Package net.sf.saxon.sort
Class SortExpression
- java.lang.Object
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- net.sf.saxon.expr.ComputedExpression
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- net.sf.saxon.sort.SortExpression
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,Container
,Expression
,InstructionInfoProvider
public class SortExpression extends ComputedExpression
Expression equivalent to the imaginary syntax expr sortby (sort-key)+- See Also:
- Serialized Form
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Field Summary
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Fields inherited from class net.sf.saxon.expr.ComputedExpression
locationId, staticProperties
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Fields inherited from interface net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, PROCESS_METHOD
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Constructor Summary
Constructors Constructor Description SortExpression(Expression select, SortKeyDefinition[] sortKeys)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description int
computeCardinality()
Determine the static cardinalityint
computeSpecialProperties()
Get the static properties of this expression (other than its type).void
display(int level, java.io.PrintStream out, Configuration config)
Diagnostic print of expression structure.ItemType
getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possibleboolean
isSortKey(Expression child)
Test whether a given expression is one of the sort keysSequenceIterator
iterate(XPathContext context)
Enumerate the results of the expressionjava.util.Iterator
iterateSubExpressions()
Get the immediate sub-expressions of this expression.Expression
optimize(Optimizer opt, StaticContext env, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.Expression
promote(PromotionOffer offer)
Offer promotion for this subexpression.boolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionExpression
simplify(StaticContext env)
Simplify an expressionExpression
typeCheck(StaticContext env, ItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.ComputedExpression
adoptChildExpression, checkPermittedContents, computeDependencies, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, getCardinality, getColumnNumber, getConstructType, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getInstructionInfo, getIntrinsicDependencies, getLineNumber, getLocationId, getLocationProvider, getParentExpression, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, hasBadParentPointer, markTailFunctionCalls, process, resetStaticProperties, setLocationId, setParentExpression, setParentExpression, suppressValidation, typeError
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Constructor Detail
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SortExpression
public SortExpression(Expression select, SortKeyDefinition[] sortKeys)
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Method Detail
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iterateSubExpressions
public java.util.Iterator iterateSubExpressions()
Get the immediate sub-expressions of this expression. Default implementation returns a zero-length array, appropriate for an expression that has no sub-expressions.- Specified by:
iterateSubExpressions
in interfaceExpression
- Overrides:
iterateSubExpressions
in classComputedExpression
- Returns:
- an iterator containing the sub-expressions of this expression
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Specified by:
replaceSubExpression
in interfaceContainer
- Overrides:
replaceSubExpression
in classComputedExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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simplify
public Expression simplify(StaticContext env) throws XPathException
Simplify an expression- Specified by:
simplify
in interfaceExpression
- Overrides:
simplify
in classComputedExpression
- Parameters:
env
- the static context- Returns:
- the simplified expression
- Throws:
XPathException
- if an error is discovered during expression rewriting
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typeCheck
public Expression typeCheck(StaticContext env, ItemType contextItemType) throws XPathException
Type-check the expression- Parameters:
env
- the static context of the expressioncontextItemType
- the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set toType.ITEM_TYPE
- Returns:
- the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations
- Throws:
StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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optimize
public Expression optimize(Optimizer opt, StaticContext env, ItemType contextItemType) throws XPathException
Perform optimisation of an expression and its subexpressions.This method is called after all references to functions and variables have been resolved to the declaration of the function or variable, and after all type checking has been done.
- Parameters:
opt
- the optimizer in use. This provides access to supporting functions; it also allows different optimization strategies to be used in different circumstances.env
- the static context of the expressioncontextItemType
- the static type of "." at the point where this expression is invoked. The parameter is set to null if it is known statically that the context item will be undefined. If the type of the context item is not known statically, the argument is set toType.ITEM_TYPE
- Returns:
- the original expression, rewritten if appropriate to optimize execution
- Throws:
StaticError
- if an error is discovered during this phase (typically a type error)XPathException
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promote
public Expression promote(PromotionOffer offer) throws XPathException
Offer promotion for this subexpression. The offer will be accepted if the subexpression is not dependent on the factors (e.g. the context item) identified in the PromotionOffer. By default the offer is not accepted - this is appropriate in the case of simple expressions such as constant values and variable references where promotion would give no performance advantage. This method is always called at compile time.- Specified by:
promote
in interfaceExpression
- Overrides:
promote
in classComputedExpression
- Parameters:
offer
- details of the offer, for example the offer to move expressions that don't depend on the context to an outer level in the containing expression- Returns:
- if the offer is not accepted, return this expression unchanged. Otherwise return the result of rewriting the expression to promote this subexpression
- Throws:
XPathException
- if any error is detected
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isSortKey
public boolean isSortKey(Expression child)
Test whether a given expression is one of the sort keys
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computeCardinality
public int computeCardinality()
Determine the static cardinality- Specified by:
computeCardinality
in classComputedExpression
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getItemType
public ItemType getItemType(TypeHierarchy th)
Determine the data type of the items returned by the expression, if possible- Parameters:
th
-- Returns:
- a value such as Type.STRING, Type.BOOLEAN, Type.NUMBER, Type.NODE, or Type.ITEM (meaning not known in advance)
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computeSpecialProperties
public int computeSpecialProperties()
Get the static properties of this expression (other than its type). The result is bit-significant. These properties are used for optimizations. In general, if property bit is set, it is true, but if it is unset, the value is unknown.- Overrides:
computeSpecialProperties
in classComputedExpression
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Enumerate the results of the expression- Specified by:
iterate
in interfaceExpression
- Overrides:
iterate
in classComputedExpression
- Parameters:
context
- supplies the context for evaluation- Returns:
- a SequenceIterator that can be used to iterate over the result of the expression
- Throws:
XPathException
- if any dynamic error occurs evaluating the expression
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display
public void display(int level, java.io.PrintStream out, Configuration config)
Description copied from interface:Expression
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Parameters:
level
- indentation level for this expressionout
- Output destination
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