org.basex.query.xpath.expr
Class Filter

java.lang.Object
  extended by org.basex.query.ExprInfo
      extended by org.basex.query.xpath.expr.Expr
          extended by 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 2005-08, ISC License, Tim Petrowsky

Constructor Summary
Filter(Expr e, Preds p)
          Constructor.
 
Method Summary
 java.lang.String color()
          Returns a string description of the expression.
 Expr comp(XPContext ctx)
          Optimizes the expression.
 Nod eval(XPContext ctx)
          Evaluates the expression with the specified context set.
 void plan(Serializer ser)
          Recursively sends the abstract syntax of this expression to the specified serializer.
 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 org.basex.query.ExprInfo
info, name
 
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

eval

public Nod eval(XPContext ctx)
         throws QueryException
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:
QueryException - evaluation exception

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

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

comp

public Expr comp(XPContext ctx)
          throws QueryException
Description copied from class: Expr
Optimizes the expression.

Specified by:
comp in class Expr
Parameters:
ctx - expression context
Returns:
optimized Expression
Throws:
QueryException - evaluation exception

plan

public void plan(Serializer ser)
          throws java.io.IOException
Description copied from class: ExprInfo
Recursively sends the abstract syntax of this expression to the specified serializer.

Specified by:
plan in class ExprInfo
Parameters:
ser - serializer
Throws:
java.io.IOException - exception

color

public java.lang.String color()
Description copied from class: ExprInfo
Returns a string description of the expression. Contrary to the ExprInfo.toString() method, the current expressions aren't included in the output.

Overrides:
color in class ExprInfo
Returns:
result of check

toString

public java.lang.String toString()
Specified by:
toString in class ExprInfo