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https://issues.apache.org/jira/browse/HIVE-7659?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Rui Li reassigned HIVE-7659:
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Assignee: Rui Li
> Unnecessary sort in query plan
> ------------------------------
>
> 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
>
> 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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