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From "Suresh Ollala (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DRILL-4147) Union All operator runs in a single fragment
Date Tue, 16 Aug 2016 21:42:22 GMT

     [ https://issues.apache.org/jira/browse/DRILL-4147?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Suresh Ollala updated DRILL-4147:
---------------------------------
    Reviewer: Robert Hou

> 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
>             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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