create table tuser(
  id serial primary key,
  name text
);

create or replace function fti_sequence_id() returns trigger as $_$
declare 
  v_seq_name text;
  v_id   int;
  v_curr int;
begin
  v_seq_name := TG_ARGV[ 1 ];
  v_id := NEW.id;  --имя serial-поля - id 
  begin
    v_curr := currval(v_seq_name);
  exception
    when OTHERS then v_curr :=  0 ;
  end;
   --при одновременной явной вставке id из разных процессов будут проблемы 
  if v_id > v_curr then
    raise notice 'setval(\'%\',%)', v_seq_name, v_id;
    perform setval(v_seq_name, v_id);
  end if;
  return NEW;
end;
$_$ language plpgsql;

create trigger ti_tuser_sequence after insert on tuser 
  for each row execute procedure fti_sequence_id('id', 'tuser_id_seq');


insert into tuser select  2 , 'петров';
insert into tuser select  3 , 'сидоров';
insert into tuser select s.i, 'кузнецов' from generate_series( 4 , 10 ) s(i);
insert into tuser select  1 , 'иванов';

insert into tuser (name) select 'козлов';
select currval('tuser_id_seq');