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From "Lefty Leverenz (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-279) Implement predicate push down for hive queries
Date Tue, 26 Jan 2016 08:42:39 GMT

    [ https://issues.apache.org/jira/browse/HIVE-279?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15116932#comment-15116932
] 

Lefty Leverenz commented on HIVE-279:
-------------------------------------

Doc note:  This added *hive.optimize.ppd* with a default value of false in 0.4.0.  The default
was changed to true in 0.4.0 by HIVE-626.

* [Configuration Properties -- hive.optimize.ppd | https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties#ConfigurationProperties-hive.optimize.ppd]

> Implement predicate push down for hive queries
> ----------------------------------------------
>
>                 Key: HIVE-279
>                 URL: https://issues.apache.org/jira/browse/HIVE-279
>             Project: Hive
>          Issue Type: New Feature
>          Components: Query Processor
>    Affects Versions: 0.6.0
>            Reporter: Prasad Chakka
>            Assignee: Prasad Chakka
>             Fix For: 0.4.0
>
>         Attachments: hive-279.2.patch, hive-279.3.patch, hive-279.4.patch, hive-279.5.patch,
hive-279.6.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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