Index/Seq Scan Problem

Hi all,

Now I know you're all cringing at the subject. I've been trying to resolve this as
much as I can by reading through the many many other posts of similar problems, but
I'm at the end of my tether.

Here's the scenario.

Firstly, I'm using PostgreSQL 7.2 - I know it's a bit behind in the updates, and if
you think upgrading will solve the problem, great, but I have my doubts - particularly
being a production environment. I have a table with 597041 rows. It contains 14
columns, 10 are int4, 4 are int8. It has a three-column primary key on three of the
int8 columns. The definition is as follows:

Column | Type | Modifiers
--------------------+---------+--------------------
playerid | bigint | not null
teamid | bigint | not null
gameid | bigint | not null
completegameteamid | bigint | not null default 0
nsendoff | integer | not null default 0
nsinbin | integer | not null default 0
bcaptain | integer | not null default 0
bgoalkicker | integer | not null default 0
npts | integer | not null default 0
nfwdtries | integer | not null default 0
nfieldgoals | integer | not null default 0
ngoals | integer | not null default 0
ntries | integer | not null default 0
teammakeupid | integer | not null

There are two indexes:
ix_completegameteam_gameteam (on gameid, teamid)
ix_completegameteam_game (on gameid)

Plus of course the primary key on gameid, teamid, playerid. completegameteamid used to
be the primary key using a sequence, but I got rid of it since it served no purpose.

Each combination of gameid, teamid has 0-17 rows associated with it, guaranteed.
Therefore, the index on gameid, teamid should, as far as I can tell, always return 17
or less rows, and should be easily the most efficient means to pick up the data.

The entire database has a regular schedule of VACUUM ANALYZE, run nightly.

Here's an explain result on a basic query:

explain analyze select * from completegameteam where gameid = 40292 and teamid = 1747;
NOTICE: QUERY PLAN:

Seq Scan on completegameteam (cost=0.00..16917.12 rows=1 width=72) (actual
time=330.82..799.46 rows=17 loops=1)
Total runtime: 799.58 msec

EXPLAIN

On increasing the statistics for gameid and teamid from 10 to 100 and doing an
analyze, the explain analyze changes:

explain analyze select * from completegameteam where gameid = 40292 and teamid = 1747;
NOTICE: QUERY PLAN:

Seq Scan on completegameteam (cost=0.00..16917.12 rows=1 width=72) (actual
time=378.29..1743.27 rows=17 loops=1)
Total runtime: 1743.39 msec

EXPLAIN

On turning off sequence scans:

=# set enable_seqscan = 0;
SET VARIABLE
# explain analyze select * from completegameteam where gameid = 40292 and teamid =
1747;
NOTICE: QUERY PLAN:

Seq Scan on completegameteam (cost=100000000.00..100016917.12 rows=1 width=72)
(actual time=330.05..2698.87 rows=17 loops=1)
Total runtime: 2698.97 msec

EXPLAIN

I'm really getting stuck on this. I even ran a CLUSTER on the table on the gameid,
teamid index hoping that would help but to no avail.

Any advice? Any more information I need to supply?

Thanks,

Chris