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From "He Yongqiang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1194) sorted merge join
Date Wed, 03 Mar 2010 19:32:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1194?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12840829#action_12840829
] 

He Yongqiang commented on HIVE-1194:
------------------------------------

btw, i just checked the results without map join hints. The results are consistent.

> sorted merge join
> -----------------
>
>                 Key: HIVE-1194
>                 URL: https://issues.apache.org/jira/browse/HIVE-1194
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: He Yongqiang
>             Fix For: 0.6.0
>
>         Attachments: hive-1194-2010-02-28.patch, hive-1194-2010-3-2.2.patch, hive-1194-2010-3-2.patch
>
>
> If the input tables are sorted on the join key, and a mapjoin is being performed, it
is useful to exploit the sorted properties of the table.
> This can lead to substantial cpu savings - this needs to work across bucketed map joins
also.
> Since, sorted properties of a table are not enforced currently, a new parameter can be
added to specify to use the sort-merge join.

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