QSqlRelation update

I don't know if There is an error or I can't find the correct solution, I will try to explain:

I have a QSqlRelationalTableModel with a QSqlRelation set, and a QSqlRelationalDelegate set in the correspondent view. When I add a register in the foreign table, I don't know how to update this relation, I always see the old values in the QSqlRelationalDelegate's combo box. I've tried the select() and reset() methods of the model, and re-set the relation. None of them work.

I think there is not QTableView's fault because it is created every time I want view the model. i.e., the program have to destroy it (and QSqlRelationalDelegate) every time I want to add a register in the foreign table, because it is the centralWidget of a QMainWindow.

Please excuse my limited English, corrections are welcome.