org.eigenbase.rel.rules
Class PushSemiJoinPastProjectRule

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

public class PushSemiJoinPastProjectRule
extends RelOptRule

PushSemiJoinPastProjectRule implements the rule for pushing semijoins down in a tree past a project in order to trigger other rules that will convert semijoins.

SemiJoinRel(ProjectRel(X), Y) --> ProjectRel(SemiJoinRel(X, Y))

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/PushSemiJoinPastProjectRule.java#8 $

Author:

Zelaine Fong

Field Summary

static PushSemiJoinPastProjectRule

instance

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

private

PushSemiJoinPastProjectRule() Creates a PushSemiJoinPastProjectRule.

Method Summary

private RexNode	adjustCondition(ProjectRel project, SemiJoinRel semiJoin) Pulls the project above the semijoin and returns the resulting semijoin condition.
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 PushSemiJoinPastProjectRule instance

Constructor Detail

PushSemiJoinPastProjectRule

private PushSemiJoinPastProjectRule()

Creates a PushSemiJoinPastProjectRule.

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)

adjustCondition

private RexNode adjustCondition(ProjectRel project,
                                SemiJoinRel semiJoin)

Pulls the project above the semijoin and returns the resulting semijoin condition. As a result, the semijoin condition should be modified such that references to the LHS of a semijoin should now reference the children of the project that's on the LHS.

Parameters:

project - ProjectRel on the LHS of the semijoin

semiJoin - the semijoin

Returns:

the modified semijoin condition