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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-17767) Rewrite correlated EXISTS/IN subqueries into LEFT SEMI JOIN
Date Fri, 03 Nov 2017 15:36:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-17767?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16237779#comment-16237779
] 

Ashutosh Chauhan commented on HIVE-17767:
-----------------------------------------

Looks like few tests need update.

> Rewrite correlated EXISTS/IN subqueries into LEFT SEMI JOIN
> -----------------------------------------------------------
>
>                 Key: HIVE-17767
>                 URL: https://issues.apache.org/jira/browse/HIVE-17767
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>            Priority: Major
>         Attachments: HIVE-17767.1.patch, HIVE-17767.2.patch, HIVE-17767.3.patch, HIVE-17767.4.patch
>
>
> Currently such queries are written into group by + inner join with value generator and
is inefficient. Value generator consists of join with outer query to fetch all correlated
values. This value generator could be completely eliminated if such queries are instead rewritten
into LEFT SEMI JOIN.
> Note that to do this first hive need to support LEFT SEMI JOIN with non-equi condition
(HIVE-17766).



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