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https://issues.apache.org/jira/browse/HIVE-6348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16048697#comment-16048697
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Vineet Garg commented on HIVE-6348:
-----------------------------------
{{HiveSortRemoveRule}} removes HiveSortLimit only if it is created by
HiveSortJoinReduceRule "If it is not created by HiveSortJoinReduceRule, we
cannot remove it" {{HiveSortMergeRule}} seems to merge two HiveSortLimit into
one which isn't the case here. So I don't think there is any existing rule
covering this case.
> 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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