net.sf.saxon.expr

Class SingletonIntersectExpression

java.lang.Object

net.sf.saxon.expr.Expression

net.sf.saxon.expr.BinaryExpression

net.sf.saxon.expr.VennExpression

net.sf.saxon.expr.SingletonIntersectExpression

All Implemented Interfaces:

SourceLocator, IdentityComparable, InstructionInfo

public class SingletonIntersectExpression
extends VennExpression

This expression is equivalent to (A intersect B) in the case where A has cardinality zero-or-one. This is handled as a special case because the standard sort-merge algorithm involves an unnecessary sort on B.

Field Summary

Fields inherited from class net.sf.saxon.expr.BinaryExpression

operand0, operand1, operator

Fields inherited from class net.sf.saxon.expr.Expression

EFFECTIVE_BOOLEAN_VALUE, EVALUATE_METHOD, ITEM_FEED_METHOD, ITERATE_METHOD, locationId, MAX_SEQUENCE_LENGTH, MAX_STRING_LENGTH, PROCESS_METHOD, staticProperties, UNBOUNDED_LOWER, UNBOUNDED_UPPER, WATCH_METHOD

Constructor Summary

Constructors

Constructor and Description
SingletonIntersectExpression(Expression p1, int op, Expression p2) Special case of an intersect expression where the first argument is a singleton

Method Summary

Methods

Modifier and Type	Method and Description
Expression	copy() Copy an expression.
protected String	displayOperator() Display the operator used by this binary expression
boolean	effectiveBooleanValue(XPathContext c) Get the effective boolean value.
String	getExpressionName() Get a name identifying the kind of expression, in terms meaningful to a user.
SequenceIterator	iterate(XPathContext c) Iterate over the value of the expression.
Expression	optimize(ExpressionVisitor visitor, ContextItemStaticInfo contextItemType) Perform optimisation of an expression and its subexpressions.
Expression	simplify(ExpressionVisitor visitor) Simplify the expression
Expression	typeCheck(ExpressionVisitor visitor, ContextItemStaticInfo contextInfo) Type-check the expression

Methods inherited from class net.sf.saxon.expr.VennExpression

computeCardinality, computeSpecialProperties, equals, gatherComponents, getExpressionCompiler, getItemType, getStreamingAdjunct, hashCode, operands, toPattern, unordered

Methods inherited from class net.sf.saxon.expr.BinaryExpression

explain, explainExtraAttributes, getArguments, getOperands, getOperator, isAssociative, isCommutative, isInverse, promote, replaceOperand, setFlattened, toShortString, toString

Methods inherited from class net.sf.saxon.expr.Expression

addToPathMap, adoptChildExpression, checkForUpdatingSubexpressions, checkPermittedContents, clearStreamabilityData, computeDependencies, computeStaticProperties, doPromotion, dynamicError, evaluateAsString, evaluateItem, evaluatePendingUpdates, explain, getCardinality, getColumnNumber, getConfiguration, getConstructType, getContainer, getDependencies, getEvaluationMethod, getHostLanguage, getImplementationMethod, getIntegerBounds, getIntrinsicDependencies, getLineNumber, getLocationId, getObjectName, getPosture, getProperties, getProperty, getPublicId, getSlotsUsed, getSpecialProperties, getStreamability, getSweep, getSystemId, hasVariableBinding, identityHashCode, implementsStaticTypeCheck, isIdentical, isSubtreeExpression, isUpdatingExpression, isVacuousExpression, iterateEvents, makeStreamingAdjunct, markTailFunctionCalls, operandList, process, resetLocalStaticProperties, setContainer, setEvaluationMethod, setFiltered, setLocationId, setPostureAndSweep, staticTypeCheck, suppressValidation, toStreamingPattern, typeError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

SingletonIntersectExpression

public SingletonIntersectExpression(Expression p1,
                            int op,
                            Expression p2)

Special case of an intersect expression where the first argument is a singleton

Parameters:

p1 - the first argument, always a singleton

op - the operator, always Token.INTERSECT

p2 - the second argument

Method Detail

simplify

public Expression simplify(ExpressionVisitor visitor)
                    throws XPathException

Simplify the expression

Overrides:

simplify in class Expression

Parameters:

visitor - an expression visitor

Returns:

the simplified expression

Throws:

XPathException - if an error is discovered during expression rewriting

typeCheck

public Expression typeCheck(ExpressionVisitor visitor,
                   ContextItemStaticInfo contextInfo)
                     throws XPathException

Type-check the expression

Overrides:

typeCheck in class VennExpression

Parameters:

visitor - an expression visitor

contextInfo - Information available statically about the context item: whether it is (possibly) absent; its static type; its streaming posture.

Returns:

the original expression, rewritten to perform necessary run-time type checks, and to perform other type-related optimizations

Throws:

XPathException - if an error is discovered during this phase (typically a type error)

optimize

public Expression optimize(ExpressionVisitor visitor,
                  ContextItemStaticInfo 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 class VennExpression

Parameters:

visitor - an expression visitor

contextItemType - 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 to Type.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)

copy

public Expression copy()

Copy an expression. This makes a deep copy.

Overrides:

copy in class VennExpression

Returns:

the copy of the original expression

iterate

public SequenceIterator iterate(XPathContext c)
                         throws XPathException

Iterate over the value of the expression. The result will always be sorted in document order, with duplicates eliminated

Overrides:

iterate in class VennExpression

Parameters:

c - The context for evaluation

Returns:

a SequenceIterator representing the union of the two operands

Throws:

XPathException - if any dynamic error occurs evaluating the expression

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathContext c)
                              throws XPathException

Get the effective boolean value. In the case of a union expression, this is reduced to an OR expression, for efficiency

Overrides:

effectiveBooleanValue in class VennExpression

Parameters:

c - The context in which the expression is to be evaluated

Returns:

the effective boolean value

Throws:

XPathException - if any dynamic error occurs evaluating the expression

getExpressionName

public String getExpressionName()

Description copied from class: VennExpression

Get a name identifying the kind of expression, in terms meaningful to a user.

Overrides:

getExpressionName in class VennExpression

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.

displayOperator

protected String displayOperator()

Display the operator used by this binary expression

Overrides:

displayOperator in class BinaryExpression

Returns:

String representation of the operator (for diagnostic display only)