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https://issues.apache.org/jira/browse/HIVE-15227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15672331#comment-15672331
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Vineet Garg commented on HIVE-15227:
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[~ashutoshc] I discussed this with [~jcamachorodriguez] today and it looks like
Hive does group by before doing left semi join anyway. e.g. {noformat} select a
from t1 left semi join t2 on t1.a=t2.b {noformat} will generate GBY on t2.b
before doing Left Semi Join.
Is there any improvement which physical Left Semi Join operator has in this
case ?
> Optimize join + gby into semijoin
> ---------------------------------
>
> Key: HIVE-15227
> URL: https://issues.apache.org/jira/browse/HIVE-15227
> Project: Hive
> Issue Type: Bug
> Components: Logical Optimizer
> Reporter: Ashutosh Chauhan
> Assignee: Ashutosh Chauhan
> Attachments: HIVE-15227.patch
>
>
> Calcite has a rule which can do this transformation. Lets take advantage of
> this since Hive has native Left semi join operator.
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