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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-4781) LEFT SEMI JOIN generates wrong results when the number of rows belonging to a single key of the right table exceed hive.join.emit.interval
Date Tue, 02 Jul 2013 02:54:22 GMT

    [ https://issues.apache.org/jira/browse/HIVE-4781?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13697440#comment-13697440
] 

Hudson commented on HIVE-4781:
------------------------------

Integrated in Hive-trunk-hadoop2 #267 (See [https://builds.apache.org/job/Hive-trunk-hadoop2/267/])
    HIVE-4781 : Adding new data files for tests. Missed in original commit. (Revision 1498238)

     Result = ABORTED
hashutosh : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1498238
Files : 
* /hive/trunk/data/files/leftsemijoin_mr_t1.txt
* /hive/trunk/data/files/leftsemijoin_mr_t2.txt

                
> LEFT SEMI JOIN generates wrong results when the number of rows belonging to a single
key of the right table exceed hive.join.emit.interval
> ------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-4781
>                 URL: https://issues.apache.org/jira/browse/HIVE-4781
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 0.12.0
>            Reporter: Yin Huai
>            Assignee: Yin Huai
>             Fix For: 0.12.0
>
>         Attachments: HIVE-4781.txt, wrong_semi_join.txt
>
>
> Suppose that we have a query shown below
> {code:sql}
> SELECT key FROM t1 LEFT SEMI JOIN t2 ON (t1.key=t2.key);
> {\code}
> When the number of rows of t2 is larger than hive.join.emit.interval, JoinOperator will
emit rows from t1, which will result in redundant output.
> Let's say t1 is
> {code}
> 1
> {\code}
> and t2 is
> {code}
> 1
> 1
> 1
> 1
> {\code}
> When hive.join.emit.interval=1, the output of above query will be
> {code}
> 1
> 1
> 1
> 1
> {\code}
> The correct result should be 
> {code}
> 1
> {\code}
> This problem cannot be found in unit test. Because there is a GBY operator inserted before
JoinOperator and we have only 1 mapper, the output of map phase only has distinct keys.
> Please apply the patch 'wrong_semi_join.txt' attached below and use 
> {code}
> ant test -Dtestcase=TestMinimrCliDriver -Dqfile="left_semi_join.q" -Dtest.silent=false
> {\code} to replay the problem. The wrong result can be found in 
> {code}
> <hive_root_dir>/build/ql/test/logs/clientpositive
> {\code}

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