org.exist.xquery
Class BindingExpression

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

All Implemented Interfaces:

Expression

Direct Known Subclasses:

ForExpr, LetExpr, QuantifiedExpression

public abstract class BindingExpression

extends AbstractExpression

Abstract superclass for the variable binding expressions "for" and "let".

Author:

Wolfgang Meier

Field Summary

protected Expression	inputSequence
protected static Logger	LOG
protected OrderSpec[]	orderSpecs
protected static SequenceType	POSITIONAL_VAR_TYPE
protected Expression	returnExpr
protected SequenceType	sequenceType
protected java.lang.String	varName
protected Expression	whereExpr

Fields inherited from class org.exist.xquery.AbstractExpression

astNode, context, contextDocSet, contextId

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

BindingExpression(XQueryContext context)

Method Summary

void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
abstract void	analyze(AnalyzeContextInfo contextInfo, OrderSpec[] orderBy)
protected Sequence	applyWhereExpression(Sequence contextSequence)
protected boolean	checkOrderSpecs(Sequence in) Check all order specs to see if we can process them in one single step.
protected static void	clearContext(int contextId, Sequence seq)
Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
abstract Sequence	eval(Sequence contextSequence, Item contextItem, Sequence resultSequence)
DocumentSet	preselect(DocumentSet in_docs)
void	resetState() Called to inform an expression that it should reset to its initial state.
int	returnsType() The static return type of the expression.
protected static void	setContext(int contextId, Sequence seq)
void	setInputSequence(Expression sequence)
void	setOrderSpecs(OrderSpec[] specs)
void	setReturnExpression(Expression expr)
void	setSequenceType(SequenceType type) Set the sequence type of the variable (as specified in the "as" clause).
void	setVariable(java.lang.String qname)
void	setWhereExpression(Expression expr)

Methods inherited from class org.exist.xquery.AbstractExpression

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

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.exist.xquery.Expression

dump

Field Detail

LOG

protected static final Logger LOG

POSITIONAL_VAR_TYPE

protected static final SequenceType POSITIONAL_VAR_TYPE

varName

protected java.lang.String varName

sequenceType

protected SequenceType sequenceType

inputSequence

protected Expression inputSequence

returnExpr

protected Expression returnExpr

whereExpr

protected Expression whereExpr

orderSpecs

protected OrderSpec[] orderSpecs

Constructor Detail

BindingExpression

public BindingExpression(XQueryContext context)

Method Detail

setVariable

public void setVariable(java.lang.String qname)

setSequenceType

public void setSequenceType(SequenceType type)

Set the sequence type of the variable (as specified in the "as" clause).

Parameters:

type -

setInputSequence

public void setInputSequence(Expression sequence)

setReturnExpression

public void setReturnExpression(Expression expr)

setWhereExpression

public void setWhereExpression(Expression expr)

setOrderSpecs

public void setOrderSpecs(OrderSpec[] specs)

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

analyze

public abstract void analyze(AnalyzeContextInfo contextInfo,
                             OrderSpec[] orderBy)
                      throws XPathException

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 AbstractExpression

Throws:

XPathException

eval

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

Throws:

XPathException

applyWhereExpression

protected Sequence applyWhereExpression(Sequence contextSequence)
                                 throws XPathException

Throws:

XPathException

checkOrderSpecs

protected boolean checkOrderSpecs(Sequence in)

Check all order specs to see if we can process them in one single step. In general, this is possible if all order expressions return nodes.

Returns:

preselect

public DocumentSet preselect(DocumentSet in_docs)
                      throws XPathException

Throws:

XPathException

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

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

setContext

protected static final void setContext(int contextId,
                                       Sequence seq)

clearContext

protected static final void clearContext(int contextId,
                                         Sequence seq)