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From "Zoltan Haindrich (JIRA)" <>
Subject [jira] [Commented] (HIVE-17767) Rewrite correlated EXISTS/IN subqueries into LEFT SEMI JOIN
Date Wed, 08 Nov 2017 18:47:00 GMT


Zoltan Haindrich commented on HIVE-17767:

[~vgarg] I think you've developed this on a separate branch which was forked before the "cross
product" warning stabilization; so I've added an addendum to change back the order. for the
following files:

> Rewrite correlated EXISTS/IN subqueries into LEFT SEMI JOIN
> -----------------------------------------------------------
>                 Key: HIVE-17767
>                 URL:
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>         Attachments: HIVE-17767.1.patch, HIVE-17767.2.patch, HIVE-17767.3.patch, HIVE-17767.4.patch,
HIVE-17767.5.patch, HIVE-17767.6.patch, HIVE-17767.7.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
> Note that to do this first hive need to support LEFT SEMI JOIN with non-equi condition

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