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

Direct Known Subclasses:

ValueComparison

public class GeneralComparison

extends BinaryOp

A general XQuery/XPath2 comparison expression.

Author:

wolf

Field Summary

protected CachedResult	cached The class might cache the entire results of a previous execution.
protected Expression	collationArg Extra argument (to standard functions starts-with/contains etc.) to indicate the collation to be used for string comparisons.
protected boolean	inWhereClause Set to true if this expression is called within the where clause of a FLWOR expression.
protected int	relation The type of operator used for the comparison, i.e.
protected int	truncation Truncation flags: when comparing with a string value, the search string may be truncated with a single * wildcard.

Fields inherited from class org.exist.xquery.PathExpr

inPredicate, keepVirtual, LOG, source, steps

Fields inherited from class org.exist.xquery.AbstractExpression

astNode, context, contextDocSet, contextId

Fields inherited from interface org.exist.xquery.Expression

EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, 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	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
static boolean	compareAtomic(java.text.Collator collator, AtomicValue lv, AtomicValue rv, boolean backwardsCompatible, int truncation, int relation)
protected boolean	compareValues(java.text.Collator collator, AtomicValue lv, AtomicValue rv) Cast the atomic operands into a comparable type and compare them.
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.
protected Sequence	genericCompare(Sequence contextSequence, Item contextItem) Generic, slow implementation.
protected java.text.Collator	getCollator(Sequence contextSequence)
int	getDependencies() Returns Dependency.DEFAULT_DEPENDENCIES.
protected Sequence	nodeSetCompare(NodeSet nodes, Sequence contextSequence)
protected Sequence	nodeSetCompare(Sequence contextSequence) Optimized implementation, which can be applied if the left operand returns a node set.
protected Sequence	quickNodeSetCompare(Sequence contextSequence) Optimized implementation: first checks if a range index is defined on the nodes in the left argument.
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)
protected void	simplify() Possibly switch operands to simplify execution
protected void	switchOperands()
java.lang.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, getContext, getDocumentSet, getExpression, getLastExpression, getLength, getLiteralValue, getSource, isValid, replaceLastExpression, reset, setContext, setPrimaryAxis, setSource

Methods inherited from class org.exist.xquery.AbstractExpression

eval, getCardinality, getContextDocSet, getContextId, getExpressionId, setASTNode

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.exist.xquery.CompiledXQuery

eval

Field Detail

relation

protected int relation

The type of operator used for the comparison, i.e. =, !=, <, > ... One of the constants declared in class Constants.

truncation

protected int truncation

Truncation flags: when comparing with a string value, the search string may be truncated with a single * wildcard. See the constants declared in class Constants. The standard functions starts-with, ends-with and contains are transformed into a general comparison with wildcard. Hence the need to consider wildcards here.

cached

protected CachedResult cached

The class might cache the entire results of a previous execution.

collationArg

protected Expression collationArg

Extra argument (to standard functions starts-with/contains etc.) to indicate the collation to be used for string comparisons.

inWhereClause

protected boolean inWhereClause

Set to true if this expression is called within the where clause of a FLWOR expression.

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

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

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

Throws:

XPathException

genericCompare

protected Sequence genericCompare(Sequence contextSequence,
                                  Item contextItem)
                           throws XPathException

Generic, slow implementation. Applied if none of the possible optimizations can be used.

Parameters:

contextSequence -

contextItem -

Returns:

Throws:

XPathException

nodeSetCompare

protected Sequence nodeSetCompare(Sequence contextSequence)
                           throws XPathException

Optimized implementation, which can be applied if the left operand returns a node set. In this case, the left expression is executed first. All matching context nodes are then passed to the right expression.

Throws:

XPathException

nodeSetCompare

protected Sequence nodeSetCompare(NodeSet nodes,
                                  Sequence contextSequence)
                           throws XPathException

Throws:

XPathException

quickNodeSetCompare

protected Sequence quickNodeSetCompare(Sequence contextSequence)
                                throws XPathException

Optimized implementation: first checks if a range index is defined on the nodes in the left argument. If that fails, check if we can use the fulltext index to speed up the search. Otherwise, fall back to nodeSetCompare(NodeSet, Sequence).

Throws:

XPathException

compareValues

protected boolean compareValues(java.text.Collator collator,
                                AtomicValue lv,
                                AtomicValue rv)
                         throws XPathException

Cast the atomic operands into a comparable type and compare them.

Throws:

XPathException

compareAtomic

public static boolean compareAtomic(java.text.Collator collator,
                                    AtomicValue lv,
                                    AtomicValue rv,
                                    boolean backwardsCompatible,
                                    int truncation,
                                    int relation)
                             throws XPathException

Throws:

XPathException

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

toString

public java.lang.String toString()

Overrides:

toString in class PathExpr

switchOperands

protected void switchOperands()

simplify

protected void simplify()

Possibly switch operands to simplify execution

getCollator

protected java.text.Collator getCollator(Sequence contextSequence)
                                  throws XPathException

Throws:

XPathException

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