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https://issues.apache.org/jira/browse/HIVE-6348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16056874#comment-16056874
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Ashutosh Chauhan commented on HIVE-6348:
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I am not sure why can't order by removed in these cases. There is no contract 
that scripts and UDFs will see data in any particular order. So, its perfectly 
alright to remove sorts in such cases.

> Order by/Sort by in subquery
> ----------------------------
>
>                 Key: HIVE-6348
>                 URL: https://issues.apache.org/jira/browse/HIVE-6348
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Gunther Hagleitner
>            Assignee: Rui Li
>            Priority: Minor
>              Labels: sub-query
>         Attachments: HIVE-6348.1.patch, HIVE-6348.2.patch, HIVE-6348.3.patch
>
>
> select * from (select * from foo order by c asc) bar order by c desc;
> in hive sorts the data set twice. The optimizer should probably remove any 
> order by/sort by in the sub query unless you use 'limit '. Could even go so 
> far as barring it at the semantic level.



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