Bug #115121 different precision in MySQL5.7.42andMySQL8.3.0

• Submitted: 25 May 9:09
• Modified: 27 May 9:40
• Reporter: Ecee no
• Status: Not a Bug
• Category: MySQL Server
• Severity: S3 (Non-critical)
• Version: 8.3.0
• OS: Any
• CPU Architecture: Any

[25 May 9:09] Ecee no

Description:
Time rounding may be different in Insert and Select. Even different between a query、subquery 、view. 
Could you respond to that? Why are the results different? Is this expected behavior or a bug?
Thanks.

How to repeat:
1. reuslt is 00:00:00.00002
select maketime(2.4/time '08:30:23.01',2.4/time '08:30:23.01',2.4/time '08:30:23.01') f14;

2. reuslt is 00:00:00.00003
select * from (select maketime(2.4/time '08:30:23.01',2.4/time '08:30:23.01',2.4/time '08:30:23.01')) f14;

drop view if exists v1;
CREATE OR REPLACE VIEW v1 as select maketime(2.4/time '08:30:23.01',2.4/time '08:30:23.01',2.4/time '08:30:23.01') f14;
select * from v1;

drop table if exists t1;
CREATE table t1(f14 time(6)) as select maketime(2.4/time '08:30:23.01',2.4/time '08:30:23.01',2.4/time '08:30:23.01') f14;
select * from t1;

[27 May 9:40] MySQL Verification Team

Hi Mr. no,

Thank you for your bug report.

We have managed to repeat it with mysql 8.4.0.

However, it is not a bug.

It is not a bug, because floating point arithmetics is involved in the test case and it is, by definition, very prone to the rounding errors.

Not a bug.