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Posted to issues@hive.apache.org by "Gopal V (JIRA)" <ji...@apache.org> on 2018/08/13 05:12:00 UTC

[jira] [Commented] (HIVE-20370) Vectorization: Add Native Vector MapJoin hash table optimization for Left/Right Outer Joins when there are no Small Table values

    [ https://issues.apache.org/jira/browse/HIVE-20370?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16577838#comment-16577838 ] 

Gopal V commented on HIVE-20370:
--------------------------------

Zero rows on the outer side is often found within MERGE statements with the dynamic semi-join enabled (i.e all rows are new primary keys and there's no rows to update).

> Vectorization: Add Native Vector MapJoin hash table optimization for Left/Right Outer Joins when there are no Small Table values
> --------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-20370
>                 URL: https://issues.apache.org/jira/browse/HIVE-20370
>             Project: Hive
>          Issue Type: Bug
>          Components: Hive
>            Reporter: Matt McCline
>            Assignee: Matt McCline
>            Priority: Critical
>         Attachments: HIVE-20370.01.patch
>
>
> Similar to Native Vector MapJoin's InnerBigOnly optimization that uses an efficient Hash Multi-Set with a counter instead of a Hash Map with an empty value, do the same for Outer joins.



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