[IMPALA-6300] Decimal modulo sometimes returns incorrect results

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: Impala 2.8.0, Impala 2.9.0, Impala 2.10.0, Impala 2.11.0
• Fix Version/s: Impala 2.12.0
• Component/s: Backend
• Labels: correctness
• Target Version: Impala 2.12.0
• Epic Color: ghx-label-4
• Assignee: Taras Bobrovytsky
• Reporter: Taras Bobrovytsky
• Created: 09/Dec/17 02:18
• Updated: 05/Jan/18 22:40
• Resolved: 05/Jan/18 22:40

Description

The following query returns an incorrect result:

select cast(11111 as decimal(6,1)) % cast(2 as decimal(8,6))

Result:

-1.901888

We get this result with both decimal_v1 and decimal_v2.

Modifying the query by removing one of the 1's has the following effect:

select cast(1111 as decimal(6,1)) % cast(2 as decimal(8,6))

Result:

1.000000