org.exist.xquery
Class LocationStep

java.lang.Object
  org.exist.xquery.AbstractExpression
      org.exist.xquery.Step
          org.exist.xquery.LocationStep

All Implemented Interfaces:

Expression

public class LocationStep
extends Step

Processes all location path steps (like descendant::*, ancestor::XXX). The results of the first evaluation of the expression are cached for the lifetime of the object and only reloaded if the context sequence (as passed to the eval(Sequence, Item) method) has changed.

Field Summary

protected boolean	applyPredicate
protected CachedResult	cached
protected DocumentSet	currentDocs
protected NodeSet	currentSet
protected boolean	inUpdate
protected UpdateListener	listener
protected boolean	optimized
protected Expression	parent
protected int	parentDeps
protected boolean	preloadedData
protected boolean	useDirectAttrSelect
protected boolean	useDirectChildSelect

Fields inherited from class org.exist.xquery.Step

abbreviatedStep, axis, hasPositionalPredicate, inPredicate, LOG, predicates, staticReturnType, test

Fields inherited from class org.exist.xquery.AbstractExpression

column, context, contextDocSet, contextId, line, unordered

Fields inherited from interface org.exist.xquery.Expression

DOT_TEST, EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_NODE_CONSTRUCTOR, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NEED_INDEX_INFO, NO_CONTEXT_ID, NON_STREAMABLE, POSITIONAL_PREDICATE, SINGLE_STEP_EXECUTION, UNORDERED, USE_TREE_TRAVERSAL

Constructor Summary

LocationStep(XQueryContext context, int axis)
Creates a new LocationStep instance.

LocationStep(XQueryContext context, int axis, NodeTest test)
Creates a new LocationStep instance.

Method Summary

void	accept(ExpressionVisitor visitor) The method accept
void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
protected Sequence	applyPredicate(Sequence outerSequence, Sequence contextSequence) The method applyPredicate
Sequence	eval(Sequence contextSequence, Item contextItem) The method eval
protected Sequence	getAncestors(XQueryContext context, Sequence contextSequence) The method getAncestors
protected Sequence	getAttributes(XQueryContext context, Sequence contextSequence) The method getAttributes
protected Sequence	getChildren(XQueryContext context, Sequence contextSequence) The method getChildren
int	getDependencies() Returns Dependency.DEFAULT_DEPENDENCIES.
protected Sequence	getDescendants(XQueryContext context, Sequence contextSequence) The method getDescendants
protected DocumentSet	getDocumentSet(NodeSet contextSet) The method getDocumentSet
protected Sequence	getFollowing(XQueryContext context, Sequence contextSequence) The method getFollowing
Expression	getParentExpression() The method getParent
protected Sequence	getParents(XQueryContext context, Sequence contextSequence) The method getParents
protected Sequence	getPreceding(XQueryContext context, Sequence contextSequence) The method getPreceding
protected Sequence	getSelf(XQueryContext context, Sequence contextSequence) The method getSelf
protected Sequence	getSiblings(XQueryContext context, Sequence contextSequence) The method getSiblings
protected boolean	hasPreloadedData() If the current path expression depends on local variables from a for expression, we can optimize by preloading entire element or attribute sets.
java.lang.Boolean	match(Sequence contextSequence, Item contextItem)
protected boolean	matchAttributes(XQueryContext context, Sequence contextSequence)
protected java.lang.Boolean	matchChildren(XQueryContext context, Sequence contextSequence)
protected void	registerUpdateListener() The method registerUpdateListener
void	resetState(boolean postOptimization) Called to inform an expression that it should reset to its initial state.
void	setPreloadedData(DocumentSet docs, NodeSet nodes) The method setPreloadedData
void	setUseDirectAttrSelect(boolean useDirectAttrSelect) The method setUseDirectAttrSelect

Methods inherited from class org.exist.xquery.Step

addPredicate, dump, getAxis, getCardinality, getPredicates, getPrimaryAxis, getTest, hasPredicates, insertPredicate, isAbbreviated, returnsType, setAbbreviated, setAxis, setPrimaryAxis, setTest, toString

Methods inherited from class org.exist.xquery.AbstractExpression

allowMixNodesInReturn, eval, getColumn, getContext, getContextDocSet, getContextId, getExpressionId, getLine, getParent, getSource, getSubExpression, getSubExpressionCount, needsReset, setASTNode, setContextDocSet, setContextId, setLocation, simplify

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

currentSet

protected NodeSet currentSet

currentDocs

protected DocumentSet currentDocs

listener

protected UpdateListener listener

parent

protected Expression parent

cached

protected CachedResult cached

parentDeps

protected int parentDeps

preloadedData

protected boolean preloadedData

optimized

protected boolean optimized

inUpdate

protected boolean inUpdate

useDirectAttrSelect

protected boolean useDirectAttrSelect

useDirectChildSelect

protected boolean useDirectChildSelect

applyPredicate

protected boolean applyPredicate

Constructor Detail

LocationStep

public LocationStep(XQueryContext context,
                    int axis)

Creates a new LocationStep instance.

Parameters:

context - a XQueryContext value

axis - an int value

LocationStep

public LocationStep(XQueryContext context,
                    int axis,
                    NodeTest test)

Creates a new LocationStep instance.

Parameters:

context - a XQueryContext value

axis - an int value

test - a NodeTest value

Method Detail

getDependencies

public int getDependencies()

Description copied from class: AbstractExpression

Returns Dependency.DEFAULT_DEPENDENCIES.

Specified by:

getDependencies in interface Expression

Overrides:

getDependencies in class AbstractExpression

Returns:

set of bit-flags

See Also:

Expression.getDependencies()

hasPreloadedData

protected boolean hasPreloadedData()

If the current path expression depends on local variables from a for expression, we can optimize by preloading entire element or attribute sets.

Returns:

Whether or not we can optimize

setPreloadedData

public void setPreloadedData(DocumentSet docs,
                             NodeSet nodes)

The method setPreloadedData

Parameters:

docs - a DocumentSet value

nodes - a NodeSet value

applyPredicate

protected Sequence applyPredicate(Sequence outerSequence,
                                  Sequence contextSequence)
                           throws XPathException

The method applyPredicate

Parameters:

outerSequence - a Sequence value

contextSequence - a Sequence value

Returns:

a Sequence value

Throws:

XPathException - if an error occurs

analyze

public void analyze(AnalyzeContextInfo contextInfo)
             throws XPathException

Description copied from interface: Expression

Statically analyze the expression and its subexpressions. During the static analysis phase, the query engine can detect unknown variables and some type errors.

Specified by:

analyze in interface Expression

Overrides:

analyze in class Step

Throws:

XPathException

eval

public Sequence eval(Sequence contextSequence,
                     Item contextItem)
              throws XPathException

The method eval

Specified by:

eval in interface Expression

Specified by:

eval in class Step

Parameters:

contextSequence - a Sequence value

contextItem - an Item value

Returns:

a Sequence value

Throws:

XPathException - if an error occurs

getSelf

protected Sequence getSelf(XQueryContext context,
                           Sequence contextSequence)
                    throws XPathException

The method getSelf

Parameters:

context - a XQueryContext value

contextSequence - a NodeSet value

Returns:

a Sequence value

Throws:

XPathException

getAttributes

protected Sequence getAttributes(XQueryContext context,
                                 Sequence contextSequence)
                          throws XPathException

The method getAttributes

Parameters:

context - a XQueryContext value

contextSequence - a NodeSet value

Returns:

a NodeSet value

Throws:

XPathException

getChildren

protected Sequence getChildren(XQueryContext context,
                               Sequence contextSequence)
                        throws XPathException

The method getChildren

Parameters:

context - a XQueryContext value

contextSequence - the context sequence

Returns:

a NodeSet value

Throws:

XPathException

getDescendants

protected Sequence getDescendants(XQueryContext context,
                                  Sequence contextSequence)
                           throws XPathException

The method getDescendants

Parameters:

context - a XQueryContext value

contextSequence - the context sequence

Returns:

a NodeSet value

Throws:

XPathException

getSiblings

protected Sequence getSiblings(XQueryContext context,
                               Sequence contextSequence)
                        throws XPathException

The method getSiblings

Parameters:

context - a XQueryContext value

contextSequence - a NodeSet value

Returns:

a NodeSet value

Throws:

XPathException

getPreceding

protected Sequence getPreceding(XQueryContext context,
                                Sequence contextSequence)
                         throws XPathException

The method getPreceding

Parameters:

context - a XQueryContext value

contextSequence - a Sequence value

Returns:

a NodeSet value

Throws:

XPathException - if an error occurs

getFollowing

protected Sequence getFollowing(XQueryContext context,
                                Sequence contextSequence)
                         throws XPathException

The method getFollowing

Parameters:

context - a XQueryContext value

contextSequence - a Sequence value

Returns:

a NodeSet value

Throws:

XPathException - if an error occurs

getAncestors

protected Sequence getAncestors(XQueryContext context,
                                Sequence contextSequence)
                         throws XPathException

The method getAncestors

Parameters:

context - a XQueryContext value

contextSequence - a Sequence value

Returns:

a NodeSet value

Throws:

XPathException

getParents

protected Sequence getParents(XQueryContext context,
                              Sequence contextSequence)
                       throws XPathException

The method getParents

Parameters:

context - a XQueryContext value

contextSequence - a Sequence value

Returns:

a NodeSet value

Throws:

XPathException

getDocumentSet

protected DocumentSet getDocumentSet(NodeSet contextSet)

The method getDocumentSet

Parameters:

contextSet - a NodeSet value

Returns:

a DocumentSet value

getParentExpression

public Expression getParentExpression()

The method getParent

Returns:

an Expression value

setUseDirectAttrSelect

public void setUseDirectAttrSelect(boolean useDirectAttrSelect)

The method setUseDirectAttrSelect

Parameters:

useDirectAttrSelect - a boolean value

registerUpdateListener

protected void registerUpdateListener()

The method registerUpdateListener

accept

public void accept(ExpressionVisitor visitor)

The method accept

Specified by:

accept in interface Expression

Overrides:

accept in class AbstractExpression

Parameters:

visitor - an ExpressionVisitor value

resetState

public void resetState(boolean postOptimization)

Description copied from interface: Expression

Called to inform an expression that it should reset to its initial state. All cached data in the expression object should be dropped. For example, the xmldb:document() function calls this method whenever the input document set has changed.

Specified by:

resetState in interface Expression

Overrides:

resetState in class Step

match

public java.lang.Boolean match(Sequence contextSequence,
                               Item contextItem)
                        throws XPathException

Specified by:

match in interface Expression

Overrides:

match in class AbstractExpression

Throws:

XPathException

matchChildren

protected java.lang.Boolean matchChildren(XQueryContext context,
                                          Sequence contextSequence)
                                   throws XPathException

Throws:

XPathException

matchAttributes

protected boolean matchAttributes(XQueryContext context,
                                  Sequence contextSequence)
                           throws XPathException

Throws:

XPathException