Stuck using Sequential Scan

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I have a problem where I have the table format listed below. I have the
primary key tsyslog_id and the index built against it. However, when I
select a unique row, it will only ever do a seq scan even after I turn off
all other types except indexscan. I understand you cannot fully turn off seq
scan.

Syslog_TArchive size: 1,426,472,960 bytes
syslog_tarchive_pkey size: 132,833,280 bytes
archhost_idx size: 300,802,048 bytes
tarchdatetime_idx size: 159,293,440 bytes
tarchhostid_idx size: 362,323,968 bytes

I cannot run vacuum more than once a day because of its heavy IO penalty. I
run analyze once an hour. However, if I run analyze then explain, I see no
difference in the planners decisions. What am I missing?

TSyslog=# \d syslog_tarchive;
Table "public.syslog_tarchive"
Column | Type |
Modifiers
- ------------+------------------------+-------------------------------------------------------------------------
tsyslog_id | bigint | not null default
nextval('public.syslog_tarchive_tsyslog_id_seq'::text)
facility | integer |
severity | integer |
date | date |
time | time without time zone |
host | character varying(128) |
message | text |
Indexes:
"syslog_tarchive_pkey" primary key, btree (tsyslog_id)
"archhost_idx" btree (host)
"tarchdatetime_idx" btree (date, "time")
"tarchhostid_idx" btree (tsyslog_id, host)

TSyslog=# explain select * from tsyslog where tsyslog_id=431650835;
QUERY PLAN
- -------------------------------------------------------------------------
Seq Scan on tsyslog (cost=100000000.00..100000058.20 rows=2 width=187)
Filter: (tsyslog_id = 431650835)
(2 rows)

- --

- --------------------------------------------------
Jeremy M. Guthrie jeremy(dot)guthrie(at)berbee(dot)com
Senior Network Engineer Phone: 608-298-1061
Berbee Fax: 608-288-3007
5520 Research Park Drive NOC: 608-298-1102
Madison, WI 53711
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