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https://issues.apache.org/jira/browse/HIVE-9039?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pengcheng Xiong updated HIVE-9039:
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Attachment: HIVE-9039.09-WIP.patch
address (1) union distinct, union order by limit in select statement. Now limit
can not be in the non-final sub select statement. (2) Need to do more for
fromstatement. It seems that "from src select key select value;" will pass the
semantic analyzer but will fail in the task compilation. Then, how to address
from src select key select value limit 1 union all from src select key select
value limit 1? And, it seems that traditional DBMS will not support from...
select... Then, what standard should we follow?
> Support Union Distinct
> ----------------------
>
> Key: HIVE-9039
> URL: https://issues.apache.org/jira/browse/HIVE-9039
> Project: Hive
> Issue Type: New Feature
> Reporter: Pengcheng Xiong
> Assignee: Pengcheng Xiong
> 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-WIP.patch
>
>
> 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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