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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-16462) Vectorization: Enabling hybrid grace disables specialization of all reduce side joins
Date Tue, 18 Apr 2017 18:26:41 GMT

    [ https://issues.apache.org/jira/browse/HIVE-16462?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15973240#comment-15973240
] 

Gopal V commented on HIVE-16462:
--------------------------------

+1

For reference, the crucial statement in the .q.out is 

{{Fast Hash Table and No Hybrid Hash Join IS true}}

> Vectorization: Enabling hybrid grace disables specialization of all reduce side joins
> -------------------------------------------------------------------------------------
>
>                 Key: HIVE-16462
>                 URL: https://issues.apache.org/jira/browse/HIVE-16462
>             Project: Hive
>          Issue Type: Bug
>          Components: Vectorization
>            Reporter: Jason Dere
>            Assignee: Jason Dere
>         Attachments: HIVE-16462.1.patch
>
>
> Observed by [~gopalv].
> Having grace hash join enabled prevents the specialized vector hash joins during the
vectorizer stage of query planning. However hive.llap.enable.grace.join.in.llap will later
disable grace hash join (LlapDecider runs after Vectorizer). If we can disable the grace hash
join before vectorization kicks in then we can still benefit from the specialized vector hash
joins.
> This can be special cased for the llap.execution.mode=only case.



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