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From "Apache Spark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-8317) Do not push sort into shuffle in Exchange operator
Date Tue, 14 Jul 2015 23:43:05 GMT

    [ https://issues.apache.org/jira/browse/SPARK-8317?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14627285#comment-14627285
] 

Apache Spark commented on SPARK-8317:
-------------------------------------

User 'JoshRosen' has created a pull request for this issue:
https://github.com/apache/spark/pull/7407

> 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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