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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2284) bucketized map join should allow join key as a superset of bucketized columns
Date Fri, 15 Jul 2011 20:29:59 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13066183#comment-13066183
] 

Namit Jain commented on HIVE-2284:
----------------------------------

I didnt understand the changes in build.xml

Why is TestContribCliDriver removed ?

> bucketized map join should allow join key as a superset of bucketized columns
> -----------------------------------------------------------------------------
>
>                 Key: HIVE-2284
>                 URL: https://issues.apache.org/jira/browse/HIVE-2284
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Ning Zhang
>            Assignee: Ning Zhang
>             Fix For: 0.8.0
>
>         Attachments: HIVE-2284.patch
>
>
> Currently bucketized mapjoin only allow the join keys being exactly the same as bucketized
columns. This is too restrictive and is missing some optimization opportunities. 
> If tables S and T are both bucketized on column A with the same # of buckets, and the
query is something like:
> <code> 
> SELECT /*+ MAPJOIN (S) */ ...
> FROM S join T 
>   ON (S.A = T.A AND S.B = T.B)
> <code>
> We should allow bucketized mapjoin since it's straightforward that bucket 1 from S join
with bucket 2 from T on such join condition must be empty. 

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