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https://issues.apache.org/jira/browse/HIVE-12788?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15092739#comment-15092739
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Chaoyu Tang commented on HIVE-12788:
------------------------------------
[~pxiong] Thanks for reviewing the patch. Yeah, I agree with you that it is
ideal that we should optimize every subquery whenever possible, and will look
into this possibility. But I wonder if we can treat it as a further enhancement
with a separate JIRA so that here we can at least unblock the critical query
data incorrect issue? Thanks
> Setting hive.optimize.union.remove to TRUE will break UNION ALL with
> aggregate functions
> ----------------------------------------------------------------------------------------
>
> Key: HIVE-12788
> URL: https://issues.apache.org/jira/browse/HIVE-12788
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Affects Versions: 1.1.1
> Reporter: Eric Lin
> Assignee: Chaoyu Tang
> Attachments: HIVE-12788.1.patch, HIVE-12788.patch
>
>
> See the test case below:
> {code}
> 0: jdbc:hive2://localhost:10000/default> create table test (a int);
> 0: jdbc:hive2://localhost:10000/default> insert overwrite table test values
> (1);
> 0: jdbc:hive2://localhost:10000/default> set hive.optimize.union.remove=true;
> No rows affected (0.01 seconds)
> 0: jdbc:hive2://localhost:10000/default> set
> hive.mapred.supports.subdirectories=true;
> No rows affected (0.007 seconds)
> 0: jdbc:hive2://localhost:10000/default> SELECT COUNT(1) FROM test UNION ALL
> SELECT COUNT(1) FROM test;
> +----------+--+
> | _u1._c0 |
> +----------+--+
> +----------+--+
> {code}
> UNION ALL without COUNT function will work as expected:
> {code}
> 0: jdbc:hive2://localhost:10000/default> select * from test UNION ALL SELECT
> * FROM test;
> +--------+--+
> | _u1.a |
> +--------+--+
> | 1 |
> | 1 |
> +--------+--+
> {code}
> Run the same query without setting hive.mapred.supports.subdirectories and
> hive.optimize.union.remove to true will give correct result:
> {code}
> 0: jdbc:hive2://localhost:10000/default> set hive.optimize.union.remove;
> +-----------------------------------+--+
> | set |
> +-----------------------------------+--+
> | hive.optimize.union.remove=false |
> +-----------------------------------+--+
> 0: jdbc:hive2://localhost:10000/default> SELECT COUNT(1) FROM test UNION ALL
> SELECT COUNT(1) FROM test;
> +----------+--+
> | _u1._c0 |
> +----------+--+
> | 1 |
> | 1 |
> +----------+--+
> {code}
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