[jira] [Resolved] (IMPALA-6292) Decimal v2 subtraction hits a DCHECK

["Taras Bobrovytsky (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IMPALA-6292?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Taras Bobrovytsky resolved IMPALA-6292.
---------------------------------------
       Resolution: Fixed
    Fix Version/s: Impala 2.11.0

{code}
commit 542dc227c613e2fbe2b9a4f98817f395b2d1238c
Author: Taras Bobrovytsky <tb...@cloudera.com>
Date:   Thu Dec 7 16:51:35 2017 -0800

    IMPALA-6292: Fix incorrect DCHECK in decimal subtraction
    
    When subtracting two decimals, and one of them is large, we incorrectly
    hit a DCHECK if the intermediate result was equal to 10^39-1, which is
    MAX_UNSCALED_DECIMAL16. We fix the problem by changing the condition in
    the DCHECK from "less than" to "less than or equal to".
    
    Testing:
    - Added expr tests that reproduce the issue.
    
    Change-Id: I42d42ad85efe32b7a0db0d2353385939fee09934
    Reviewed-on: http://gerrit.cloudera.org:8080/8796
    Reviewed-by: Tim Armstrong <ta...@cloudera.com>
    Tested-by: Impala Public Jenkins
{code}

> Decimal v2 subtraction hits a DCHECK
> ------------------------------------
>
>                 Key: IMPALA-6292
>                 URL: https://issues.apache.org/jira/browse/IMPALA-6292
>             Project: IMPALA
>          Issue Type: Bug
>          Components: Backend
>    Affects Versions: Impala 2.11.0
>            Reporter: Taras Bobrovytsky
>            Assignee: Taras Bobrovytsky
>            Priority: Blocker
>             Fix For: Impala 2.11.0
>
>
> The following query causes a DCHECK when executed with decimal_v2 enabled:
> {code}
> select cast(1 as decimal(13,12)) - cast(0.99999999999999999999999999999999999999 as decimal(38,38))
> {code}
> DCHECK:
> {code}
> decimal-value.inline.h:274] Check failed: abs(right) < DecimalUtil::MAX_UNSCALED_DECIMAL16
> {code}
> This was found using fuzz testing.



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