com.metamatrix.query.rewriter
Class VariableSubstitutionVisitor

java.lang.Object
  com.metamatrix.query.sql.LanguageVisitor
      com.metamatrix.query.sql.visitor.ExpressionMappingVisitor
          com.metamatrix.query.rewriter.VariableSubstitutionVisitor

public class VariableSubstitutionVisitor
extends ExpressionMappingVisitor

This visitor class will traverse a language object tree, it finds variables in the language object and replaces the variable with a Reference obj.,/p>

This will also evaluate special variables INPUT and CHANGING by looking at the user's query, it finds these special variables it replaces the variable with a value(in case of INPUT) of the corresponding variable in set the user command or replace it with a constant of boolean value (in case CHANGING) indicating if the variable value is set on the user's command.

The easiest way to use this visitor is to call the static method which creates the the visitor by passing it the Language Object and the variable context to be looked up. The public visit() methods should NOT be called directly.

Constructor Summary

VariableSubstitutionVisitor(java.util.Map variableValues, int commandType)
Construct a new visitor with the list of references.

Method Summary

Expression	replaceExpression(Expression expr) Common pattern used by visit methods in this Visitor
static void	substituteVariables(LanguageObject obj, java.util.Map variableValues, int commandType) Helper to visit the language object specified and replace any variables a Reference obj, and collect the references returned.
void	visit(Update obj)
void	visit(XQuery obj)

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

Methods inherited from class java.lang.Object

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

Constructor Detail

VariableSubstitutionVisitor

public VariableSubstitutionVisitor(java.util.Map variableValues,
                                   int commandType)

Construct a new visitor with the list of references.

Parameters:

references - A list of references on to be collected

Method Detail

visit

public void visit(XQuery obj)

Overrides:

visit in class LanguageVisitor

visit

public void visit(Update obj)

Overrides:

visit in class LanguageVisitor

replaceExpression

public Expression replaceExpression(Expression expr)

Common pattern used by visit methods in this Visitor

Overrides:

replaceExpression in class ExpressionMappingVisitor

Parameters:

expr -

Returns:

substituteVariables

public static final void substituteVariables(LanguageObject obj,
                                             java.util.Map variableValues,
                                             int commandType)
                                      throws QueryValidatorException

Helper to visit the language object specified and replace any variables a Reference obj, and collect the references returned.

Parameters:

obj - The Language object that is to be visited

commandType - The command type of the user command invoking this procedure

forwardReferences - If references in the variable values should be substituted into expressions in this command

Throws:

QueryValidatorException

QueryValidatorException