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Posted to issues@drill.apache.org by "Vitalii Diravka (JIRA)" <ji...@apache.org> on 2018/04/03 09:04:00 UTC
[jira] [Assigned] (DRILL-3130) Project can be pushed below union
all / union to improve performance
[ 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 & 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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