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From "Vitalii Diravka (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (DRILL-3130) Project can be pushed below union all / union to improve performance
Date Tue, 03 Apr 2018 09:04:00 GMT

     [ https://issues.apache.org/jira/browse/DRILL-3130?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vitalii Diravka reassigned DRILL-3130:
--------------------------------------

    Assignee: Vitalii Diravka  (was: Sean Hsuan-Yi Chu)

> Project can be pushed below union all / union to improve performance
> --------------------------------------------------------------------
>
>                 Key: DRILL-3130
>                 URL: https://issues.apache.org/jira/browse/DRILL-3130
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Query Planning &amp; Optimization
>            Reporter: Sean Hsuan-Yi Chu
>            Assignee: Vitalii Diravka
>            Priority: Major
>             Fix For: 1.1.0
>
>
> A query such as 
> {code}
> Select a from 
> (select a, b, c, ..., union all select a, b, c, ...)
> {code}
> will perform Union-All over all the specified columns on the two sides, despite the fact
that only one column is asked for at the end. Ideally, we should perform ProjectPushDown rule
for Union & Union-All to avoid them to generate results which will be discarded at the
end.



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