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https://issues.apache.org/jira/browse/SPARK-8317?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Armbrust resolved SPARK-8317.
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Resolution: Fixed
Fix Version/s: 1.5.0
Issue resolved by pull request 6772
[https://github.com/apache/spark/pull/6772]
> Do not push sort into shuffle in Exchange operator
> --------------------------------------------------
>
> Key: SPARK-8317
> URL: https://issues.apache.org/jira/browse/SPARK-8317
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Reporter: Josh Rosen
> Assignee: Josh Rosen
> Fix For: 1.5.0
>
>
> In some cases, Spark SQL pushes sorting operations into the shuffle layer by
> specifying a key ordering as part of the shuffle dependency. I think that we
> should not do this:
> - Since we do not delegate aggregation to Spark's shuffle, specifying the
> keyOrdering as part of the shuffle has no effect on the shuffle map side.
> - By performing the shuffle ourselves (by inserting a sort operator after the
> shuffle instead), we can use the Exchange planner to choose specialized
> sorting implementations based on the types of rows being sorted.
> - We can remove some complexity from SqlSerializer2 by not requiring it to
> know about sort orderings, since SQL's own sort operators will already
> perform the necessary defensive copying.
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