def time_bookings_query
    @query_bookings ||= if params[:set_filter] == '3' || session[:tt_user_bookings_query].nil?
      query = TimeBookingQuery.new :name => 'x', :filters => {}
      query.build_from_params(params)
      session[:tt_user_bookings_query] = {:filters => query.filters, :group_by => query.group_by, :column_names => query.column_names}