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.

Author:

wolf

Field Summary

protected CachedResult	cached
protected DocumentSet	currentDocs
protected NodeSet	currentSet
protected boolean	inUpdate
protected UpdateListener	listener
protected Expression	parent
protected int	parentDeps
protected boolean	preload

Fields inherited from class org.exist.xquery.Step

axis, contextId, inPredicate, LOG, predicates, test

Fields inherited from class org.exist.xquery.AbstractExpression

astNode, context, contextDocSet

Fields inherited from interface org.exist.xquery.Expression

EXPRESSION_ID_INVALID, IGNORE_CONTEXT, IN_PREDICATE, IN_UPDATE, IN_WHERE_CLAUSE, NO_CONTEXT_ID, SINGLE_STEP_EXECUTION

Constructor Summary

LocationStep(XQueryContext context, int axis)

LocationStep(XQueryContext context, int axis, NodeTest test)

Method Summary

void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
protected Sequence	applyPredicate(Sequence outerSequence, Sequence contextSequence)
Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
protected NodeSet	getAncestors(XQueryContext context, NodeSet contextSet)
protected NodeSet	getAttributes(XQueryContext context, NodeSet contextSet)
protected NodeSet	getChildren(XQueryContext context, NodeSet contextSet)
int	getDependencies() Returns Dependency.DEFAULT_DEPENDENCIES.
protected NodeSet	getDescendants(XQueryContext context, NodeSet contextSet)
protected DocumentSet	getDocumentSet(NodeSet contextSet)
protected NodeSet	getFollowing(XQueryContext context, NodeSet contextSet)
protected StoredNode	getNextSibling(NodeImpl node)
protected NodeSet	getParents(XQueryContext context, NodeSet contextSet)
protected NodeSet	getPreceding(XQueryContext context, NodeSet contextSet)
protected Sequence	getSelf(XQueryContext context, NodeSet contextSet)
protected Sequence	getSelfAtomic(Sequence contextSequence)
protected NodeSet	getSiblings(XQueryContext context, NodeSet contextSet)
protected boolean	preloadNodeSets() If the current path expression depends on local variables from a for expression, we can optimize by preloading entire element or attribute sets.
protected void	registerUpdateListener()
void	resetState() Called to inform an expression that it should reset to its initial state.

Methods inherited from class org.exist.xquery.Step

addPredicate, dump, getAxis, returnsType, setAxis, setPrimaryAxis, setTest, toString

Methods inherited from class org.exist.xquery.AbstractExpression

eval, getASTNode, getCardinality, getContextDocSet, getContextId, getExpressionId, setASTNode, setContextDocSet

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

preload

protected boolean preload

inUpdate

protected boolean inUpdate

Constructor Detail

LocationStep

public LocationStep(XQueryContext context,
                    int axis)

LocationStep

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

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

See Also:

Expression.getDependencies()

preloadNodeSets

protected boolean preloadNodeSets()

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

Returns:

applyPredicate

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

Throws:

XPathException

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

Description copied from interface: Expression

Evaluate the expression represented by this object. Depending on the context in which this expression is executed, either the context sequence, the context item or both of them may be set. An implementing class should know how to handle this. The general contract is as follows: if the Dependency.CONTEXT_ITEM bit is set in the bit field returned by Expression.getDependencies(), the eval method will be called once for every item in the context sequence. The contextItem parameter will be set to the current item. Otherwise, the eval method will only be called once for the whole context sequence and contextItem will be null. eXist tries to process the entire context set in one, single step whenever possible. Thus, most classes only expect context to contain a list of nodes which represents the current context of the expression. The position() function in XPath is an example for an expression, which requires both, context sequence and context item to be set. The context sequence might be a node set, a sequence of atomic values or a single node or atomic value.

Specified by:

eval in interface Expression

Specified by:

eval in class Step

Throws:

XPathException

getSelf

protected Sequence getSelf(XQueryContext context,
                           NodeSet contextSet)

Parameters:

context -

contextSet -

Returns:

getSelfAtomic

protected Sequence getSelfAtomic(Sequence contextSequence)
                          throws XPathException

Throws:

XPathException

getAttributes

protected NodeSet getAttributes(XQueryContext context,
                                NodeSet contextSet)

getChildren

protected NodeSet getChildren(XQueryContext context,
                              NodeSet contextSet)

getDescendants

protected NodeSet getDescendants(XQueryContext context,
                                 NodeSet contextSet)

getSiblings

protected NodeSet getSiblings(XQueryContext context,
                              NodeSet contextSet)

getNextSibling

protected StoredNode getNextSibling(NodeImpl node)

getPreceding

protected NodeSet getPreceding(XQueryContext context,
                               NodeSet contextSet)
                        throws XPathException

Throws:

XPathException

getFollowing

protected NodeSet getFollowing(XQueryContext context,
                               NodeSet contextSet)
                        throws XPathException

Throws:

XPathException

getAncestors

protected NodeSet getAncestors(XQueryContext context,
                               NodeSet contextSet)

getParents

protected NodeSet getParents(XQueryContext context,
                             NodeSet contextSet)

getDocumentSet

protected DocumentSet getDocumentSet(NodeSet contextSet)

registerUpdateListener

protected void registerUpdateListener()

resetState

public void resetState()

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 document() function calls this method whenever the input document set has changed.

Specified by:

resetState in interface Expression

Overrides:

resetState in class Step