text: -- [er]it tests  column name of 'group by' clause with a expression which used '||' operator.
  create class DML_0001 
  ( 	int_col integer,
  var_col varchar(20),
  set_col set (int, varchar(10)) );
  insert into DML_0001 values (1,'test1', {1,'test1'});
  insert into DML_0001 values (2,'test1', {1,'test1'});
  insert into DML_0001 values (3,'test2', {1,'test2'});
  insert into DML_0001 values (4,'test1', {2,'test1'});
  insert into DML_0001 values (5,'test2', {2,'test2'});
  select max(int_col), var_col, set_col from DML_0001 group by var_col || '1';
  drop class DML_0001;