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https://issues.apache.org/jira/browse/HIVE-7063?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14046699#comment-14046699
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Harish Butani commented on HIVE-7063:
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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: https://issues.apache.org/jira/browse/HIVE-7063
> 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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