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https://issues.apache.org/jira/browse/HIVE-8089?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14138005#comment-14138005
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Sergey Shelukhin edited comment on HIVE-8089 at 9/17/14 9:23 PM:
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it seems that ordering in the subquery should have no effect on any outer
limits, and outer limits cannot have effect on nested query.
So if I have numbers 1..10, and so select N from (select N order by N limit 5),
that should return 1..5.
If we have select N from (select N order by N) limit 5 we can return any 5
numbers in any order, because it's just like select N from table limit 5 - no
order is guaranteed...
I will take a look if this is easy to make this behavior more "user-friendly"
was (Author: sershe):
it seems that ordering in the subquery should have no effect on any outer
limits, and outer limits cannot have effect on nested query.
So if I sort numbers 1..10, and so select N from (select N order by N limit 5),
that should return 1..5.
If we have select N from (select N order by N) limit 5 we can return any 5
numbers in any order, because it's just like select N from table limit 5 - no
order is guaranteed...
I will take a look if this is easy to make this behavior more "user-friendly"
> Ordering is lost when limit is put in outer query
> -------------------------------------------------
>
> Key: HIVE-8089
> URL: https://issues.apache.org/jira/browse/HIVE-8089
> Project: Hive
> Issue Type: Bug
> Reporter: Laljo John Pullokkaran
> Assignee: Sergey Shelukhin
>
> It seems like hive supports order by, limit in sub queries (compiler doesn't
> complain). However ordering seems to be lost based on where you place the
> limit. I haven't debugged the issue.
> ex:
> select key, c_int from (select key, c_int from (select key, c_int from t1
> order by c_int limit 5)t1)t1;
> null NULL
> null NULL
> 1 1
> 1 1
> 1 1
> select key, c_int from (select key, c_int from (select key, c_int from t1
> order by c_int)t1 limit 5)t1;
> 1 1
> 1 1
> 1 1
> null NULL
> null NULL
> select key, c_int from (select key, c_int from (select key, c_int from t1
> order by c_int limit 5)t1 limit 5)t1;
> 1 1
> 1 1
> 1 1
> null NULL
> null NULL
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