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Re: [PATCH] Don't bail with legitimate -N/-B options

From: Magnus Hagander <magnus(at)hagander(dot)net>
To: Andreas Kling <andreas(dot)kling(at)acgnystrom(dot)se>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: [PATCH] Don't bail with legitimate -N/-B options
Date: 2008-02-16 21:09:10
Message-ID: 47B750F6.3040201@hagander.net (view raw or flat)
Thread:
Lists: pgsql-bugs
Andreas Kling wrote:
> Greetings,
> 
> Starting PostgreSQL 8.3.0 with the default options used by Gentoo Linux 
> (-N 40 -B 80) causes it to bail with an error message.
> 
> "the number of buffers (-B) must be at least twice the number of allowed 
> connections (-N) and at least 16"
> 
> The problem is that NBuffers is actually "max autovacuum connections" + 
> NBuffers.
> 
> My attached patch fixes this by adding "max autovacuum connections" * 2 
> to NBuffers before the check.

Anybody know *why* Gentoo does such a thing? Having shared buffers at 
the very lowest possible boundary just seems counterproductive.  Plus, 
the normal way to set these things would be in postgresql.conf, why 
override them on the commandline?

It's not the first time I've seen people complain about this, it'd be 
good to know why.

Those are not comments on the actual patch, of course. For that one, it 
looks to me like it's the wrong fix. I don't think we should be adding 
to shared buffers like that - if somebody asked for a specific value 
they should get that. But in that case the error message needs to be 
changed, since it's misleading.


//Magnus

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