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From "Vineet Garg (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-17493) Improve PKFK cardinality estimation in Physical planning
Date Wed, 13 Sep 2017 21:18:01 GMT

    [ https://issues.apache.org/jira/browse/HIVE-17493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16165298#comment-16165298
] 

Vineet Garg commented on HIVE-17493:
------------------------------------

Yeah looks like it. I'll rebase and re-upload the patch.

> Improve PKFK cardinality estimation in Physical planning
> --------------------------------------------------------
>
>                 Key: HIVE-17493
>                 URL: https://issues.apache.org/jira/browse/HIVE-17493
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Planning
>            Reporter: Vineet Garg
>            Assignee: Vineet Garg
>         Attachments: HIVE-17493.1.patch, HIVE-17493.2.patch
>
>
> Cardinality estimation of a join, after PK-FK relation has been ascertained, could be
improved if parent of the join operator is LEFT outer or RIGHT outer join.
> Currently estimation is done by estimating reduction of rows occurred on PK side, then
multiplying the reduction to FK side row count. This estimation of reduction currently doesn't
distinguish b/w INNER or OUTER joins. This could be improved to handle outer joins better.
> TPC-DS query45 is impacted by this.



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