See https://mariadb.com/kb/en/create-table/#default-column-option

Thanks for pointing out the documentation I missed. But this still only works on only blob and text columns.

This ticket is for any column type. In my example, updatedBy is currentUser.. I wouldn't want to take the overhead of text for something that is usually less than 50 characters.

Also, ON UPDATE does not work with text.

MariaDB [test]> CREATE TABLE t1 (

    -> lottoNumber int(11) DEFAULT myUDF(),

    -> updatedBy varchar(255) DEFAULT CURRENT_USER() ON UPDATE CURRENT_USER()

    -> );

ERROR 1901 (HY000): Function or expression '`myUDF`()' cannot be used in the DEFAULT clause of `lottoNumber`

MariaDB [test]> CREATE TABLE t1 ( myCol longtext DEFAULT JSON_OBJECT('a',1,'b',2));

Query OK, 0 rows affected (0.015 sec)

MariaDB [test]> CREATE TABLE t1 ( updatedBy text DEFAULT CURRENT_USER() ON UPDATE CURRENT_USER() );

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'CURRENT_USER() )' at line 1

MariaDB [test]> CREATE TABLE t1 ( updatedBy text DEFAULT CURRENT_USER() );

Query OK, 0 rows affected (0.020 sec)

ON UPDATE is a non-standard historical extension for TIMESTAMP columns. Use triggers instead.
Otherwise expressions can be used in DEFAULT for any column time. See https://mariadb.com/kb/en/create-table/#default-column-option

I just showed you that it doesn't work for int or varchar. .. it doesnt work for any column type.

The documentation for "DEFAULT Column Option" seems to suggest that as of MariaDB 10.2.1, one can create tables with a DEFAULT option set to a function or and expression, which I understand to mean - it is possible to create a table with a column default value calling a user function.

If I try to do that, I get something like this:

Function or expression '`my_function`()' cannot be used in the DEFAULT clause of `my_column` 

I think this is what the OP was talking about.