[jira] [Assigned] (HIVE-3952) merge map-job followed by map-reduce job

["Vinod Kumar Vavilapalli (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HIVE-3952?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Vinod Kumar Vavilapalli reassigned HIVE-3952:
---------------------------------------------

    Assignee: Vinod Kumar Vavilapalli

I'd like to take a stab at it..
                
> merge map-job followed by map-reduce job
> ----------------------------------------
>
>                 Key: HIVE-3952
>                 URL: https://issues.apache.org/jira/browse/HIVE-3952
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: Vinod Kumar Vavilapalli
>
> Consider the query like:
> select count(*) FROM
>         ( select idOne, idTwo, value FROM
>               bigTable                                       
>               JOIN                                                                
>               smallTableOne on (bigTable.idOne = smallTableOne.idOne)                                                   
>           ) firstjoin                                                             
>             JOIN                                                                  
>             smallTableTwo on (firstjoin.idTwo = smallTableTwo.idTwo);
> where smallTableOne and smallTableTwo are smaller than hive.auto.convert.join.noconditionaltask.size and
> hive.auto.convert.join.noconditionaltask is set to true.
> The joins are collapsed into mapjoins, and it leads to a map-only job
> (for the map-joins) followed by a map-reduce job (for the group by).
> Ideally, the map-only job should be merged with the following map-reduce job.

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