Hi. I have a question about auth_assignment table structure.
create table `auth_assignment` ( `item_name` varchar(64) not null, `user_id` varchar(64) not null, `created_at` integer, primary key (`item_name`, `user_id`), foreign key (`item_name`) references `auth_item` (`name`) on delete cascade on update cascade ) engine InnoDB;
Is it normal, that field user_id is varchar and not int? Why not int with normal index on this field?