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From "amit hadke (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-4147) Union All operator runs in a single fragment
Date Tue, 01 Dec 2015 03:20:10 GMT
amit hadke created DRILL-4147:

             Summary: 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

A User noticed that running select  from a single directory is much faster than union all
on two directories.

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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