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Posted to issues@spark.apache.org by "Apache Spark (JIRA)" <ji...@apache.org> on 2015/06/12 02:17:00 UTC
[jira] [Commented] (SPARK-8317) Do not push sort into shuffle in
Exchange operator
[ https://issues.apache.org/jira/browse/SPARK-8317?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14582724#comment-14582724 ]
Apache Spark commented on SPARK-8317:
-------------------------------------
User 'JoshRosen' has created a pull request for this issue:
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
>
> 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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