Received: from localhost (unknown [200.46.204.182]) by postgresql.org (Postfix) with ESMTP id 5E19F2E0D6A for ; Sun, 18 Nov 2007 10:42:04 -0400 (AST) Received: from postgresql.org ([200.46.204.71]) by localhost (mx1.hub.org [200.46.204.182]) (amavisd-maia, port 10024) with ESMTP id 21681-10 for ; Sun, 18 Nov 2007 10:41:56 -0400 (AST) Received: from wa-out-1112.google.com (wa-out-1112.google.com [209.85.146.181]) by postgresql.org (Postfix) with ESMTP id 8EF992E07DD for ; Sun, 18 Nov 2007 10:42:01 -0400 (AST) Received: by wa-out-1112.google.com with SMTP id m38so1913979waf for ; Sun, 18 Nov 2007 06:41:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=QqtT3o8iWukheKhH+OZjHcr4yPYEqdpSVURz2qkKEpI=; b=dematAn4HAVMMuwWiyiWNguEjoqZdGW8N6NXW0AcInH1mJFxCMUhb9oJUh9WlclAPLGYj/Veo4e51L8Glhf2BpcnXvm8Zl1PNRh1FPa9o1Quz0AHXO5J1MeogMXi0i2NJkf9SFMVMLyDUkuC3Al5BNnrGL/HBRqw2ZGhaDo+fvc= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=L9HgpkSOusV6WLrlL/FTyT0S5uHpHyGdy1lRqxPIlVIlngTf2yiIefkq9ACau5pkrhiAoh/UFqcQ9TlAGID+9dqrVc00A3spYwrvWD/RvsuFc+WdV9kXyE4/6KDFB0GKTvQcDBsC8sCphFlsaBZ37wX3/6Phsj5sqgpwmOiNceM= Received: by 10.114.59.1 with SMTP id h1mr521474waa.1195396919827; Sun, 18 Nov 2007 06:41:59 -0800 (PST) Received: by 10.114.171.20 with HTTP; Sun, 18 Nov 2007 06:41:59 -0800 (PST) Message-ID: Date: Sun, 18 Nov 2007 08:41:59 -0600 From: "Scott Marlowe" To: "Simon Riggs" Subject: Re: work_mem and shared_buffers Cc: "Campbell, Lance" , "Heikki Linnakangas" , pgsql-performance@postgresql.org In-Reply-To: <1195396179.4217.1.camel@ebony.site> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <47349F4E.5070204@enterprisedb.com> <1195396179.4217.1.camel@ebony.site> X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200711/256 X-Sequence-Number: 27671 On Nov 18, 2007 8:29 AM, Simon Riggs wrote: > On Fri, 2007-11-09 at 13:12 -0600, Scott Marlowe wrote: > > > Note that my best time was at around 16 Meg work_mem. This data set > > is MUCH bigger than 16 Meg, it's around 300-400 Meg. But work_mem > > optimized out at 16 Meg. Btw, I tried it going as high as 768 Meg, > > and it was still slower than 16M. > > Remember that what you have shown is that for *this* dataset 16Mb is the > optimum value. It is not a recommended value for all cases. Actually, on this particular machine, it's held true for all the datasets that are on it. But I agree that it's only true for those particular datasets, and more importantly, this machine. But my real point was that if you haven't tested various settings on your machine, you don't know if you're helping or hurting with various changes to work_mem