuple);

	table_close(attrel, RowExclusiveLock);

	/* make changes visible */
	CommandCounterIncrement();

	ObjectAddressSubSet(address, RelationRelationId,
						RelationGetRelid(rel), attnum);
	return address;
}


/*
 * Preparation phase for SET LOGGED/UNLOGGED
 *
 * This verifies that we're not trying to change a temp table.  Also,
 * existing foreign key constraints are checked to avoid ending up with
 * permanent tables referencing unlogged tables.
 */
static void
ATPrepChangePersistence(AlteredTableInfo *tab, Relation rel, bool toLogged)
{
	Relation	pg_constraint;
	HeapTuple	tuple;
	SysScanDesc scan;
	ScanKeyData skey[1];

	/*
	 * Disallow changing status for a temp table.  Also verify whether we can
	 * get away with doing nothing; in such cases we don't need to run the
	 * checks below, either.
	 */
	switch (rel->rd_rel->relpersistence)
	{
		case RELPERSISTENCE_TEMP:
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					 errmsg("cannot change logged status of table \"%s\" because it is temporary",
							RelationGetRelationName(rel)),
					 errtable(rel)));
			break;
		case RELPERSISTENCE_PERMANENT:
			if (toLogged)
				/* nothing to do */
				return;
			break;
		case RELPERSISTENCE_UNLOGGED:
			if (!toLogged)
				/* nothing to do */
				return;
			break;
	}

	/*
	 * Check that the table is not part of any publication when changing to
	 * UNLOGGED, as UNLOGGED tables can't be published.
	 */
	if (!toLogged &&
		GetRelationPublications(RelationGetRelid(rel)) != NIL)
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("cannot change table \"%s\" to unlogged because it is part of a publication",
						RelationGetRelationName(rel)),
				 errdetail("Unlogged relations cannot be replicated.")));

	/*
	 * Check existing foreign key constraints to preserve the invariant that
	 * permanent tables cannot reference unlogged ones.  Self-referencing
	 * foreign keys can safely be ignored.
	 */
	pg_constraint = table_open(ConstraintRelationId, AccessShareLock);

	/*
	 * Scan conrelid if changing to permanent, else confrelid.  This also
	 * determines whether a useful index exists.
	 */
	ScanKeyInit(&skey[0],
				toLogged ? Anum_pg_constraint_conrelid :
				Anum_pg_constraint_confrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	scan = systable_beginscan(pg_constraint,
							  toLogged ? ConstraintRelidTypidNameIndexId : InvalidOid,
							  true, NULL, 1, skey);

	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
	{
		Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tuple);

		if (con->contype == CONSTRAINT_FOREIGN)
		{
			Oid			foreignrelid;
			Relation	foreignrel;

			/* the opposite end of what we used as scankey */
			foreignrelid = toLogged ? con->confrelid : con->conrelid;

			/* ignore if self-referencing */
			if (RelationGetRelid(rel) == foreignrelid)
				continue;

			foreignrel = relation_open(foreignrelid, AccessShareLock);

			if (toLogged)
			{
				if (!RelationIsPermanent(foreignrel))
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
							 errmsg("could not change table \"%s\" to logged because it references unlogged table \"%s\"",
									RelationGetRelationName(rel),
									RelationGetRelationName(foreignrel)),
							 errtableconstraint(rel, NameStr(con->conname))));
			}
			else
			{
				if (RelationIsPermanent(foreignrel))
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_TABLE_DEFINITION),
							 errmsg("could not change table \"%s\" to unlogged because it references logged table \"%s\"",
									RelationGetRelationName(rel),
									RelationGetRelationName(foreignrel)),
							 errtableconstraint(rel, NameStr(con->conname))));
			}

			relation_close(foreignrel, AccessShareLock);
		}
	}

	systable_endscan(scan);

	table_close(pg_constraint, AccessShareLock);

	/* force rewrite if necessary; see comment in ATRewriteTables */
	tab->rewrite |= AT_REWRITE_ALTER_PERSISTENCE;
	if (toLogged)
		tab->newrelpersistence = RELPERSISTENCE_PERMANENT;
	else
		tab->newrelpersistence = RELPERSISTENCE_UNLOGGED;
	tab->chgPersistence = true;
}

/*
 * Execute ALTER TABLE SET SCHEMA
 */
ObjectAddress
AlterTableNamespace(AlterObjectSchemaStmt *stmt, Oid *oldschema)
{
	Relation	rel;
	Oid			relid;
	Oid			oldNspOid;
	Oid			nspOid;
	RangeVar   *newrv;
	ObjectAddresses *objsMoved;
	ObjectAddress myself;

	relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
									 stmt->missing_ok ? RVR_MISSING_OK : 0,
									 RangeVarCallbackForAlterRelation,
									 stmt);

	if (!OidIsValid(relid))
	{
		ereport(NOTICE,
				(errmsg("relation \"%s\" does not exist, skipping",
						stmt->relation->relname)));
		return InvalidObjectAddress;
	}

	rel = relation_open(relid, NoLock);

	oldNspOid = RelationGetNamespace(rel);

	/* If it's an owned sequence, disallow moving it by itself. */
	if (rel->rd_rel->relkind == RELKIND_SEQUENCE)
	{
		Oid			tableId;
		int32		colId;

		if (sequenceIsOwned(relid, DEPENDENCY_AUTO, &tableId, &colId) ||
			sequenceIsOwned(relid, DEPENDENCY_INTERNAL, &tableId, &colId))
			ereport(ERROR,
					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
					 errmsg("cannot move an owned sequence into another schema"),
					 errdetail("Sequence \"%s\" is linked to table \"%s\".",
							   RelationGetRelationName(rel),
							   get_rel_name(tableId))));
	}

	/* Get and lock schema OID and check its permissions. */
	newrv = makeRangeVar(stmt->newschema, RelationGetRelationName(rel), -1);
	nspOid = RangeVarGetAndCheckCreationNamespace(newrv, NoLock, NULL);

	/* common checks on switching namespaces */
	CheckSetNamespace(oldNspOid, nspOid);

	objsMoved = new_object_addresses();
	AlterTableNamespaceInternal(rel, oldNspOid, nspOid, objsMoved);
	free_object_addresses(objsMoved);

	ObjectAddressSet(myself, RelationRelationId, relid);

	if (oldschema)
		*oldschema = oldNspOid;

	/* close rel, but keep lock until commit */
	relation_close(rel, NoLock);

	return myself;
}

/*
 * The guts of relocating a table or materialized view to another namespace:
 * besides moving the relation itself, its dependent objects are relocated to
 * the new schema.
 */
void
AlterTableNamespaceInternal(Relation rel, Oid oldNspOid, Oid nspOid,
							ObjectAddresses *objsMoved)
{
	Relation	classRel;

	Assert(objsMoved != NULL);

	/* OK, modify the pg_class row and pg_depend entry */
	classRel = table_open(RelationRelationId, RowExclusiveLock);

	AlterRelationNamespaceInternal(classRel, RelationGetRelid(rel), oldNspOid,
								   nspOid, true, objsMoved);

	/* Fix the table's row type too, if it has one */
	if (OidIsValid(rel->rd_rel->reltype))
		AlterTypeNamespaceInternal(rel->rd_rel->reltype, nspOid,
								   false,	/* isImplicitArray */
								   false,	/* ignoreDependent */
								   false,	/* errorOnTableType */
								   objsMoved);

	/* Fix other dependent stuff */
	AlterIndexNamespaces(classRel, rel, oldNspOid, nspOid, objsMoved);
	AlterSeqNamespaces(classRel, rel, oldNspOid, nspOid,
					   objsMoved, AccessExclusiveLock);
	AlterConstraintNamespaces(RelationGetRelid(rel), oldNspOid, nspOid,
							  false, objsMoved);

	table_close(classRel, RowExclusiveLock);
}

/*
 * The guts of relocating a relation to another namespace: fix the pg_class
 * entry, and the pg_depend entry if any.  Caller must already have
 * opened and write-locked pg_class.
 */
void
AlterRelationNamespaceInternal(Relation classRel, Oid relOid,
							   Oid oldNspOid, Oid newNspOid,
							   bool hasDependEntry,
							   ObjectAddresses *objsMoved)
{
	HeapTuple	classTup;
	Form_pg_class classForm;
	ObjectAddress thisobj;
	bool		already_done = false;

	/* no rel lock for relkind=c so use LOCKTAG_TUPLE */
	classTup = SearchSysCacheLockedCopy1(RELOID, ObjectIdGetDatum(relOid));
	if (!HeapTupleIsValid(classTup))
		elog(ERROR, "cache lookup failed for relation %u", relOid);
	classForm = (Form_pg_class) GETSTRUCT(classTup);

	Assert(classForm->relnamespace == oldNspOid);

	thisobj.classId = RelationRelationId;
	thisobj.objectId = relOid;
	thisobj.objectSubId = 0;

	/*
	 * If the object has already been moved, don't move it again.  If it's
	 * already in the right place, don't move it, but still fire the object
	 * access hook.
	 */
	already_done = object_address_present(&thisobj, objsMoved);
	if (!already_done && oldNspOid != newNspOid)
	{
		ItemPointerData otid = classTup->t_self;

		/* check for duplicate name (more friendly than unique-index failure) */
		if (get_relname_relid(NameStr(classForm->relname),
							  newNspOid) != InvalidOid)
			ereport(ERROR,
					(errcode(ERRCODE_DUPLICATE_TABLE),
					 errmsg("relation \"%s\" already exists in schema \"%s\"",
							NameStr(classForm->relname),
							get_namespace_name(newNspOid))));

		/* classTup is a copy, so OK to scribble on */
		classForm->relnamespace = newNspOid;

		CatalogTupleUpdate(classRel, &otid, classTup);
		UnlockTuple(classRel, &otid, InplaceUpdateTupleLock);


		/* Update dependency on schema if caller said so */
		if (hasDependEntry &&
			changeDependencyFor(RelationRelationId,
								relOid,
								NamespaceRelationId,
								oldNspOid,
								newNspOid) != 1)
			elog(ERROR, "could not change schema dependency for relation \"%s\"",
				 NameStr(classForm->relname));
	}
	else
		UnlockTuple(classRel, &classTup->t_self, InplaceUpdateTupleLock);
	if (!already_done)
	{
		add_exact_object_address(&thisobj, objsMoved);

		InvokeObjectPostAlterHook(RelationRelationId, relOid, 0);
	}

	heap_freetuple(classTup);
}

/*
 * Move all indexes for the specified relation to another namespace.
 *
 * Note: we assume adequate permission checking was done by the caller,
 * and that the caller has a suitable lock on the owning relation.
 */
static void
AlterIndexNamespaces(Relation classRel, Relation rel,
					 Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved)
{
	List	   *indexList;
	ListCell   *l;

	indexList = RelationGetIndexList(rel);

	foreach(l, indexList)
	{
		Oid			indexOid = lfirst_oid(l);
		ObjectAddress thisobj;

		thisobj.classId = RelationRelationId;
		thisobj.objectId = indexOid;
		thisobj.objectSubId = 0;

		/*
		 * Note: currently, the index will not have its own dependency on the
		 * namespace, so we don't need to do changeDependencyFor(). There's no
		 * row type in pg_type, either.
		 *
		 * XXX this objsMoved test may be pointless -- surely we have a single
		 * dependency link from a relation to each index?
		 */
		if (!object_address_present(&thisobj, objsMoved))
		{
			AlterRelationNamespaceInternal(classRel, indexOid,
										   oldNspOid, newNspOid,
										   false, objsMoved);
			add_exact_object_address(&thisobj, objsMoved);
		}
	}

	list_free(indexList);
}

/*
 * Move all identity and SERIAL-column sequences of the specified relation to another
 * namespace.
 *
 * Note: we assume adequate permission checking was done by the caller,
 * and that the caller has a suitable lock on the owning relation.
 */
static void
AlterSeqNamespaces(Relation classRel, Relation rel,
				   Oid oldNspOid, Oid newNspOid, ObjectAddresses *objsMoved,
				   LOCKMODE lockmode)
{
	Relation	depRel;
	SysScanDesc scan;
	ScanKeyData key[2];
	HeapTuple	tup;

	/*
	 * SERIAL sequences are those having an auto dependency on one of the
	 * table's columns (we don't care *which* column, exactly).
	 */
	depRel = table_open(DependRelationId, AccessShareLock);

	ScanKeyInit(&key[0],
				Anum_pg_depend_refclassid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationRelationId));
	ScanKeyInit(&key[1],
				Anum_pg_depend_refobjid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(rel)));
	/* we leave refobjsubid unspecified */

	scan = systable_beginscan(depRel, DependReferenceIndexId, true,
							  NULL, 2, key);

	while (HeapTupleIsValid(tup = systable_getnext(scan)))
	{
		Form_pg_depend depForm = (Form_pg_depend) GETSTRUCT(tup);
		Relation	seqRel;

		/* skip dependencies other than auto dependencies on columns */
		if (depForm->refobjsubid == 0 ||
			depForm->classid != RelationRelationId ||
			depForm->objsubid != 0 ||
			!(depForm->deptype == DEPENDENCY_AUTO || depForm->deptype == DEPENDENCY_INTERNAL))
			continue;

		/* Use relation_open just in case it's an index */
		seqRel = relation_open(depForm->objid, lockmode);

		/* skip non-sequence relations */
		if (RelationGetForm(seqRel)->relkind != RELKIND_SEQUENCE)
		{
			/* No need to keep the lock */
			relation_close(seqRel, lockmode);
			continue;
		}

		/* Fix the pg_class and pg_depend entries */
		AlterRelationNamespaceInternal(classRel, depForm->objid,
									   oldNspOid, newNspOid,
									   true, objsMoved);

		/*
		 * Sequences used to have entries in pg_type, but no longer do.  If we
		 * ever re-instate that, we'll need to move the pg_type entry to the
		 * new namespace, too (using AlterTypeNamespaceInternal).
		 */
		Assert(RelationGetForm(seqRel)->reltype == InvalidOid);

		/* Now we can close it.  Keep the lock till end of transaction. */
		relation_close(seqRel, NoLock);
	}

	systable_endscan(scan);

	relation_close(depRel, AccessShareLock);
}


/*
 * This code supports
 *	CREATE TEMP TABLE ... ON COMMIT { DROP | PRESERVE ROWS | DELETE ROWS }
 *
 * Because we only support this for TEMP tables, it's sufficient to remember
 * the state in a backend-local data structure.
 */

/*
 * Register a newly-created relation's ON COMMIT action.
 */
void
register_on_commit_action(Oid relid, OnCommitAction action)
{
	OnCommitItem *oc;
	MemoryContext oldcxt;

	/*
	 * We needn't bother registering the relation unless there is an ON COMMIT
	 * action we need to take.
	 */
	if (action == ONCOMMIT_NOOP || action == ONCOMMIT_PRESERVE_ROWS)
		return;

	oldcxt = MemoryContextSwitchTo(CacheMemoryContext);

	oc = (OnCommitItem *) palloc(sizeof(OnCommitItem));
	oc->relid = relid;
	oc->oncommit = action;
	oc->creating_subid = GetCurrentSubTransactionId();
	oc->deleting_subid = InvalidSubTransactionId;

	/*
	 * We use lcons() here so that ON COMMIT actions are processed in reverse
	 * order of registration.  That might not be essential but it seems
	 * reasonable.
	 */
	on_commits = lcons(oc, on_commits);

	MemoryContextSwitchTo(oldcxt);
}

/*
 * Unregister any ON COMMIT action when a relation is deleted.
 *
 * Actually, we only mark the OnCommitItem entry as to be deleted after commit.
 */
void
remove_on_commit_action(Oid relid)
{
	ListCell   *l;

	foreach(l, on_commits)
	{
		OnCommitItem *oc = (OnCommitItem *) lfirst(l);

		if (oc->relid == relid)
		{
			oc->deleting_subid = GetCurrentSubTransactionId();
			break;
		}
	}
}

/*
 * Perform ON COMMIT actions.
 *
 * This is invoked just before actually committing, since it's possible
 * to encounter errors.
 */
void
PreCommit_on_commit_actions(void)
{
	ListCell   *l;
	List	   *oids_to_truncate = NIL;
	List	   *oids_to_drop = NIL;

	foreach(l, on_commits)
	{
		OnCommitItem *oc = (OnCommitItem *) lfirst(l);

		/* Ignore entry if already dropped in this xact */
		if (oc->deleting_subid != InvalidSubTransactionId)
			continue;

		switch (oc->oncommit)
		{
			case ONCOMMIT_NOOP:
			case ONCOMMIT_PRESERVE_ROWS:
				/* Do nothing (there shouldn't be such entries, actually) */
				break;
			case ONCOMMIT_DELETE_ROWS:

				/*
				 * If this transaction hasn't accessed any temporary
				 * relations, we can skip truncating ON COMMIT DELETE ROWS
				 * tables, as they must still be empty.
				 */
				if ((MyXactFlags & XACT_FLAGS_ACCESSEDTEMPNAMESPACE))
					oids_to_truncate = lappend_oid(oids_to_truncate, oc->relid);
				break;
			case ONCOMMIT_DROP:
				oids_to_drop = lappend_oid(oids_to_drop, oc->relid);
				break;
		}
	}

	/*
	 * Truncate relations before dropping so that all dependencies between
	 * relations are removed after they are worked on.  Doing it like this
	 * might be a waste as it is possible that a relation being truncated will
	 * be dropped anyway due to its parent being dropped, but this makes the
	 * code more robust because of not having to re-check that the relation
	 * exists at truncation time.
	 */
	if (oids_to_truncate != NIL)
		heap_truncate(oids_to_truncate);

	if (oids_to_drop != NIL)
	{
		ObjectAddresses *targetObjects = new_object_addresses();

		foreach(l, oids_to_drop)
		{
			ObjectAddress object;

			object.classId = RelationRelationId;
			object.objectId = lfirst_oid(l);
			object.objectSubId = 0;

			Assert(!object_address_present(&object, targetObjects));

			add_exact_object_address(&object, targetObjects);
		}

		/*
		 * Object deletion might involve toast table access (to clean up
		 * toasted catalog entries), so ensure we have a valid snapshot.
		 */
		PushActiveSnapshot(GetTransactionSnapshot());

		/*
		 * Since this is an automatic drop, rather than one directly initiated
		 * by the user, we pass the PERFORM_DELETION_INTERNAL flag.
		 */
		performMultipleDeletions(targetObjects, DROP_CASCADE,
								 PERFORM_DELETION_INTERNAL | PERFORM_DELETION_QUIETLY);

		PopActiveSnapshot();

#ifdef USE_ASSERT_CHECKING

		/*
		 * Note that table deletion will call remove_on_commit_action, so the
		 * entry should get marked as deleted.
		 */
		foreach(l, on_commits)
		{
			OnCommitItem *oc = (OnCommitItem *) lfirst(l);

			if (oc->oncommit != ONCOMMIT_DROP)
				continue;

			Assert(oc->deleting_subid != InvalidSubTransactionId);
		}
#endif
	}
}

/*
 * Post-commit or post-abort cleanup for ON COMMIT management.
 *
 * All we do here is remove no-longer-needed OnCommitItem entries.
 *
 * During commit, remove entries that were deleted during this transaction;
 * during abort, remove those created during this transaction.
 */
void
AtEOXact_on_commit_actions(bool isCommit)
{
	ListCell   *cur_item;

	foreach(cur_item, on_commits)
	{
		OnCommitItem *oc = (OnCommitItem *) lfirst(cur_item);

		if (isCommit ? oc->deleting_subid != InvalidSubTransactionId :
			oc->creating_subid != InvalidSubTransactionId)
		{
			/* cur_item must be removed */
			on_commits = foreach_delete_current(on_commits, cur_item);
			pfree(oc);
		}
		else
		{
			/* cur_item must be preserved */
			oc->creating_subid = InvalidSubTransactionId;
			oc->deleting_subid = InvalidSubTransactionId;
		}
	}
}

/*
 * Post-subcommit or post-subabort cleanup for ON COMMIT management.
 *
 * During subabort, we can immediately remove entries created during this
 * subtransaction.  During subcommit, just relabel entries marked during
 * this subtransaction as being the parent's responsibility.
 */
void
AtEOSubXact_on_commit_actions(bool isCommit, SubTransactionId mySubid,
							  SubTransactionId parentSubid)
{
	ListCell   *cur_item;

	foreach(cur_item, on_commits)
	{
		OnCommitItem *oc = (OnCommitItem *) lfirst(cur_item);

		if (!isCommit && oc->creating_subid == mySubid)
		{
			/* cur_item must be removed */
			on_commits = foreach_delete_current(on_commits, cur_item);
			pfree(oc);
		}
		else
		{
			/* cur_item must be preserved */
			if (oc->creating_subid == mySubid)
				oc->creating_subid = parentSubid;
			if (oc->deleting_subid == mySubid)
				oc->deleting_subid = isCommit ? parentSubid : InvalidSubTransactionId;
		}
	}
}

/*
 * This is intended as a callback for RangeVarGetRelidExtended().  It allows
 * the relation to be locked only if (1) it's a plain or partitioned table,
 * materialized view, or TOAST table and (2) the current user is the owner (or
 * the superuser) or has been granted MAINTAIN.  This meets the
 * permission-checking needs of CLUSTER, REINDEX TABLE, and REFRESH
 * MATERIALIZED VIEW; we expose it here so that it can be used by all.
 */
void
RangeVarCallbackMaintainsTable(const RangeVar *relation,
							   Oid relId, Oid oldRelId, void *arg)
{
	char		relkind;
	AclResult	aclresult;

	/* Nothing to do if the relation was not found. */
	if (!OidIsValid(relId))
		return;

	/*
	 * If the relation does exist, check whether it's an index.  But note that
	 * the relation might have been dropped between the time we did the name
	 * lookup and now.  In that case, there's nothing to do.
	 */
	relkind = get_rel_relkind(relId);
	if (!relkind)
		return;
	if (relkind != RELKIND_RELATION && relkind != RELKIND_TOASTVALUE &&
		relkind != RELKIND_MATVIEW && relkind != RELKIND_PARTITIONED_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a table or materialized view", relation->relname)));

	/* Check permissions */
	aclresult = pg_class_aclcheck(relId, GetUserId(), ACL_MAINTAIN);
	if (aclresult != ACLCHECK_OK)
		aclcheck_error(aclresult,
					   get_relkind_objtype(get_rel_relkind(relId)),
					   relation->relname);
}

/*
 * Callback to RangeVarGetRelidExtended() for TRUNCATE processing.
 */
static void
RangeVarCallbackForTruncate(const RangeVar *relation,
							Oid relId, Oid oldRelId, void *arg)
{
	HeapTuple	tuple;

	/* Nothing to do if the relation was not found. */
	if (!OidIsValid(relId))
		return;

	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relId));
	if (!HeapTupleIsValid(tuple))	/* should not happen */
		elog(ERROR, "cache lookup failed for relation %u", relId);

	truncate_check_rel(relId, (Form_pg_class) GETSTRUCT(tuple));
	truncate_check_perms(relId, (Form_pg_class) GETSTRUCT(tuple));

	ReleaseSysCache(tuple);
}

/*
 * Callback for RangeVarGetRelidExtended().  Checks that the current user is
 * the owner of the relation, or superuser.
 */
void
RangeVarCallbackOwnsRelation(const RangeVar *relation,
							 Oid relId, Oid oldRelId, void *arg)
{
	HeapTuple	tuple;

	/* Nothing to do if the relation was not found. */
	if (!OidIsValid(relId))
		return;

	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relId));
	if (!HeapTupleIsValid(tuple))	/* should not happen */
		elog(ERROR, "cache lookup failed for relation %u", relId);

	if (!object_ownercheck(RelationRelationId, relId, GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relId)),
					   relation->relname);

	if (!allowSystemTableMods &&
		IsSystemClass(relId, (Form_pg_class) GETSTRUCT(tuple)))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						relation->relname)));

	ReleaseSysCache(tuple);
}

/*
 * Common RangeVarGetRelid callback for rename, set schema, and alter table
 * processing.
 */
static void
RangeVarCallbackForAlterRelation(const RangeVar *rv, Oid relid, Oid oldrelid,
								 void *arg)
{
	Node	   *stmt = (Node *) arg;
	ObjectType	reltype;
	HeapTuple	tuple;
	Form_pg_class classform;
	AclResult	aclresult;
	char		relkind;

	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
	if (!HeapTupleIsValid(tuple))
		return;					/* concurrently dropped */
	classform = (Form_pg_class) GETSTRUCT(tuple);
	relkind = classform->relkind;

	/* Must own relation. */
	if (!object_ownercheck(RelationRelationId, relid, GetUserId()))
		aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(get_rel_relkind(relid)), rv->relname);

	/* No system table modifications unless explicitly allowed. */
	if (!allowSystemTableMods && IsSystemClass(relid, classform))
		ereport(ERROR,
				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
				 errmsg("permission denied: \"%s\" is a system catalog",
						rv->relname)));

	/*
	 * Extract the specified relation type from the statement parse tree.
	 *
	 * Also, for ALTER .. RENAME, check permissions: the user must (still)
	 * have CREATE rights on the containing namespace.
	 */
	if (IsA(stmt, RenameStmt))
	{
		aclresult = object_aclcheck(NamespaceRelationId, classform->relnamespace,
									GetUserId(), ACL_CREATE);
		if (aclresult != ACLCHECK_OK)
			aclcheck_error(aclresult, OBJECT_SCHEMA,
						   get_namespace_name(classform->relnamespace));
		reltype = ((RenameStmt *) stmt)->renameType;
	}
	else if (IsA(stmt, AlterObjectSchemaStmt))
		reltype = ((AlterObjectSchemaStmt *) stmt)->objectType;

	else if (IsA(stmt, AlterTableStmt))
		reltype = ((AlterTableStmt *) stmt)->objtype;
	else
	{
		elog(ERROR, "unrecognized node type: %d", (int) nodeTag(stmt));
		reltype = OBJECT_TABLE; /* placate compiler */
	}

	/*
	 * For compatibility with prior releases, we allow ALTER TABLE to be used
	 * with most other types of relations (but not composite types). We allow
	 * similar flexibility for ALTER INDEX in the case of RENAME, but not
	 * otherwise.  Otherwise, the user must select the correct form of the
	 * command for the relation at issue.
	 */
	if (reltype == OBJECT_SEQUENCE && relkind != RELKIND_SEQUENCE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a sequence", rv->relname)));

	if (reltype == OBJECT_VIEW && relkind != RELKIND_VIEW)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a view", rv->relname)));

	if (reltype == OBJECT_MATVIEW && relkind != RELKIND_MATVIEW)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a materialized view", rv->relname)));

	if (reltype == OBJECT_FOREIGN_TABLE && relkind != RELKIND_FOREIGN_TABLE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a foreign table", rv->relname)));

	if (reltype == OBJECT_TYPE && relkind != RELKIND_COMPOSITE_TYPE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not a composite type", rv->relname)));

	if (reltype == OBJECT_INDEX && relkind != RELKIND_INDEX &&
		relkind != RELKIND_PARTITIONED_INDEX
		&& !IsA(stmt, RenameStmt))
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is not an index", rv->relname)));

	/*
	 * Don't allow ALTER TABLE on composite types. We want people to use ALTER
	 * TYPE for that.
	 */
	if (reltype != OBJECT_TYPE && relkind == RELKIND_COMPOSITE_TYPE)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is a composite type", rv->relname),
		/* translator: %s is an SQL ALTER command */
				 errhint("Use %s instead.",
						 "ALTER TYPE")));

	/*
	 * Don't allow ALTER TABLE .. SET SCHEMA on relations that can't be moved
	 * to a different schema, such as indexes and TOAST tables.
	 */
	if (IsA(stmt, AlterObjectSchemaStmt))
	{
		if (relkind == RELKIND_INDEX || relkind == RELKIND_PARTITIONED_INDEX)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot change schema of index \"%s\"",
							rv->relname),
					 errhint("Change the schema of the table instead.")));
		else if (relkind == RELKIND_COMPOSITE_TYPE)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot change schema of composite type \"%s\"",
							rv->relname),
			/* translator: %s is an SQL ALTER command */
					 errhint("Use %s instead.",
							 "ALTER TYPE")));
		else if (relkind == RELKIND_TOASTVALUE)
			ereport(ERROR,
					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
					 errmsg("cannot change schema of TOAST table \"%s\"",
							rv->relname),
					 errhint("Change the schema of the table instead.")));
	}

	ReleaseSysCache(tuple);
}

/*
 * Transform any expressions present in the partition key
 *
 * Returns a transformed PartitionSpec.
 */
static PartitionSpec *
transformPartitionSpec(Relation rel, PartitionSpec *partspec)
{
	PartitionSpec *newspec;
	ParseState *pstate;
	ParseNamespaceItem *nsitem;
	ListCell   *l;

	newspec = makeNode(PartitionSpec);

	newspec->strategy = partspec->strategy;
	newspec->partParams = NIL;
	newspec->location = partspec->location;

	/* Check valid number of columns for strategy */
	if (partspec->strategy == PARTITION_STRATEGY_LIST &&
		list_length(partspec->partParams) != 1)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
				 errmsg("cannot use \"list\" partition strategy with more than one column")));

	/*
	 * Create a dummy ParseState and insert the target relation as its sole
	 * rangetable entry.  We need a ParseState for transformExpr.
	 */
	pstate = make_parsestate(NULL);
	nsitem = addRangeTableEntryForRelation(pstate, rel, AccessShareLock,
										   NULL, false, true);
	addNSItemToQuery(pstate, nsitem, true, true, true);

	/* take care of any partition expressions */
	foreach(l, partspec->partParams)
	{
		PartitionElem *pelem = lfirst_node(PartitionElem, l);

		if (pelem->expr)
		{
			/* Copy, to avoid scribbling on the input */
			pelem = copyObject(pelem);

			/* Now do parse transformation of the expression */
			pelem->expr = transformExpr(pstate, pelem->expr,
										EXPR_KIND_PARTITION_EXPRESSION);

			/* we have to fix its collations too */
			assign_expr_collations(pstate, pelem->expr);
		}

		newspec->partParams = lappend(newspec->partParams, pelem);
	}

	return newspec;
}

/*
 * Compute per-partition-column information from a list of PartitionElems.
 * Expressions in the PartitionElems must be parse-analyzed already.
 */
static void
ComputePartitionAttrs(ParseState *pstate, Relation rel, List *partParams, AttrNumber *partattrs,
					  List **partexprs, Oid *partopclass, Oid *partcollation,
					  PartitionStrategy strategy)
{
	int			attn;
	ListCell   *lc;
	Oid			am_oid;

	attn = 0;
	foreach(lc, partParams)
	{
		PartitionElem *pelem = lfirst_node(PartitionElem, lc);
		Oid			atttype;
		Oid			attcollation;

		if (pelem->name != NULL)
		{
			/* Simple attribute reference */
			HeapTuple	atttuple;
			Form_pg_attribute attform;

			atttuple = SearchSysCacheAttName(RelationGetRelid(rel),
											 pelem->name);
			if (!HeapTupleIsValid(atttuple))
				ereport(ERROR,
						(errcode(ERRCODE_UNDEFINED_COLUMN),
						 errmsg("column \"%s\" named in partition key does not exist",
								pelem->name),
						 parser_errposition(pstate, pelem->location)));
			attform = (Form_pg_attribute) GETSTRUCT(atttuple);

			if (attform->attnum <= 0)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("cannot use system column \"%s\" in partition key",
								pelem->name),
						 parser_errposition(pstate, pelem->location)));

			/*
			 * Stored generated columns cannot work: They are computed after
			 * BEFORE triggers, but partition routing is done before all
			 * triggers.  Maybe virtual generated columns could be made to
			 * work, but then they would need to be handled as an expression
			 * below.
			 */
			if (attform->attgenerated)
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("cannot use generated column in partition key"),
						 errdetail("Column \"%s\" is a generated column.",
								   pelem->name),
						 parser_errposition(pstate, pelem->location)));

			partattrs[attn] = attform->attnum;
			atttype = attform->atttypid;
			attcollation = attform->attcollation;
			ReleaseSysCache(atttuple);
		}
		else
		{
			/* Expression */
			Node	   *expr = pelem->expr;
			char		partattname[16];
			Bitmapset  *expr_attrs = NULL;
			int			i;

			Assert(expr != NULL);
			atttype = exprType(expr);
			attcollation = exprCollation(expr);

			/*
			 * The expression must be of a storable type (e.g., not RECORD).
			 * The test is the same as for whether a table column is of a safe
			 * type (which is why we needn't check for the non-expression
			 * case).
			 */
			snprintf(partattname, sizeof(partattname), "%d", attn + 1);
			CheckAttributeType(partattname,
							   atttype, attcollation,
							   NIL, CHKATYPE_IS_PARTKEY);

			/*
			 * Strip any top-level COLLATE clause.  This ensures that we treat
			 * "x COLLATE y" and "(x COLLATE y)" alike.
			 */
			while (IsA(expr, CollateExpr))
				expr = (Node *) ((CollateExpr *) expr)->arg;

			/*
			 * Examine all the columns in the partition key expression. When
			 * the whole-row reference is present, examine all the columns of
			 * the partitioned table.
			 */
			pull_varattnos(expr, 1, &expr_attrs);
			if (bms_is_member(0 - FirstLowInvalidHeapAttributeNumber, expr_attrs))
			{
				expr_attrs = bms_add_range(expr_attrs,
										   1 - FirstLowInvalidHeapAttributeNumber,
										   RelationGetNumberOfAttributes(rel) - FirstLowInvalidHeapAttributeNumber);
				expr_attrs = bms_del_member(expr_attrs, 0 - FirstLowInvalidHeapAttributeNumber);
			}

			i = -1;
			while ((i = bms_next_member(expr_attrs, i)) >= 0)
			{
				AttrNumber	attno = i + FirstLowInvalidHeapAttributeNumber;

				Assert(attno != 0);

				/*
				 * Cannot allow system column references, since that would
				 * make partition routing impossible: their values won't be
				 * known yet when we need to do that.
				 */
				if (attno < 0)
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
							 errmsg("partition key expressions cannot contain system column references")));

				/*
				 * Stored generated columns cannot work: They are computed
				 * after BEFORE triggers, but partition routing is done before
				 * all triggers.  Virtual generated columns could probably
				 * work, but it would require more work elsewhere (for example
				 * SET EXPRESSION would need to check whether the column is
				 * used in partition keys).  Seems safer to prohibit for now.
				 */
				if (TupleDescAttr(RelationGetDescr(rel), attno - 1)->attgenerated)
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
							 errmsg("cannot use generated column in partition key"),
							 errdetail("Column \"%s\" is a generated column.",
									   get_attname(RelationGetRelid(rel), attno, false)),
							 parser_errposition(pstate, pelem->location)));
			}

			if (IsA(expr, Var) &&
				((Var *) expr)->varattno > 0)
			{

				/*
				 * User wrote "(column)" or "(column COLLATE something)".
				 * Treat it like simple attribute anyway.
				 */
				partattrs[attn] = ((Var *) expr)->varattno;
			}
			else
			{
				partattrs[attn] = 0;	/* marks the column as expression */
				*partexprs = lappend(*partexprs, expr);

				/*
				 * transformPartitionSpec() should have already rejected
				 * subqueries, aggregates, window functions, and SRFs, based
				 * on the EXPR_KIND_ for partition expressions.
				 */

				/*
				 * Preprocess the expression before checking for mutability.
				 * This is essential for the reasons described in
				 * contain_mutable_functions_after_planning.  However, we call
				 * expression_planner for ourselves rather than using that
				 * function, because if constant-folding reduces the
				 * expression to a constant, we'd like to know that so we can
				 * complain below.
				 *
				 * Like contain_mutable_functions_after_planning, assume that
				 * expression_planner won't scribble on its input, so this
				 * won't affect the partexprs entry we saved above.
				 */
				expr = (Node *) expression_planner((Expr *) expr);

				/*
				 * Partition expressions cannot contain mutable functions,
				 * because a given row must always map to the same partition
				 * as long as there is no change in the partition boundary
				 * structure.
				 */
				if (contain_mutable_functions(expr))
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
							 errmsg("functions in partition key expression must be marked IMMUTABLE")));

				/*
				 * While it is not exactly *wrong* for a partition expression
				 * to be a constant, it seems better to reject such keys.
				 */
				if (IsA(expr, Const))
					ereport(ERROR,
							(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
							 errmsg("cannot use constant expression as partition key")));
			}
		}

		/*
		 * Apply collation override if any
		 */
		if (pelem->collation)
			attcollation = get_collation_oid(pelem->collation, false);

		/*
		 * Check we have a collation iff it's a collatable type.  The only
		 * expected failures here are (1) COLLATE applied to a noncollatable
		 * type, or (2) partition expression had an unresolved collation. But
		 * we might as well code this to be a complete consistency check.
		 */
		if (type_is_collatable(atttype))
		{
			if (!OidIsValid(attcollation))
				ereport(ERROR,
						(errcode(ERRCODE_INDETERMINATE_COLLATION),
						 errmsg("could not determine which collation to use for partition expression"),
						 errhint("Use the COLLATE clause to set the collation explicitly.")));
		}
		else
		{
			if (OidIsValid(attcollation))
				ereport(ERROR,
						(errcode(ERRCODE_DATATYPE_MISMATCH),
						 errmsg("collations are not supported by type %s",
								format_type_be(atttype))));
		}

		partcollation[attn] = attcollation;

		/*
		 * Identify the appropriate operator class.  For list and range
		 * partitioning, we use a btree operator class; hash partitioning uses
		 * a hash operator class.
		 */
		if (strategy == PARTITION_STRATEGY_HASH)
			am_oid = HASH_AM_OID;
		else
			am_oid = BTREE_AM_OID;

		if (!pelem->opclass)
		{
			partopclass[attn] = GetDefaultOpClass(atttype, am_oid);

			if (!OidIsValid(partopclass[attn]))
			{
				if (strategy == PARTITION_STRATEGY_HASH)
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_OBJECT),
							 errmsg("data type %s has no default operator class for access method \"%s\"",
									format_type_be(atttype), "hash"),
							 errhint("You must specify a hash operator class or define a default hash operator class for the data type.")));
				else
					ereport(ERROR,
							(errcode(ERRCODE_UNDEFINED_OBJECT),
							 errmsg("data type %s has no default operator class for access method \"%s\"",
									format_type_be(atttype), "btree"),
							 errhint("You must specify a btree operator class or define a default btree operator class for the data type.")));
			}
		}
		else
			partopclass[attn] = ResolveOpClass(pelem->opclass,
											   atttype,
											   am_oid == HASH_AM_OID ? "hash" : "btree",
											   am_oid);

		attn++;
	}
}

/*
 * PartConstraintImpliedByRelConstraint
 *		Do scanrel's existing constraints imply the partition constraint?
 *
 * "Existing constraints" include its check constraints and column-level
 * not-null constraints.  partConstraint describes the partition constraint,
 * in implicit-AND form.
 */
bool
PartConstraintImpliedByRelConstraint(Relation scanrel,
									 List *partConstraint)
{
	List	   *existConstraint = NIL;
	TupleConstr *constr = RelationGetDescr(scanrel)->constr;
	int			i;

	if (constr && constr->has_not_null)
	{
		int			natts = scanrel->rd_att->natts;

		for (i = 1; i <= natts; i++)
		{
			CompactAttribute *att = TupleDescCompactAttr(scanrel->rd_att, i - 1);

			/* invalid not-null constraint must be ignored here */
			if (att->attnullability == ATTNULLABLE_VALID && !att->attisdropped)
			{
				Form_pg_attribute wholeatt = TupleDescAttr(scanrel->rd_att, i - 1);
				NullTest   *ntest = makeNode(NullTest);

				ntest->arg = (Expr *) makeVar(1,
											  i,
											  wholeatt->atttypid,
											  wholeatt->atttypmod,
											  wholeatt->attcollation,
											  0);
				ntest->nulltesttype = IS_NOT_NULL;

				/*
				 * argisrow=false is correct even for a composite column,
				 * because attnotnull does not represent a SQL-spec IS NOT
				 * NULL test in such a case, just IS DISTINCT FROM NULL.
				 */
				ntest->argisrow = false;
				ntest->location = -1;
				existConstraint = lappend(existConstraint, ntest);
			}
		}
	}

	return ConstraintImpliedByRelConstraint(scanrel, partConstraint, existConstraint);
}

/*
 * ConstraintImpliedByRelConstraint
 *		Do scanrel's existing constraints imply the given constraint?
 *
 * testConstraint is the constraint to validate. provenConstraint is a
 * caller-provided list of conditions which this function may assume
 * to be true. Both provenConstraint and testConstraint must be in
 * implicit-AND form, must only contain immutable clauses, and must
 * contain only Vars with varno = 1.
 */
bool
ConstraintImpliedByRelConstraint(Relation scanrel, List *testConstraint, List *provenConstraint)
{
	List	   *existConstraint = list_copy(provenConstraint);
	TupleConstr *constr = RelationGetDescr(scanrel)->constr;
	int			num_check,
				i;

	num_check = (constr != NULL) ? constr->num_check : 0;
	for (i = 0; i < num_check; i++)
	{
		Node	   *cexpr;

		/*
		 * If this constraint hasn't been fully validated yet, we must ignore
		 * it here.
		 */
		if (!constr->check[i].ccvalid)
			continue;

		/*
		 * NOT ENFORCED constraints are always marked as invalid, which should
		 * have been ignored.
		 */
		Assert(constr->check[i].ccenforced);

		cexpr = stringToNode(constr->check[i].ccbin);

		/*
		 * Run each expression through const-simplification and
		 * canonicalization.  It is necessary, because we will be comparing it
		 * to similarly-processed partition constraint expressions, and may
		 * fail to detect valid matches without this.
		 */
		cexpr = eval_const_expressions(NULL, cexpr);
		cexpr = (Node *) canonicalize_qual((Expr *) cexpr, true);

		existConstraint = list_concat(existConstraint,
									  make_ands_implicit((Expr *) cexpr));
	}

	/*
	 * Try to make the proof.  Since we are comparing CHECK constraints, we
	 * need to use weak implication, i.e., we assume existConstraint is
	 * not-false and try to prove the same for testConstraint.
	 *
	 * Note that predicate_implied_by assumes its first argument is known
	 * immutable.  That should always be true for both NOT NULL and partition
	 * constraints, so we don't test it here.
	 */
	return predicate_implied_by(testConstraint, existConstraint, true);
}

/*
 * QueuePartitionConstraintValidation
 *
 * Add an entry to wqueue to have the given partition constraint validated by
 * Phase 3, for the given relation, and all its children.
 *
 * We first verify whether the given constraint is implied by pre-existing
 * relation constraints; if it is, there's no need to scan the table to
 * validate, so don't queue in that case.
 */
static void
QueuePartitionConstraintValidation(List **wqueue, Relation scanrel,
								   List *partConstraint,
								   bool validate_default)
{
	/*
	 * Based on the table's existing constraints, determine whether or not we
	 * may skip scanning the table.
	 */
	if (PartConstraintImpliedByRelConstraint(scanrel, partConstraint))
	{
		if (!validate_default)
			ereport(DEBUG1,
					(errmsg_internal("partition constraint for table \"%s\" is implied by existing constraints",
									 RelationGetRelationName(scanrel))));
		else
			ereport(DEBUG1,
					(errmsg_internal("updated partition constraint for default partition \"%s\" is implied by existing constraints",
									 RelationGetRelationName(scanrel))));
		return;
	}

	/*
	 * Constraints proved insufficient. For plain relations, queue a
	 * validation item now; for partitioned tables, recurse to process each
	 * partition.
	 */
	if (scanrel->rd_rel->relkind == RELKIND_RELATION)
	{
		AlteredTableInfo *tab;

		/* Grab a work queue entry. */
		tab = ATGetQueueEntry(wqueue, scanrel);
		Assert(tab->partition_constraint == NULL);
		tab->partition_constraint = (Expr *) linitial(partConstraint);
		tab->validate_default = validate_default;
	}
	else if (scanrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
	{
		PartitionDesc partdesc = RelationGetPartitionDesc(scanrel, true);
		int			i;

		for (i = 0; i < partdesc->nparts; i++)
		{
			Relation	part_rel;
			List	   *thisPartConstraint;

			/*
			 * This is the minimum lock we need to prevent deadlocks.
			 */
			part_rel = table_open(partdesc->oids[i], AccessExclusiveLock);

			/*
			 * Adjust the constraint for scanrel so that it matches this
			 * partition's attribute numbers.
			 */
			thisPartConstraint =
				map_partition_varattnos(partConstraint, 1,
										part_rel, scanrel);

			QueuePartitionConstraintValidation(wqueue, part_rel,
											   thisPartConstraint,
											   validate_default);
			table_close(part_rel, NoLock);	/* keep lock till commit */
		}
	}
}

/*
 * ALTER TABLE <name> ATTACH PARTITION <partition-name> FOR VALUES
 *
 * Return the address of the newly attached partition.
 */
static ObjectAddress
ATExecAttachPartition(List **wqueue, Relation rel, PartitionCmd *cmd,
					  AlterTableUtilityContext *context)
{
	Relation	attachrel,
				catalog;
	List	   *attachrel_children;
	List	   *partConstraint;
	SysScanDesc scan;
	ScanKeyData skey;
	AttrNumber	attno;
	int			natts;
	TupleDesc	tupleDesc;
	ObjectAddress address;
	const char *trigger_name;
	Oid			defaultPartOid;
	List	   *partBoundConstraint;
	ParseState *pstate = make_parsestate(NULL);

	pstate->p_sourcetext = context->queryString;

	/*
	 * We must lock the default partition if one exists, because attaching a
	 * new partition will change its partition constraint.
	 */
	defaultPartOid =
		get_default_oid_from_partdesc(RelationGetPartitionDesc(rel, true));
	if (OidIsValid(defaultPartOid))
		LockRelationOid(defaultPartOid, AccessExclusiveLock);

	attachrel = table_openrv(cmd->name, AccessExclusiveLock);

	/*
	 * XXX I think it'd be a good idea to grab locks on all tables referenced
	 * by FKs at this point also.
	 */

	/*
	 * Must be owner of both parent and source table -- parent was checked by
	 * ATSimplePermissions call in ATPrepCmd
	 */
	ATSimplePermissions(AT_AttachPartition, attachrel,
						ATT_TABLE | ATT_PARTITIONED_TABLE | ATT_FOREIGN_TABLE);

	/* A partition can only have one parent */
	if (attachrel->rd_rel->relispartition)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("\"%s\" is already a partition",
						RelationGetRelationName(attachrel))));

	if (OidIsValid(attachrel->rd_rel->reloftype))
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot attach a typed table as partition")));

	/*
	 * Table being attached should not already be part of inheritance; either
	 * as a child table...
	 */
	catalog = table_open(InheritsRelationId, AccessShareLock);
	ScanKeyInit(&skey,
				Anum_pg_inherits_inhrelid,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(attachrel)));
	scan = systable_beginscan(catalog, InheritsRelidSeqnoIndexId, true,
							  NULL, 1, &skey);
	if (HeapTupleIsValid(systable_getnext(scan)))
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot attach inheritance child as partition")));
	systable_endscan(scan);

	/* ...or as a parent table (except the case when it is partitioned) */
	ScanKeyInit(&skey,
				Anum_pg_inherits_inhparent,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(attachrel)));
	scan = systable_beginscan(catalog, InheritsParentIndexId, true, NULL,
							  1, &skey);
	if (HeapTupleIsValid(systable_getnext(scan)) &&
		attachrel->rd_rel->relkind == RELKIND_RELATION)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot attach inheritance parent as partition")));
	systable_endscan(scan);
	table_close(catalog, AccessShareLock);

	/*
	 * Prevent circularity by seeing if rel is a partition of attachrel. (In
	 * particular, this disallows making a rel a partition of itself.)
	 *
	 * We do that by checking if rel is a member of the list of attachrel's
	 * partitions provided the latter is partitioned at all.  We want to avoid
	 * having to construct this list again, so we request the strongest lock
	 * on all partitions.  We need the strongest lock, because we may decide
	 * to scan them if we find out that the table being attached (or its leaf
	 * partitions) may contain rows that violate the partition constraint. If
	 * the table has a constraint that would prevent such rows, which by
	 * definition is present in all the partitions, we need not scan the
	 * table, nor its partitions.  But we cannot risk a deadlock by taking a
	 * weaker lock now and the stronger one only when needed.
	 */
	attachrel_children = find_all_inheritors(RelationGetRelid(attachrel),
											 AccessExclusiveLock, NULL);
	if (list_member_oid(attachrel_children, RelationGetRelid(rel)))
		ereport(ERROR,
				(errcode(ERRCODE_DUPLICATE_TABLE),
				 errmsg("circular inheritance not allowed"),
				 errdetail("\"%s\" is already a child of \"%s\".",
						   RelationGetRelationName(rel),
						   RelationGetRelationName(attachrel))));

	/* If the parent is permanent, so must be all of its partitions. */
	if (rel->rd_rel->relpersistence != RELPERSISTENCE_TEMP &&
		attachrel->rd_rel->relpersistence == RELPERSISTENCE_TEMP)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot attach a temporary relation as partition of permanent relation \"%s\"",
						RelationGetRelationName(rel))));

	/* Temp parent cannot have a partition that is itself not a temp */
	if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
		attachrel->rd_rel->relpersistence != RELPERSISTENCE_TEMP)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot attach a permanent relation as partition of temporary relation \"%s\"",
						RelationGetRelationName(rel))));

	/* If the parent is temp, it must belong to this session */
	if (rel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
		!rel->rd_islocaltemp)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot attach as partition of temporary relation of another session")));

	/* Ditto for the partition */
	if (attachrel->rd_rel->relpersistence == RELPERSISTENCE_TEMP &&
		!attachrel->rd_islocaltemp)
		ereport(ERROR,
				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
				 errmsg("cannot attach temporary relation of another session as partition")));

	/*
	 * Check if attachrel has any identity columns or any columns that aren't
	 * in the parent.
	 */
	tupleDesc = RelationGetDescr(attachrel);
	natts = tupleDesc->natts;
	for (attno = 1; attno <= natts; attno++)
	{
		Form_pg_attribute attribute = TupleDescAttr(tupleDesc, attno - 1);
		char	   *attributeName = NameStr(attribute->attname);

		/* Ignore dropped */
		if (attribute->attisdropped)
			continue;

		if (attribute->attidentity)
			ereport(ERROR,
					errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					errmsg("table \"%s\" being attached contains an identity column \"%s\"",
						   RelationGetRelationName(attachrel), attributeName),
					errdetail("The new partition may not contain an identity column."));

		/* Try to find the column in parent (matching on column name) */
		if (!SearchSysCacheExists2(ATTNAME,
								   ObjectIdGetDatum(RelationGetRelid(rel)),
								   CStringGetDatum(attributeName)))
			ereport(ERROR,
					(errcode(ERRCODE_DATATYPE_MISMATCH),
					 errmsg("table \"%s\" contains column \"%s\" not found in parent \"%s\"",
							RelationGetRelationName(attachrel), attributeName,
							RelationGetRelationName(rel)),
					 errdetail("The new partition may contain only the columns present in parent.")));
	}

	/*
	 * If child_rel has row-level triggers with transition tables, we
	 * currently don't allow it to become a partition.  See also prohibitions
	 * in ATExecAddInherit() and CreateTrigger().
	 */
	trigger_name = FindTriggerIncompatibleWithInheritance(attachrel->trigdesc);
	if (trigger_name != NULL)
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("trigger \"%s\" prevents table \"%s\" from becoming a partition",
						trigger_name, RelationGetRelationName(attachrel)),
				 errdetail("ROW triggers with transition tables are not supported on partitions.")));

	/*
	 * Check that the new partition's bound is valid and does not overlap any
	 * of existing partitions of the parent - note that it does not return on
	 * error.
	 */
	check_new_partition_bound(RelationGetRelationName(attachrel), rel,
							  cmd->bound, pstate);

	/* OK to create inheritance.  Rest of the checks performed there */
	CreateInheritance(attachrel, rel, true);

	/* Update the pg_class entry. */
	StorePartitionBound(attachrel, rel, cmd->bound);

	/* Ensure there exists a correct set of indexes in the partition. */
	AttachPartitionEnsureIndexes(wqueue, rel, attachrel);

	/* and triggers */
	CloneRowTriggersToPartition(rel, attachrel);

	/*
	 * Clone foreign key constraints.  Callee is responsible for setting up
	 * for phase 3 constraint verification.
	 */
	CloneForeignKeyConstraints(wqueue, rel, attachrel);

	/*
	 * Generate partition constraint from the partition bound specification.
	 * If the parent itself is a partition, make sure to include its
	 * constraint as well.
	 */
	partBoundConstraint = get_qual_from_partbound(rel, cmd->bound);

	/*
	 * Use list_concat_copy() to avoid modifying partBoundConstraint in place,
	 * since it's needed later to construct the constraint expression for
	 * validating against the default partition, if any.
	 */
	partConstraint = list_concat_copy(partBoundConstraint,
									  RelationGetPartitionQual(rel));

	/* Skip validation if there are no constraints to validate. */
	if (partConstraint)
	{
		/*
		 * Run the partition quals through const-simplification similar to
		 * check constraints.  We skip canonicalize_qual, though, because
		 * partition quals should be in canonical form already.
		 */
		partConstraint =
			(List *) eval_const_expressions(NULL,
											(Node *) partConstraint);

		/* XXX this sure looks wrong */
		partConstraint = list_make1(make_ands_explicit(partConstraint));

		/*
		 * Adjust the generated constraint to match this partition's attribute
		 * numbers.
		 */
		partConstraint = map_partition_varattnos(partConstraint, 1, attachrel,
												 rel);

		/* Validate partition constraints against the table being attached. */
		QueuePartitionConstraintValidation(wqueue, attachrel, partConstraint,
										   false);
	}

	/*
	 * If we're attaching a partition other than the default partition and a
	 * default one exists, then that partition's partition constraint changes,
	 * so add an entry to the work queue to validate it, too.  (We must not do
	 * this when the partition being attached is the default one; we already
	 * did it above!)
	 */
	if (OidIsValid(defaultPartOid))
	{
		Relation	defaultrel;
		List	   *defPartConstraint;

		Assert(!cmd->bound->is_default);

		/* we already hold a lock on the default partition */
		defaultrel = table_open(defaultPartOid, NoLock);
		defPartConstraint =
			get_proposed_default_constraint(partBoundConstraint);

		/*
		 * Map the Vars in the constraint expression from rel's attnos to
		 * defaultrel's.
		 */
		defPartConstraint =
			map_partition_varattnos(defPartConstraint,
									1, defaultrel, rel);
		QueuePartitionConstraintValidation(wqueue, defaultrel,
										   defPartConstraint, true);

		/* keep our lock until commit. */
		table_close(defaultrel, NoLock);
	}

	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(attachrel));

	/*
	 * If the partition we just attached is partitioned itself, invalidate
	 * relcache for all descendent partitions too to ensure that their
	 * rd_partcheck expression trees are rebuilt; partitions already locked at
	 * the beginning of this function.
	 */
	if (attachrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
	{
		ListCell   *l;

		foreach(l, attachrel_children)
		{
			CacheInvalidateRelcacheByRelid(lfirst_oid(l));
		}
	}

	/* keep our lock until commit */
	table_close(attachrel, NoLock);

	return address;
}

/*
 * AttachPartitionEnsureIndexes
 *		subroutine for ATExecAttachPartition to create/match indexes
 *
 * Enforce the indexing rule for partitioned tables during ALTER TABLE / ATTACH
 * PARTITION: every partition must have an index attached to each index on the
 * partitioned table.
 */
static void
AttachPartitionEnsureIndexes(List **wqueue, Relation rel, Relation attachrel)
{
	List	   *idxes;
	List	   *attachRelIdxs;
	Relation   *attachrelIdxRels;
	IndexInfo **attachInfos;
	ListCell   *cell;
	MemoryContext cxt;
	MemoryContext oldcxt;

	cxt = AllocSetContextCreate(CurrentMemoryContext,
								"AttachPartitionEnsureIndexes",
								ALLOCSET_DEFAULT_SIZES);
	oldcxt = MemoryContextSwitchTo(cxt);

	idxes = RelationGetIndexList(rel);
	attachRelIdxs = RelationGetIndexList(attachrel);
	attachrelIdxRels = palloc(sizeof(Relation) * list_length(attachRelIdxs));
	attachInfos = palloc(sizeof(IndexInfo *) * list_length(attachRelIdxs));

	/* Build arrays of all existing indexes and their IndexInfos */
	foreach_oid(cldIdxId, attachRelIdxs)
	{
		int			i = foreach_current_index(cldIdxId);

		attachrelIdxRels[i] = index_open(cldIdxId, AccessShareLock);
		attachInfos[i] = BuildIndexInfo(attachrelIdxRels[i]);
	}

	/*
	 * If we're attaching a foreign table, we must fail if any of the indexes
	 * is a constraint index; otherwise, there's nothing to do here.  Do this
	 * before starting work, to avoid wasting the effort of building a few
	 * non-unique indexes before coming across a unique one.
	 */
	if (attachrel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
	{
		foreach(cell, idxes)
		{
			Oid			idx = lfirst_oid(cell);
			Relation	idxRel = index_open(idx, AccessShareLock);

			if (idxRel->rd_index->indisunique ||
				idxRel->rd_index->indisprimary)
				ereport(ERROR,
						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
						 errmsg("cannot attach foreign table \"%s\" as partition of partitioned table \"%s\"",
								RelationGetRelationName(attachrel),
								RelationGetRelationName(rel)),
						 errdetail("Partitioned table \"%s\" contains unique indexes.",
								   RelationGetRelationName(rel))));
			index_close(idxRel, AccessShareLock);
		}

		goto out;
	}

	/*
	 * For each index on the partitioned table, find a matching one in the
	 * partition-to-be; if one is not found, create one.
	 */
	foreach(cell, idxes)
	{
		Oid			idx = lfirst_oid(cell);
		Relation	idxRel = index_open(idx, AccessShareLock);
		IndexInfo  *info;
		AttrMap    *attmap;
		bool		found = false;
		Oid			constraintOid;

		/*
		 * Ignore indexes in the partitioned table other than partitioned
		 * indexes.
		 */
		if (idxRel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
		{
			index_close(idxRel, AccessShareLock);
			continue;
		}

		/* construct an indexinfo to compare existing indexes against */
		info = BuildIndexInfo(idxRel);
		attmap = build_attrmap_by_name(RelationGetDescr(attachrel),
									   RelationGetDescr(rel),
									   false);
		constraintOid = get_relation_idx_constraint_oid(RelationGetRelid(rel), idx);

		/*
		 * Scan the list of existing indexes in the partition-to-be, and mark
		 * the first matching, valid, unattached one we find, if any, as
		 * partition of the parent index.  If we find one, we're done.
		 */
		for (int i = 0; i < list_length(attachRelIdxs); i++)
		{
			Oid			cldIdxId = RelationGetRelid(attachrelIdxRels[i]);
			Oid			cldConstrOid = InvalidOid;

			/* does this index have a parent?  if so, can't use it */
			if (attachrelIdxRels[i]->rd_rel->relispartition)
				continue;

			/* If this index is invalid, can't use it */
			if (!attachrelIdxRels[i]->rd_index->indisvalid)
				continue;

			if (CompareIndexInfo(attachInfos[i], info,
								 attachrelIdxRels[i]->rd_indcollation,
								 idxRel->rd_indcollation,
								 attachrelIdxRels[i]->rd_opfamily,
								 idxRel->rd_opfamily,
								 attmap))
			{
				/*
				 * If this index is being created in the parent because of a
				 * constraint, then the child needs to have a constraint also,
				 * so look for one.  If there is no such constraint, this
				 * index is no good, so keep looking.
				 */
				if (OidIsValid(constraintOid))
				{
					cldConstrOid =
						get_relation_idx_constraint_oid(RelationGetRelid(attachrel),
														cldIdxId);
					/* no dice */
					if (!OidIsValid(cldConstrOid))
						continue;

					/* Ensure they're both the same type of constraint */
					if (get_constraint_type(constraintOid) !=
						get_constraint_type(cldConstrOid))
						continue;
				}

				/* bingo. */
				IndexSetParentIndex(attachrelIdxRels[i], idx);
				if (OidIsValid(constraintOid))
					ConstraintSetParentConstraint(cldConstrOid, constraintOid,
												  RelationGetRelid(attachrel));
				found = true;

				CommandCounterIncrement();
				break;
			}
		}

		/*
		 * If no suitable index was found in the partition-to-be, create one
		 * now.  Note that if this is a PK, not-null constraints must already
		 * exist.
		 */
		if (!found)
		{
			IndexStmt  *stmt;
			Oid			conOid;

			stmt = generateClonedIndexStmt(NULL,
										   idxRel, attmap,
										   &conOid);
			DefineIndex(RelationGetRelid(attachrel), stmt, InvalidOid,
						RelationGetRelid(idxRel),
						conOid,
						-1,
						true, false, false, false, false);
		}

		index_close(idxRel, AccessShareLock);
	}

out:
	/* Clean up. */
	for (int i = 0; i < list_length(attachRelIdxs); i++)
		index_close(attachrelIdxRels[i], AccessShareLock);
	MemoryContextSwitchTo(oldcxt);
	MemoryContextDelete(cxt);
}

/*
 * CloneRowTriggersToPartition
 *		subroutine for ATExecAttachPartition/DefineRelation to create row
 *		triggers on partitions
 */
static void
CloneRowTriggersToPartition(Relation parent, Relation partition)
{
	Relation	pg_trigger;
	ScanKeyData key;
	SysScanDesc scan;
	HeapTuple	tuple;
	MemoryContext perTupCxt;

	ScanKeyInit(&key, Anum_pg_trigger_tgrelid, BTEqualStrategyNumber,
				F_OIDEQ, ObjectIdGetDatum(RelationGetRelid(parent)));
	pg_trigger = table_open(TriggerRelationId, RowExclusiveLock);
	scan = systable_beginscan(pg_trigger, TriggerRelidNameIndexId,
							  true, NULL, 1, &key);

	perTupCxt = AllocSetContextCreate(CurrentMemoryContext,
									  "clone trig", ALLOCSET_SMALL_SIZES);

	while (HeapTupleIsValid(tuple = systable_getnext(scan)))
	{
		Form_pg_trigger trigForm = (Form_pg_trigger) GETSTRUCT(tuple);
		CreateTrigStmt *trigStmt;
		Node	   *qual = NULL;
		Datum		value;
		bool		isnull;
		List	   *cols = NIL;
		List	   *trigargs = NIL;
		MemoryContext oldcxt;

		/*
		 * Ignore statement-level triggers; those are not cloned.
		 */
		if (!TRIGGER_FOR_ROW(trigForm->tgtype))
			continue;

		/*
		 * Don't clone internal triggers, because the constraint cloning code
		 * will.
		 */
		if (trigForm->tgisinternal)
			continue;

		/*
		 * Complain if we find an unexpected trigger type.
		 */
		if (!TRIGGER_FOR_BEFORE(trigForm->tgtype) &&
			!TRIGGER_FOR_AFTER(trigForm->tgtype))
			elog(ERROR, "unexpected trigger \"%s\" found",
				 NameStr(trigForm->tgname));

		/* Use short-lived context for CREATE TRIGGER */
		oldcxt = MemoryContextSwitchTo(perTupCxt);

		/*
		 * If there is a WHEN clause, generate a 'cooked' version of it that's
		 * appropriate for the partition.
		 */
		value = heap_getattr(tuple, Anum_pg_trigger_tgqual,
							 RelationGetDescr(pg_trigger), &isnull);
		if (!isnull)
		{
			qual = stringToNode(TextDatumGetCString(value));
			qual = (Node *) map_partition_varattnos((List *) qual, PRS2_OLD_VARNO,
													partition, parent);
			qual = (Node *) map_partition_varattnos((List *) qual, PRS2_NEW_VARNO,
													partition, parent);
		}

		/*
		 * If there is a column list, transform it to a list of column names.
		 * Note we don't need to map this list in any way ...
		 */
		if (trigForm->tgattr.dim1 > 0)
		{
			int			i;

			for (i = 0; i < trigForm->tgattr.dim1; i++)
			{
				Form_pg_attribute col;

				col = TupleDescAttr(parent->rd_att,
									trigForm->tgattr.values[i] - 1);
				cols = lappend(cols,
							   makeString(pstrdup(NameStr(col->attname))));
			}
		}

		/* Reconstruct trigger arguments list. */
		if (trigForm->tgnargs > 0)
		{
			char	   *p;

			value = heap_getattr(tuple, Anum_pg_trigger_tgargs,
								 RelationGetDescr(pg_trigger), &isnull);
			if (isnull)
				elog(ERROR, "tgargs is null for trigger \"%s\" in partition \"%s\"",
					 NameStr(trigForm->tgname), RelationGetRelationName(partition));

			p = (char *) VARDATA_ANY(DatumGetByteaPP(value));

			for (int i = 0; i < trigForm->tgnargs; i++)
			{
				trigargs = lappend(trigargs, makeString(pstrdup(p)));
				p += strlen(p) + 1;
			}
		}

		trigStmt = makeNode(CreateTrigStmt);
		trigStmt->replace = false;
		trigStmt->isconstraint = OidIsValid(trigForm->tgconstraint);
		trigStmt->trigname = NameStr(trigForm->tgname);
		trigStmt->relation = NULL;
		trigStmt->funcname = NULL;	/* passed separately */
		trigStmt->args = trigargs;
		trigStmt->row = true;
		trigStmt->timing = trigForm->tgtype & TRIGGER_TYPE_TIMING_MASK;
		trigStmt->events = trigForm->tgtype & TRIGGER_TYPE_EVENT_MASK;
		trigStmt->columns = cols;
		trigStmt->whenClause = NULL;	/* passed separately */
		trigStmt->transitionRels = NIL; /* not supported at present */
		trigStmt->deferrable = trigForm->tgdeferrable;
		trigStmt->initdeferred = trigForm->tginitdeferred;
		trigStmt->constrrel = NULL; /* passed separately */

		CreateTriggerFiringOn(trigStmt, NULL, RelationGetRelid(partition),
							  trigForm->tgconstrrelid, InvalidOid, InvalidOid,
							  trigForm->tgfoid, trigForm->oid, qual,
							  false, true, trigForm->tgenabled);

		MemoryContextSwitchTo(oldcxt);
		MemoryContextReset(perTupCxt);
	}

	MemoryContextDelete(perTupCxt);

	systable_endscan(scan);
	table_close(pg_trigger, RowExclusiveLock);
}

/*
 * ALTER TABLE DETACH PARTITION
 *
 * Return the address of the relation that is no longer a partition of rel.
 *
 * If concurrent mode is requested, we run in two transactions.  A side-
 * effect is that this command cannot run in a multi-part ALTER TABLE.
 * Currently, that's enforced by the grammar.
 *
 * The strategy for concurrency is to first modify the partition's
 * pg_inherit catalog row to make it visible to everyone that the
 * partition is detached, lock the partition against writes, and commit
 * the transaction; anyone who requests the partition descriptor from
 * that point onwards has to ignore such a partition.  In a second
 * transaction, we wait until all transactions that could have seen the
 * partition as attached are gone, then we remove the rest of partition
 * metadata (pg_inherits and pg_class.relpartbounds).
 */
static ObjectAddress
ATExecDetachPartition(List **wqueue, AlteredTableInfo *tab, Relation rel,
					  RangeVar *name, bool concurrent)
{
	Relation	partRel;
	ObjectAddress address;
	Oid			defaultPartOid;
	PartitionDesc partdesc;

	/*
	 * We must lock the default partition, because detaching this partition
	 * will change its partition constraint.
	 */
	partdesc = RelationGetPartitionDesc(rel, true);
	defaultPartOid = get_default_oid_from_partdesc(partdesc);
	if (OidIsValid(defaultPartOid))
	{
		/*
		 * Concurrent detaching when a default partition exists is not
		 * supported. The main problem is that the default partition
		 * constraint would change.  And there's a definitional problem: what
		 * should happen to the tuples that are being inserted that belong to
		 * the partition being detached?  Putting them on the partition being
		 * detached would be wrong, since they'd become "lost" after the
		 * detaching completes but we cannot put them in the default partition
		 * either until we alter its partition constraint.
		 *
		 * I think we could solve this problem if we effected the constraint
		 * change before committing the first transaction.  But the lock would
		 * have to remain AEL and it would cause concurrent query planning to
		 * be blocked, so changing it that way would be even worse.
		 */
		if (concurrent)
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("cannot detach partitions concurrently when a default partition exists")));
		LockRelationOid(defaultPartOid, AccessExclusiveLock);
	}

	/*
	 * In concurrent mode, the partition is locked with share-update-exclusive
	 * in the first transaction.  This allows concurrent transactions to be
	 * doing DML to the partition.
	 */
	partRel = table_openrv(name, concurrent ? ShareUpdateExclusiveLock :
						   AccessExclusiveLock);

	/*
	 * Check inheritance conditions and either delete the pg_inherits row (in
	 * non-concurrent mode) or just set the inhdetachpending flag.
	 */
	if (!concurrent)
		RemoveInheritance(partRel, rel, false);
	else
		MarkInheritDetached(partRel, rel);

	/*
	 * Ensure that foreign keys still hold after this detach.  This keeps
	 * locks on the referencing tables, which prevents concurrent transactions
	 * from adding rows that we wouldn't see.  For this to work in concurrent
	 * mode, it is critical that the partition appears as no longer attached
	 * for the RI queries as soon as the first transaction commits.
	 */
	ATDetachCheckNoForeignKeyRefs(partRel);

	/*
	 * Concurrent mode has to work harder; first we add a new constraint to
	 * the partition that matches the partition constraint.  Then we close our
	 * existing transaction, and in a new one wait for all processes to catch
	 * up on the catalog updates we've done so far; at that point we can
	 * complete the operation.
	 */
	if (concurrent)
	{
		Oid			partrelid,
					parentrelid;
		LOCKTAG		tag;
		char	   *parentrelname;
		char	   *partrelname;

		/*
		 * For strategies other than hash, add a constraint to the partition
		 * being detached which supplants the partition constraint. For hash
		 * we cannot do that, because the constraint would reference the
		 * partitioned table OID, possibly causing problems later.
		 */
		if (partdesc->boundinfo->strategy != PARTITION_STRATEGY_HASH)
			DetachAddConstraintIfNeeded(wqueue, partRel);

		/*
		 * We're almost done now; the only traces that remain are the
		 * pg_inherits tuple and the partition's relpartbounds.  Before we can
		 * remove those, we need to wait until all transactions that know that
		 * this is a partition are gone.
		 */

		/*
		 * Remember relation OIDs to re-acquire them later; and relation names
		 * too, for error messages if something is dropped in between.
		 */
		partrelid = RelationGetRelid(partRel);
		parentrelid = RelationGetRelid(rel);
		parentrelname = MemoryContextStrdup(PortalContext,
											RelationGetRelationName(rel));
		partrelname = MemoryContextStrdup(PortalContext,
										  RelationGetRelationName(partRel));

		/* Invalidate relcache entries for the parent -- must be before close */
		CacheInvalidateRelcache(rel);

		table_close(partRel, NoLock);
		table_close(rel, NoLock);
		tab->rel = NULL;

		/* Make updated catalog entry visible */
		PopActiveSnapshot();
		CommitTransactionCommand();

		StartTransactionCommand();

		/*
		 * Now wait.  This ensures that all queries that were planned
		 * including the partition are finished before we remove the rest of
		 * catalog entries.  We don't need or indeed want to acquire this
		 * lock, though -- that would block later queries.
		 *
		 * We don't need to concern ourselves with waiting for a lock on the
		 * partition itself, since we will acquire AccessExclusiveLock below.
		 */
		SET_LOCKTAG_RELATION(tag, MyDatabaseId, parentrelid);
		WaitForLockersMultiple(list_make1(&tag), AccessExclusiveLock, false);

		/*
		 * Now acquire locks in both relations again.  Note they may have been
		 * removed in the meantime, so care is required.
		 */
		rel = try_relation_open(parentrelid, ShareUpdateExclusiveLock);
		partRel = try_relation_open(partrelid, AccessExclusiveLock);

		/* If the relations aren't there, something bad happened; bail out */
		if (rel == NULL)
		{
			if (partRel != NULL)	/* shouldn't happen */
				elog(WARNING, "dangling partition \"%s\" remains, can't fix",
					 partrelname);
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("partitioned table \"%s\" was removed concurrently",
							parentrelname)));
		}
		if (partRel == NULL)
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("partition \"%s\" was removed concurrently", partrelname)));

		tab->rel = rel;
	}

	/*
	 * Detaching the partition might involve TOAST table access, so ensure we
	 * have a valid snapshot.
	 */
	PushActiveSnapshot(GetTransactionSnapshot());

	/* Do the final part of detaching */
	DetachPartitionFinalize(rel, partRel, concurrent, defaultPartOid);

	PopActiveSnapshot();

	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(partRel));

	/* keep our lock until commit */
	table_close(partRel, NoLock);

	return address;
}

/*
 * Second part of ALTER TABLE .. DETACH.
 *
 * This is separate so that it can be run independently when the second
 * transaction of the concurrent algorithm fails (crash or abort).
 */
static void
DetachPartitionFinalize(Relation rel, Relation partRel, bool concurrent,
						Oid defaultPartOid)
{
	Relation	classRel;
	List	   *fks;
	ListCell   *cell;
	List	   *indexes;
	Datum		new_val[Natts_pg_class];
	bool		new_null[Natts_pg_class],
				new_repl[Natts_pg_class];
	HeapTuple	tuple,
				newtuple;
	Relation	trigrel = NULL;
	List	   *fkoids = NIL;

	if (concurrent)
	{
		/*
		 * We can remove the pg_inherits row now. (In the non-concurrent case,
		 * this was already done).
		 */
		RemoveInheritance(partRel, rel, true);
	}

	/* Drop any triggers that were cloned on creation/attach. */
	DropClonedTriggersFromPartition(RelationGetRelid(partRel));

	/*
	 * Detach any foreign keys that are inherited.  This includes creating
	 * additional action triggers.
	 */
	fks = copyObject(RelationGetFKeyList(partRel));
	if (fks != NIL)
		trigrel = table_open(TriggerRelationId, RowExclusiveLock);

	/*
	 * It's possible that the partition being detached has a foreign key that
	 * references a partitioned table.  When that happens, there are multiple
	 * pg_constraint rows for the partition: one points to the partitioned
	 * table itself, while the others point to each of its partitions.  Only
	 * the topmost one is to be considered here; the child constraints must be
	 * left alone, because conceptually those aren't coming from our parent
	 * partitioned table, but from this partition itself.
	 *
	 * We implement this by collecting all the constraint OIDs in a first scan
	 * of the FK array, and skipping in the loop below those constraints whose
	 * parents are listed here.
	 */
	foreach_node(ForeignKeyCacheInfo, fk, fks)
		fkoids = lappend_oid(fkoids, fk->conoid);

	foreach(cell, fks)
	{
		ForeignKeyCacheInfo *fk = lfirst(cell);
		HeapTuple	contup;
		Form_pg_constraint conform;

		contup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fk->conoid));
		if (!HeapTupleIsValid(contup))
			elog(ERROR, "cache lookup failed for constraint %u", fk->conoid);
		conform = (Form_pg_constraint) GETSTRUCT(contup);

		/*
		 * Consider only inherited foreign keys, and only if their parents
		 * aren't in the list.
		 */
		if (conform->contype != CONSTRAINT_FOREIGN ||
			!OidIsValid(conform->conparentid) ||
			list_member_oid(fkoids, conform->conparentid))
		{
			ReleaseSysCache(contup);
			continue;
		}

		/*
		 * The constraint on this table must be marked no longer a child of
		 * the parent's constraint, as do its check triggers.
		 */
		ConstraintSetParentConstraint(fk->conoid, InvalidOid, InvalidOid);

		/*
		 * Also, look up the partition's "check" triggers corresponding to the
		 * ENFORCED constraint being detached and detach them from the parent
		 * triggers. NOT ENFORCED constraints do not have these triggers;
		 * therefore, this step is not needed.
		 */
		if (fk->conenforced)
		{
			Oid			insertTriggerOid,
						updateTriggerOid;

			GetForeignKeyCheckTriggers(trigrel,
									   fk->conoid, fk->confrelid, fk->conrelid,
									   &insertTriggerOid, &updateTriggerOid);
			Assert(OidIsValid(insertTriggerOid));
			TriggerSetParentTrigger(trigrel, insertTriggerOid, InvalidOid,
									RelationGetRelid(partRel));
			Assert(OidIsValid(updateTriggerOid));
			TriggerSetParentTrigger(trigrel, updateTriggerOid, InvalidOid,
									RelationGetRelid(partRel));
		}

		/*
		 * Lastly, create the action triggers on the referenced table, using
		 * addFkRecurseReferenced, which requires some elaborate setup (so put
		 * it in a separate block).  While at it, if the table is partitioned,
		 * that function will recurse to create the pg_constraint rows and
		 * action triggers for each partition.
		 *
		 * Note there's no need to do addFkConstraint() here, because the
		 * pg_constraint row already exists.
		 */
		{
			Constraint *fkconstraint;
			int			numfks;
			AttrNumber	conkey[INDEX_MAX_KEYS];
			AttrNumber	confkey[INDEX_MAX_KEYS];
			Oid			conpfeqop[INDEX_MAX_KEYS];
			Oid			conppeqop[INDEX_MAX_KEYS];
			Oid			conffeqop[INDEX_MAX_KEYS];
			int			numfkdelsetcols;
			AttrNumber	confdelsetcols[INDEX_MAX_KEYS];
			Relation	refdRel;

			DeconstructFkConstraintRow(contup,
									   &numfks,
									   conkey,
									   confkey,
									   conpfeqop,
									   conppeqop,
									   conffeqop,
									   &numfkdelsetcols,
									   confdelsetcols);

			/* Create a synthetic node we'll use throughout */
			fkconstraint = makeNode(Constraint);
			fkconstraint->contype = CONSTRAINT_FOREIGN;
			fkconstraint->conname = pstrdup(NameStr(conform->conname));
			fkconstraint->deferrable = conform->condeferrable;
			fkconstraint->initdeferred = conform->condeferred;
			fkconstraint->is_enforced = conform->conenforced;
			fkconstraint->skip_validation = true;
			fkconstraint->initially_valid = conform->convalidated;
			/* a few irrelevant fields omitted here */
			fkconstraint->pktable = NULL;
			fkconstraint->fk_attrs = NIL;
			fkconstraint->pk_attrs = NIL;
			fkconstraint->fk_matchtype = conform->confmatchtype;
			fkconstraint->fk_upd_action = conform->confupdtype;
			fkconstraint->fk_del_action = conform->confdeltype;
			fkconstraint->fk_del_set_cols = NIL;
			fkconstraint->old_conpfeqop = NIL;
			fkconstraint->old_pktable_oid = InvalidOid;
			fkconstraint->location = -1;

			/* set up colnames, used to generate the constraint name */
			for (int i = 0; i < numfks; i++)
			{
				Form_pg_attribute att;

				att = TupleDescAttr(RelationGetDescr(partRel),
									conkey[i] - 1);

				fkconstraint->fk_attrs = lappend(fkconstraint->fk_attrs,
												 makeString(NameStr(att->attname)));
			}

			refdRel = table_open(fk->confrelid, ShareRowExclusiveLock);

			addFkRecurseReferenced(fkconstraint, partRel,
								   refdRel,
								   conform->conindid,
								   fk->conoid,
								   numfks,
								   confkey,
								   conkey,
								   conpfeqop,
								   conppeqop,
								   conffeqop,
								   numfkdelsetcols,
								   confdelsetcols,
								   true,
								   InvalidOid, InvalidOid,
								   conform->conperiod);
			table_close(refdRel, NoLock);	/* keep lock till end of xact */
		}

		ReleaseSysCache(contup);
	}
	list_free_deep(fks);
	if (trigrel)
		table_close(trigrel, RowExclusiveLock);

	/*
	 * Any sub-constraints that are in the referenced-side of a larger
	 * constraint have to be removed.  This partition is no longer part of the
	 * key space of the constraint.
	 */
	foreach(cell, GetParentedForeignKeyRefs(partRel))
	{
		Oid			constrOid = lfirst_oid(cell);
		ObjectAddress constraint;

		ConstraintSetParentConstraint(constrOid, InvalidOid, InvalidOid);
		deleteDependencyRecordsForClass(ConstraintRelationId,
										constrOid,
										ConstraintRelationId,
										DEPENDENCY_INTERNAL);
		CommandCounterIncrement();

		ObjectAddressSet(constraint, ConstraintRelationId, constrOid);
		performDeletion(&constraint, DROP_RESTRICT, 0);
	}

	/* Now we can detach indexes */
	indexes = RelationGetIndexList(partRel);
	foreach(cell, indexes)
	{
		Oid			idxid = lfirst_oid(cell);
		Oid			parentidx;
		Relation	idx;
		Oid			constrOid;
		Oid			parentConstrOid;

		if (!has_superclass(idxid))
			continue;

		parentidx = get_partition_parent(idxid, false);
		Assert((IndexGetRelation(parentidx, false) == RelationGetRelid(rel)));

		idx = index_open(idxid, AccessExclusiveLock);
		IndexSetParentIndex(idx, InvalidOid);

		/*
		 * If there's a constraint associated with the index, detach it too.
		 * Careful: it is possible for a constraint index in a partition to be
		 * the child of a non-constraint index, so verify whether the parent
		 * index does actually have a constraint.
		 */
		constrOid = get_relation_idx_constraint_oid(RelationGetRelid(partRel),
													idxid);
		parentConstrOid = get_relation_idx_constraint_oid(RelationGetRelid(rel),
														  parentidx);
		if (OidIsValid(parentConstrOid) && OidIsValid(constrOid))
			ConstraintSetParentConstraint(constrOid, InvalidOid, InvalidOid);

		index_close(idx, NoLock);
	}

	/* Update pg_class tuple */
	classRel = table_open(RelationRelationId, RowExclusiveLock);
	tuple = SearchSysCacheCopy1(RELOID,
								ObjectIdGetDatum(RelationGetRelid(partRel)));
	if (!HeapTupleIsValid(tuple))
		elog(ERROR, "cache lookup failed for relation %u",
			 RelationGetRelid(partRel));
	Assert(((Form_pg_class) GETSTRUCT(tuple))->relispartition);

	/* Clear relpartbound and reset relispartition */
	memset(new_val, 0, sizeof(new_val));
	memset(new_null, false, sizeof(new_null));
	memset(new_repl, false, sizeof(new_repl));
	new_val[Anum_pg_class_relpartbound - 1] = (Datum) 0;
	new_null[Anum_pg_class_relpartbound - 1] = true;
	new_repl[Anum_pg_class_relpartbound - 1] = true;
	newtuple = heap_modify_tuple(tuple, RelationGetDescr(classRel),
								 new_val, new_null, new_repl);

	((Form_pg_class) GETSTRUCT(newtuple))->relispartition = false;
	CatalogTupleUpdate(classRel, &newtuple->t_self, newtuple);
	heap_freetuple(newtuple);
	table_close(classRel, RowExclusiveLock);

	/*
	 * Drop identity property from all identity columns of partition.
	 */
	for (int attno = 0; attno < RelationGetNumberOfAttributes(partRel); attno++)
	{
		Form_pg_attribute attr = TupleDescAttr(partRel->rd_att, attno);

		if (!attr->attisdropped && attr->attidentity)
			ATExecDropIdentity(partRel, NameStr(attr->attname), false,
							   AccessExclusiveLock, true, true);
	}

	if (OidIsValid(defaultPartOid))
	{
		/*
		 * If the relation being detached is the default partition itself,
		 * remove it from the parent's pg_partitioned_table entry.
		 *
		 * If not, we must invalidate default partition's relcache entry, as
		 * in StorePartitionBound: its partition constraint depends on every
		 * other partition's partition constraint.
		 */
		if (RelationGetRelid(partRel) == defaultPartOid)
			update_default_partition_oid(RelationGetRelid(rel), InvalidOid);
		else
			CacheInvalidateRelcacheByRelid(defaultPartOid);
	}

	/*
	 * Invalidate the parent's relcache so that the partition is no longer
	 * included in its partition descriptor.
	 */
	CacheInvalidateRelcache(rel);

	/*
	 * If the partition we just detached is partitioned itself, invalidate
	 * relcache for all descendent partitions too to ensure that their
	 * rd_partcheck expression trees are rebuilt; must lock partitions before
	 * doing so, using the same lockmode as what partRel has been locked with
	 * by the caller.
	 */
	if (partRel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
	{
		List	   *children;

		children = find_all_inheritors(RelationGetRelid(partRel),
									   AccessExclusiveLock, NULL);
		foreach(cell, children)
		{
			CacheInvalidateRelcacheByRelid(lfirst_oid(cell));
		}
	}
}

/*
 * ALTER TABLE ... DETACH PARTITION ... FINALIZE
 *
 * To use when a DETACH PARTITION command previously did not run to
 * completion; this completes the detaching process.
 */
static ObjectAddress
ATExecDetachPartitionFinalize(Relation rel, RangeVar *name)
{
	Relation	partRel;
	ObjectAddress address;
	Snapshot	snap = GetActiveSnapshot();

	partRel = table_openrv(name, AccessExclusiveLock);

	/*
	 * Wait until existing snapshots are gone.  This is important if the
	 * second transaction of DETACH PARTITION CONCURRENTLY is canceled: the
	 * user could immediately run DETACH FINALIZE without actually waiting for
	 * existing transactions.  We must not complete the detach action until
	 * all such queries are complete (otherwise we would present them with an
	 * inconsistent view of catalogs).
	 */
	WaitForOlderSnapshots(snap->xmin, false);

	DetachPartitionFinalize(rel, partRel, true, InvalidOid);

	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(partRel));

	table_close(partRel, NoLock);

	return address;
}

/*
 * DetachAddConstraintIfNeeded
 *		Subroutine for ATExecDetachPartition.  Create a constraint that
 *		takes the place of the partition constraint, but avoid creating
 *		a dupe if a constraint already exists which implies the needed
 *		constraint.
 */
static void
DetachAddConstraintIfNeeded(List **wqueue, Relation partRel)
{
	List	   *constraintExpr;

	constraintExpr = RelationGetPartitionQual(partRel);
	constraintExpr = (List *) eval_const_expressions(NULL, (Node *) constraintExpr);

	/*
	 * Avoid adding a new constraint if the needed constraint is implied by an
	 * existing constraint
	 */
	if (!PartConstraintImpliedByRelConstraint(partRel, constraintExpr))
	{
		AlteredTableInfo *tab;
		Constraint *n;

		tab = ATGetQueueEntry(wqueue, partRel);

		/* Add constraint on partition, equivalent to the partition constraint */
		n = makeNode(Constraint);
		n->contype = CONSTR_CHECK;
		n->conname = NULL;
		n->location = -1;
		n->is_no_inherit = false;
		n->raw_expr = NULL;
		n->cooked_expr = nodeToString(make_ands_explicit(constraintExpr));
		n->is_enforced = true;
		n->initially_valid = true;
		n->skip_validation = true;
		/* It's a re-add, since it nominally already exists */
		ATAddCheckNNConstraint(wqueue, tab, partRel, n,
							   true, false, true, ShareUpdateExclusiveLock);
	}
}

/*
 * DropClonedTriggersFromPartition
 *		subroutine for ATExecDetachPartition to remove any triggers that were
 *		cloned to the partition when it was created-as-partition or attached.
 *		This undoes what CloneRowTriggersToPartition did.
 */
static void
DropClonedTriggersFromPartition(Oid partitionId)
{
	ScanKeyData skey;
	SysScanDesc scan;
	HeapTuple	trigtup;
	Relation	tgrel;
	ObjectAddresses *objects;

	objects = new_object_addresses();

	/*
	 * Scan pg_trigger to search for all triggers on this rel.
	 */
	ScanKeyInit(&skey, Anum_pg_trigger_tgrelid, BTEqualStrategyNumber,
				F_OIDEQ, ObjectIdGetDatum(partitionId));
	tgrel = table_open(TriggerRelationId, RowExclusiveLock);
	scan = systable_beginscan(tgrel, TriggerRelidNameIndexId,
							  true, NULL, 1, &skey);
	while (HeapTupleIsValid(trigtup = systable_getnext(scan)))
	{
		Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(trigtup);
		ObjectAddress trig;

		/* Ignore triggers that weren't cloned */
		if (!OidIsValid(pg_trigger->tgparentid))
			continue;

		/*
		 * Ignore internal triggers that are implementation objects of foreign
		 * keys, because these will be detached when the foreign keys
		 * themselves are.
		 */
		if (OidIsValid(pg_trigger->tgconstrrelid))
			continue;

		/*
		 * This is ugly, but necessary: remove the dependency markings on the
		 * trigger so that it can be removed.
		 */
		deleteDependencyRecordsForClass(TriggerRelationId, pg_trigger->oid,
										TriggerRelationId,
										DEPENDENCY_PARTITION_PRI);
		deleteDependencyRecordsForClass(TriggerRelationId, pg_trigger->oid,
										RelationRelationId,
										DEPENDENCY_PARTITION_SEC);

		/* remember this trigger to remove it below */
		ObjectAddressSet(trig, TriggerRelationId, pg_trigger->oid);
		add_exact_object_address(&trig, objects);
	}

	/* make the dependency removal visible to the deletion below */
	CommandCounterIncrement();
	performMultipleDeletions(objects, DROP_RESTRICT, PERFORM_DELETION_INTERNAL);

	/* done */
	free_object_addresses(objects);
	systable_endscan(scan);
	table_close(tgrel, RowExclusiveLock);
}

/*
 * Before acquiring lock on an index, acquire the same lock on the owning
 * table.
 */
struct AttachIndexCallbackState
{
	Oid			partitionOid;
	Oid			parentTblOid;
	bool		lockedParentTbl;
};

static void
RangeVarCallbackForAttachIndex(const RangeVar *rv, Oid relOid, Oid oldRelOid,
							   void *arg)
{
	struct AttachIndexCallbackState *state;
	Form_pg_class classform;
	HeapTuple	tuple;

	state = (struct AttachIndexCallbackState *) arg;

	if (!state->lockedParentTbl)
	{
		LockRelationOid(state->parentTblOid, AccessShareLock);
		state->lockedParentTbl = true;
	}

	/*
	 * If we previously locked some other heap, and the name we're looking up
	 * no longer refers to an index on that relation, release the now-useless
	 * lock.  XXX maybe we should do *after* we verify whether the index does
	 * not actually belong to the same relation ...
	 */
	if (relOid != oldRelOid && OidIsValid(state->partitionOid))
	{
		UnlockRelationOid(state->partitionOid, AccessShareLock);
		state->partitionOid = InvalidOid;
	}

	/* Didn't find a relation, so no need for locking or permission checks. */
	if (!OidIsValid(relOid))
		return;

	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relOid));
	if (!HeapTupleIsValid(tuple))
		return;					/* concurrently dropped, so nothing to do */
	classform = (Form_pg_class) GETSTRUCT(tuple);
	if (classform->relkind != RELKIND_PARTITIONED_INDEX &&
		classform->relkind != RELKIND_INDEX)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
				 errmsg("\"%s\" is not an index", rv->relname)));
	ReleaseSysCache(tuple);

	/*
	 * Since we need only examine the heap's tupledesc, an access share lock
	 * on it (preventing any DDL) is sufficient.
	 */
	state->partitionOid = IndexGetRelation(relOid, false);
	LockRelationOid(state->partitionOid, AccessShareLock);
}

/*
 * ALTER INDEX i1 ATTACH PARTITION i2
 */
static ObjectAddress
ATExecAttachPartitionIdx(List **wqueue, Relation parentIdx, RangeVar *name)
{
	Relation	partIdx;
	Relation	partTbl;
	Relation	parentTbl;
	ObjectAddress address;
	Oid			partIdxId;
	Oid			currParent;
	struct AttachIndexCallbackState state;

	/*
	 * We need to obtain lock on the index 'name' to modify it, but we also
	 * need to read its owning table's tuple descriptor -- so we need to lock
	 * both.  To avoid deadlocks, obtain lock on the table before doing so on
	 * the index.  Furthermore, we need to examine the parent table of the
	 * partition, so lock that one too.
	 */
	state.partitionOid = InvalidOid;
	state.parentTblOid = parentIdx->rd_index->indrelid;
	state.lockedParentTbl = false;
	partIdxId =
		RangeVarGetRelidExtended(name, AccessExclusiveLock, 0,
								 RangeVarCallbackForAttachIndex,
								 &state);
	/* Not there? */
	if (!OidIsValid(partIdxId))
		ereport(ERROR,
				(errcode(ERRCODE_UNDEFINED_OBJECT),
				 errmsg("index \"%s\" does not exist", name->relname)));

	/* no deadlock risk: RangeVarGetRelidExtended already acquired the lock */
	partIdx = relation_open(partIdxId, AccessExclusiveLock);

	/* we already hold locks on both tables, so this is safe: */
	parentTbl = relation_open(parentIdx->rd_index->indrelid, AccessShareLock);
	partTbl = relation_open(partIdx->rd_index->indrelid, NoLock);

	ObjectAddressSet(address, RelationRelationId, RelationGetRelid(partIdx));

	/*
	 * Check if the index is already attached to the correct parent,
	 * ultimately attempting one round of validation if already the case.
	 */
	currParent = partIdx->rd_rel->relispartition ?
		get_partition_parent(partIdxId, false) : InvalidOid;
	if (currParent != RelationGetRelid(parentIdx))
	{
		IndexInfo  *childInfo;
		IndexInfo  *parentInfo;
		AttrMap    *attmap;
		bool		found;
		int			i;
		PartitionDesc partDesc;
		Oid			constraintOid,
					cldConstrId = InvalidOid;

		/*
		 * If this partition already has an index attached, refuse the
		 * operation.
		 */
		refuseDupeIndexAttach(parentIdx, partIdx, partTbl);

		if (OidIsValid(currParent))
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
							RelationGetRelationName(partIdx),
							RelationGetRelationName(parentIdx)),
					 errdetail("Index \"%s\" is already attached to another index.",
							   RelationGetRelationName(partIdx))));

		/* Make sure it indexes a partition of the other index's table */
		partDesc = RelationGetPartitionDesc(parentTbl, true);
		found = false;
		for (i = 0; i < partDesc->nparts; i++)
		{
			if (partDesc->oids[i] == state.partitionOid)
			{
				found = true;
				break;
			}
		}
		if (!found)
			ereport(ERROR,
					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
					 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
							RelationGetRelationName(partIdx),
							RelationGetRelationName(parentIdx)),
					 errdetail("Index \"%s\" is not an index on any partition of table \"%s\".",
							   RelationGetRelationName(partIdx),
							   RelationGetRelationName(parentTbl))));

		/* Ensure the indexes are compatible */
		childInfo = BuildIndexInfo(partIdx);
		parentInfo = BuildIndexInfo(parentIdx);
		attmap = build_attrmap_by_name(RelationGetDescr(partTbl),
									   RelationGetDescr(parentTbl),
									   false);
		if (!CompareIndexInfo(childInfo, parentInfo,
							  partIdx->rd_indcollation,
							  parentIdx->rd_indcollation,
							  partIdx->rd_opfamily,
							  parentIdx->rd_opfamily,
							  attmap))
			ereport(ERROR,
					(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
					 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
							RelationGetRelationName(partIdx),
							RelationGetRelationName(parentIdx)),
					 errdetail("The index definitions do not match.")));

		/*
		 * If there is a constraint in the parent, make sure there is one in
		 * the child too.
		 */
		constraintOid = get_relation_idx_constraint_oid(RelationGetRelid(parentTbl),
														RelationGetRelid(parentIdx));

		if (OidIsValid(constraintOid))
		{
			cldConstrId = get_relation_idx_constraint_oid(RelationGetRelid(partTbl),
														  partIdxId);
			if (!OidIsValid(cldConstrId))
				ereport(ERROR,
						(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
						 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
								RelationGetRelationName(partIdx),
								RelationGetRelationName(parentIdx)),
						 errdetail("The index \"%s\" belongs to a constraint in table \"%s\" but no constraint exists for index \"%s\".",
								   RelationGetRelationName(parentIdx),
								   RelationGetRelationName(parentTbl),
								   RelationGetRelationName(partIdx))));
		}

		/*
		 * If it's a primary key, make sure the columns in the partition are
		 * NOT NULL.
		 */
		if (parentIdx->rd_index->indisprimary)
			verifyPartitionIndexNotNull(childInfo, partTbl);

		/* All good -- do it */
		IndexSetParentIndex(partIdx, RelationGetRelid(parentIdx));
		if (OidIsValid(constraintOid))
			ConstraintSetParentConstraint(cldConstrId, constraintOid,
										  RelationGetRelid(partTbl));

		free_attrmap(attmap);

		validatePartitionedIndex(parentIdx, parentTbl);
	}
	else if (!parentIdx->rd_index->indisvalid)
	{
		/*
		 * The index is attached, but the parent is still invalid; see if it
		 * can be validated now.
		 */
		validatePartitionedIndex(parentIdx, parentTbl);
	}

	relation_close(parentTbl, AccessShareLock);
	/* keep these locks till commit */
	relation_close(partTbl, NoLock);
	relation_close(partIdx, NoLock);

	return address;
}

/*
 * Verify whether the given partition already contains an index attached
 * to the given partitioned index.  If so, raise an error.
 */
static void
refuseDupeIndexAttach(Relation parentIdx, Relation partIdx, Relation partitionTbl)
{
	Oid			existingIdx;

	existingIdx = index_get_partition(partitionTbl,
									  RelationGetRelid(parentIdx));
	if (OidIsValid(existingIdx))
		ereport(ERROR,
				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
				 errmsg("cannot attach index \"%s\" as a partition of index \"%s\"",
						RelationGetRelationName(partIdx),
						RelationGetRelationName(parentIdx)),
				 errdetail("Another index is already attached for partition \"%s\".",
						   RelationGetRelationName(partitionTbl))));
}

/*
 * Verify whether the set of attached partition indexes to a parent index on
 * a partitioned table is complete.  If it is, mark the parent index valid.
 *
 * This should be called each time a partition index is attached.
 */
static void
validatePartitionedIndex(Relation partedIdx, Relation partedTbl)
{
	Relation	inheritsRel;
	SysScanDesc scan;
	ScanKeyData key;
	int			tuples = 0;
	HeapTuple	inhTup;
	bool		updated = false;

	Assert(partedIdx->rd_rel->relkind == RELKIND_PARTITIONED_INDEX);

	/*
	 * Scan pg_inherits for this parent index.  Count each valid index we find
	 * (verifying the pg_index entry for each), and if we reach the total
	 * amount we expect, we can mark this parent index as valid.
	 */
	inheritsRel = table_open(InheritsRelationId, AccessShareLock);
	ScanKeyInit(&key, Anum_pg_inherits_inhparent,
				BTEqualStrategyNumber, F_OIDEQ,
				ObjectIdGetDatum(RelationGetRelid(partedIdx)));
	scan = systable_beginscan(inheritsRel, InheritsParentIndexId, true,
							  NULL, 1, &key);
	while ((inhTup = systable_getnext(scan)) != NULL)
	{
		Form_pg_inherits inhForm = (Form_pg_inherits) GETSTRUCT(inhTup);
		HeapTuple	indTup;
		Form_pg_index indexForm;

		indTup = SearchSysCache1(INDEXRELID,
								 ObjectIdGetDatum(inhForm->inhrelid));
		if (!HeapTupleIsValid(indTup))
			elog(ERROR, "cache lookup failed for index %u", inhForm->inhrelid);
		indexForm = (Form_pg_index) GETSTRUCT(indTup);
		if (indexForm->indisvalid)
			tuples += 1;
		ReleaseSysCache(indTup);
	}

	/* Done with pg_inherits */
	systable_endscan(scan);
	table_close(inheritsRel, AccessShareLock);

	/*
	 * If we found as many inherited indexes as the partitioned table has
	 * partitions, we're good; update pg_index to set indisvalid.
	 */
	if (tuples == RelationGetPartitionDesc(partedTbl, true)->nparts)
	{
		Relation	idxRel;
		HeapTuple	indTup;
		Form_pg_index indexForm;

		idxRel = table_open(IndexRelationId, RowExclusiveLock);
		indTup = SearchSysCacheCopy1(INDEXRELID,
									 ObjectIdGetDatum(RelationGetRelid(partedIdx)));
		if (!HeapTupleIsValid(indTup))
			elog(ERROR, "cache lookup failed for index %u",
				 RelationGetRelid(partedIdx));
		indexForm = (Form_pg_index) GETSTRUCT(indTup);

		indexForm->indisvalid = true;
		updated = true;

		CatalogTupleUpdate(idxRel, &indTup->t_self, indTup);

		table_close(idxRel, RowExclusiveLock);
		heap_freetuple(indTup);
	}

	/*
	 * If this index is in turn a partition of a larger index, validating it
	 * might cause the parent to become valid also.  Try that.
	 */
	if (updated && partedIdx->rd_rel->relispartition)
	{
		Oid			parentIdxId,
					parentTblId;
		Relation	parentIdx,
					parentTbl;

		/* make sure we see the validation we just did */
		CommandCounterIncrement();

		parentIdxId = get_partition_parent(RelationGetRelid(partedIdx), false);
		parentTblId = get_partition_parent(RelationGetRelid(partedTbl), false);
		parentIdx = relation_open(parentIdxId, AccessExclusiveLock);
		parentTbl = relation_open(parentTblId, AccessExclusiveLock);
		Assert(!parentIdx->rd_index->indisvalid);

		validatePartitionedIndex(parentIdx, parentTbl);

		relation_close(parentIdx, AccessExclusiveLock);
		relation_close(parentTbl, AccessExclusiveLock);
	}
}

/*
 * When attaching an index as a partition of a partitioned index which is a
 * primary key, verify that all the columns in the partition are marked NOT
 * NULL.
 */
static void
verifyPartitionIndexNotNull(IndexInfo *iinfo, Relation partition)
{
	for (int i = 0; i < iinfo->ii_NumIndexKeyAttrs; i++)
	{
		Form_pg_attribute att = TupleDescAttr(RelationGetDescr(partition),
											  iinfo->ii_IndexAttrNumbers[i] - 1);

		if (!att->attnotnull)
			ereport(ERROR,
					errcode(ERRCODE_INVALID_TABLE_DEFINITION),
					errmsg("invalid primary key definition"),
					errdetail("Column \"%s\" of relation \"%s\" is not marked NOT NULL.",
							  NameStr(att->attname),
							  RelationGetRelationName(partition)));
	}
}

/*
 * Return an OID list of constraints that reference the given relation
 * that are marked as having a parent constraints.
 */
static List *
GetParentedForeignKeyRefs(Relation partition)
{
	Relation	pg_constraint;
	HeapTuple	tuple;
	SysScanDesc scan;
	ScanKeyData key[2];
	List	   *constraints = NIL;

	/*
	 * If no indexes, or no columns are referenceable by FKs, we can avoid the
	 * scan.
	 */
	if (RelationGetIndexList(partition) == NIL ||
		bms_is_empty(RelationGetIndexAttrBitmap(partition,
												INDEX_ATTR_BITMAP_KEY)))
		return NIL;

	/* Search for constraints referencing this table */
	pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
	ScanKeyInit(&key[0],
				Anum_pg_constraint_confrelid, BTEqualStrategyNumber,
				F_OIDEQ, ObjectIdGetDatum(RelationGetRelid(partition)));
	ScanKeyInit(&key[1],
				Anum_pg_constraint_contype, BTEqualStrategyNumber,
				F_CHAREQ, CharGetDatum(CONSTRAINT_FOREIGN));

	/* XXX This is a seqscan, as we don't have a usable index */
	scan = systable_beginscan(pg_constraint, InvalidOid, true, NULL, 2, key);
	while ((tuple = systable_getnext(scan)) != NULL)
	{
		Form_pg_constraint constrForm = (Form_pg_constraint) GETSTRUCT(tuple);

		/*
		 * We only need to process constraints that are part of larger ones.
		 */
		if (!OidIsValid(constrForm->conparentid))
			continue;

		constraints = lappend_oid(constraints, constrForm->oid);
	}

	systable_endscan(scan);
	table_close(pg_constraint, AccessShareLock);

	return constraints;
}

/*
 * During DETACH PARTITION, verify that any foreign keys pointing to the
 * partitioned table would not become invalid.  An error is raised if any
 * referenced values exist.
 */
static void
ATDetachCheckNoForeignKeyRefs(Relation partition)
{
	List	   *constraints;
	ListCell   *cell;

	constraints = GetParentedForeignKeyRefs(partition);

	foreach(cell, constraints)
	{
		Oid			constrOid = lfirst_oid(cell);
		HeapTuple	tuple;
		Form_pg_constraint constrForm;
		Relation	rel;
		Trigger		trig = {0};

		tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constrOid));
		if (!HeapTupleIsValid(tuple))
			elog(ERROR, "cache lookup failed for constraint %u", constrOid);
		constrForm = (Form_pg_constraint) GETSTRUCT(tuple);

		Assert(OidIsValid(constrForm->conparentid));
		Assert(constrForm->confrelid == RelationGetRelid(partition));

		/* prevent data changes into the referencing table until commit */
		rel = table_open(constrForm->conrelid, ShareLock);

		trig.tgoid = InvalidOid;
		trig.tgname = NameStr(constrForm->conname);
		trig.tgenabled = TRIGGER_FIRES_ON_ORIGIN;
		trig.tgisinternal = true;
		trig.tgconstrrelid = RelationGetRelid(partition);
		trig.tgconstrindid = constrForm->conindid;
		trig.tgconstraint = constrForm->oid;
		trig.tgdeferrable = false;
		trig.tginitdeferred = false;
		/* we needn't fill in remaining fields */

		RI_PartitionRemove_Check(&trig, rel, partition);

		ReleaseSysCache(tuple);

		table_close(rel, NoLock);
	}
}

/*
 * resolve column compression specification to compression method.
 */
static char
GetAttributeCompression(Oid atttypid, const char *compression)
{
	char		cmethod;

	if (compression == NULL || strcmp(compression, "default") == 0)
		return InvalidCompressionMethod;

	/*
	 * To specify a nondefault method, the column data type must be toastable.
	 * Note this says nothing about whether the column's attstorage setting
	 * permits compression; we intentionally allow attstorage and
	 * attcompression to be independent.  But with a non-toastable type,
	 * attstorage could not be set to a value that would permit compression.
	 *
	 * We don't actually need to enforce this, since nothing bad would happen
	 * if attcompression were non-default; it would never be consulted.  But
	 * it seems more user-friendly to complain about a certainly-useless
	 * attempt to set the property.
	 */
	if (!TypeIsToastable(atttypid))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("column data type %s does not support compression",
						format_type_be(atttypid))));

	cmethod = CompressionNameToMethod(compression);
	if (!CompressionMethodIsValid(cmethod))
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("invalid compression method \"%s\"", compression)));

	return cmethod;
}

/*
 * resolve column storage specification
 */
static char
GetAttributeStorage(Oid atttypid, const char *storagemode)
{
	char		cstorage = 0;

	if (pg_strcasecmp(storagemode, "plain") == 0)
		cstorage = TYPSTORAGE_PLAIN;
	else if (pg_strcasecmp(storagemode, "external") == 0)
		cstorage = TYPSTORAGE_EXTERNAL;
	else if (pg_strcasecmp(storagemode, "extended") == 0)
		cstorage = TYPSTORAGE_EXTENDED;
	else if (pg_strcasecmp(storagemode, "main") == 0)
		cstorage = TYPSTORAGE_MAIN;
	else if (pg_strcasecmp(storagemode, "default") == 0)
		cstorage = get_typstorage(atttypid);
	else
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("invalid storage type \"%s\"",
						storagemode)));

	/*
	 * safety check: do not allow toasted storage modes unless column datatype
	 * is TOAST-aware.
	 */
	if (!(cstorage == TYPSTORAGE_PLAIN || TypeIsToastable(atttypid)))
		ereport(ERROR,
				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
				 errmsg("column data type %s can only have storage PLAIN",
						format_type_be(atttypid))));

	return cstorage;
}
