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https://issues.apache.org/jira/browse/HIVE-12963?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15143204#comment-15143204
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Sergey Shelukhin commented on HIVE-12963:
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[~ashutoshc] can you comment? I am not very familiar with this code. Do we have
a good test for this?
> LIMIT statement with SORT BY creates additional MR job with hardcoded only
> one reducer
> --------------------------------------------------------------------------------------
>
> Key: HIVE-12963
> URL: https://issues.apache.org/jira/browse/HIVE-12963
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Affects Versions: 1.0.0, 1.2.1, 0.13
> Reporter: Alina Abramova
> Assignee: Alina Abramova
> Attachments: HIVE-12963.1.patch, HIVE-12963.2.patch,
> HIVE-12963.3.patch, HIVE-12963.4.patch
>
>
> I execute query:
> hive> select age from test1 sort by age.age limit 10;
> Total jobs = 2
> Launching Job 1 out of 2
> Number of reduce tasks not specified. Estimated from input data size: 1
> Launching Job 2 out of 2
> Number of reduce tasks determined at compile time: 1
> When I have a large number of rows then the last stage of the job takes a
> long time. I think we could allow to user choose number of reducers of last
> job or refuse extra MR job.
> The same behavior I observed with querie:
> hive> create table new_test as select age from test1 group by age.age limit
> 10;
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