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Posted to issues@hive.apache.org by "Lefty Leverenz (JIRA)" <ji...@apache.org> on 2017/11/01 03:59:00 UTC

[jira] [Commented] (HIVE-17936) Dynamic Semijoin Reduction : markSemiJoinForDPP marks unwanted semijoin branches

    [ https://issues.apache.org/jira/browse/HIVE-17936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16233621#comment-16233621 ] 

Lefty Leverenz commented on HIVE-17936:
---------------------------------------

I left some comments on RB.

> Dynamic Semijoin Reduction : markSemiJoinForDPP marks unwanted semijoin branches
> --------------------------------------------------------------------------------
>
>                 Key: HIVE-17936
>                 URL: https://issues.apache.org/jira/browse/HIVE-17936
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Deepak Jaiswal
>            Assignee: Deepak Jaiswal
>            Priority: Major
>         Attachments: HIVE-17936.1.patch, HIVE-17936.2.patch
>
>
> In method markSemiJoinForDPP (HIVE-17399), the nDVs comparison should not have equality as there is a chance that the values are same on both sides and the branch is still marked as good when it shouldn't be.
> Add a configurable factor to see how useful this is if nDVs on smaller side are only slightly less than that on TS side.



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