org.basex.query.xpath.locpath
Class LocPath

java.lang.Object
  org.basex.query.ExprInfo
      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 2005-08, 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 if only existence of path has to be checked.
boolean	checkAxes() Checks if the specified location step has suitable index axes.
java.lang.String	color() Returns a string description of the expression.
Expr	comp(XPContext ctx) Optimizes the expression.
abstract Nod	eval(XPContext ctx) Evaluates the expression with the specified context set.
IndexToken	indexable(XPContext ctx, Expr exp, Comp cmp) Checks if the path is indexable.
LocPath	invertPath(Step curr) Inverts a location path.
void	plan(Serializer ser) Recursively sends the abstract syntax of this expression to the specified serializer.
boolean	sameAs(Expr cmp) Checks current and specified expression for equivalence.
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

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

Field Detail

steps

public Steps steps

List of location steps.

Constructor Detail

LocPath

public LocPath()

Method Detail

eval

public abstract 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

comp

public final 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

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

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

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

addPosPred

public final void addPosPred(XPContext ctx)

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

Parameters:

ctx - query context

indexable

public final IndexToken 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

checkAxes

public final boolean checkAxes()

Checks if the specified location step has suitable index axes.

Returns:

true result of check

invertPath

public final LocPath invertPath(Step curr)

Inverts a location path.

Parameters:

curr - current location step

Returns:

inverted path

plan

public final 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 final 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