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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5159) ProjectMergeRule in Drill should operate on RelNodes with same convention trait.
Date Tue, 03 Jan 2017 17:13:58 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5159?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15795565#comment-15795565
] 

ASF GitHub Bot commented on DRILL-5159:
---------------------------------------

Github user jinfengni commented on a diff in the pull request:

    https://github.com/apache/drill/pull/705#discussion_r94443444
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillMergeProjectRule.java
---
    @@ -48,6 +50,12 @@ public boolean matches(RelOptRuleCall call) {
         Project topProject = call.rel(0);
         Project bottomProject = call.rel(1);
     
    +    // Make sure both projects be LogicalProject.
    +    if (topProject.getTraitSet().getTrait(ConventionTraitDef.INSTANCE) != Convention.NONE
||
    --- End diff --
    
    You are right that the current Drill specific MergeProjectRule extends from Calcite's
version and the only difference is to check complex output expression. Therefore, it make
senses the currently Drill MergeProjectRule operates on Calcite logical convention only. 
    
    Yes, in the future, we would consider allowing merging 2 DrillProjectRels. That should
be another instance of rule, which operates on DRILL_LOGICAL convention only.  


> ProjectMergeRule in Drill should operate on RelNodes with same convention trait.
> --------------------------------------------------------------------------------
>
>                 Key: DRILL-5159
>                 URL: https://issues.apache.org/jira/browse/DRILL-5159
>             Project: Apache Drill
>          Issue Type: Bug
>          Components: Query Planning & Optimization
>            Reporter: Jinfeng Ni
>            Assignee: Aman Sinha
>
> Drill extended version of  Calcite's ProjectMergeRule is used in a VolcanoPlanner where
RelNodes with different convention could match with this rule. 
> For instance, we could see this rule could be invoked when a DrillProject on top of a
LogicalProject. Also, since the output RelNode is built from the default Project RelFactory,
such rule execution could end up with a LogicalProject.
> {code}
> DrillProject                transform          
> \                                  ===>               LogicalProject
> LogicalProject
> {code}
>  
> This leads to un-necessary rule execution, or in certain case could lead to an infinite
loop.  
> The proposed fix is to check matched RelNodes to make sure that they do have Calcite
Logical convention. That way, both inputs and output of this rule would have same convention
trait.  This should reduce planning time, and avoid the possiblity of loop.



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