How to avoid "Seq Scans"?

Hi all.

In PG 8.2.4 I have a 4+M rows table like this:

create table t (
f1 bigint,
f2 text,
f3 text
);

create index i_t_1 on t( f1 );
create index i_t_2 on t( f2 );
create index i_t_2 on t( f3 );

I'd need to write a stored function that should do the
following:

for rec in select * from t order by f2,f2 loop
...
end loop;

This loop is increadibly slow. Infact the friendly explain tells me
that:

test=# explain select * from t order by f2,f3;
QUERY PLAN
---------------------------------------------------------------------------------
Sort (cost=958786.20..970734.55 rows=4779338 width=28)
Sort Key: f2,f3
-> Seq Scan on t (cost=0.00..85501.38 rows=4779338 width=28)

I'd like to know a hint about a technicque to avoid the sequential
scan!

Thanks.

--
Vincenzo Romano
--
Maybe Computer will never become as intelligent as Humans.
For sure they won't ever become so stupid. [VR-1988]