org.basex.query.xpath.locpath
Class LocPath

java.lang.Object
  org.basex.query.xpath.expr.Expr
      org.basex.query.xpath.locpath.LocPath

Direct Known Subclasses:

LocPathAbs, LocPathRel

public abstract class LocPath
extends Expr

LocationPath (absolute or relative).

Author:

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

Field Summary

Steps

steps List of location steps.

Constructor Summary

LocPath()

Method Summary

void	addPosPred(XPContext ctx) Limit evaluation of predicates to first hit when only existence of path has to be checked...
boolean	checkAxes() Checks if the specified location step has suitable index axes.
Expr	compile(XPContext ctx) Tries to optimize the Expression.
abstract NodeSet	eval(XPContext ctx) Evaluates the expression with the specified context set.
Index.TYPE	indexable(XPContext ctx, Expr exp, Comp cmp) Checks if the path is indexable.
LocPath	invertPath(Step curr) Inverts a location path.
boolean	sameAs(Expr cmp) Checks current and specified expression for equivalence.
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, toString

Methods inherited from class java.lang.Object

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

Field Detail

steps

public Steps steps

List of location steps.

Constructor Detail

LocPath

public LocPath()

Method Detail

addPosPred

public final void addPosPred(XPContext ctx)

Limit evaluation of predicates to first hit when only existence of path has to be checked...

Parameters:

ctx - query context

checkAxes

public final boolean checkAxes()

Checks if the specified location step has suitable index axes.

Returns:

true result of check

compile

public final 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 abstract 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

indexable

public final Index.TYPE indexable(XPContext ctx,
                                  Expr exp,
                                  Comp cmp)

Checks if the path is indexable.

Parameters:

ctx - query context

exp - expression which must be a literal

cmp - comparator

Returns:

result of check

invertPath

public final LocPath invertPath(Step curr)

Inverts a location path.

Parameters:

curr - current location step

Returns:

inverted path

sameAs

public final boolean sameAs(Expr cmp)

Description copied from class: Expr

Checks current and specified expression for equivalence.

Overrides:

sameAs in class Expr

Parameters:

cmp - expression to be compared

Returns:

result of check

usesPos

public final 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 final 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