Received: from localhost (unknown [200.46.204.183]) by postgresql.org (Postfix) with ESMTP id B964264FD25 for ; Tue, 14 Oct 2008 12:36:49 -0300 (ADT) Received: from postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 64662-09 for ; Tue, 14 Oct 2008 12:36:41 -0300 (ADT) X-Greylist: delayed 00:09:50.560221 by SQLgrey-1.7.6 Received: from smtpgw.bnl.gov (smtpgw.bnl.gov [130.199.3.132]) by postgresql.org (Postfix) with ESMTP id 524A564FCE9 for ; Tue, 14 Oct 2008 12:36:41 -0300 (ADT) X-IronPort-AV: E=Sophos;i="4.33,410,1220241600"; d="scan'208";a="9148155" Received: from rcf.rhic.bnl.gov ([130.199.54.7]) by smtpgw.sec.bnl.local with ESMTP/TLS/DHE-RSA-AES256-SHA; 14 Oct 2008 11:26:48 -0400 Received: from bnl.gov (nuvi.rhic.bnl.gov [130.199.80.30]) by rcf.rhic.bnl.gov (8.13.1/8.13.1) with ESMTP id m9EFQmV4025343 for ; Tue, 14 Oct 2008 11:26:48 -0400 Message-ID: <48F4BA38.8030900@bnl.gov> Date: Tue, 14 Oct 2008 11:26:48 -0400 From: Irina Sourikova User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030922 X-Accept-Language: en-us, en MIME-Version: 1.0 To: pgsql-admin@postgresql.org Subject: What constitutes a transaction when reading BLOBs? Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Maia Mailguard 1.0.1 X-Archive-Number: 200810/102 X-Sequence-Number: 30558 Hi, We have a read-only database with large BLOBs, and the field 'xact_commit' of pg_stat_database is incremented by thousands every minute. The number of concurrent connections is about 5-10. What is considered a transaction in general and when BLOBs are involved and how does it affect the autovacuum? Thank you, Irina -- Irina Sourikova Brookhaven National Laboratory phone: +1-631-344-3776 Physics Department, Bldg 510 C fax: +1-631-344-3253 Upton, NY 11973-5000 email: irina@bnl.gov