[jira] [Commented] (HIVE-2845) Add support for index joins in Hive

["Srinivasan Sembakkam Rajivelu (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-2845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13235353#comment-13235353 ] 

Srinivasan Sembakkam Rajivelu commented on HIVE-2845:
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Could you please explain in which use case this will be useful. Because I feel that there is a space overhead for storing the index is also there. 

And there is already a map join optimization implemented in Hive,
http://www.facebook.com/notes/facebook-engineering/join-optimization-in-apache-hive/470667928919

So this index creation will be helpful do u think??
                
> Add support for index joins in Hive
> -----------------------------------
>
>                 Key: HIVE-2845
>                 URL: https://issues.apache.org/jira/browse/HIVE-2845
>             Project: Hive
>          Issue Type: New Feature
>            Reporter: Namit Jain
>              Labels: gsoc, gsoc2012
>
> Hive supports indexes, which are used for filters currently.
> It would be very useful to add support for index-based joins in Hive.
> If 2 tables A and B are being joined, and an index exists on the join key of A,
> B can be scanned (by the mappers), and for each row in B, a lookup for the corresponding row in A can be performed.
> This can be very useful for some usecases.

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