org.eigenbase.rel.rules
Class PullUpProjectsOnTopOfMultiJoinRule

java.lang.Object
  org.eigenbase.relopt.RelOptRule
      org.eigenbase.rel.rules.PullUpProjectsAboveJoinRule
          org.eigenbase.rel.rules.PullUpProjectsOnTopOfMultiJoinRule

public class PullUpProjectsOnTopOfMultiJoinRule
extends PullUpProjectsAboveJoinRule

PullUpProjectsOnTopOfMultiJoinRule implements the rule for pulling ProjectRels that are on top of a MultiJoinRel and beneath a JoinRel so the ProjectRel appears above the JoinRel. In the process of doing so, also save away information about the respective fields that are referenced in the expressions in the ProjectRel we're pulling up, as well as the join condition, in the resultant MultiJoinRels

For example, if we have the following subselect:

      (select X.x1, Y.y1 from X, Y
          where X.x2 = Y.y2 and X.x3 = 1 and Y.y3 = 2)

The MultiJoinRel associated with (X, Y) associates x1 with X and y1 with Y. Although x3 and y3 need to be read due to the filters, they are not required after the row scan has completed and therefore are not saved. The join fields, x2 and y2, are also tracked separately.

Note that by only pulling up projects that are on top of MultiJoinRels, we preserve projections on top of row scans.

See the superclass for details on restrictions regarding which ProjectRels cannot be pulled.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/PullUpProjectsOnTopOfMultiJoinRule.java#7 $

Author:

Zelaine Fong

Field Summary

static PullUpProjectsOnTopOfMultiJoinRule	instanceLeftProjectChild
static PullUpProjectsOnTopOfMultiJoinRule	instanceRightProjectChild
static PullUpProjectsOnTopOfMultiJoinRule	instanceTwoProjectChildren

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

PullUpProjectsOnTopOfMultiJoinRule(RelOptRuleOperand operand, String description)

Method Summary

protected RelNode	getProjectChild(RelOptRuleCall call, ProjectRel project, boolean leftChild) Returns the child of the project that will be used as input into the new JoinRel once the projects are pulled above the JoinRel.
protected ProjectRel	getRightChild(RelOptRuleCall call)
protected boolean	hasLeftChild(RelOptRuleCall call)
protected boolean	hasRightChild(RelOptRuleCall call)

Methods inherited from class org.eigenbase.rel.rules.PullUpProjectsAboveJoinRule

onMatch

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

instanceTwoProjectChildren

public static final PullUpProjectsOnTopOfMultiJoinRule instanceTwoProjectChildren

instanceLeftProjectChild

public static final PullUpProjectsOnTopOfMultiJoinRule instanceLeftProjectChild

instanceRightProjectChild

public static final PullUpProjectsOnTopOfMultiJoinRule instanceRightProjectChild

Constructor Detail

PullUpProjectsOnTopOfMultiJoinRule

public PullUpProjectsOnTopOfMultiJoinRule(RelOptRuleOperand operand,
                                          String description)

Method Detail

hasLeftChild

protected boolean hasLeftChild(RelOptRuleCall call)

Overrides:

hasLeftChild in class PullUpProjectsAboveJoinRule

Parameters:

call - RelOptRuleCall

Returns:

true if the rule was invoked with a left project child

hasRightChild

protected boolean hasRightChild(RelOptRuleCall call)

Overrides:

hasRightChild in class PullUpProjectsAboveJoinRule

Parameters:

call - RelOptRuleCall

Returns:

true if the rule was invoked with 2 children

getRightChild

protected ProjectRel getRightChild(RelOptRuleCall call)

Overrides:

getRightChild in class PullUpProjectsAboveJoinRule

Parameters:

call - RelOptRuleCall

Returns:

ProjectRel corresponding to the right child

getProjectChild

protected RelNode getProjectChild(RelOptRuleCall call,
                                  ProjectRel project,
                                  boolean leftChild)

Description copied from class: PullUpProjectsAboveJoinRule

Returns the child of the project that will be used as input into the new JoinRel once the projects are pulled above the JoinRel.

Overrides:

getProjectChild in class PullUpProjectsAboveJoinRule

Parameters:

call - RelOptRuleCall

project - project RelNode

leftChild - true if the project corresponds to the left projection

Returns:

child of the project that will be used as input into the new JoinRel once the projects are pulled above the JoinRel