text: select pg_sleep(0.1); -- make sure this transaction starts after the first transaction.
  begin;
  select 'sql 2', * from t_currency where id = 1 for update;
  update t_currency set name='name' where id = 1;
  select 'sql 2', * from t_currency where id = 1;
  update t_currency set id=3 where id = 1;
  select 'sql 2: commit';
  commit;
  