org.eigenbase.rel.rules
Class PushSemiJoinPastJoinRule

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

public class PushSemiJoinPastJoinRule
extends RelOptRule

PushSemiJoinPastJoinRule implements the rule for pushing semijoins down in a tree past a join in order to trigger other rules that will convert semijoins. SemiJoinRel(JoinRel(X, Y), Z) --> JoinRel(SemiJoinRel(X, Z), Y) or SemiJoinRel(JoinRel(X, Y), Z) --> JoinRel(X, SemiJoinRel(Y, Z)) Whether this first or second conversion is applied depends on which operands actually participate in the semijoin.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/PushSemiJoinPastJoinRule.java#15 $

Author:

Zelaine Fong

Field Summary

static PushSemiJoinPastJoinRule

instance

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

private

PushSemiJoinPastJoinRule() Creates a PushSemiJoinPastJoinRule.

Method Summary

void	onMatch(RelOptRuleCall call) Receives notification about a rule match.
private void	setJoinAdjustments(int[] adjustments, int nFieldsX, int nFieldsY, int nFieldsZ, int adjustY, int adjustZ) Sets an array to reflect how much each index corresponding to a field needs to be adjusted.

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 PushSemiJoinPastJoinRule instance

Constructor Detail

PushSemiJoinPastJoinRule

private PushSemiJoinPastJoinRule()

Creates a PushSemiJoinPastJoinRule.

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)

setJoinAdjustments

private void setJoinAdjustments(int[] adjustments,
                                int nFieldsX,
                                int nFieldsY,
                                int nFieldsZ,
                                int adjustY,
                                int adjustZ)

Sets an array to reflect how much each index corresponding to a field needs to be adjusted. The array corresponds to fields in a 3-way join between (X, Y, and Z). X remains unchanged, but Y and Z need to be adjusted by some fixed amount as determined by the input.

Parameters:

adjustments - array to be filled out

nFieldsX - number of fields in X

nFieldsY - number of fields in Y

nFieldsZ - number of fields in Z

adjustY - the amount to adjust Y by

adjustZ - the amount to adjust Z by