org.eigenbase.rel.rules
Class UnionEliminatorRule

java.lang.Object
  org.eigenbase.relopt.RelOptRule
      org.eigenbase.rel.rules.UnionEliminatorRule

public class UnionEliminatorRule
extends RelOptRule

UnionEliminatorRule checks to see if its possible to optimize a Union call by eliminating the Union operator altogether in the case the call consists of only one input.

Since:

Feb 4, 2005

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/UnionEliminatorRule.java#3 $

Author:

Wael Chatila

Field Summary

static UnionEliminatorRule

instance

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

private

UnionEliminatorRule() Creates a UnionEliminatorRule.

Method Summary

void	onMatch(RelOptRuleCall call) Receives notification about a rule match.

Methods inherited from class org.eigenbase.relopt.RelOptRule

convert, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, matches, mergeTraitsAndConvert, mergeTraitsAndConvert, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

instance

public static final UnionEliminatorRule instance

Constructor Detail

UnionEliminatorRule

private UnionEliminatorRule()

Creates a UnionEliminatorRule.

Method Detail

onMatch

public void onMatch(RelOptRuleCall call)

Description copied from class: RelOptRule

Receives notification about a rule match. 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 RelOptRuleCall.transformTo(org.eigenbase.rel.RelNode) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

call - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)