Member DbModelPrivate::data (const QModelIndex &idx, int role=Qt::DisplayRole) const: column.t_display_;
Member DbModelPrivate::setColumnCallback (int table_index, int column_index, DbColumn::Callback value, void *user_data): the cells in main table are also stored locally; this is a design flaw as we should only store a reference in DbModelCol.
Member DbModelPrivate::setOrder (int column, Qt::SortOrder order, int table_index=0)