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From "Rui Li (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-7659) Unnecessary sort in query plan [Spark Branch]
Date Fri, 15 Aug 2014 01:55:18 GMT

     [ https://issues.apache.org/jira/browse/HIVE-7659?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Rui Li updated HIVE-7659:
-------------------------

    Attachment: HIVE-7659.2-spark.patch

Update patch according to review

> 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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