[IMPALA-1879] mod() function doesn't always interpret fractional arguments as DECIMAL

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Duplicate
• Affects Version/s: Impala 2.2
• Component/s: Frontend
• Labels: sql-language
• Target Version: Product Backlog
• Assignee: Unassigned
• Reporter: John Russell
• Created: 11/Mar/15 20:39
• Updated: 16/Nov/17 18:09
• Resolved: 16/Nov/17 01:20

Description

In constructing examples for the mod() function, I noticed that with some combinations of arguments the DECIMAL overload was not chosen, leading to rounding errors:

select mod(9.9,3);
+--------------------+
| mod(9.9, 3)        |
+--------------------+
| 0.8999996185302734 |
+--------------------+

If I use a cast or a more obviously DECIMAL literal for the second argument, I get the expected result:

select mod(9.9, cast(3 as decimal(2,1)));
+-----------------------------------+
| mod(9.9, cast(3 as decimal(2,1))) |
+-----------------------------------+
| 0.9                               |
+-----------------------------------+

select mod(9.9,3.0);
+---------------+
| mod(9.9, 3.0) |
+---------------+
| 0.9           |
+---------------+

Issue Links

• duplicates: IMPALA-2233 Impala should not choose a function signature that results in loss of precision
• duplicates: IMPALA-3437 Consider changing arithmetic conversions to produce decimal in more cases
• relates to: IMPALA-5936 Difference between the % Operator and Mod function with large decimal values