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From "Gunther Hagleitner (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-8745) Joins on decimal keys return different results whether they are run as reduce join or map join
Date Thu, 06 Nov 2014 08:05:34 GMT

    [ https://issues.apache.org/jira/browse/HIVE-8745?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14199970#comment-14199970
] 

Gunther Hagleitner commented on HIVE-8745:
------------------------------------------

[~xuefuz] [~jdere] is right. You can't have it both ways. I don't see how you create an object
that compares as equal on the byte-level but then magically reconstructs additional information
on deserialization. You could add info to the value part of the MR key/value tuple but that's
an unnecessarily complex solution. As [~jdere] says: This is a regression and I think we should
revert HIVE-7373.

The other option would be to pad all values to the column spec and make sure we compute the
spec as the max for the join keys. I'm not sure why you were against that in the first place
- it seems that's what most DBs do. However, that's complicated and should be tackled in 0.15.0.

> Joins on decimal keys return different results whether they are run as reduce join or
map join
> ----------------------------------------------------------------------------------------------
>
>                 Key: HIVE-8745
>                 URL: https://issues.apache.org/jira/browse/HIVE-8745
>             Project: Hive
>          Issue Type: Bug
>    Affects Versions: 0.14.0
>            Reporter: Gunther Hagleitner
>            Assignee: Jason Dere
>            Priority: Critical
>             Fix For: 0.14.0
>
>         Attachments: join_test.q
>
>
> See attached .q file to reproduce. The difference seems to be whether trailing 0s are
considered the same value or not.



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