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From "Ashish Thusoo (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-279) Implement predicate push down for hive queries
Date Tue, 31 Mar 2009 02:27:50 GMT

    [ https://issues.apache.org/jira/browse/HIVE-279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12693975#action_12693975
] 

Ashish Thusoo commented on HIVE-279:
------------------------------------

+1

Looks good to me.

A few things to watch out for before you upload the complete patch..

1. ppd_gby_join.q is missing.
2. Would be great to have a join test case where the left and right ourter joins are part
of the same join operator.
3. Also would be great to have a join test case where there is a three way join and the join
operators do not merge.
4. Also a test case with UDFs (not the rand one) that gets pushed down would also be awesome.


Otherwise looks quite cool to me. 

> Implement predicate push down for hive queries
> ----------------------------------------------
>
>                 Key: HIVE-279
>                 URL: https://issues.apache.org/jira/browse/HIVE-279
>             Project: Hadoop Hive
>          Issue Type: New Feature
>          Components: Query Processor
>    Affects Versions: 0.2.0
>            Reporter: Prasad Chakka
>            Assignee: Prasad Chakka
>         Attachments: hive-279.2.patch, hive-279.3.patch, hive-279.4.patch, hive-279.5.patch,
hive-279.patch
>
>
> 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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