[DRILL-2199] Wrong results while using case expression with decimal data type

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Assignee: Mehant Baid
• Reporter: Mehant Baid
• Created: 10/Feb/15 08:28
• Updated: 12/Feb/15 23:00
• Resolved: 12/Feb/15 23:00

Description

Consider the below SQL statement:

"select
case when true then cast(employee_id as decimal(15, 5)) else cast('0.0' as decimal(5, 2)) end
from cp.`employee.json` where employee_id = 1"

This should return 1.00000 instead Drill returns 100000. In the case statement the first expression (condition expression) is nullable and the else expression is non-nullable. For our codegen to work correctly we make the non-nullable expression also nullable using convertToNullableXHolder() functions. These functions however do not preserve the scale and precision of the input, hence the output we get is the unscaled value of the decimal.

Fix is to make the converToNullableDecimalHolder() functions preserve the scale and precision by returning the correct major type.