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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-3276) optimize union sub-queries
Date Thu, 16 Aug 2012 18:33:38 GMT

     [ https://issues.apache.org/jira/browse/HIVE-3276?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Namit Jain updated HIVE-3276:
-----------------------------

    Status: Patch Available  (was: Open)

ShimLoader changes are copied from HIVE-3029, only to run tests on hadoop 23.
Once HIVE-3029 is checked in, this file will be reverted

Also, to run tests for thew newly added tests only on hadoop 23:

ant clean package


ant test -Dhadoop.mr.rev=23 -Dtest.print.classpath=true -Dhadoop.version=2.0.0-alpha -Dhadoop.security.version=2.0.0-alpha
-Dtestcase=TestCliDriver -Dqfile=union_remove_1.q,union_remove_2.q,union_remove_3.q,union_remove_4.q,union_remove_5.q,union_remove_6.q,union_remove_7.q,union_remove_8.q,union_remove_9.q,union_remove_10.q,union_remove_11.q,union_remove_12.q,union_remove_13.q,union_remove_14.q,union_remove_15.q,union_remove_16.q,union_remove_17.q,union_remove_18.q

                
> optimize union sub-queries
> --------------------------
>
>                 Key: HIVE-3276
>                 URL: https://issues.apache.org/jira/browse/HIVE-3276
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Namit Jain
>            Assignee: Namit Jain
>         Attachments: HIVE-3276.1.patch, hive.3276.2.patch, hive.3276.3.patch
>
>
> It might be a good idea to optimize simple union queries containing map-reduce jobs in
at least one of the sub-qeuries.
> For eg:
> a query like:
> insert overwrite table T1 partition P1
> select * from 
> (
>   subq1
>     union all
>   subq2
> ) u;
> today creates 3 map-reduce jobs, one for subq1, another for subq2 and 
> the final one for the union. 
> It might be a good idea to optimize this. Instead of creating the union 
> task, it might be simpler to create a move task (or something like a move
> task), where the outputs of the two sub-queries will be moved to the final 
> directory. This can easily extend to more than 2 sub-queries in the union.
> This is only useful if there is a select * followed by filesink after the
> union. This can be independently useful, and also be used to optimize the
> skewed joins https://cwiki.apache.org/Hive/skewed-join-optimization.html

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