org.basex.query.xpath.expr
Class Equality

java.lang.Object
  org.basex.query.xpath.expr.Expr
      org.basex.query.xpath.expr.DualExpr
          org.basex.query.xpath.expr.Comparison
              org.basex.query.xpath.expr.Equality

public final class Equality
extends Comparison

Equality Expression Able to express equality or inequality.

Author:

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

Field Summary

Fields inherited from class org.basex.query.xpath.expr.Comparison

type

Fields inherited from class org.basex.query.xpath.expr.DualExpr

expr1, expr2

Constructor Summary

Equality(Expr e1, Expr e2, Comp t)
Constructor.

Method Summary

Expr	compile(XPContext ctx) Tries to optimize the Expression.
Path	indexEquivalent(XPContext ctx, Step curr) For predicate optimization.
int	indexSizes(XPContext ctx, Step curr, int min) For predicate optimization.

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

eval, simple, toString

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

usesPos, usesSize

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

returnedValue, sameAs

Methods inherited from class java.lang.Object

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

Constructor Detail

Equality

public Equality(Expr e1,
                Expr e2,
                Comp t)

Constructor.

Parameters:

e1 - first expression

e2 - second expression to compare with first

t - EqualityExpr.EQUALS or EqualityExpr.NOT_EQUALS

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

indexEquivalent

public Path indexEquivalent(XPContext ctx,
                            Step curr)

Description copied from class: Expr

For predicate optimization. If possible return an expression yielding the same results using the index. This may not do any changes to the current expression.

Overrides:

indexEquivalent in class Expr

Parameters:

ctx - root

curr - the LocationStep this Expression is a predicate of

Returns:

Equivalent index-expression or null

indexSizes

public int indexSizes(XPContext ctx,
                      Step curr,
                      int min)

Description copied from class: Expr

For predicate optimization. If possible return the number of entries an index returns. This may not do any changes to the current expression.

Overrides:

indexSizes in class Expr

Parameters:

ctx - root

curr - the LocationStep this Expression is a predicate of

min - current minimum size

Returns:

Equivalent index-expression or null