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