optimising data load

Hi all,

I'm (still) working on an application to regularly populate my database with some data provided from
a third party DB.

I'm still having really bad performance problems.
There are 300,000 records to be inserted, but I'm only getting 10,000/hour.
30 hours to populate a single table is just not on. There must be something seriously bad going on.

I have to update to different databases: live, and an update log.

I've included explains for both the db's below.

I have a few questions:

1) Can it really be right that it is going this slow ?
I'm running Redhat Linux with kernel 2.4.7, and postgres 7.1.3

2) Can anyone see a way to optimise these queries further ?

3) Is it likely to be quicker if I use a query to obtain ol.line, and then generate a CSV file for use with COPY ?

Thanks
JohnT

--- LIVE ---
explain INSERT INTO orderlines (theorder,type,stock,line,ordercurrent,sellingquant,price,discount,vatrate,comment)
SELECT oh.theorder,'P',' 0310',coalesce(ol.line+1,1),5,0,.52,0,0,'' FROM orderheader oh
LEFT OUTER JOIN orderlines ol ON oh.theorder = ol.theorder
WHERE oh.account=' MILN1' AND oh.delivery=1 AND oh.thedate='2002-06-01' AND oh.ordertype='O'
ORDER BY ol.line DESC LIMIT 1;
NOTICE: QUERY PLAN:

Subquery Scan *SELECT* (cost=47.41..47.41 rows=1 width=12)
-> Limit (cost=47.41..47.41 rows=1 width=12)
-> Sort (cost=47.41..47.41 rows=1 width=12)
-> Nested Loop (cost=0.00..47.40 rows=1 width=12)
-> Index Scan using orderheader_account on orderheader oh (cost=0.00..21.64 rows=1 width=4)
-> Index Scan using orderlines_pkey on orderlines ol (cost=0.00..25.54 rows=17 width=8)

EXPLAIN

--- UPDATE LOG ---
explain INSERT INTO orderlinesupdates (theorder,type,stock,line,ordercurrent,sellingquant,price,discount,vatrate,comment,updated,utype,origin)
SELECT oh.theorder,'P',' 0310',coalesce(ol.line,ol2.line+1,1),5,0,.52,0,0,'',128,'+','C' FROM orderheaderupdates oh
LEFT OUTER JOIN orderlinesupdates ol ON oh.theorder = ol.theorder AND ol.stock=' 0310'
LEFT OUTER JOIN orderlinesupdates ol2 ON oh.theorder = ol2.theorder
WHERE oh.account=' MILN1' AND oh.delivery=1 AND oh.thedate='2002-06-01' AND oh.ordertype='O'
ORDER BY oh.updated DESC, ol.line DESC, ol2.line DESC LIMIT 1;
NOTICE: QUERY PLAN:

Subquery Scan *SELECT* (cost=81.29..81.29 rows=1 width=36)
-> Limit (cost=81.29..81.29 rows=1 width=36)
-> Sort (cost=81.29..81.29 rows=1 width=36)
-> Nested Loop (cost=0.00..81.28 rows=1 width=36)
-> Nested Loop (cost=0.00..52.47 rows=1 width=28)
-> Index Scan using orderheaderupdates_account on orderheaderupdates oh (cost=0.00..23.62 rows=1 width=8)
-> Index Scan using orderlinesupdates_theorder on orderlinesupdates ol
(cost=0.00..28.60 rows=17 width=20)
-> Index Scan using orderlinesupdates_theorder on orderlinesupdates ol2 (cost=0.00..28.60 rows=17 width=8)

EXPLAIN