Package net.sf.saxon.expr
Class FilterExpression
- java.lang.Object
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- net.sf.saxon.expr.Expression
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- net.sf.saxon.expr.FilterExpression
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- All Implemented Interfaces:
java.io.Serializable
,javax.xml.transform.SourceLocator
,LocationProvider
,SaxonLocator
,EvaluableItem
,SequenceIterable
,InstructionInfo
,org.xml.sax.Locator
public final class FilterExpression extends Expression
A FilterExpression contains a base expression and a filter predicate, which may be an integer expression (positional filter), or a boolean expression (qualifier)- See Also:
- Serialized Form
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Field Summary
Fields Modifier and Type Field Description static int
FILTERED
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Fields inherited from class net.sf.saxon.expr.Expression
EVALUATE_METHOD, ITERATE_METHOD, locationId, PROCESS_METHOD, staticProperties
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Constructor Summary
Constructors Constructor Description FilterExpression(Expression start, Expression filter)
Constructor
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description PathMap.PathMapNodeSet
addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap.int
computeCardinality()
Get the static cardinality of this expressionint
computeDependencies()
Determine which aspects of the context the expression depends on.int
computeSpecialProperties()
Get the static properties of this expression (other than its type).Expression
copy()
Copy an expression.boolean
equals(java.lang.Object other)
Is this expression the same as another expression?void
explain(ExpressionPresenter out)
Diagnostic print of expression structure.Expression
getBaseExpression()
Get the underlying expressionExpression
getFilter()
Get the filter expressionItemType
getItemType(TypeHierarchy th)
Get the data type of the items returnedint
hashCode()
get HashCode for comparing two expressionsboolean
hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedlyboolean
isIndependentNumericFilter()
Determine whether the filter is a simple independent numeric, that is, an expression that satisfies the following conditions: (a) its value is numeric; (b) the value does not depend on the context item or position; (c) the cardinality is zero or one.boolean
isPositional(TypeHierarchy th)
Determine if the filter is positionalboolean
isSimpleBooleanFilter()
Test if the filter always returns a singleton booleanSequenceIterator
iterate(XPathContext context)
Iterate over the results, returning them in the correct orderjava.util.Iterator
iterateSubExpressions()
Get the immediate subexpressions of this expressionExpression
optimize(ExpressionVisitor visitor, ItemType contextItemType)
Perform optimisation of an expression and its subexpressions.Expression
promote(PromotionOffer offer)
Promote this expression if possibleboolean
replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpressionExpression
simplify(ExpressionVisitor visitor)
Simplify an expressionjava.lang.String
toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath.Expression
typeCheck(ExpressionVisitor visitor, ItemType contextItemType)
Type-check the expression-
Methods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeStaticProperties, display, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, findParentOf, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, implementsStaticTypeCheck, isUpdatingExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Field Detail
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FILTERED
public static final int FILTERED
- See Also:
- Constant Field Values
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Constructor Detail
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FilterExpression
public FilterExpression(Expression start, Expression filter)
Constructor- Parameters:
start
- A node-set expression denoting the absolute or relative set of nodes from which the navigation path should start.filter
- An expression defining the filter predicate
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Method Detail
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getItemType
public ItemType getItemType(TypeHierarchy th)
Get the data type of the items returned- Specified by:
getItemType
in classExpression
- Parameters:
th
- the type hierarchy cache- Returns:
- an integer representing the data type
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getBaseExpression
public Expression getBaseExpression()
Get the underlying expression- Returns:
- the expression being filtered
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getFilter
public Expression getFilter()
Get the filter expression- Returns:
- the expression acting as the filter predicate
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isPositional
public boolean isPositional(TypeHierarchy th)
Determine if the filter is positional- Parameters:
th
- the Type Hierarchy (for cached access to type information)- Returns:
- true if the value of the filter depends on the position of the item against which it is evaluated
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isSimpleBooleanFilter
public boolean isSimpleBooleanFilter()
Test if the filter always returns a singleton boolean- Returns:
- true if the filter is a simple boolean expression
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isIndependentNumericFilter
public boolean isIndependentNumericFilter()
Determine whether the filter is a simple independent numeric, that is, an expression that satisfies the following conditions: (a) its value is numeric; (b) the value does not depend on the context item or position; (c) the cardinality is zero or one.- Returns:
- true if the filter is a numeric value that does not depend on the context item or position
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simplify
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Simplify an expression- Overrides:
simplify
in classExpression
- Parameters:
visitor
- the expression visitor- Returns:
- the simplified expression
- Throws:
XPathException
- if any failure occurs
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typeCheck
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Type-check the expression- Overrides:
typeCheck
in classExpression
- Parameters:
visitor
- the expression visitorcontextItemType
- the type of the context item for this expression- Returns:
- the expression after type-checking (potentially modified to add run-time checks and/or conversions)
- Throws:
XPathException
- if an error is discovered during this phase (typically a type error)
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optimize
public Expression optimize(ExpressionVisitor visitor, 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.
- Overrides:
optimize
in classExpression
- Parameters:
visitor
- an expression visitorcontextItemType
- 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:
XPathException
- if an error is discovered during this phase (typically a type error)
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addToPathMap
public PathMap.PathMapNodeSet addToPathMap(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet)
Add a representation of this expression to a PathMap. The PathMap captures a map of the nodes visited by an expression in a source tree.- Overrides:
addToPathMap
in classExpression
- Parameters:
pathMap
- the PathMap to which the expression should be addedpathMapNodeSet
-- Returns:
- the pathMapNode representing the focus established by this expression, in the case where this expression is the first operand of a path expression or filter expression
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promote
public Expression promote(PromotionOffer offer) throws XPathException
Promote this expression if possible- Overrides:
promote
in classExpression
- Parameters:
offer
- details of the promotion that is possible- Returns:
- the promoted expression (or the original expression, unchanged)
- Throws:
XPathException
- if any error is detected
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iterateSubExpressions
public java.util.Iterator iterateSubExpressions()
Get the immediate subexpressions of this expression- Overrides:
iterateSubExpressions
in classExpression
- Returns:
- the subexpressions, as an array
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hasLoopingSubexpression
public boolean hasLoopingSubexpression(Expression child)
Given an expression that is an immediate child of this expression, test whether the evaluation of the parent expression causes the child expression to be evaluated repeatedly- Overrides:
hasLoopingSubexpression
in classExpression
- Parameters:
child
- the immediate subexpression- Returns:
- true if the child expression is evaluated repeatedly
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replaceSubExpression
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression- Overrides:
replaceSubExpression
in classExpression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression- Returns:
- true if the original subexpression is found
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computeCardinality
public int computeCardinality()
Get the static cardinality of this expression- Specified by:
computeCardinality
in classExpression
- Returns:
- the cardinality. The method attempts to determine the case where the filter predicate is guaranteed to select at most one item from the sequence being filtered
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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 classExpression
- Returns:
- the static properties of the expression, as a bit-significant value
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equals
public boolean equals(java.lang.Object other)
Is this expression the same as another expression?- Overrides:
equals
in classjava.lang.Object
- Parameters:
other
- the expression to be compared with this one- Returns:
- true if the two expressions are statically equivalent
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hashCode
public int hashCode()
get HashCode for comparing two expressions- Overrides:
hashCode
in classjava.lang.Object
- Returns:
- the hash code
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iterate
public SequenceIterator iterate(XPathContext context) throws XPathException
Iterate over the results, returning them in the correct order- Specified by:
iterate
in interfaceSequenceIterable
- Overrides:
iterate
in classExpression
- Parameters:
context
- the dynamic context for the evaluation- Returns:
- an iterator over the expression results
- Throws:
XPathException
- if any dynamic error occurs
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computeDependencies
public int computeDependencies()
Determine which aspects of the context the expression depends on. The result is a bitwise-or'ed value composed from constants such as XPathContext.VARIABLES and XPathContext.CURRENT_NODE- Overrides:
computeDependencies
in classExpression
- Returns:
- the dependencies
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copy
public Expression copy()
Copy an expression. This makes a deep copy.- Specified by:
copy
in classExpression
- Returns:
- the copy of the original expression
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toString
public java.lang.String toString()
The toString() method for an expression attempts to give a representation of the expression in an XPath-like form, but there is no guarantee that the syntax will actually be true XPath. In the case of XSLT instructions, the toString() method gives an abstracted view of the syntax- Overrides:
toString
in classExpression
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explain
public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.- Specified by:
explain
in classExpression
- Parameters:
out
- the ExpressionPresenter to be used
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