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Posted to issues@hive.apache.org by "Vineet Garg (JIRA)" <ji...@apache.org> on 2017/11/01 01:21:00 UTC

[jira] [Updated] (HIVE-17767) Rewrite correlated EXISTS/IN subqueries into LEFT SEMI JOIN

     [ https://issues.apache.org/jira/browse/HIVE-17767?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vineet Garg updated HIVE-17767:
-------------------------------
    Status: Open  (was: Patch Available)

> 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
>
>
> 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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