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https://issues.apache.org/jira/browse/HIVE-9039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15374832#comment-15374832
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wangwenli commented on HIVE-9039:
---------------------------------
this issue will cause backward compatibility problem, sql like this cann't
work anymore:
select s1.key as k, s2.value as v from src s1 join src s2 on (s1.key = s2.key)
limit 10
union all
select s1.key as k, s2.value as v from src s1 join src s2 on (s1.key = s2.key)
limit 10;
must change to :
select * from (select s1.key as k, s2.value as v from src s1 join src s2 on
(s1.key = s2.key) limit 10)a
union all
select * from (select s1.key as k, s2.value as v from src s1 join src s2 on
(s1.key = s2.key) limit 10)b;
> Support Union Distinct
> ----------------------
>
> Key: HIVE-9039
> URL: https://issues.apache.org/jira/browse/HIVE-9039
> Project: Hive
> Issue Type: New Feature
> Components: Query Planning
> Reporter: Pengcheng Xiong
> Assignee: Pengcheng Xiong
> Fix For: 1.2.0
>
> Attachments: HIVE-9039.01.patch, HIVE-9039.02.patch,
> HIVE-9039.03.patch, HIVE-9039.04.patch, HIVE-9039.05.patch,
> HIVE-9039.06.patch, HIVE-9039.07.patch, HIVE-9039.08.patch,
> HIVE-9039.09.patch, HIVE-9039.10.patch, HIVE-9039.11.patch,
> HIVE-9039.12.patch, HIVE-9039.13.patch, HIVE-9039.14.patch,
> HIVE-9039.15.patch, HIVE-9039.16.patch, HIVE-9039.17.patch,
> HIVE-9039.18.patch, HIVE-9039.19.patch, HIVE-9039.20.patch,
> HIVE-9039.21.patch, HIVE-9039.22.patch, HIVE-9039.23.patch
>
>
> CLEAR LIBRARY CACHE
> Current version (Hive 0.14) does not support union (or union distinct). It
> only supports union all. In this patch, we try to add this new feature by
> rewriting union distinct to union all followed by group by.
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