code: protected <T> int updateField (
          final Table<T> table, final T object, String field)
          throws PersistenceException
      {
          final FieldMask mask = table.getFieldMask();
          mask.setModified(field);
          return executeUpdate(new Operation<Integer>() {
              public Integer invoke (Connection conn, DatabaseLiaison liaison)
                  throws SQLException, PersistenceException
              {
                  return table.update(conn, object, mask);
              }
          });
      }
docs: Updates the specified field in the supplied object (which must
  correspond to the supplied table).
  
  @return the number of rows modified by the update.