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https://issues.apache.org/jira/browse/SPARK-2554?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Armbrust reassigned SPARK-2554:
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Assignee: Michael Armbrust
> CountDistinct and SumDistinct should do partial aggregation
> -----------------------------------------------------------
>
> Key: SPARK-2554
> URL: https://issues.apache.org/jira/browse/SPARK-2554
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 1.0.1, 1.0.2
> Reporter: Cheng Lian
> Assignee: Michael Armbrust
>
> {{CountDistinct}} and {{SumDistinct}} should first do a partial aggregation
> and return unique value sets in each partition as partial results. Shuffle IO
> can be greatly reduced in in cases that there are only a few unique values.
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