org.exist.xquery
Class GeneralComparison

java.lang.Object
  org.exist.xquery.AbstractExpression
      org.exist.xquery.PathExpr
          org.exist.xquery.BinaryOp
              org.exist.xquery.GeneralComparison

All Implemented Interfaces:

CompiledXQuery, Expression, Optimizable, CompiledExpression

Direct Known Subclasses:

ValueComparison

public class GeneralComparison
extends BinaryOp
implements Optimizable

A general XQuery/XPath2 comparison expression.

Author:

wolf

Field Summary

Fields inherited from interface org.exist.xquery.Expression

DOT_TEST, EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NEED_INDEX_INFO, NO_CONTEXT_ID, SINGLE_STEP_EXECUTION

Constructor Summary

GeneralComparison(XQueryContext context, Expression left, Expression right, int relation)

GeneralComparison(XQueryContext context, Expression left, Expression right, int relation, int truncation)

GeneralComparison(XQueryContext context, int relation)

GeneralComparison(XQueryContext context, int relation, int truncation)

Method Summary

void	accept(ExpressionVisitor visitor) Start traversing the expression tree using the specified ExpressionVisitor.
void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
boolean	canOptimize(Sequence contextSequence)
void	dump(ExpressionDumper dumper) Write a diagnostic dump of the expression to the passed ExpressionDumper.
Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
int	getDependencies() Returns Dependency.DEFAULT_DEPENDENCIES.
int	getOptimizeAxis()
int	getRelation()
boolean	hasUsedIndex()
boolean	optimizeOnSelf()
NodeSet	preSelect(Sequence contextSequence, boolean useContext)
void	resetState() Called to inform an expression that it should reset to its initial state.
int	returnsType() The static return type of the expression.
void	setCollation(Expression collationArg)
String	toString()

Methods inherited from class org.exist.xquery.BinaryOp

getLeft, getRight, setContextDocSet, setLeft, setRight

Methods inherited from class org.exist.xquery.PathExpr

add, add, addPath, addPredicate, dump, getASTNode, getCardinality, getContext, getDocumentSet, getExpression, getLastExpression, getLength, getLiteralValue, getParent, getSource, isValid, replaceExpression, replaceLastExpression, reset, setContext, setPrimaryAxis, setSource

Methods inherited from class org.exist.xquery.AbstractExpression

eval, getContextDocSet, getContextId, getExpressionId, setASTNode

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.exist.xquery.Expression

eval, getASTNode, getCardinality, getContextDocSet, getContextId, getExpressionId, setASTNode, setContextDocSet, setPrimaryAxis

Methods inherited from interface org.exist.xquery.CompiledXQuery

eval

Constructor Detail

GeneralComparison

public GeneralComparison(XQueryContext context,
                         int relation)

GeneralComparison

public GeneralComparison(XQueryContext context,
                         int relation,
                         int truncation)

GeneralComparison

public GeneralComparison(XQueryContext context,
                         Expression left,
                         Expression right,
                         int relation)

GeneralComparison

public GeneralComparison(XQueryContext context,
                         Expression left,
                         Expression right,
                         int relation,
                         int truncation)

Method Detail

analyze

public void analyze(AnalyzeContextInfo contextInfo)
             throws XPathException

Description copied from interface: Expression

Statically analyze the expression and its subexpressions. During the static analysis phase, the query engine can detect unknown variables and some type errors.

Specified by:

analyze in interface Expression

Overrides:

analyze in class BinaryOp

Throws:

XPathException

canOptimize

public boolean canOptimize(Sequence contextSequence)

Specified by:

canOptimize in interface Optimizable

optimizeOnSelf

public boolean optimizeOnSelf()

Specified by:

optimizeOnSelf in interface Optimizable

getOptimizeAxis

public int getOptimizeAxis()

Specified by:

getOptimizeAxis in interface Optimizable

returnsType

public int returnsType()

Description copied from interface: Expression

The static return type of the expression. This method should return one of the type constants defined in class Type. If the return type cannot be determined statically, return Type.ITEM.

Specified by:

returnsType in interface Expression

Overrides:

returnsType in class BinaryOp

getDependencies

public int getDependencies()

Description copied from class: AbstractExpression

Returns Dependency.DEFAULT_DEPENDENCIES.

Specified by:

getDependencies in interface Expression

Overrides:

getDependencies in class PathExpr

Returns:

set of bit-flags

See Also:

Expression.getDependencies()

getRelation

public int getRelation()

preSelect

public NodeSet preSelect(Sequence contextSequence,
                         boolean useContext)
                  throws XPathException

Specified by:

preSelect in interface Optimizable

Throws:

XPathException

eval

public Sequence eval(Sequence contextSequence,
                     Item contextItem)
              throws XPathException

Description copied from interface: Expression

Evaluate the expression represented by this object. Depending on the context in which this expression is executed, either the context sequence, the context item or both of them may be set. An implementing class should know how to handle this. The general contract is as follows: if the Dependency.CONTEXT_ITEM bit is set in the bit field returned by Expression.getDependencies(), the eval method will be called once for every item in the context sequence. The contextItem parameter will be set to the current item. Otherwise, the eval method will only be called once for the whole context sequence and contextItem will be null. eXist tries to process the entire context set in one, single step whenever possible. Thus, most classes only expect context to contain a list of nodes which represents the current context of the expression. The position() function in XPath is an example for an expression, which requires both, context sequence and context item to be set. The context sequence might be a node set, a sequence of atomic values or a single node or atomic value.

Specified by:

eval in interface Expression

Specified by:

eval in class BinaryOp

Parameters:

contextSequence - the current context sequence.

contextItem - a single item, taken from context. This defines the item, the expression should work on.

Throws:

XPathException

hasUsedIndex

public boolean hasUsedIndex()

dump

public void dump(ExpressionDumper dumper)

Description copied from interface: Expression

Write a diagnostic dump of the expression to the passed ExpressionDumper.

Specified by:

dump in interface Expression

Overrides:

dump in class PathExpr

Parameters:

dumper - the expression dumper to write to

toString

public String toString()

Overrides:

toString in class PathExpr

setCollation

public void setCollation(Expression collationArg)

resetState

public void resetState()

Description copied from interface: Expression

Called to inform an expression that it should reset to its initial state. All cached data in the expression object should be dropped. For example, the document() function calls this method whenever the input document set has changed.

Specified by:

resetState in interface Expression

Overrides:

resetState in class PathExpr

accept

public void accept(ExpressionVisitor visitor)

Description copied from interface: Expression

Start traversing the expression tree using the specified ExpressionVisitor.

Specified by:

accept in interface Expression

Overrides:

accept in class PathExpr