Getter method gets called on save even if you don't have any validations or callback.
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activemodel-3.2.13/lib/active_model/dirty.rb:143:in `attribute_change'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activemodel-3.2.13/lib/active_model/dirty.rb:117:in `block in changes'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activemodel-3.2.13/lib/active_model/dirty.rb:117:in `map'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activemodel-3.2.13/lib/active_model/dirty.rb:117:in `changes'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/attribute_methods/dirty.rb:23:in `save'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/transactions.rb:259:in `block (2 levels) in save'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/transactions.rb:313:in `block in with_transaction_returning_status'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/connection_adapters/abstract/database_statements.rb:192:in `transaction'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/transactions.rb:208:in `transaction'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/transactions.rb:311:in `with_transaction_returning_status'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/transactions.rb:259:in `block in save'"
"/home/user/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/transactions.rb:270:in `rollback_active_record_state!'"
"/home/usha/.rvm/gems/ruby-1.9.3-p194/gems/activerecord-3.2.13/lib/active_record/transactions.rb:258:in `save'"
So if you override getter for an attribute, make sure that it still performs its original function