The following applies to rails 2, rails 3 and rails 4:
http://guides.rubyonrails.org/v3.2.13/active_record_validations_callbacks.html#skipping-callbacks
It provides a list of methods that skip callbacks, explaining why it is dangerous to use them without careful consideration. Reprinted here under the provisions of the Creative Commons Attribution-Share Alike 3.0 License.
12 Skipping Callbacks
Just as with validations, it is also possible to skip callbacks. These
methods should be used with caution, however, because important
business rules and application logic may be kept in callbacks.
Bypassing them without understanding the potential implications may
lead to invalid data.
- decrement
- decrement_counter
- delete
- delete_all
- find_by_sql
- increment
- increment_counter
- toggle
- touch
- update_column
- update_all
- update_counters
