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From "Andrew Sherman (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-18008) Add optimization rule to remove gby from right side of left semi-join
Date Fri, 10 Nov 2017 01:03:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-18008?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16246853#comment-16246853
] 

Andrew Sherman commented on HIVE-18008:
---------------------------------------

Thanks

> Add optimization rule to remove gby from right side of left semi-join
> ---------------------------------------------------------------------
>
>                 Key: HIVE-18008
>                 URL: https://issues.apache.org/jira/browse/HIVE-18008
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>         Attachments: HIVE-18008.1.patch, HIVE-18008.2.patch
>
>
> Group by (on same keys as semi join) as right side of Left semi join is unnecessary and
could be removed. We see this pattern in subqueries with explicit distinct keyword e.g.
> {code:sql}
> explain select * from src b where b.key in (select distinct key from src a where a.value
= b.value)
> {code}



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