org.eigenbase.rel.rules
Class SwapJoinRule

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

public class SwapJoinRule
extends RelOptRule

SwapJoinRule permutes the inputs to a join. Outer joins cannot be permuted.

Since:

Nov 26, 2003

Version:

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

Author:

jhyde

Nested Class Summary

private static class

SwapJoinRule.VariableReplacer Walks over an expression, replacing references to fields of the left and right inputs.

Field Summary

static SwapJoinRule

instance The singleton

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

private

SwapJoinRule() Creates a SwapJoinRule.

Method Summary

void	onMatch(RelOptRuleCall call) Receives notification about a rule match.
static RelNode	swap(JoinRel join) Returns a relational expression with the inputs switched round.
static RelNode	swap(JoinRel join, boolean swapOuterJoins)

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 SwapJoinRule instance

The singleton

Constructor Detail

SwapJoinRule

private SwapJoinRule()

Creates a SwapJoinRule.

Method Detail

swap

public static RelNode swap(JoinRel join)

Returns a relational expression with the inputs switched round. Does not modify join. Returns null if the join cannot be swapped (for example, because it is an outer join).

swap

public static RelNode swap(JoinRel join,
                           boolean swapOuterJoins)

Parameters:

join - join to be swapped

swapOuterJoins - whether outer joins should be swapped

Returns:

swapped join if swapping possible; else null

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)