Marking Activerecord object as dirty

ActiveRecord::Dirty keeps track of changes through the '=' operator for the attribute. You can use the attr_will_change! method to specify if a attribute will be modified in place. There's an example at: http://ryandaigle.com/articles/2008/3/31/what-s-new-in-edge-rails-d...

I suppose it would be too costly do have some kind of a diff logic run before the call to save, to see if some attributes have changed?

Do c.text = c.text.sub("bar") instead.