The default value can be set once in #column_defaults

Rather than doing it every time an instance is instantiated.

activerecord/lib/active_record/locking/optimistic.rb

@@ -168,16 +168,16 @@ module ActiveRecord
           super
         end
 
-        # If the locking column has no default value set,
-        # start the lock version at zero. Note we can't use
-        # <tt>locking_enabled?</tt> at this point as
-        # <tt>@attributes</tt> may not have been initialized yet.
-        def initialize_attributes(attributes, options = {}) #:nodoc:
-          if attributes.key?(locking_column) && lock_optimistically
-            attributes[locking_column] ||= 0
-          end
+        def column_defaults
+          @column_defaults ||= begin
+            defaults = super
 
-          attributes
+            if defaults.key?(locking_column) && lock_optimistically
+              defaults[locking_column] ||= 0
+            end
+
+            defaults
+          end
         end
       end
     end

activerecord/lib/active_record/model_schema.rb

@@ -312,6 +312,13 @@ module ActiveRecord
         @relation             = nil
       end
 
+      # This is a hook for use by modules that need to do extra stuff to
+      # attributes when they are initialized. (e.g. attribute
+      # serialization)
+      def initialize_attributes(attributes, options = {}) #:nodoc:
+        attributes
+      end
+
       private
 
       # Guesses the table name, but does not decorate it with prefix and suffix information.