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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11531) Add mysql-style LIMIT support to Hive, or improve ROW_NUMBER performance-wise
Date Fri, 13 Nov 2015 21:21:11 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11531?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15004738#comment-15004738
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Sergey Shelukhin commented on HIVE-11531:
-----------------------------------------

It looks like many q.out files changed due to "Offset" being added. In any case, I think there's
no need to output the offset 0, because that is the implied default for LIMIT. If you return
null from the method, the explain setting will not be output.

The rest looks good to me, except for some spacing inconsistent with the surrounding file
(e.g. ==2 w/o spaces when processing TOK_LIMIT, etc).

[~jcamachorodriguez] can you take a look at Calcite related changes, would this work with
Calcite?



> Add mysql-style LIMIT support to Hive, or improve ROW_NUMBER performance-wise
> -----------------------------------------------------------------------------
>
>                 Key: HIVE-11531
>                 URL: https://issues.apache.org/jira/browse/HIVE-11531
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Sergey Shelukhin
>            Assignee: Hui Zheng
>         Attachments: HIVE-11531.WIP.1.patch, HIVE-11531.WIP.2.patch, HIVE-11531.patch
>
>
> For any UIs that involve pagination, it is useful to issue queries in the form SELECT
... LIMIT X,Y where X,Y are coordinates inside the result to be paginated (which can be extremely
large by itself). At present, ROW_NUMBER can be used to achieve this effect, but optimizations
for LIMIT such as TopN in ReduceSink do not apply to ROW_NUMBER. We can add first class support
for "skip" to existing limit, or improve ROW_NUMBER for better performance



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