how to use array with "holes" ?

Hi.

I want to use array for store some values (bytes_in and bytes_out) and
use array index as "id". But I got an errors...
My example function extract traf_id, bytes_in, bytes_out and try to
fill an array, like this

CREATE OR REPLACE FUNCTION myf_test() RETURNS void
AS $$
DECLARE
 p_tmp RECORD;
 p_last_cpnt RECORD;
 p_bytes_in bigint[];
 p_bytes_out bigint[];
 i int;
BEGIN
 SELECT * INTO p_last_cpnt FROM nn_cpnt WHERE account_id = 5 ORDER BY
date_time DESC, cpnt_id DESC LIMIT 1;
 IF FOUND THEN
  FOR p_tmp IN SELECT ttc_id, bytes_in, bytes_out FROM nn_cpnt_traf
WHERE cpnt_id = p_last_cpnt.cpnt_id ORDER BY ttc_id LOOP
   --RAISE NOTICE '[%] -> [%] [%]', p_tmp.ttc_id, p_tmp.bytes_in,
p_tmp.bytes_out;
   i := p_tmp.ttc_id;
   RAISE NOTICE 'i = [%]', i;
   p_bytes_in[i] := p_tmp.bytes_in;
   p_bytes_out[i] := p_tmp.bytes_out;
   RAISE NOTICE 'p_bytes_in[%] = [%] / p_bytes_out[%] = [%]', i,
p_bytes_in[i], i, p_bytes_out[i];
  END LOOP;
 END IF;
 -- ... some work. And I prepare to "INSERT INTO tbl" from my array.
So I iterate through my array (but now I just RAISE NOTICE here).
 FOR i IN COALESCE(array_lower(p_bytes_in,1),1) ..
COALESCE(array_upper(p_bytes_in,1),-1) LOOP
   RAISE NOTICE 'p_bytes_in[%] = [%] / p_bytes_out[%] = [%]', i,
p_bytes_in[i], i, p_bytes_out[i];
 END LOOP;
END;
$$
LANGUAGE plpgsql;

But
=# SELECT myf_test();
NOTICE:  i = [1]
NOTICE:  p_bytes_in[1] = [1907262814] / p_bytes_out[1] = [9308877139]
NOTICE:  i = [5]
ERROR:  invalid array subscripts
CONTEXT:  PL/pgSQL function "myf_test" line 14 at assignment

There are "hole" between 1 and 5, so I think that is the problem... I
try to use temporary table (truncate it always before computations),
but it seems slowly than arrays. I think arrays are less complicated
so they operate faster.
Please, help. Explain me how to use array?
--
engineer