Re: [SQL] inserts/updates problem under stressing ! - Mailing list pgsql-sql

From Vadim Mikheev
Subject Re: [SQL] inserts/updates problem under stressing !
Date
Msg-id 379BFF7E.BD57269E@krs.ru
Whole thread Raw
In response to Re: [SQL] inserts/updates problem under stressing !  (Oleg Bartunov <oleg@sai.msu.su>)
Responses Re: [SQL] inserts/updates problem under stressing !  (Oleg Bartunov <oleg@sai.msu.su>)
List pgsql-sql
Oleg Bartunov wrote:
> 
> >
> > SELECT FOR UPDATE will not help: if there was no record for
> > particular key then nothing will be locked and two records with
> > the same key will be inserted.
> >
> > Oleg, use LOCK IN SHARE ROW EXCLUSIVE MODE.
> 
> Thanks Vadim. Just tried this, but still I see a difference between
> count hits (accumulated) from db and access_log. In my test these numbers are:
> 95 and 109. So I lost 14 hits ! And no errors !
> In my handler I have now:
> 
> my $sth = $dbh->do("LOCK TABLE hits IN SHARE ROW EXCLUSIVE MODE");
> my $sth = $dbh->do("SELECT acc_hits($1)") || die $dbh->errstr;
> 
> am I right ?

You should run LOCK and SELECT inside BEGIN/END (i.e. in
the same transaction), do you?

Vadim


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