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https://issues.apache.org/jira/browse/HIVE-15331?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Jason Dere updated HIVE-15331:
------------------------------
       Resolution: Fixed
    Fix Version/s: 2.2.0
     Release Note: 
The resulting precision/scale of decimal arithmetic has been changed in the 
case where the precision/scale exceeds the maximum precision of 38.

When reducing the precision/scale down to the Hive limit of 38, the new 
behavior is to reduce the scale to preserve the integer portion of the 
precision, while leaving a minimum of 6 digits for the scale.

The previous behavior was to always shrink the integer portion of the precision 
first before the scale.
           Status: Resolved  (was: Patch Available)

Committed to master

> Decimal multiplication with high precision/scale often returns NULL
> -------------------------------------------------------------------
>
>                 Key: HIVE-15331
>                 URL: https://issues.apache.org/jira/browse/HIVE-15331
>             Project: Hive
>          Issue Type: Bug
>          Components: Types
>            Reporter: Jason Dere
>            Assignee: Jason Dere
>             Fix For: 2.2.0
>
>         Attachments: HIVE-15331.1.patch, HIVE-15331.2.patch, 
> HIVE-15331.3.patch
>
>
> {noformat}
> create temporary table dec (a decimal(38,18));
> insert into dec values(100.0);
> hive> select a*a from dec;
> OK
> NULL
> Time taken: 0.165 seconds, Fetched: 1 row(s)
> {noformat}
> Looks like the reason is because the result of decimal(38,18) * 
> decimal(38,18) only has 2 digits of precision for integers:
> {noformat}
> hive> set hive.explain.user=false;
> hive> explain select a*a from dec;
> OK
> STAGE DEPENDENCIES:
>   Stage-0 is a root stage
> STAGE PLANS:
>   Stage: Stage-0
>     Fetch Operator
>       limit: -1
>       Processor Tree:
>         TableScan
>           alias: dec
>           Select Operator
>             expressions: (a * a) (type: decimal(38,36))
>             outputColumnNames: _col0
>             ListSink
> Time taken: 0.039 seconds, Fetched: 15 row(s)
> {noformat}



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