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From "Navis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3639) join order across mutiple joins
Date Tue, 30 Oct 2012 08:46:13 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13486741#comment-13486741
] 

Navis commented on HIVE-3639:
-----------------------------

If join type is same, reordering could be a good optimization point. Doing HIVE-3464, I've
had similar thoughts.
                
> join order across mutiple joins
> -------------------------------
>
>                 Key: HIVE-3639
>                 URL: https://issues.apache.org/jira/browse/HIVE-3639
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>
> This came up during a discussion with Sambavi - please add any details I may
> have missed.
> For a query of the form:
> select ..
> from
> A join B on A.c1 = B.c1
> join C on B.c2=C.c2;
> A,B are joined first and the result is then joined with C.
> This is clearly sub-optimal if A is the largest table, in which case
> B and C should be joined first, and then the result should be joined with A.

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