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https://issues.apache.org/jira/browse/SPARK-23973?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Wenchen Fan resolved SPARK-23973.
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Resolution: Fixed
Assignee: Marco Gaido
Fix Version/s: 2.4.0
> Remove consecutive sorts
> ------------------------
>
> Key: SPARK-23973
> URL: https://issues.apache.org/jira/browse/SPARK-23973
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.4.0
> Reporter: Henry Robinson
> Assignee: Marco Gaido
> Priority: Minor
> Fix For: 2.4.0
>
>
> As a follow-on from SPARK-23375, it would be easy to remove redundant sorts
> in the following kind of query:
> {code}
> Seq((1), (3)).toDF("int").orderBy('int.asc).orderBy('int.desc).explain()
> == Physical Plan ==
> *(2) Sort [int#35 DESC NULLS LAST], true, 0
> +- Exchange rangepartitioning(int#35 DESC NULLS LAST, 200)
> +- *(1) Sort [int#35 ASC NULLS FIRST], true, 0
> +- Exchange rangepartitioning(int#35 ASC NULLS FIRST, 200)
> +- LocalTableScan [int#35]
> {code}
> There's no need to perform {{(1) Sort}}. Since the sort operator isn't
> stable, AFAIK, it should be ok to remove a sort on any column that gets
> 'overwritten' by a subsequent one in this way.
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