org.exist.xquery
Class LogicalOp

java.lang.Object
  org.exist.xquery.AbstractExpression
      org.exist.xquery.PathExpr
          org.exist.xquery.BinaryOp
              org.exist.xquery.LogicalOp

All Implemented Interfaces:

CompiledXQuery, Expression, RewritableExpression, org.xmldb.api.base.CompiledExpression

Direct Known Subclasses:

OpAnd, OpOr

public abstract class LogicalOp
extends BinaryOp

Base class for the boolean operators "and" and "or".

Field Summary

protected boolean	optimize If set to true, the boolean operation is processed as a set operation on two node sets.
protected Expression	parent
protected boolean	rewritable

Fields inherited from class org.exist.xquery.BinaryOp

inWhereClause

Fields inherited from class org.exist.xquery.PathExpr

inPredicate, keepVirtual, LOG, staticContext, steps

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

LogicalOp(XQueryContext context)

Method Summary

void	analyze(AnalyzeContextInfo contextInfo) Statically analyze the expression and its subexpressions.
abstract Sequence	eval(Sequence contextSequence, Item contextItem) Evaluate the expression represented by this object.
int	getDependencies() Returns Dependency.DEFAULT_DEPENDENCIES.
Expression	getParent()
boolean	isRewritable()
int	returnsType() The static return type of the expression.

Methods inherited from class org.exist.xquery.BinaryOp

getLeft, getRight, setContextDocSet, setLeft, setRight, simplify

Methods inherited from class org.exist.xquery.PathExpr

accept, add, add, addPath, addPredicate, allowMixNodesInReturn, dump, dump, getCardinality, getColumn, getContext, getDocumentSet, getExpression, getLastExpression, getLength, getLine, getLiteralValue, getPrimaryAxis, getSubExpression, getSubExpressionCount, isValid, replaceExpression, replaceLastExpression, reset, resetState, setContext, setPrimaryAxis, setUseStaticContext, toString

Methods inherited from class org.exist.xquery.AbstractExpression

eval, getContextDocSet, getContextId, getExpressionId, getSource, match, needsReset, setASTNode, setContextId, setLocation

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.exist.xquery.CompiledXQuery

eval, getSource

Field Detail

optimize

protected boolean optimize

If set to true, the boolean operation is processed as a set operation on two node sets. This is only possible within a predicate expression and if both operands return nodes. The predicate class can then filter out the matching nodes from the context set.

rewritable

protected boolean rewritable

parent

protected Expression parent

Constructor Detail

LogicalOp

public LogicalOp(XQueryContext context)

Parameters:

context -

Method Detail

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 BinaryOp

Parameters:

contextSequence - the current context sequence.

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

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 BinaryOp

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

Overrides:

returnsType in class BinaryOp

getDependencies

public int getDependencies()

Description copied from class: AbstractExpression

Returns Dependency.DEFAULT_DEPENDENCIES.

Specified by:

getDependencies in interface Expression

Overrides:

getDependencies in class PathExpr

Returns:

set of bit-flags

See Also:

Expression.getDependencies()

getParent

public Expression getParent()

Specified by:

getParent in interface Expression

Overrides:

getParent in class PathExpr

isRewritable

public boolean isRewritable()