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Posted to issues@spark.apache.org by "Reynold Xin (JIRA)" <ji...@apache.org> on 2017/11/02 13:21:00 UTC
[jira] [Resolved] (SPARK-22408) RelationalGroupedDataset's distinct
pivot value calculation launches unnecessary stages
[ https://issues.apache.org/jira/browse/SPARK-22408?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Reynold Xin resolved SPARK-22408.
---------------------------------
Resolution: Fixed
Assignee: Patrick Woody
Fix Version/s: 2.3.0
> RelationalGroupedDataset's distinct pivot value calculation launches unnecessary stages
> ---------------------------------------------------------------------------------------
>
> Key: SPARK-22408
> URL: https://issues.apache.org/jira/browse/SPARK-22408
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 2.2.0
> Reporter: Patrick Woody
> Assignee: Patrick Woody
> Fix For: 2.3.0
>
>
> When calculating the distinct values for a pivot in RelationalGroupedDataset (https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/RelationalGroupedDataset.scala#L322), we sort before doing a take(maxValues + 1).
> We should be able to improve this by adding a global limit before the sort, which should reduce the work of the sort, and by simply doing a collect to avoid multiple launching multiple stages as a part of the take.
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