From: Craig A. James <cjames@modgraph-usa.com>
To: Michael Fuhr <mike@fuhr.org>
Cc: Pgsql-Performance <pgsql-performance@postgresql.org>
Subject: Re: Perl DBD and an alarming problem
Date: Thu, 17 Nov 2005 13:04:21 -0800
Message-ID: <437CF055.6020602@modgraph-usa.com> (raw)
In-Reply-To: <20051117002344.GA55377@winnie.fuhr.org>
References: <BF9F6C0E.13B4A%llonergan@greenplum.com>
<1132136225.5711.4.camel@Panoramix>
<437B9DA9.2030806@modgraph-usa.com>
<20051117002344.GA55377@winnie.fuhr.org>
Thanks for the info on alarm and timeouts, this was a big help. One further comment:
Michael Fuhr wrote:
>> eval {
>> local $SIG{ALRM} = sub {die("Timeout");};
>> $time = gettimeofday;
>> alarm 20;
>> $sth = $dbh->prepare("a query that may take a long time...");
>> $sth->execute();
>> alarm 0;
>> };
>> if ($@ && $@ =~ /Timeout/) {
>> my $elapsed = gettimeofday - $time;
>> print "Timed out after $elapsed seconds";
>> }
>>
>>Now the mystery: It works, but it hardly matters what time I use for the
>>alarm call, the actual alarm event always happens at 26 seconds...
>
>
> High-level languages' signal handlers don't always work well with
> low-level libraries...
>
> Is there a reason you're using alarm() in the client instead of
> setting statement_timeout on the server?
statement_timeout solved the problem, thanks VERY much for the pointer. To answer your question, I use alarm() because all the books and web references said that was how to do it. :-). I've used alarm() with Perl (with a 3rd-party C lib that had a potential infinite loop) very successfully.
So thanks for the pointer to statement_timeout. But...
When I set statement_timeout in the config file, it just didn't do anything - it never timed out (PG 8.0.3). I finally found in the documentation that I can do "set statement_timeout = xxx" from PerlDBI on a per-client basis, and that works.
Craig
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To: pgsql-performance@postgresql.org
Cc: cjames@modgraph-usa.com, mike@fuhr.org
Subject: Re: Perl DBD and an alarming problem
In-Reply-To: <437CF055.6020602@modgraph-usa.com>
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