When moving from MySQL 5.7 to MariaDB 10.2, roles are not usable. This seems to persist, even if the MariaDB instance is further upgraded (first noticed on a production 10.3 server).

Steps I have taken to replicate this issue:

• Create fresh EC2 instance, running Ubuntu 18.04 LTS
• Run apt update / apt upgrade
• Install mysql-server (installs 5.7.30-0ubuntu0.18.04.1)
• Proceed through installation process accepting defaults, ensure once finished server has started
• Stop the server, uninstall the MySQL package, install the MariaDB package as per here
• Stop the server, start without grant tables, update root user to use 'unix_socket' instead of 'auth_socket' (via FLUSH PRIVILEGES; ALTER USER `root`@`localhost` IDENTIFIED VIA unix_socket;)

The below test script now shows roles don't work (on a straight MariaDB install, `is_role` would be 'Y' and the `SET ROLE` would work as expected:

MariaDB [(none)]> CREATE ROLE `aRole`;

Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> SET ROLE `aRole`;

Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> FLUSH PRIVILEGES;

Query OK, 0 rows affected (0.00 sec)

MariaDB [(none)]> SET ROLE `aRole`;

ERROR 1959 (OP000): Invalid role specification `aRole`

MariaDB [(none)]> SELECT `User`, `is_role` FROM `mysql`.`user`;

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

| User             | is_role |

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

| root             | N       |

| mysql.session    | N       |

| mysql.sys        | N       |

| debian-sys-maint | N       |

| aRole            | N       |

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

5 rows in set (0.00 sec)

(Running the select prior to the FLUSH PRIVILEGES; has the same result)