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Posted to issues@spark.apache.org by "Apache Spark (Jira)" <ji...@apache.org> on 2021/11/02 03:43:00 UTC
[jira] [Commented] (SPARK-37193)
DynamicJoinSelection.shouldDemoteBroadcastHashJoin should not apply to
outer joins
[ https://issues.apache.org/jira/browse/SPARK-37193?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17437125#comment-17437125 ]
Apache Spark commented on SPARK-37193:
--------------------------------------
User 'ekoifman' has created a pull request for this issue:
https://github.com/apache/spark/pull/34464
> DynamicJoinSelection.shouldDemoteBroadcastHashJoin should not apply to outer joins
> ----------------------------------------------------------------------------------
>
> Key: SPARK-37193
> URL: https://issues.apache.org/jira/browse/SPARK-37193
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.1.1
> Reporter: Eugene Koifman
> Priority: Major
>
> {{DynamicJoinSelection.shouldDemoteBroadcastHashJoin}} will prevent AQE from converting Sort merge join into a broadcast join because SMJ is faster when the side that would be broadcast has a lot of empty partitions.
> This makes sense for inner joins which can short circuit if one side is empty.
> For (left,right) outer join, the streaming side still has to be processed so demoting broadcast join doesn't have the same advantage.
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