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Posted to issues@spark.apache.org by "Wenchen Fan (Jira)" <ji...@apache.org> on 2019/11/04 07:01:00 UTC
[jira] [Resolved] (SPARK-29343) Eliminate sorts without limit in
the subquery of Join/Aggregation
[ https://issues.apache.org/jira/browse/SPARK-29343?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Wenchen Fan resolved SPARK-29343.
---------------------------------
Fix Version/s: 3.0.0
Resolution: Fixed
Issue resolved by pull request 26011
[https://github.com/apache/spark/pull/26011]
> Eliminate sorts without limit in the subquery of Join/Aggregation
> -----------------------------------------------------------------
>
> Key: SPARK-29343
> URL: https://issues.apache.org/jira/browse/SPARK-29343
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.0.0
> Reporter: EdisonWang
> Assignee: EdisonWang
> Priority: Major
> Fix For: 3.0.0
>
>
> The {{Sort}} without {{Limit}} operator in {{Join/GroupBy}} subquery is useless.
>
> For example, {{select count(1) from (select a from test1 order by a)}} is equal to {{select count(1) from (select a from test1)}}.
> 'select * from (select a from test1 order by a) t1 join (select b from test2) t2 on t1.a = t2.b' is equal to {{select * from (select a from test1) t1 join (select b from test2) t2 on t1.a = t2.b}}.
> Remove useless {{Sort}} operator can import performance.
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