org.exist.xquery
Class Step

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

All Implemented Interfaces:

Expression

Direct Known Subclasses:

LocationStep, RootNode, SimpleStep

public abstract class Step
extends AbstractExpression

Field Summary

Fields inherited from interface org.exist.xquery.Expression

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

Constructor Summary

Step(XQueryContext context, int axis)

Step(XQueryContext context, int axis, NodeTest test)

Method Summary

void	addPredicate(Expression expr)
void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
void	dump(ExpressionDumper dumper) Write a diagnostic dump of the expression to the passed ExpressionDumper.
abstract Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
int	getAxis()
int	getCardinality() The default cardinality is Cardinality.EXACTLY_ONE.
List	getPredicates()
NodeTest	getTest()
boolean	hasPredicates()
void	insertPredicate(Expression previous, Expression predicate)
void	resetState() Called to inform an expression that it should reset to its initial state.
int	returnsType() The static return type of the expression.
void	setAxis(int axis)
void	setPrimaryAxis(int axis)
void	setTest(NodeTest test)
String	toString()

Methods inherited from class org.exist.xquery.AbstractExpression

accept, eval, getASTNode, getContextDocSet, getContextId, getDependencies, getExpressionId, setASTNode, setContextDocSet

Methods inherited from class java.lang.Object

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

Constructor Detail

Step

public Step(XQueryContext context,
            int axis)

Step

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

Method Detail

addPredicate

public void addPredicate(Expression expr)

insertPredicate

public void insertPredicate(Expression previous,
                            Expression predicate)

hasPredicates

public boolean hasPredicates()

getPredicates

public List getPredicates()

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.

Throws:

XPathException

eval

public abstract 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 AbstractExpression

Parameters:

contextSequence - the current context sequence.

contextItem - a single item, taken from context. This defines the item, the expression should work on.

Throws:

XPathException

getAxis

public int getAxis()

setPrimaryAxis

public void setPrimaryAxis(int axis)

Specified by:

setPrimaryAxis in interface Expression

Overrides:

setPrimaryAxis in class AbstractExpression

dump

public void dump(ExpressionDumper dumper)

Description copied from interface: Expression

Write a diagnostic dump of the expression to the passed ExpressionDumper.

Parameters:

dumper - the expression dumper to write to

toString

public String toString()

Overrides:

toString in class Object

returnsType

public int returnsType()

Description copied from interface: Expression

The static return type of the expression. This method should return one of the type constants defined in class Type. If the return type cannot be determined statically, return Type.ITEM.

Specified by:

returnsType in interface Expression

Specified by:

returnsType in class AbstractExpression

getCardinality

public int getCardinality()

Description copied from class: AbstractExpression

The default cardinality is Cardinality.EXACTLY_ONE.

Specified by:

getCardinality in interface Expression

Overrides:

getCardinality in class AbstractExpression

setAxis

public void setAxis(int axis)

setTest

public void setTest(NodeTest test)

getTest

public NodeTest getTest()

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 AbstractExpression