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From "Fern (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-4506) use one map reduce to join multiple small tables
Date Mon, 06 May 2013 11:50:15 GMT

     [ https://issues.apache.org/jira/browse/HIVE-4506?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Fern updated HIVE-4506:
-----------------------

             Priority: Minor  (was: Major)
          Description: 
I know we can use map side join for small table.
by my test, if I use HQL like this
------
select /*+mapjoin(b,c)*/...
from a
left join b
on ...
left join c
on ...
-------
b and c are both small tables, I expect do the join in one map reduce using map side join.
Actually, it would generate two map-reduce by sequence.


Sorry, currently I am just a user of hive and not dig into the code, so I this is what I expect
and have no idea about how to improve. 
    Affects Version/s: 0.10.0
              Summary: use one map reduce to join multiple small tables   (was: join multi
small tables )
    
> use one map reduce to join multiple small tables 
> -------------------------------------------------
>
>                 Key: HIVE-4506
>                 URL: https://issues.apache.org/jira/browse/HIVE-4506
>             Project: Hive
>          Issue Type: Wish
>    Affects Versions: 0.10.0
>            Reporter: Fern
>            Priority: Minor
>
> I know we can use map side join for small table.
> by my test, if I use HQL like this
> ------
> select /*+mapjoin(b,c)*/...
> from a
> left join b
> on ...
> left join c
> on ...
> -------
> b and c are both small tables, I expect do the join in one map reduce using map side
join. Actually, it would generate two map-reduce by sequence.
> Sorry, currently I am just a user of hive and not dig into the code, so I this is what
I expect and have no idea about how to improve. 

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