Ruby On Rails in UA/Программирование на ROR/Удаление связи при has and belongs to many/RE: Удаление связи при has and belongs to many

Если я правильно понят твою задачу ты просто хочешь почистить таблицу и удалить все записи из таблицы Role

destroy_all(conditions = nil)
Destroys the objects for all the records that match the condition by instantiating each object and calling the destroy method. Example:

Role.destroy_all "last_login < '2004-04-04'" Role.destroy_all "id not null" #удалит все без разбора

delete_all(conditions = nil)

Deletes the records matching conditions without instantiating the records first, and hence not calling the destroy method and invoking callbacks. This is a single SQL query, much more efficient than destroy_all.
Options

conditions Conditions are specified the same way as with find method.
Example
Post.delete_all "person_id = 5 AND (category = 'Something' OR category = 'Else')"
This deletes the affected posts all at once with a single DELETE query. If you need to destroy dependent associations or call your before_ or after_destroy callbacks, use the destroy_all method instead.