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Posted to issues@drill.apache.org by "ASF GitHub Bot (Jira)" <ji...@apache.org> on 2022/06/16 16:36:00 UTC

[jira] [Commented] (DRILL-4147) Union All operator runs in a single fragment

    [ https://issues.apache.org/jira/browse/DRILL-4147?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17555188#comment-17555188 ] 

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

hsuanyi closed pull request #288: DRILL-4147: Change UnionPrel's DrillDistributionTrait to be ANY to al…
URL: https://github.com/apache/drill/pull/288




> 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
>            Priority: Major
>             Fix For: 1.8.0
>
>
> 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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