Package net.sf.saxon.expr
Class FilterExpression
java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.FilterExpression
- All Implemented Interfaces:
Serializable
,SourceLocator
,LocationProvider
,SaxonLocator
,ContextSwitchingExpression
,InstructionInfo
,Locator
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:
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Field Summary
FieldsFields inherited from class net.sf.saxon.expr.Expression
EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, EVENT_FEED_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, PUSH_SELECTION, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionaddToPathMap
(PathMap pathMap, PathMap.PathMapNodeSet pathMapNodeSet) Add a representation of this expression to a PathMap.int
Get the static cardinality of this expressionint
Determine which aspects of the context the expression depends on.int
Get the static properties of this expression (other than its type).copy()
Copy an expression.boolean
Is this expression the same as another expression?void
Diagnostic print of expression structure.Get the subexpression that is evaluated in the new contextGet the underlying expressionGet a name identifying the kind of expression, in terms meaningful to a user.Get the filter expressionFor an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis.Get the data type of the items returnedint
hashCode()
get HashCode for comparing two expressionsboolean
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
boolean
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
Determine if the filter is positionalboolean
Test if the filter always returns a singleton booleaniterate
(XPathContext context) Iterate over the results, returning them in the correct orderGet the immediate sub-expressions of this expression that are evaluated with the same focus (context item, position, and size) as the parent expression.Get the immediate subexpressions of this expressionoptimize
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Perform optimisation of an expression and its subexpressions.promote
(PromotionOffer offer, Expression parent) Promote this expression if possibleboolean
replaceSubExpression
(Expression original, Expression replacement) Replace one subexpression by a replacement subexpressionsimplify
(ExpressionVisitor visitor) Simplify an expressiontoString()
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.typeCheck
(ExpressionVisitor visitor, ExpressionVisitor.ContextItemType contextItemType) Type-check the expressionMethods inherited from class net.sf.saxon.expr.Expression
adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, computeStaticProperties, doPromotion, dynamicError, effectiveBooleanValue, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getColumnNumber, getConstructType, getContainer, getDependencies, getEvaluationMethod, getExecutable, getHostLanguage, getImplementationMethod, getIntrinsicDependencies, getLineNumber, getLineNumber, getLocationId, getLocationProvider, getObjectName, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getSystemId, getSystemId, hasVariableBinding, implementsStaticTypeCheck, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, markTailFunctionCalls, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setFlattened, setLocationId, staticTypeCheck, suppressValidation, typeError
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Field Details
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FILTERED
public static final int FILTERED- See Also:
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Constructor Details
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FilterExpression
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 Details
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getExpressionName
Get a name identifying the kind of expression, in terms meaningful to a user.- Overrides:
getExpressionName
in classExpression
- Returns:
- a name identifying the kind of expression, in terms meaningful to a user. The name will always be in the form of a lexical XML QName, and should match the name used in explain() output displaying the expression.
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getItemType
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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getControllingExpression
Get the underlying expression- Specified by:
getControllingExpression
in interfaceContextSwitchingExpression
- Returns:
- the expression being filtered
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isFilterIsPositional
public boolean isFilterIsPositional()- Returns:
- the boolean of filter is positional
- See Also:
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com.saxonica.bytecode.FilterExpressionCompiler
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getControlledExpression
Get the subexpression that is evaluated in the new context- Specified by:
getControlledExpression
in interfaceContextSwitchingExpression
- Returns:
- the subexpression evaluated in the context set by the controlling expression
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getFilter
Get the filter expression- Returns:
- the expression acting as the filter predicate
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isPositional
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
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, ExpressionVisitor.ContextItemType 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, ExpressionVisitor.ContextItemType 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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getIntegerBounds
For an expression that returns an integer or a sequence of integers, get a lower and upper bound on the values of the integers that may be returned, from static analysis. The default implementation returns null, meaning "unknown" or "not applicable". Other implementations return an array of two IntegerValue objects, representing the lower and upper bounds respectively. The values UNBOUNDED_LOWER and UNBOUNDED_UPPER are used by convention to indicate that the value may be arbitrarily large. The values MAX_STRING_LENGTH and MAX_SEQUENCE_LENGTH are used to indicate values limited by the size of a string or the size of a sequence.- Overrides:
getIntegerBounds
in classExpression
- Returns:
- the lower and upper bounds of integer values in the result, or null to indicate unknown or not applicable.
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addToPathMap
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
- the PathMapNodeSet to which the paths embodied in this expression should be added- 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
Promote this expression if possible- Overrides:
promote
in classExpression
- Parameters:
offer
- details of the promotion that is possibleparent
-- Returns:
- the promoted expression (or the original expression, unchanged)
- Throws:
XPathException
- if any error is detected
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iterateSubExpressions
Get the immediate subexpressions of this expression- Overrides:
iterateSubExpressions
in classExpression
- Returns:
- the subexpressions, as an array
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iterateSameFocusSubExpressions
Get the immediate sub-expressions of this expression that are evaluated with the same focus (context item, position, and size) as the parent expression.- Overrides:
iterateSameFocusSubExpressions
in classExpression
- Returns:
- an iterator containing those sub-expressions of this expression that are evaluated with the same focus as the parent expression
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hasLoopingSubexpression
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
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
Is this expression the same as another expression? -
hashCode
public int hashCode()get HashCode for comparing two expressions -
iterate
Iterate over the results, returning them in the correct order- 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
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
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
- Returns:
- a representation of the expression as a string
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explain
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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