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From "Vineet Garg (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (HIVE-21537) Scalar query rewrite could be improved to not generate an extra join if subquery is guaranteed to produce atmost one row
Date Thu, 28 Mar 2019 22:37:00 GMT

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

Vineet Garg reassigned HIVE-21537:
----------------------------------


> 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
>
> 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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