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From "Prasad Chakka (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-279) Implement predicate push down for hive queries
Date Sat, 07 Feb 2009 01:10:59 GMT
Implement predicate push down for hive queries
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                 Key: HIVE-279
                 URL: https://issues.apache.org/jira/browse/HIVE-279
             Project: Hadoop Hive
          Issue Type: New Feature
    Affects Versions: 0.2.0
            Reporter: Prasad Chakka
            Assignee: Prasad Chakka


Push predicates that are expressed in outer queries into inner queries where possible so that
rows will get filtered out sooner.
eg.

select a.*, b.* from a join b on (a.uid = b.uid) where a.age = 20 and a.gender = 'm'

current compiler generates the filter predicate in the reducer after the join so all the rows
have to be passed from mapper to reducer. by pushing the filter predicate to the mapper, query
performance should improve.


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