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https://issues.apache.org/jira/browse/SPARK-4367?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14254454#comment-14254454
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Cheng Hao commented on SPARK-4367:
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I am working on updating the Aggregation Function Interface right now, this is
the second sub task of the change, see
https://issues.apache.org/jira/browse/SPARK-4366 (first sub task) . Sorry, I
didn't describe it in details.
> Process the "distinct" value before shuffling for aggregation
> -------------------------------------------------------------
>
> Key: SPARK-4367
> URL: https://issues.apache.org/jira/browse/SPARK-4367
> Project: Spark
> Issue Type: Sub-task
> Components: SQL
> Reporter: Cheng Hao
>
> Most of aggregate function(e.g average) with "distinct" value will requires
> all of the records in the same group to be shuffled into a single node,
> however, as part of the optimization, those records can be partially
> aggregated before shuffling, that probably reduces the overhead of shuffling
> significantly.
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