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From "Rui Li (JIRA)" <>
Subject [jira] [Assigned] (HIVE-7659) Unnecessary sort in query plan
Date Thu, 14 Aug 2014 09:06:14 GMT


Rui Li reassigned HIVE-7659:

    Assignee: Rui Li

> Unnecessary sort in query plan
> ------------------------------
>                 Key: HIVE-7659
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>          Components: Spark
>            Reporter: Rui Li
>            Assignee: Rui Li
> 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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