Updating a decimal column with scale smaller than the source column returns an error

MariaDB [test]> create table c1 (a decimal(2,2), b decimal(4,4))engine=columnstore;

Query OK, 0 rows affected (0.268 sec)

MariaDB [test]> insert into c1 values (0.09, 0.0009);

Query OK, 1 row affected (5.187 sec)

MariaDB [test]> select * from c1;

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

| a    | b      |

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

| 0.09 | 0.0009 |

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

1 row in set (0.099 sec)

MariaDB [test]> UPDATE c1 SET a=b;

ERROR 1264 (22003): CAL0002: IDB-2025: Data truncated for column 'a' 

MariaDB [test]> select * from c1;

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

| a    | b      |

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

| 0.09 | 0.0009 |

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

1 row in set (0.022 sec)

MariaDB [test]> create table i1 as select * from c1;

Query OK, 1 row affected (0.032 sec)

Records: 1  Duplicates: 0  Warnings: 0

MariaDB [test]> UPDATE i1 SET a=b;

Query OK, 1 row affected, 1 warning (0.003 sec)

Rows matched: 1  Changed: 1  Warnings: 1

MariaDB [test]> show warnings;

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

| Level | Code | Message                                |

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

| Note  | 1265 | Data truncated for column 'a' at row 1 |

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

1 row in set (0.000 sec)

MariaDB [test]> select * from i1;

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

| a    | b      |

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

| 0.00 | 0.0009 |

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

1 row in set (0.001 sec)

MariaDB [test]> show variables like '%sql_mode%';

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

| Variable_name | Value                                                                                     |

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

| sql_mode      | STRICT_TRANS_TABLES,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION |

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

1 row in set (0.004 sec)