[jira] [Commented] (HIVE-7659) Unnecessary sort in query plan [Spark Branch]

["Brock Noland (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-7659?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14098077#comment-14098077 ] 

Brock Noland commented on HIVE-7659:
------------------------------------

+1 pending tests

> Unnecessary sort in query plan [Spark Branch]
> ---------------------------------------------
>
>                 Key: HIVE-7659
>                 URL: https://issues.apache.org/jira/browse/HIVE-7659
>             Project: Hive
>          Issue Type: Improvement
>          Components: Spark
>            Reporter: Rui Li
>            Assignee: Rui Li
>         Attachments: HIVE-7659-spark.patch, HIVE-7659.2-spark.patch
>
>
> For hive on spark.
> Currently we rely on the sort order in RS to decide whether we need a sortByKey transformation. However a simple group by query will also have the sort order set to '+'.
> Consider the query: select key from table group by key. The RS in the map work will have sort order set to '+', thus requiring a sortByKey shuffle.
> To avoid the unnecessary sort, we should either use another way to decide if there has to be a sort shuffle, or we should set the sort order only when sort is really needed.



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