Query plan for NOT IN

mnw21-modmine-r13features-copy=# select count(*) from project;
count
-------
10
(1 row)

mnw21-modmine-r13features-copy=# select count(*) from intermineobject;
count
----------
26344616
(1 row)

mnw21-modmine-r13features-copy=# \d intermineobject;
Table "public.intermineobject"
Column | Type | Modifiers
--------+---------+-----------
object | text |
id | integer | not null
class | text |
Indexes:
"intermineobject_pkey" UNIQUE, btree (id)

mnw21-modmine-r13features-copy=# explain select * from project where id
NOT IN (SELECT id FROM intermineobject);
QUERY PLAN
------------------------------------------------------------------------------------
Seq Scan on project (cost=1476573.93..1476575.05 rows=5 width=183)
Filter: (NOT (hashed SubPlan 1))
SubPlan 1
-> Seq Scan on intermineobject (cost=0.00..1410720.74 rows=26341274 width=4)
(4 rows)

This query plan seems to me to be a little slow. Surely it could iterate
through the ten project rows and perform ten index lookups in the big
table?

Matthew

--
Riker: Our memory pathways have become accustomed to your sensory input.
Data: I understand - I'm fond of you too, Commander. And you too Counsellor