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From "Gunther Hagleitner (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-2693) Add DECIMAL data type
Date Wed, 19 Dec 2012 01:42:12 GMT

    [ https://issues.apache.org/jira/browse/HIVE-2693?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13535548#comment-13535548
] 

Gunther Hagleitner commented on HIVE-2693:
------------------------------------------

Solution Number 1 would be nice, but I don't think we'll be able to do that. Any time we convert
to double in an intermediate step we lose precision - and I don't think it can be recovered
by using string or anything else afterwards. That seems to be just in the nature of floating
point operations. We could round to fewer digits in the conversion for instance, but that
will probably just cause issues elsewhere.

Not converting to double also seems a bad choice. That would change some very fundamental
behavior in hive. All of a sudden "select 3.14 * 2 ..." would return BigDecimal instead of
double. Not good.

So, I am in favor of throwing an error. At least we'll fail early and don't send users on
a wild goose chase. Although it's not ideal either: The where clause issue wouldn't have happened
for instance. But we probably don't want to bar explicit casts ("cast (3.14 as decimal)")
even though they probably won't do what anyone thinks they do. Or do we want to disallow them?

                
> Add DECIMAL data type
> ---------------------
>
>                 Key: HIVE-2693
>                 URL: https://issues.apache.org/jira/browse/HIVE-2693
>             Project: Hive
>          Issue Type: New Feature
>          Components: Query Processor, Types
>    Affects Versions: 0.10.0
>            Reporter: Carl Steinbach
>            Assignee: Prasad Mujumdar
>         Attachments: 2693_7.patch, 2693_8.patch, 2693_fix_all_tests1.patch, HIVE-2693-10.patch,
HIVE-2693-11.patch, HIVE-2693-12-SortableSerDe.patch, HIVE-2693-13.patch, HIVE-2693-1.patch.txt,
HIVE-2693-all.patch, HIVE-2693-fix.patch, HIVE-2693.patch, HIVE-2693-take3.patch, HIVE-2693-take4.patch
>
>
> Add support for the DECIMAL data type. HIVE-2272 (TIMESTAMP) provides a nice template
for how to do this.

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