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https://issues.apache.org/jira/browse/SPARK-23755?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dongjoon Hyun updated SPARK-23755:
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Affects Version/s: (was: 3.0.0)
3.1.0
> [Performance] Distinct elimination
> ----------------------------------
>
> Key: SPARK-23755
> URL: https://issues.apache.org/jira/browse/SPARK-23755
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Affects Versions: 3.1.0
> Reporter: Ioana Delaney
> Priority: Major
>
> The Distinct requirement can be removed if it is proved that the operation
> produces unique output.
>
> {code}
> select distinct d.deptno /* PK */, e.empname
> from employee e, department d
> where e.empno = d.mgrno /*PK = FK*/
> {code}
> *Internal query after rewrite:*
> {code}
> select d.deptno, e.empname
> from employee e, department d
> where e.empno = d.mgrno
> {code}
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