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From "Prasad Chakka (JIRA)" <>
Subject [jira] Updated: (HIVE-279) Implement predicate push down for hive queries
Date Thu, 19 Feb 2009 03:47:02 GMT


Prasad Chakka updated HIVE-279:

    Attachment: hive-279.patch

this is a drop for initial review since i suspect there will be lot of comments :). it should
work for all cases except for multi-insert queries.

i have not enabled this by default but added a new config param called hive.optimize.ppd to
enable this feature. 

i have not modified existing testcases but added couple of new testcases. will add more while
uploading final patch.

> Implement predicate push down for hive queries
> ----------------------------------------------
>                 Key: HIVE-279
>                 URL:
>             Project: Hadoop Hive
>          Issue Type: New Feature
>    Affects Versions: 0.2.0
>            Reporter: Prasad Chakka
>            Assignee: Prasad Chakka
>         Attachments: 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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