Class PushSemiJoinPastProjectRule

  extended by org.eigenbase.relopt.RelOptRule
      extended by 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))

$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/ $
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


public static final PushSemiJoinPastProjectRule instance
Constructor Detail


private PushSemiJoinPastProjectRule()
Creates a PushSemiJoinPastProjectRule.

Method Detail


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
call - Rule call
See Also:


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.

project - ProjectRel on the LHS of the semijoin
semiJoin - the semijoin
the modified semijoin condition