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From "Namit Jain (JIRA)" <>
Subject [jira] Commented: (HIVE-1194) sorted merge join
Date Thu, 25 Feb 2010 01:18:30 GMT


Namit Jain commented on HIVE-1194:

A new optimization step will be created which will convert the mapjoin to a sortmergejoin

> sorted merge join
> -----------------
>                 Key: HIVE-1194
>                 URL:
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: He Yongqiang
>             Fix For: 0.6.0
> 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
> 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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