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From "Lefty Leverenz (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-9039) Support Union Distinct
Date Wed, 11 Feb 2015 08:15:12 GMT

    [ https://issues.apache.org/jira/browse/HIVE-9039?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14315759#comment-14315759
] 

Lefty Leverenz commented on HIVE-9039:
--------------------------------------

Nicely done, [~pxiong].  I added emphasis for version changes at the beginning and trimmed
the version note at the end.  Feel free to change things back again if you disagree.

Some minor questions:

1.  In this example, should there be a space before "a" and "b" (after the parentheses) or
is it optional?
{code}
SELECT key FROM (SELECT key FROM src ORDER BY key LIMIT 10)a
UNION
SELECT key FROM (SELECT key FROM src1 ORDER BY key LIMIT 10)b
{code}

2.  Does DISTRIBUTE BY belong in the first half of this sentence, or should it be removed
from the second half?  And can "after the last one" be rephrased "after the last SELECT of
the UNION" or something similar?
{quote}
To apply an ORDER BY, SORT BY, CLUSTER BY or LIMIT clause to the entire UNION result, place
the ORDER BY, SORT BY, CLUSTER BY, DISTRIBUTE BY or LIMIT after the last one. 
{quote}

Thanks.

> 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
>              Labels: TODOC1.2
>             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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