[jira] [Commented] (HIVE-4952) When hive.join.emit.interval is small, queries optimized by Correlation Optimizer may generate wrong results

["Phabricator (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-4952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13726488#comment-13726488 ] 

Phabricator commented on HIVE-4952:
-----------------------------------

ashutoshc has accepted the revision "HIVE-4952 [jira] When hive.join.emit.interval is small, queries optimized by Correlation Optimizer may generate wrong results".

  +1

REVISION DETAIL
  https://reviews.facebook.net/D11889

BRANCH
  HIVE-4952

ARCANIST PROJECT
  hive

To: JIRA, ashutoshc, yhuai

                
> 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
>         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.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira