disable_referential_integrity

# File activerecord/lib/active_record/connection_adapters/mysql_adapter.rb, line 275
      def disable_referential_integrity #:nodoc:
        old = select_value("SELECT @@FOREIGN_KEY_CHECKS")

        begin
          update("SET FOREIGN_KEY_CHECKS = 0")
          yield
        ensure
          update("SET FOREIGN_KEY_CHECKS = #{old}")
        end
      end