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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-4952) When hive.join.emit.interval is small, queries optimized by Correlation Optimizer may generate wrong results
Date Fri, 02 Aug 2013 14:17:50 GMT

    [ https://issues.apache.org/jira/browse/HIVE-4952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13727696#comment-13727696
] 

Hudson commented on HIVE-4952:
------------------------------

SUCCESS: Integrated in Hive-trunk-h0.21 #2239 (See [https://builds.apache.org/job/Hive-trunk-h0.21/2239/])
HIVE-4952 : When hive.join.emit.interval is small, queries optimized by Correlation Optimizer
may generate wrong results (Yin Huai via Ashutosh Chauhan) (hashutosh: http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1509542)
* /hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/exec/DemuxOperator.java
* /hive/trunk/ql/src/java/org/apache/hadoop/hive/ql/optimizer/correlation/QueryPlanTreeTransformation.java
* /hive/trunk/ql/src/test/queries/clientpositive/correlationoptimizer15.q
* /hive/trunk/ql/src/test/results/clientpositive/correlationoptimizer15.q.out

                
> When hive.join.emit.interval is small, queries optimized by Correlation Optimizer may
generate wrong results
> ------------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-4952
>                 URL: https://issues.apache.org/jira/browse/HIVE-4952
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 0.12.0
>            Reporter: Yin Huai
>            Assignee: Yin Huai
>             Fix For: 0.12.0
>
>         Attachments: HIVE-4952.D11889.1.patch, HIVE-4952.D11889.2.patch, replay.txt
>
>
> If we have a query like this ...
> {code:sql}
> SELECT xx.key, xx.cnt, yy.key
> FROM
> (SELECT x.key as key, count(1) as cnt FROM src1 x JOIN src1 y ON (x.key = y.key) group
by x.key) xx
> JOIN src yy
> ON xx.key=yy.key;
> {\code}
> After Correlation Optimizer, the operator tree in the reducer will be 
> {code}
>      JOIN2
>        |
>        |
>       MUX
>      /   \
>     /     \
>    GBY     |
>     |      |
>   JOIN1    |
>     \     /
>      \   /
>      DEMUX
> {\code}
> For JOIN2, the right table will arrive at this operator first. If hive.join.emit.interval
is small, e.g. 1, JOIN2 will output the results even it has not got any row from the left
table. The logic related hive.join.emit.interval in JoinOperator assumes that inputs will
be ordered by the tag. But, if a query has been optimized by Correlation Optimizer, this assumption
may not hold for those JoinOperators inside the reducer.

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