method private _cb__edit_column = fun () ->
    match self#_get_selection with
      | Some (_, Some (path, column)) ->
          let defaults = { CGUI.cgi_name       = column.SQL_db.col_name;
                           CGUI.cgi_comment    = column.SQL_db.col_comment;
                           CGUI.cgi_type       = column.SQL_db.col_type;
                           CGUI.cgi_nullable   = column.SQL_db.col_nullable;
                           CGUI.cgi_options    = column.SQL_db.col_spec_options;
                           CGUI.cgi_spec_ty    = column.SQL_db.col_spec_ty;
                           CGUI.cgi_ocaml_type = column.SQL_db.col_ocaml_ty;
                           CGUI.cgi_sql2ml     = column.SQL_db.col_sql2ml;
                           CGUI.cgi_ml2sql     = column.SQL_db.col_ml2sql; }
          in
          let column_gui =
            new CGUI.column_gui
              (self#_column_gui_update_answer
                 (current_column_model#get_row_reference path) column)
              defaults
          in
            column_gui#start ()
      | _ -> ()