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Date: Thu, 21 Aug 2014 21:12:12 +0000 (UTC)
From: =?utf-8?Q?Sergio_Pe=C3=B1a_=28JIRA=29?= <jira@apache.org>
To: hive-dev@hadoop.apache.org
Message-ID: <JIRA.12726349.1404920346003.6033.1408655532388@arcas>
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References: <JIRA.12726349.1404920346003@arcas>
Subject: [jira] [Commented] (HIVE-7373) Hive should not remove trailing
 zeros for decimal numbers
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    [ https://issues.apache.org/jira/browse/HIVE-7373?page=3Dcom.atlassian.=
jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D14105=
969#comment-14105969 ]=20

Sergio Pe=C3=B1a commented on HIVE-7373:
-----------------------------------

It is true only if the calculations are made between the fields and/or usin=
g cast().
For instance:
{noformat}
0: jdbc:hive2://localhost:10000> select a, b, a*b, a/b, a+b, a-b, a*a from =
decimal;
+--------+-------+----------+-------+--------+--------+-----------+--+
|   a    |   b   |   _c2    |  _c3  |  _c4   |  _c5   |    _c6    |
+--------+-------+----------+-------+--------+--------+-----------+--+
| 3.140  | 1.00  | 3.14000  | 3.14  | 4.140  | 2.140  | 9.859600  |
+--------+-------+----------+-------+--------+--------+-----------+--+
{noformat}

I've just tested a calculation using constants, and they're not working as =
expected
- select 3.140 * 1.00;   <-- You need to use a cast() on these values in or=
der to get=20
  the correct results.

> Hive should not remove trailing zeros for decimal numbers
> ---------------------------------------------------------
>
>                 Key: HIVE-7373
>                 URL: https://issues.apache.org/jira/browse/HIVE-7373
>             Project: Hive
>          Issue Type: Bug
>          Components: Types
>    Affects Versions: 0.13.0, 0.13.1
>            Reporter: Xuefu Zhang
>            Assignee: Sergio Pe=C3=B1a
>              Labels: TODOC14
>             Fix For: 0.14.0
>
>         Attachments: HIVE-7373.1.patch, HIVE-7373.2.patch, HIVE-7373.3.pa=
tch, HIVE-7373.4.patch, HIVE-7373.5.patch, HIVE-7373.6.patch, HIVE-7373.6.p=
atch
>
>
> Currently Hive blindly removes trailing zeros of a decimal input number a=
s sort of standardization. This is questionable in theory and problematic i=
n practice.
> 1. In decimal context,  number 3.140000 has a different semantic meaning =
from number 3.14. Removing trailing zeroes makes the meaning lost.
> 2. In a extreme case, 0.0 has (p, s) as (1, 1). Hive removes trailing zer=
os, and then the number becomes 0, which has (p, s) of (1, 0). Thus, for a =
decimal column of (1,1), input such as 0.0, 0.00, and so on becomes NULL be=
cause the column doesn't allow a decimal number with integer part.
> Therefore, I propose Hive preserve the trailing zeroes (up to what the sc=
ale allows). With this, in above example, 0.0, 0.00, and 0.0000 will be rep=
resented as 0.0 (precision=3D1, scale=3D1) internally.


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