drop table if exists test2;
CREATE TABLE test2(i integer, txt text);
alter table test2 alter column txt set storage external;
insert into test2 values (1, lpad('x', 3000));
insert into test2 values (2, lpad('x', 3000));

DO $$
DECLARE
    r record;
    t text;
BEGIN
  FOR r in (SELECT i FROM test2)
     LOOP
       select txt into t from test2 where i=r.i;
       COMMIT;
    END LOOP;
END;
$$;