[jira] [Reopened] (HIVE-18008) Add optimization rule to remove gby from right side of left semi-join

["Vineet Garg (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-18008?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vineet Garg reopened HIVE-18008:
--------------------------------

> Add optimization rule to remove gby from right side of left semi-join
> ---------------------------------------------------------------------
>
>                 Key: HIVE-18008
>                 URL: https://issues.apache.org/jira/browse/HIVE-18008
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>         Attachments: HIVE-18008.1.patch, HIVE-18008.2.patch
>
>
> Group by (on same keys as semi join) as right side of Left semi join is unnecessary and could be removed. We see this pattern in subqueries with explicit distinct keyword e.g.
> {code:sql}
> explain select * from src b where b.key in (select distinct key from src a where a.value = b.value)
> {code}



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