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From "Sean Hsuan-Yi Chu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-3130) Project can be pushed below union all / union to improve performance
Date Mon, 01 Jun 2015 18:44:19 GMT

    [ https://issues.apache.org/jira/browse/DRILL-3130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14567769#comment-14567769
] 

Sean Hsuan-Yi Chu commented on DRILL-3130:
------------------------------------------

Review completed at :
https://reviews.apache.org/r/34528/

Commit#: bca20655283d351d5f5c4090e9047419ff22c75e

> 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 & Optimization
>            Reporter: Sean Hsuan-Yi Chu
>            Assignee: Sean Hsuan-Yi Chu
>
> 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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