saffron.rel
Class DistinctToExistsRule

java.lang.Object
  |
  +--saffron.opt.Rule
        |
        +--saffron.rel.DistinctToExistsRule

public class DistinctToExistsRule

extends Rule

Rule to translate a JavaDistinct into a JavaExists, provided that the select list contains zero columns.

Field Summary

Fields inherited from class saffron.opt.Rule

description, planner

Constructor Summary

DistinctToExistsRule()

Method Summary

void	onMatch(RuleCall call) This method is called every time the rule matches.

Methods inherited from class saffron.opt.Rule

convert, getOutConvention, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

DistinctToExistsRule

public DistinctToExistsRule()

Method Detail

onMatch

public void onMatch(RuleCall call)

Description copied from class: Rule

This method is called every time the rule matches. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RuleCall.transformTo(saffron.rel.Rel) to register the expression.

Specified by:

onMatch in class Rule