Rails model with a many-to-many relationship upon itself

many_to_many_self.rb

class Product < ActiveRecord::Base
  # ... other code

  has_and_belongs_to_many :products,
                          :join_table => "related_products",
                          :foreign_key => "product_a_id",
                          :association_foreign_key => "product_b_id",
                          :finder_sql => 'SELECT DISTINCT products.* FROM products INNER JOIN related_products ON (#{id} = related_products.product_a_id OR #{id} = related_products.product_b_id) WHERE (products.id <> #{id})',
                          :insert_sql => 'INSERT INTO related_products (product_a_id, product_b_id) VALUES (#{id}, #{record.id})',
                          :delete_sql => 'DELETE FROM related_products WHERE (product_a_id = #{id} AND product_b_id IN (#{record.id})) OR (product_a_id = #{record.id} AND product_b_id IN (#{id}))',
                          :validate => false,
                          :uniq => true

  # ... other code
end