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From "Vineet Garg (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-21537) Scalar query rewrite could be improved to not generate an extra join if subquery is guaranteed to produce atmost one row
Date Fri, 29 Mar 2019 22:00:00 GMT

     [ https://issues.apache.org/jira/browse/HIVE-21537?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Vineet Garg updated HIVE-21537:
-------------------------------
    Status: Patch Available  (was: Open)

> Scalar query rewrite could be improved to not generate an extra join if subquery is guaranteed
to produce atmost one row
> ------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-21537
>                 URL: https://issues.apache.org/jira/browse/HIVE-21537
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>    Affects Versions: 4.0.0
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>            Priority: Major
>              Labels: sub-query
>         Attachments: HIVE-21537.1.patch, HIVE-21537.2.patch, HIVE-21537.3.patch
>
>
> Currently Hive planner introduces this branch and later executes a rule to remove this
branch if it could. 
> Subquery remove rule itself could check if subquery will produce max one row (using relmetadat's
getMaxRowCount) and avoid introducing this branch.



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