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java.lang.Object
net.sf.saxon.expr.Expression
net.sf.saxon.expr.FilterExpression
public final class FilterExpression
extends Expression
Field Summary | |
static int |
Fields inherited from class net.sf.saxon.expr.Expression | |
EVALUATE_METHOD , ITERATE_METHOD , PROCESS_METHOD , locationId , staticProperties |
Constructor Summary | |
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Method Summary | |
PathMap.PathMapNodeSet |
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int |
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int |
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int |
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Expression |
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boolean |
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void |
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Expression |
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Expression |
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ItemType |
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boolean |
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int |
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boolean |
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boolean |
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boolean |
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SequenceIterator |
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Iterator |
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Expression |
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Expression |
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boolean |
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Expression |
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String |
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Expression |
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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
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 interface Expression
- 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
public int computeCardinality()
Get the static cardinality of this expression
- Overrides:
- computeCardinality in interface Expression
- 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
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 interface Expression
- Returns:
- the dependencies
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 interface Expression
- Returns:
- the static properties of the expression, as a bit-significant value
public Expression copy()
Copy an expression. This makes a deep copy.
- Overrides:
- copy in interface Expression
- Returns:
- the copy of the original expression
public boolean equals(Object other)
Is this expression the same as another expression?
- Parameters:
other
- the expression to be compared with this one
- Returns:
- true if the two expressions are statically equivalent
public void explain(ExpressionPresenter out)
Diagnostic print of expression structure. The abstract expression tree is written to the supplied output destination.
- Overrides:
- explain in interface Expression
- Parameters:
out
- the ExpressionPresenter to be used
public Expression getBaseExpression()
Get the underlying expression
- Returns:
- the expression being filtered
public Expression getFilter()
Get the filter expression
- Returns:
- the expression acting as the filter predicate
public ItemType getItemType(TypeHierarchy th)
Get the data type of the items returned
- Overrides:
- getItemType in interface Expression
- Parameters:
th
- the type hierarchy cache
- Returns:
- an integer representing the data type
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 interface Expression
- Parameters:
child
- the immediate subexpression
- Returns:
- true if the child expression is evaluated repeatedly
public int hashCode()
get HashCode for comparing two expressions
- Returns:
- the hash code
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
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
public boolean isSimpleBooleanFilter()
Test if the filter always returns a singleton boolean
- Returns:
- true if the filter is a simple boolean expression
public SequenceIterator iterate(XPathContext context) throws XPathException
Iterate over the results, returning them in the correct order
- Specified by:
- iterate in interface SequenceIterable
- Overrides:
- iterate in interface Expression
- Parameters:
context
- the dynamic context for the evaluation
- Returns:
- an iterator over the expression results
- Throws:
XPathException
- if any dynamic error occurs
public Iterator iterateSubExpressions()
Get the immediate subexpressions of this expression
- Overrides:
- iterateSubExpressions in interface Expression
- Returns:
- the subexpressions, as an array
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 interface Expression
- 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)
public Expression promote(PromotionOffer offer) throws XPathException
Promote this expression if possible
- Overrides:
- promote in interface Expression
- Parameters:
offer
- details of the promotion that is possible
- Returns:
- the promoted expression (or the original expression, unchanged)
public boolean replaceSubExpression(Expression original, Expression replacement)
Replace one subexpression by a replacement subexpression
- Overrides:
- replaceSubExpression in interface Expression
- Parameters:
original
- the original subexpressionreplacement
- the replacement subexpression
- Returns:
- true if the original subexpression is found
public Expression simplify(ExpressionVisitor visitor) throws XPathException
Simplify an expression
- Overrides:
- simplify in interface Expression
- Parameters:
visitor
- the expression visitor
- Returns:
- the simplified expression
- Throws:
XPathException
- if any failure occurs
public 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 interface Expression
public Expression typeCheck(ExpressionVisitor visitor, ItemType contextItemType) throws XPathException
Type-check the expression
- Overrides:
- typeCheck in interface Expression
- 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)