QSqlTableModel: primary key to model row

Hello,
I have a model (QSqlTableModel), loaded with a table like this:
"CREATE TABLE person (id INTEGER PRIMARY KEY, name VARCHAR(20))"
How can I get the row number of the model from the table primary key?
Is there a better way than looping thru all rows of the model?

Code:

---

int Dialog::primaryToRow(QAbstractItemModel *model, int primary)
{
    if (model == 0)
        return -1;
    for(int row=0; row < model->rowCount(); ++row)
    {
        if ( model->index(row, 0).data(Qt::DisplayRole).toInt() == primary )
            return row;
    }
    return -1;
}
 
int Dialog::rowToPrimary(QAbstractItemModel *model, int row)
{
    if (model == 0)
        return -1;
    QModelIndex index = model->index(row,0); //column 0 = primary key
    if (!index.isValid())
        return -1;
    return index.data(Qt::DisplayRole).toInt();
}

---

I cannot modify the model, so "model->filter" is no good.
My loop code works, but for a 10K rows table it is too heavy (I've a custom view which calls it twice for every row).
Any better solution? Perhaps a list "QMap<int, int>" ?

Thank you,
Nero