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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-4147) Union All operator runs in a single fragment
Date Mon, 01 Aug 2016 17:57:20 GMT

    [ https://issues.apache.org/jira/browse/DRILL-4147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15402513#comment-15402513
] 

ASF GitHub Bot commented on DRILL-4147:
---------------------------------------

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

    https://github.com/apache/drill/pull/555#discussion_r73022403
  
    --- Diff: exec/java-exec/src/test/java/org/apache/drill/TestUnionAll.java ---
    @@ -32,6 +34,9 @@
     public class TestUnionAll extends BaseTestQuery{
       private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(TestUnionAll.class);
     
    +  private static final String sliceTargetSmall = "alter session set `planner.slice_target`
= 1";
    +  private static final String sliceTargetDefault = "alter session set `planner.slice_target`
= " + ExecConstants.SLICE_TARGET_DEFAULT;
    --- End diff --
    
    ```private static final String sliceTargetDefault = "RESET `planner.slice_target`"; ```


> Union All operator runs in a single fragment
> --------------------------------------------
>
>                 Key: DRILL-4147
>                 URL: https://issues.apache.org/jira/browse/DRILL-4147
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: amit hadke
>            Assignee: Aman Sinha
>
> A User noticed that running select  from a single directory is much faster than union
all on two directories.
> (https://drill.apache.org/blog/2014/12/09/running-sql-queries-on-amazon-s3/#comment-2349732267)

> It seems like UNION ALL operator doesn't parallelize sub scans (its using SINGLETON for
distribution type). Everything is ran in single fragment.
> We may have to use SubsetTransformer in UnionAllPrule.



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