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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-12063) Pad Decimal numbers with trailing zeros to the scale of the column
Date Wed, 21 Oct 2015 22:23:27 GMT

    [ https://issues.apache.org/jira/browse/HIVE-12063?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14968082#comment-14968082
] 

Xuefu Zhang commented on HIVE-12063:
------------------------------------

Thanks, Szehon. Please note, this is actually not that far from my original thought in HIVE-7373.
My point there was that we shouldn't append zeros or trimming trailing zeros. The patch here
doesn't append zeros internally, but mainly formatting output according to the output schema.
(HIVE-7373 failed in this because it changed the internal representation.) This is in line
with other DBs, though I'm not aware of any SQL standard on this. Yes, I said that the practice
of outputting with appending zeros was questionable, but it makes sense in Hive's case as
Hive aggressively trims 0.0, 0.00, 0.000000 etc all the way to 0, which is too confusing.

BTW, all vectorization tests passed. [~jdere] or [~hagleitn], please review and comment. Thanks.

> Pad Decimal numbers with trailing zeros to the scale of the column
> ------------------------------------------------------------------
>
>                 Key: HIVE-12063
>                 URL: https://issues.apache.org/jira/browse/HIVE-12063
>             Project: Hive
>          Issue Type: Improvement
>          Components: Types
>    Affects Versions: 0.14.0, 1.0.0, 1.2.0, 1.1.0, 0.13
>            Reporter: Xuefu Zhang
>            Assignee: Xuefu Zhang
>         Attachments: HIVE-12063.1.patch, HIVE-12063.2.patch, HIVE-12063.patch
>
>
> HIVE-7373 was to address the problems of trimming tailing zeros by Hive, which caused
many problems including treating 0.0, 0.00 and so on as 0, which has different precision/scale.
Please refer to HIVE-7373 description. However, HIVE-7373 was reverted by HIVE-8745 while
the underlying problems remained. HIVE-11835 was resolved recently to address one of the problems,
where 0.0, 0.00, and so on cannot be read into decimal(1,1).
> However, HIVE-11835 didn't address the problem of showing as 0 in query result for any
decimal values such as 0.0, 0.00, etc. This causes confusion as 0 and 0.0 have different precision/scale
than 0.
> The proposal here is to pad zeros for query result to the type's scale. This not only
removes the confusion described above, but also aligns with many other DBs. Internal decimal
number representation doesn't change, however.



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