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https://issues.apache.org/jira/browse/HIVE-5996?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13846718#comment-13846718
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Thejas M Nair commented on HIVE-5996:
-------------------------------------

bq. Now, to answer the same questions, I can give right way, and I have a 
theory to tell why.
It would be great if you can document the theory, otherwise I still would need 
to look at code to understand the theory !  :)

I really appreciate the code cleanup you have been doing. But we have to be 
careful about backward compatibility. I also agree that we should not burden 
new users with historic problems.
Regarding "Once Hive is stabilized", how do we define that ? Maybe, once we 
create a list of non backward compatible changes that are important to make, we 
can make a major release version (1.x) , we can break the backward 
compatibility of certain things, and document it very well. Hopefully, that 
list of non-backward compatible changes can be kept small.

I discuss this in context of config defaults in HIVE-5875 .



> Query for sum of a long column of a table with only two rows produces wrong 
> result
> ----------------------------------------------------------------------------------
>
>                 Key: HIVE-5996
>                 URL: https://issues.apache.org/jira/browse/HIVE-5996
>             Project: Hive
>          Issue Type: Bug
>          Components: UDF
>    Affects Versions: 0.12.0
>            Reporter: Xuefu Zhang
>            Assignee: Xuefu Zhang
>         Attachments: HIVE-5996.patch
>
>
> {code}
> hive> desc test2;
> OK
> l                     bigint                  None                
> hive> select * from test2;                                 
> OK
> 6666666666666666666
> 5555555555555555555
> hive> select sum(l) from test2;
> OK
> -6224521851487329395
> {code}
> It's believed that a wrap-around error occurred. It's surprising that it 
> happens only with two rows. Same query in MySQL returns:
> {code}
> mysql> select sum(l) from test;
> +----------------------+
> | sum(l)               |
> +----------------------+
> | 12222222222222222221 |
> +----------------------+
> 1 row in set (0.00 sec)
> {code}
> Hive should accommodate large number of rows. Overflowing with only two rows 
> is very unusable.



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