create table teststmt (id serial primary key, d text);
create table teststmt_tr (pid int default pg_backend_pid(), inserted bool, data teststmt);
create view teststmt_inserted as
  select (data).id, (data).d
  from teststmt_tr
  where pid=pg_backend_pid() and inserted;
create view teststmt_deleted as
  select (data).id, (data).d
  from teststmt_tr a
  where pid=pg_backend_pid() and not inserted;

CREATE OR REPLACE FUNCTION tf_teststmt_stmt_process() RETURNS trigger LANGUAGE plpgsql AS $body$
DECLARE
  _rec teststmt%rowtype;
BEGIN
  if TG_LEVEL = 'ROW' then
    --collect 'inserted'/'deleted' rows
    if TG_OP = 'INSERT' or TG_OP = 'UPDATE' then
      insert into teststmt_tr(inserted, data) values (true, NEW);
    end if;
    if TG_OP = 'DELETE' or TG_OP = 'UPDATE' then
      insert into teststmt_tr(inserted, data) values (false, OLD);
    end if;
  else
    if TG_WHEN = 'AFTER' then
      --process set of rows
      for _rec in (select * from teststmt_inserted) loop
        raise INFO 'inserted : % %', _rec.id, _rec.d;
      end loop;
      for _rec in (select * from teststmt_deleted) loop
        raise INFO 'deleted : % %', _rec.id, _rec.d;
      end loop;
    end if;
    
    --cleanup before and after row processing
    delete from teststmt_tr where pid=pg_backend_pid();
    --vacuum teststmt_tr;
  end if;
  
  return NEW;
END;
$body$;

CREATE TRIGGER teststmt_before_stmt BEFORE INSERT or UPDATE or DELETE
  ON teststmt FOR EACH STATEMENT
  EXECUTE PROCEDURE tf_teststmt_stmt_process();
CREATE TRIGGER teststmt_after_stmt AFTER INSERT or UPDATE or DELETE
  ON teststmt FOR EACH STATEMENT
  EXECUTE PROCEDURE tf_teststmt_stmt_process();
CREATE TRIGGER teststmt_after_row AFTER INSERT or UPDATE or DELETE
  ON teststmt FOR EACH ROW
  EXECUTE PROCEDURE tf_teststmt_stmt_process();

insert into teststmt(d) select 'hello';
insert into teststmt(d) select 'world';
insert into teststmt(d) select d||'!' from teststmt;
select * from teststmt;
select * from teststmt_tr;

update teststmt set d=d||'-upd';
select * from teststmt;
select * from teststmt_tr;

delete from teststmt;
select * from teststmt;
select * from teststmt_tr;