[#MDEV-30257] Value changed after adding DISTINCT [10.3.12, 10.11.1]

Description:
In theory, the result of sql2(DISTINCT) ⊆ the result of sql1:

SELECT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql1

SELECT DISTINCT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql2

However, the value -200412310000 changed to -2147483648 after adding DISTINCT, seems like a logical bug:

mysql> select version();

+-----------------------------------------+

| version()                               |

+-----------------------------------------+

| 10.11.1-MariaDB-1:10.11.1+maria~ubu2204 |

+-----------------------------------------+

1 row in set (0.00 sec)

mysql> SELECT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql1

+---------------+

| f1            |

+---------------+

| -200412310000 |

+---------------+

1 row in set (0.00 sec)

mysql> SELECT DISTINCT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql2

+-------------+

| f1          |

+-------------+

| -2147483648 |

+-------------+

1 row in set (0.00 sec)

How to repeat:

drop table if exists t;

CREATE TABLE t (c1 DECIMAL(40,20));

INSERT INTO t VALUES (-0.0001);

SELECT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql1

SELECT DISTINCT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql2

Hope these can be helpful for your debugging:
We look for the first version of the bug in all docker images (with format x.x.x) of https://hub.docker.com/_/mariadb/tags
We found that the bug first occurred in mariadb:10.3.12, it cannot be reproduced in mariadb:10.3.11:

MariaDB [TEST]> select version();

+----------------------------------------+

| version()                              |

+----------------------------------------+

| 10.3.12-MariaDB-1:10.3.12+maria~bionic |

+----------------------------------------+

1 row in set (0.000 sec)

MariaDB [TEST]> SELECT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql1

+---------------+

| f1            |

+---------------+

| -200412310000 |

+---------------+

1 row in set (0.000 sec)

MariaDB [TEST]> SELECT DISTINCT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql2

+-------------+

| f1          |

+-------------+

| -2147483648 |

+-------------+

1 row in set (0.000 sec)

MariaDB [TEST]> select version();

+----------------------------------------+

| version()                              |

+----------------------------------------+

| 10.3.11-MariaDB-1:10.3.11+maria~bionic |

+----------------------------------------+

1 row in set (0.000 sec)

MariaDB [TEST]> SELECT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql1

+---------------+

| f1            |

+---------------+

| -200412310000 |

+---------------+

1 row in set (0.000 sec)

MariaDB [TEST]> SELECT DISTINCT (LAST_DAY('2004-12-20 21:48:16') DIV c1) AS f1 FROM t; -- sql2

+---------------+

| f1            |

+---------------+

| -200412310000 |

+---------------+

1 row in set (0.000 sec)

[MDEV-30257] Value changed after adding DISTINCT [10.3.12, 10.11.1] Created: 2022-12-17 Updated: 2023-11-28
Status:	Confirmed
Project:	MariaDB Server
Component/s:	Optimizer
Affects Version/s:	10.3.12, 10.11.1
Fix Version/s:	10.4, 10.5, 10.6, 10.11

[MDEV-30257] Value changed after adding DISTINCT [10.3.12, 10.11.1] Created: 2022-12-17 Updated: 2023-11-28