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From DaveBirdsall <...@git.apache.org>
Subject [GitHub] trafodion pull request #1543: [TRAFODION 3047] Cannot get right result using...
Date Tue, 01 May 2018 20:46:07 GMT
Github user DaveBirdsall commented on a diff in the pull request:

    https://github.com/apache/trafodion/pull/1543#discussion_r185329230
  
    --- Diff: core/sql/optimizer/RelExpr.cpp ---
    @@ -7880,11 +7880,17 @@ NABoolean GroupByAgg::tryToPullUpPredicatesInPreCodeGen(
           else
             pulledPredicates += tempPulledPreds;
     
    +      // just remove pulled up predicates from char. input
    +      ValueIdSet newInputs(getGroupAttr()->getCharacteristicInputs());
    +      myLocalExpr += selectionPred();
    +      myLocalExpr -= tempPulledPreds;
    +      myLocalExpr.weedOutUnreferenced(newInputs);
    --- End diff --
    
    Could you explain what is going on in this code? I notice that earlier in the method we
already added selectionPred() to myLocalExpr, and then removed tempPulledPreds. I'm wondering
why we are doing this again. Also, It's not obvious to me why newInputs will have different
values than myNewInputs, which went through a similar calculation. An example might help.


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