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From "Chaoyu Tang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-14251) Union All of different types resolves to incorrect data
Date Wed, 20 Jul 2016 14:37:20 GMT

    [ https://issues.apache.org/jira/browse/HIVE-14251?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15385959#comment-15385959
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Chaoyu Tang commented on HIVE-14251:
------------------------------------

[~aihuaxu] Do you know why and under what situation the string could be considered to be implicitly
converted to double? I believe it breaks your case because the date string could be converted
to double. If we add a flag to disable this implicit conversion generally in getCommonClassForUnionAll,
will it bring in possible backward type incompatibility in some queries with union all for
type string and double?

> Union All of different types resolves to incorrect data
> -------------------------------------------------------
>
>                 Key: HIVE-14251
>                 URL: https://issues.apache.org/jira/browse/HIVE-14251
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Planning
>    Affects Versions: 2.0.0
>            Reporter: Aihua Xu
>            Assignee: Aihua Xu
>         Attachments: HIVE-14251.1.patch
>
>
> create table src(c1 date, c2 int, c3 double);
> insert into src values ('2016-01-01',5,1.25);
> select * from 
> (select c1 from src union all
> select c2 from src union all
> select c3 from src) t;
> It will return NULL for the c1 values. Seems the common data type is resolved to the
last c3 which is double.



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