optimyzing

Hi

I was wondering if it could be possible to optimise such a query :

select avg(traffic) AS avg
from (select   date(time),   sum(traffic) / 1024 / 86400  AS traffic  FROM stats  WHERE ip = '212.43.217.66' AND date(time) < date('now')  GROUP BY date(time) ) AS subselect

having :                  Table "stats"Column  |            Type             | Modifiers
---------+-----------------------------+-----------ip      | inet                        | not nulltime    | timestamp without time zone | not nullpacket  | bigint                      | not nulltraffic | bigint                      | not null

I have a cron which fills this table every X minute with the total traffic 
by ip for this period.

the subselect gives me the average traffic for an IP by day (in KB/s) :
   date    |    traffic
------------+----------------2002-03-25 | 988.79816880972002-03-26 | 961.15854843702002-03-27 | 984.36130754262002-03-28 | 912.57711450652002-03-29 | 885.42811841052002-03-30 | 800.65096134892002-03-31 | 673.6354859190

and I can't get a query to have the average of that without having to do
this subselect.
     avg
----------------886.6585292820

and if it is useful :

Aggregate  (cost=1366.11..1366.11 rows=1 width=16) ->  Subquery Scan subselect  (cost=1365.34..1366.07 rows=15 width=16)       ->  Aggregate  (cost=1365.34..1366.07 rows=15 width=16)             ->  Group  (cost=1365.34..1365.71 rows=146 width=16)                   ->  Sort  (cost=1365.34..1365.34 rows=146 width=16)                         ->  Index Scan using stats_ip on stats 
(cost=0.00..1360.07 rows=146 width=16)

-- 
Mathieu Arnold