[IMPALA-4940] DECIMAL V2 multiply result type

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.9.0
• Fix Version/s: Impala 2.11.0
• Component/s: Frontend
• Epic Link: Numeric Datatype Conversions
• Target Version: Product Backlog
• Assignee: Taras Bobrovytsky
• Reporter: Daniel Hecht
• Created: 15/Feb/17 22:18
• Updated: 21/Nov/18 23:29
• Resolved: 05/Oct/17 06:07

Description

Similar to IMPALA-4370 but for multiply. Impala's current multiply result type is:

rP = P1 + P2
rS = S1 + S2
If (rP > 38) then
   rP = 38
   rS = min(38, rS)

The proposed result type under V2 is:

rP = P1 + P2 + 1
rS = S1 + S2
// createAdjustedDecimalType()
If (rP > 38) then
   minS = min(rS, 6)
   rS = rS - (rP - 38)  
   rS = max(minS, rS)
   rP = 38

However, in order for this to be useful, we need to fix IMPALA-4939. Otherwise, we can't actually compute values that need the new result type anyway.

Issue Links

• blocks: IMPALA-4924 Make DECIMAL_V2 the default mode
• is blocked by: IMPALA-4939 DECIMAL multiply overflows early
• relates to: IMPALA-4370 DECIMAL divide result type (Impala TPC-DS query 11 result lost one row)