Bug #102169 tinyint DIV a small value expression return wrong

• Submitted: 7 Jan 2021 9:42
• Modified: 7 Jan 2021 9:55
• Reporter: zetao wei
• Status: Verified
• Category: MySQL Server: DML
• Severity: S2 (Serious)
• Version: 8.0.18, 5.6.50, 5.7.32, 8.0.22
• OS: Any
• CPU Architecture: Any

[7 Jan 2021 9:42] zetao wei

Description:

mysql> select (b DIV 0.0001 / 2) as x from t3 group by x;
+-----------+
| x         |
+-----------+
| 5000.0000 |
+-----------+

mysql> select (a DIV 0.0001 / 2) as x from t3 group by x order by x;
+----------+
| x        |
+----------+
| 999.9999 |
+----------+

The result is wrong when `Using temporary`.

I think the Field_new_decimal is overflow when the DIV expression has tinyint.

How to repeat:
create table t3 (a tinyint, b int);
insert into t3 values (1, 1);
select (a DIV 0.0001 / 2) as x from t3 group by x order by x;

[7 Jan 2021 9:55] MySQL Verification Team

Hello zetao wei,

Thank you for the report and test case.

regards,
Umesh