MariaDB [xxx]> LOCK TABLE m WRITE;

Query OK, 0 rows affected (0.00 sec)

MariaDB [xxx]> START TRANSACTION;

Query OK, 0 rows affected (0.00 sec)

MariaDB [xxx]> LOCK TABLE t WRITE;

Query OK, 0 rows affected (0.00 sec)

MariaDB [xxx]> START TRANSACTION;

Query OK, 0 rows affected, 1 warning (0.00 sec)

Warning (Code 1105): external_lock: unexpected command 59

The table `m` is MyISAM but, as far as I can tell, no warning occurs with other storage engines. The table `t` is CONNECT, which seems to be the only engine that issues a warning.

I report this behavior because you probably want to be aware about inconsistencies between engines. But, to be honest, I prefer CONNECT's behavior: when a trx starts, table locks are lost, and this is something I want to know. I hope that a more informative warning will be issued, no matter which engine I am using.