exec_migration

# File activerecord/lib/active_record/migration.rb, line 863
    def exec_migration(conn, direction)
      @connection = conn
      if respond_to?(:change)
        if direction == :down
          revert { change }
        else
          change
        end
      else
        public_send(direction)
      end
    ensure
      @connection = nil
    end