Fix to support child classes of composite primary key models.

lib/composite_primary_keys/base.rb

@@ -23,11 +23,6 @@ def set_primary_keys(*keys)
           include CompositeInstanceMethods
           include CompositePrimaryKeys::ActiveRecord::AssociationPreload
         EOV
-
-        class << unscoped
-          include CompositePrimaryKeys::ActiveRecord::FinderMethods::InstanceMethods
-          include CompositePrimaryKeys::ActiveRecord::Relation::InstanceMethods
-        end
       end
 
       def composite?
@@ -89,6 +84,20 @@ def composite?
       def ids_to_s(many_ids, id_sep = CompositePrimaryKeys::ID_SEP, list_sep = ',', left_bracket = '(', right_bracket = ')')
         many_ids.map {|ids| "#{left_bracket}#{CompositePrimaryKeys::CompositeKeys.new(ids)}#{right_bracket}"}.join(list_sep)
       end
+
+      def relation #:nodoc:
+        @relation ||= begin
+          result = Relation.new(self, arel_table)
+          # CPK
+          class << result
+            include CompositePrimaryKeys::ActiveRecord::FinderMethods::InstanceMethods
+            include CompositePrimaryKeys::ActiveRecord::Relation::InstanceMethods
+          end
+          result
+        end
+
+        finder_needs_type_condition? ? @relation.where(type_condition) : @relation
+      end
     end
 
     module CompositeInstanceMethods