org.eigenbase.rel.rules
Class MergeProjectRule

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

public class MergeProjectRule
extends RelOptRule

MergeProjectRule merges a ProjectRel into another ProjectRel, provided the projects aren't projecting identical sets of input references.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/MergeProjectRule.java#9 $

Author:

Zelaine Fong

Field Summary

private boolean	force if true, always merge projects
static MergeProjectRule	instance

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

private	MergeProjectRule() Creates a MergeProjectRule.
	MergeProjectRule(boolean force) Creates a MergeProjectRule, specifying whether to always merge projects.

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 MergeProjectRule instance

force

private final boolean force

if true, always merge projects

Constructor Detail

MergeProjectRule

private MergeProjectRule()

Creates a MergeProjectRule.

MergeProjectRule

public MergeProjectRule(boolean force)

Creates a MergeProjectRule, specifying whether to always merge projects.

Parameters:

force - Whether to always merge projects

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)