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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1213) sort-merge join does not work for sub-queries
Date Fri, 12 Mar 2010 17:58:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844589#action_12844589
] 

Namit Jain commented on HIVE-1213:
----------------------------------

Consider the query;


select /*+ MAPJOIN(c) */ ...
from

(

select /*+ MAPJOIN(b) */ .. from a join b on k1

) subq
join 
c
on k2


Even if k1 and k2 are not same, this can be done in a singe map-only job. Note that this has
nothing to do with sorting/bucketing etc.


> sort-merge join does not work for sub-queries
> ---------------------------------------------
>
>                 Key: HIVE-1213
>                 URL: https://issues.apache.org/jira/browse/HIVE-1213
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: He Yongqiang
>             Fix For: 0.6.0
>
>         Attachments: Hive-1213.1.patch, Hive-1213.4.patch, Hive-1213.5.patch, Hive-1213.6.patch,
Hive-1213.7.patch
>
>
> A query like:
> select count(1) from (select /*+ MAPJOIN(x) */ from x join y ON ... ) subq;
> does not work - since there is no mapping between the join operator and the corresponding
source

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