com.metamatrix.query.sql.visitor
Class EvaluateExpressionVisitor

java.lang.Object
  com.metamatrix.query.sql.LanguageVisitor
      com.metamatrix.query.sql.visitor.ExpressionMappingVisitor
          com.metamatrix.query.sql.visitor.EvaluateExpressionVisitor

public class EvaluateExpressionVisitor
extends ExpressionMappingVisitor

This visitor simplifies Language Objects by evaluating and/or replacing Expressions within them.

The easiest way to use this visitor is to call the static methods which create the visitor and run it. The public visit() methods should NOT be called directly.

Method Summary

static boolean	isFullyEvaluatable(LanguageObject obj, boolean duringPlanning) Should be called to check if the object can fully evaluated
Expression	replaceExpression(Expression expr) Evaluate the expression.
static void	replaceExpressions(LanguageObject obj, boolean deep, ProcessorDataManager dataMgr, CommandContext context)
void	setContext(CommandContext context)
static boolean	willBecomeConstant(LanguageObject obj) Will return true if the expression can be deterministically evaluated at runtime, but it may not be evaluatable during planning

Methods inherited from class com.metamatrix.query.sql.visitor.ExpressionMappingVisitor

createAliases, getVariableValues, mapExpressions, setVariableValues, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit

Methods inherited from class com.metamatrix.query.sql.LanguageVisitor

setAbort, shouldAbort, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit

Methods inherited from class java.lang.Object

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

Method Detail

setContext

public void setContext(CommandContext context)

replaceExpression

public Expression replaceExpression(Expression expr)

Evaluate the expression. This method takes into account whether the Expression CAN be evaluated or not. This method also takes into account if the Expression is a Reference. The Reference may not be evaluatable (may not have data tuple and element map set on it), in which case this method may return the Reference itself or the Expression inside the Reference, depending on the instance variables of this visitor.

Overrides:

replaceExpression in class ExpressionMappingVisitor

Parameters:

expr -

Returns:

willBecomeConstant

public static final boolean willBecomeConstant(LanguageObject obj)

Will return true if the expression can be deterministically evaluated at runtime, but it may not be evaluatable during planning

isFullyEvaluatable

public static final boolean isFullyEvaluatable(LanguageObject obj,
                                               boolean duringPlanning)

Should be called to check if the object can fully evaluated

replaceExpressions

public static final void replaceExpressions(LanguageObject obj,
                                            boolean deep,
                                            ProcessorDataManager dataMgr,
                                            CommandContext context)
                                     throws ExpressionEvaluationException,
                                            MetaMatrixComponentException

Throws:

ExpressionEvaluationException

MetaMatrixComponentException