From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michal Szymanski <szymanskim@datera.pl>
Cc: pgsql-performance@postgresql.org
Subject: Re: Big problem with sql update operation
Date: Fri, 25 May 2007 10:28:38 -0400
Message-ID: <8751.1180103318@sss.pgh.pa.us> (raw)
In-Reply-To: <4656A4E0.7020400@datera.pl>
References: <4656A4E0.7020400@datera.pl>
Michal Szymanski <szymanskim@datera.pl> 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.
(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.)
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, szymanskim@datera.pl
Subject: Re: Big problem with sql update operation
In-Reply-To: <8751.1180103318@sss.pgh.pa.us>
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