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https://issues.apache.org/jira/browse/DRILL-3130?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Hsuan-Yi Chu resolved DRILL-3130.
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Resolution: Fixed
Fix Version/s: 1.1.0
Target Version/s: (was: Future)
> 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
> 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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