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From "Prasad Chakka (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-279) Implement predicate push down for hive queries
Date Sat, 28 Feb 2009 21:30:12 GMT

    [ https://issues.apache.org/jira/browse/HIVE-279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12677727#action_12677727
] 

Prasad Chakka commented on HIVE-279:
------------------------------------

1) will do
2) can't remove all op specific code here. gby still needs to check whether this column is
part of keys or values and value cols can't be pushed.
3) will do when possible without doing too much class casting
4) once i use specific classes instead of Node, things should be more clear and I don't see
any reason in moving to a separate directory. They are already different classes so not sure
the benefit of moving to separate directories
5) will open a new JIRA once I am done with this

colInfoMap will go away in the next patch. 


> 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
>    Affects Versions: 0.2.0
>            Reporter: Prasad Chakka
>            Assignee: Prasad Chakka
>         Attachments: hive-279.2.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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