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https://issues.apache.org/jira/browse/SPARK-8319?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-8319:
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Assignee: Josh Rosen (was: Apache Spark)
> Update logic related to key ordering in shuffle dependencies
> ------------------------------------------------------------
>
> Key: SPARK-8319
> URL: https://issues.apache.org/jira/browse/SPARK-8319
> Project: Spark
> Issue Type: Improvement
> Components: Shuffle, SQL
> Reporter: Josh Rosen
> Assignee: Josh Rosen
>
> The Tungsten ShuffleManager falls back to regular SortShuffleManager whenever
> the shuffle dependency specifies a key ordering, but technically we only need
> to fall back when an aggregator is also specified. We should update the
> fallback logic to handle this case so that the Tungsten optimizations can
> apply to more workloads.
> I also noticed that the SQL Exchange operator performs defensive copying of
> shuffle inputs when a key ordering is specified, but this is unnecessary: the
> only shuffle manager that performs sorting on the map side is
> SortShuffleManager, and it only performs sorting if an aggregator is
> specified. SQL never uses Spark's shuffle for performing aggregation, so
> this copying is unnecessary.
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