Tom Lane wrote:
Michal Szymanski <[EMAIL PROTECTED]> writes:
CREATE OR REPLACE FUNCTION test()
RETURNS void AS
$BODY$
DECLARE
BEGIN
FOR v_i IN 1..4000 LOOP
UPDATE group_fin_account_tst SET
credit = v_i
WHERE group_fin_account_tst_id = 1; -- for real procedure I
update different rows
Does updating the *same* record 4000 times per transaction reflect the
real behavior of your application? If not, this is not a good
benchmark. If so, consider redesigning your app to avoid so many
redundant updates.
Real application modifiy every time modify different row.
(For the record, the reason you see nonlinear degradation is the
accumulation of tentatively-dead versions of the row, each of which has
to be rechecked by each later update.)
There is another strange thing. We have two versions of our test
environment one with production DB copy and second genereated with
minimal data set and it is odd that update presented above on copy of
production is executing 170ms but on small DB it executing 6s !!!!
Michal Szymanski
http://blog.szymanskich.net
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