Simple indexed IN query takes 40 seconds

I found that simple IN query on indexed tables takes too much time.

dok and rid have both indexes on int dokumnr columnr and dokumnr is not
null.
PostgreSql can use index on dok or event on rid so it can executed fast.

How to make this query to run fast ?

Andrus.

note: list contain a lot of integers, output below is abbreviated in this
part.

explain analyze select
sum(rid.kogus)
from dok JOIN rid USING(dokumnr)
where dok.dokumnr in
(869906,869907,869910,869911,869914,869915,869916,869917,869918,869921,869925,869926,869928,869929,869934,869935,869936,...)

"Aggregate (cost=327569.15..327569.16 rows=1 width=9) (actual
time=39749.842..39749.846 rows=1 loops=1)"
" -> Hash Join (cost=83872.74..327537.74 rows=12563 width=9) (actual
time=25221.702..39697.249 rows=11857 loops=1)"
" Hash Cond: ("outer".dokumnr = "inner".dokumnr)"
" -> Seq Scan on rid (cost=0.00..195342.35 rows=3213135 width=13)
(actual time=0.046..26347.959 rows=3243468 loops=1)"
" -> Hash (cost=83860.76..83860.76 rows=4792 width=4) (actual
time=128.366..128.366 rows=4801 loops=1)"
" -> Bitmap Heap Scan on dok (cost=9618.80..83860.76
rows=4792 width=4) (actual time=58.667..108.611 rows=4801 loops=1)"
" Recheck Cond: ((dokumnr = 869906) OR (dokumnr = 869907)
OR (dokumnr = 869910) OR (dokumnr = 869911) OR (dokumnr = 869914) OR
(dokumnr = 869915) OR (dokumnr = 869916) OR (dokumnr = 869917) OR (dokumnr =
869918) OR (dokumnr = 869921) OR (dokumnr = 869925) OR (dokumnr = 869926) OR
(dokumnr = 869928) OR (dokumnr = 869929) OR (dokumnr = 869934) OR (dokumnr =
869935) OR (dokumnr = 869936) OR (dokumnr = 869937) OR (dokumnr = 869940) OR
(dokumnr = 869941) OR (dokumnr = 869945) OR (dokumnr = 869951) OR (dokumnr =
869964) OR (dokumnr = 869966) OR (dokumnr = 869969) OR (dokumnr = 869974) OR
(dokumnr = 869979) OR (dokumnr = 869986) OR (dokumnr = 869992) OR (dokumnr =
869993) OR (dokumnr = 869995) OR (dokumnr = 869997) OR (dokumnr = 870007) OR
(dokumnr = 870018) OR (dokumnr = 870021) OR (dokumnr = 870023) OR (dokumnr =
870025) OR (dokumnr = 870033) OR (dokumnr = 870034) OR (dokumnr = 870036) OR
(dokumnr = 870038) OR (dokumnr = 870043) OR (dokumnr = 870044) OR (dokumnr =
870046) OR (dokumnr = 870050) OR (dokumnr = 870051) OR (dokumnr = 870053) OR
(dokumnr = 870054) OR (dokumnr = 870055) OR (dokumnr = 870064) OR (dokumnr =
870066) OR (dokumnr = 870069) OR (dokumnr = 870077) OR (dokumnr = 870079) OR
(dokumnr = 870081) OR (dokumnr = 870084) OR (dokumnr = 870085) OR (dokumnr =
870090) OR (dokumnr = 870096) OR (dokumnr = 870110) OR (dokumnr = 870111) OR
(dokumnr = 870117) OR (dokumnr = 870120) OR (dokumnr = 870124) OR (dokumnr =
870130)
...
OR (dokumnr = 890907) OR (dokumnr = 890908))"
" -> BitmapOr (cost=9618.80..9618.80 rows=4801 width=0)
(actual time=58.248..58.248 rows=0 loops=1)"
" -> Bitmap Index Scan on dok_dokumnr_idx
(cost=0.00..2.00 rows=1 width=0) (actual time=0.052..0.052 rows=3 loops=1)"
" Index Cond: (dokumnr = 869906)"
" -> Bitmap Index Scan on dok_dokumnr_idx
(cost=0.00..2.00 rows=1 width=0) (actual time=0.011..0.011 rows=3 loops=1)"
" Index Cond: (dokumnr = 869907)"
" -> Bitmap Index Scan on dok_dokumnr_idx
(cost=0.00..2.00 rows=1 width=0) (actual time=0.020..0.020 rows=3 loops=1)"
" Index Cond: (dokumnr = 869910)"
" -> Bitmap Index Scan on dok_dokumnr_idx
(cost=0.00..2.00 rows=1 width=0) (actual time=0.010..0.010 rows=3 loops=1)"
" Index Cond: (dokumnr = 869911)"
" -> Bitmap Index Scan on dok_dokumnr_idx
(cost=0.00..2.00 rows=1 width=0) (actual time=0.008..0.008 rows=3 loops=1)"
" Index Cond: (dokumnr = 869914)"
...
" -> Bitmap Index Scan on dok_dokumnr_idx
(cost=0.00..2.00 rows=1 width=0) (actual time=0.008..0.008 rows=1 loops=1)"
" Index Cond: (dokumnr = 890908)"
"Total runtime: 39771.385 ms"

"PostgreSQL 8.1.4 on i686-pc-linux-gnu, compiled by GCC
i686-pc-linux-gnu-gcc (GCC) 3.4.6 (Gentoo 3.4.6-r1, ssp-3.4.5-1.0,
pie-8.7.9)"