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?