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From "Harish Butani (JIRA)" <>
Subject [jira] [Commented] (HIVE-7063) Optimize for the Top N within a Group use case
Date Sat, 28 Jun 2014 02:35:24 GMT


Harish Butani commented on HIVE-7063:

Yes, in your case we can optimize as though 'rank < 5' was specified.  Though I cannot
see a valid use case of writing a limit after a windowing expression, as you point out the
more common case is a predicate on rank.

> Optimize for the Top N within a Group use case
> ----------------------------------------------
>                 Key: HIVE-7063
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Harish Butani
>            Assignee: Harish Butani
>         Attachments: HIVE-7063.1.patch, HIVE-7063.2.patch
> It is common to rank within a Group/Partition and then only return the Top N entries
within each Group.
> With Streaming mode for Windowing, we should push the post filter on the rank into the
Windowing processing as a Limit expression.

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