problem with max and not using index on PK

Hi,
I am using PG 7.3.1

The query plan is:

mydb=# explain analyze select max(IDS) from t_sk10;                                                      QUERY PLAN

------------------------------------------------------------------------------------------------------------------------
Aggregate  (cost=61742.78..61742.78 rows=1 width=64) (actual
time=11221.42..11221.43 rows=1 loops=1)  ->  Seq Scan on t_sk10  (cost=0.00..60076.22 rows=666622 width=64)
(actual time=16.59..9968.00 rows=666622 loops=1)Total runtime: 11221.50 msec
(3 rows)

Time: 11222.68 ms

The time is very big.
For example if I start it on oracle, it take ~ 100 ms !

The column IDS is the PK. It is declared as name.
I do not know the reason for not using index in this case.

Also if I get another (not indexed column) and start also max, PG i
working 4 time quicker as oracle and it is great.

Regards,
ivan.