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From "Lefty Leverenz (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-17936) Dynamic Semijoin Reduction : markSemiJoinForDPP marks unwanted semijoin branches
Date Sun, 05 Nov 2017 03:56:01 GMT

    [ https://issues.apache.org/jira/browse/HIVE-17936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16239377#comment-16239377
] 

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

Doc note:  This adds *hive.tez.dynamic.semijoin.reduction.for.dpp.factor* to HiveConf.java,
so it needs to be documented in the wiki.

* [Configuration Properties -- Tez | https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties#ConfigurationProperties-Tez]

Added a TODOC3.0 label.

> 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
>              Labels: TODOC3.0
>             Fix For: 3.0.0
>
>         Attachments: HIVE-17936.1.patch, HIVE-17936.2.patch, HIVE-17936.3.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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