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https://issues.apache.org/jira/browse/SPARK-4485?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14217687#comment-14217687
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Apache Spark commented on SPARK-4485:
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User 'wangxiaojing' has created a pull request for this issue:
https://github.com/apache/spark/pull/3362
> Add broadcast outer join to optimize left outer join and right outer join
> --------------------------------------------------------------------------
>
> Key: SPARK-4485
> URL: https://issues.apache.org/jira/browse/SPARK-4485
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 1.1.0
> Reporter: XiaoJing wang
> Priority: Minor
> Original Estimate: 0.05h
> Remaining Estimate: 0.05h
>
> For now, spark use broadcast join instead of hash join to optimize {{inner
> join}} when the size of one side data did not reach the
> {{AUTO_BROADCASTJOIN_THRESHOLD}}
> However,Spark SQL will perform shuffle operations on each child relations
> while executing
> {{left outer join}} and {{right outer join}}. {outer join}} is more
> suitable for optimiztion with broadcast join.
> We are planning to create a {{BroadcastHashouterJoin}} to implement the
> broadcast join for {{left outer join}} and {{right outer join}}
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