--- /dev/null
+class Product < ActiveRecord::Base\r
+ set_primary_keys :id # redundant\r
+ has_many :product_tariffs, :foreign_key => :product_id\r
+ has_one :product_tariff, :foreign_key => :product_id\r
+\r
+ has_many :tariffs, :through => :product_tariffs, :foreign_key => [:tariff_id, :tariff_start_date]\r
+end\r