[FLINK-24691] FLINK SQL SUM() causes a precision error

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 1.14.0
• Fix Version/s: 1.14.3, 1.15.0
• Component/s: Table SQL / Runtime
• Labels: pull-request-available
• Release Note: This changes the result of a decimal SUM() between 1.14.0 and 1.14.1. It restores the behavior of 1.13 to be consistent with Hive/Spark.
• Assignee: Marios Trivyzas
• Reporter: Zongwen Li
• Created: 29/Oct/21 06:41
• Updated: 15/Dec/21 01:44
• Resolved: 09/Nov/21 08:05

Description

code: 

tableEnv.executeSql("select sum(cast( 1.03520274 as decimal(32, 8))) as num ").print();

expected:

1.03520274

actual:

1.03520270

 

This function is normal in version 1.13.x.

I found the code that caused the inconsistency：

org.apache.flink.table.types.logical.utils.LogicalTypeMerging#adjustPrecisionScale method was added in 1.14. Because sum() generates max precision(38) by default, it leads to special circumstances, which reduces the scale by 1.

 

Issue Links

• is related to: FLINK-24809 Check & possible fix decimal precision and scale for all Aggregate functions
• links to: GitHub Pull Request #17634