[GitHub] drill pull request #705: DRILL-5159: Make sure Drill's ProjectMergeRule oper...

[amansinha100 <gi...@git.apache.org>]

Github user amansinha100 commented on a diff in the pull request:

    https://github.com/apache/drill/pull/705#discussion_r94437725
  
    --- 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 --
    
    At first glance, it is non-intuitive that a Drill specific MergeProjectRule returns False if a DRILL_LOGICAL convention is encountered.  However, currently, this rule only checks for the complex expression (e.g convert_to_json), so your change is fine in the context of the current rule.  
    In future, would we consider allowing merging 2 DrillProjectRels ? (I think yes). 


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