org.basex.query.xpath.expr
Class Filter

java.lang.Object
  org.basex.query.xpath.expr.Expr
      org.basex.query.xpath.expr.Filter

public final class Filter
extends Expr

Filter Expression filtering a nodeset. This Expression is invalid for other types as nodesets.

Author:

Workgroup DBIS, University of Konstanz 2005-07, ISC License, Tim Petrowsky

Constructor Summary

Filter(Expr e, Preds p)
Constructor.

Method Summary

Expr	compile(XPContext ctx) Tries to optimize the Expression.
NodeSet	eval(XPContext ctx) Evaluates the expression with the specified context set.
java.lang.String	toString()
boolean	usesPos() Checks whether this Expression (or its children) make use of the position parameter.
boolean	usesSize() Checks whether this Expression (or its children) make use of the setsize parameter.

Methods inherited from class org.basex.query.xpath.expr.Expr

indexEquivalent, indexSizes, returnedValue, sameAs

Methods inherited from class java.lang.Object

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

Constructor Detail

Filter

public Filter(Expr e,
              Preds p)

Constructor.

Parameters:

e - Expression (has to result in a nodeset!)

p - Predicate to filter nodeset

Method Detail

compile

public Expr compile(XPContext ctx)
             throws EvalException

Description copied from class: Expr

Tries to optimize the Expression.

Specified by:

compile in class Expr

Parameters:

ctx - expression context

Returns:

optimized Expression

Throws:

EvalException - evaluation exception

eval

public NodeSet eval(XPContext ctx)
             throws EvalException

Description copied from class: Expr

Evaluates the expression with the specified context set. Additionally provides a context

Specified by:

eval in class Expr

Parameters:

ctx - query context

Returns:

resulting XPathValue

Throws:

EvalException - evaluation exception

toString

public java.lang.String toString()

Specified by:

toString in class Expr

usesPos

public boolean usesPos()

Description copied from class: Expr

Checks whether this Expression (or its children) make use of the position parameter. If not this allows some nice optimizations.

Specified by:

usesPos in class Expr

Returns:

whether position is used

usesSize

public boolean usesSize()

Description copied from class: Expr

Checks whether this Expression (or its children) make use of the setsize parameter. If not this allows early predicate evaluation.

Specified by:

usesSize in class Expr

Returns:

whether setsize is used