org.exist.xquery
Class GeneralComparison

java.lang.Object
  extended by org.exist.xquery.AbstractExpression
      extended by org.exist.xquery.PathExpr
          extended by org.exist.xquery.BinaryOp
              extended by org.exist.xquery.GeneralComparison
All Implemented Interfaces:
CompiledXQuery, Expression, IndexUseReporter, Optimizable, CompiledExpression
Direct Known Subclasses:
ValueComparison

public class GeneralComparison
extends BinaryOp
implements Optimizable, IndexUseReporter

A general XQuery/XPath2 comparison expression.

Author:
wolf

Nested Class Summary
static class GeneralComparison.IndexFlags
           
 
Field Summary
 
Fields inherited from interface org.exist.xquery.Expression
DOT_TEST, EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_NODE_CONSTRUCTOR, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NEED_INDEX_INFO, NO_CONTEXT_ID, SINGLE_STEP_EXECUTION, USE_TREE_TRAVERSAL
 
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)
           
static GeneralComparison.IndexFlags checkForQNameIndex(GeneralComparison.IndexFlags idxflags, XQueryContext context, Sequence contextSequence, QName contextQName)
           
 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(boolean postOptimization)
          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()
Specified by:
hasUsedIndex in interface IndexUseReporter

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)

checkForQNameIndex

public static final GeneralComparison.IndexFlags checkForQNameIndex(GeneralComparison.IndexFlags idxflags,
                                                                    XQueryContext context,
                                                                    Sequence contextSequence,
                                                                    QName contextQName)

resetState

public void resetState(boolean postOptimization)
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 xmldb: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


Copyright (C) Wolfgang Meier. All rights reserved.