Question

This is probably one of the things that all new users find out about Rails sooner or later. I just realized that rails is updating all fields with the serialize keyword, without checking if anything really changed inside. In a way that is the sensible thing to do for the generic framework.

But is there a way to override this behavior? If I can keep track of whether the values in a serialized fields have changed or not, is there a way to prevent it from being pushed in the update statement? I tried using “update_attributes” and limiting the hash to the fields of interest, but rails still updates all the serialized fields.

Suggestions?

Answer 1

Yes, that was bugging me too. This is what I did for Rails 2.3.14 (or lower):

# config/initializers/nopupdateserialize.rb

module ActiveRecord
  class Base
    class_attribute :no_serialize_update
    self.no_serialize_update = false
  end
end

module ActiveRecord2
  module Dirty

    def self.included(receiver)
      receiver.alias_method_chain :update, :dirty2
    end

    private 

    def update_with_dirty2
      if partial_updates?
        if self.no_serialize_update
          update_without_dirty(changed)
        else
          update_without_dirty(changed | (attributes.keys & self.class.serialized_attributes.keys))
        end
      else
        update_without_dirty
      end
    end

  end
end

ActiveRecord::Base.send :include, ActiveRecord2::Dirty

Then in your controller use:

model_item.no_serialize_update = true
model_item.update_attributes(params[:model_item])
model_item.increment!(:hits)
model_item.update_attribute(:nonserializedfield => "update me")

etc.

Or define it in your model if you do not expect any changes to the serialized field once created (but update_attribute(:serialized_field => “update me” still works!)

class Model < ActiveRecord::Base
  serialize :serialized_field

  def no_serialize_update
    true
  end

end