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From "Navis (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2677) Joins involving where statements with a partition do not prune correctly in left outer join
Date Tue, 21 Feb 2012 02:53:35 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13212316#comment-13212316
] 

Navis commented on HIVE-2677:
-----------------------------

For left-outer join, predicates on left condition only could be pushed down.
                
> Joins involving where statements with a partition do not prune correctly in left outer
join
> -------------------------------------------------------------------------------------------
>
>                 Key: HIVE-2677
>                 URL: https://issues.apache.org/jira/browse/HIVE-2677
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 0.7.0
>            Reporter: Jakob Homan
>
> The following query:
> {noformat}
> select t1.id as m_id, count(t2.id) as totals 
> from table1 t1 left outer join table2 t2 on (t1.id = t2.id) 
> where (datepartition ==  '2011-11-08-00') 
> group by t1.id;{noformat}
> should prune to just a single partition (datepartition ==  '2011-11-08-00') .  However,
the filter is being applied in the reducer, so a full table scan is being done as part of
the map.
> One can get the correct behavior by pushing the filter into a select statement within
the join itself:
> {noformat}select t1.id as m_id, count(p.id) as totals 
> from table1 t1 left outer join (select * from table2 where datepartition ==  '2011-11-08-00')
t2 on (t1.id = t2.id)  
> group by t1.id;{noformat}

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