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From "Jakob Homan (Created) (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-2677) Joins involving where statements with a partition do not prune correctly in left outer join
Date Fri, 23 Dec 2011 21:16:30 GMT
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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