Rails :dependent => :destroy VS :dependent => :delete_all

On a Rails' model association you can specify the :dependent option, which can take one of the following three forms:

• :destroy/:destroy_all The associated objects are destroyed alongside this object by calling their destroy method
• :delete/:delete_all All associated objects are destroyed immediately without calling their :destroy method
• :nullify All associated objects' foreign keys are set to NULL without calling their save callbacks

The difference is with the callback.

The :delete_all is made directly in your application and deletes by SQL :

DELETE * FROM users where compagny_id = XXXX

With the :destroy, there is an instantiation of all of your children. So, if you can't destroy it or if each has their own :dependent, its callbacks can be called.