Why no gtkmm equivalent for gtk_list_store_set?

[Jef Driesen <jefdriesen hotmail com>]

Is there a reason why there is no equivalent gtkmm function for 
gtk_list_store_set? Because changing multiple columns at once is really 
MUCH faster than changing one column at a time.

In my application I noticed a speed difference of 75 times (1500ms vs 
20ms)! The treeview model has 11 columns and around 850 rows, and I'm 
using this piece of code to fill the model (from an sqlite database):

clock_t start = clock ();

while (cmd.step()) {
   // USING GTKMM FUNCTIONS
   Gtk::TreeModel::Row row = *(store->append());
   row[m_columns.number] = cmd.column_int(0);
   row[m_columns.datetime] = cmd.column_text(1);
   // other columns here

   // USING GTK+ FUNCTIONS
   GtkTreeIter iter;
   gtk_list_store_append(GTK_LIST_STORE(store->gobj()),&iter);
   gtk_list_store_set(GTK_LIST_STORE(store->gobj()),&iter,
      m_columns.m_number.index(), cmd.column_int(0),
      m_columns.m_datetime.index(), cmd.column_text(1),
      // other columns here
      -1
   );
}

clock_t finish = clock ();
double duration = (double)(finish - start) / CLOCKS_PER_SEC);
printf("Time: %f ms\n", 1000.0 * duration);