Received: from localhost (unknown [200.46.204.183]) by mail.postgresql.org (Postfix) with ESMTP id 8AD2864FCC6 for ; Mon, 10 Nov 2008 04:21:56 -0400 (AST) Received: from mail.postgresql.org ([200.46.204.86]) by localhost (mx1.hub.org [200.46.204.183]) (amavisd-maia, port 10024) with ESMTP id 03328-10 for ; Mon, 10 Nov 2008 04:21:56 -0400 (AST) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from gmp-eb-inf-1.sun.com (gmp-eb-inf-1.sun.com [192.18.6.21]) by mail.postgresql.org (Postfix) with ESMTP id E17B064FD37 for ; Mon, 10 Nov 2008 04:21:44 -0400 (AST) Received: from fe-emea-09.sun.com (gmp-eb-lb-2-fe2.eu.sun.com [192.18.6.11]) by gmp-eb-inf-1.sun.com (8.13.7+Sun/8.12.9) with ESMTP id mAA8LgqM005470 for ; Mon, 10 Nov 2008 08:21:42 GMT Received: from conversion-daemon.fe-emea-09.sun.com by fe-emea-09.sun.com (Sun Java System Messaging Server 6.2-8.04 (built Feb 28 2007)) id <0KA300J01YQ34000@fe-emea-09.sun.com> (original mail from Zdenek.Kotala@Sun.COM) for pgsql-hackers@postgresql.org; Mon, 10 Nov 2008 08:21:42 +0000 (GMT) Received: from [192.168.1.101] ([89.102.158.6]) by fe-emea-09.sun.com (Sun Java System Messaging Server 6.2-8.04 (built Feb 28 2007)) with ESMTPSA id <0KA300AZ0Z82A300@fe-emea-09.sun.com>; Mon, 10 Nov 2008 08:21:39 +0000 (GMT) Date: Mon, 10 Nov 2008 09:21:48 +0100 From: Zdenek Kotala Subject: Re: WIP: Page space reservation (pgupgrade) In-reply-to: <603c8f070811092028r52b523d0o542513d5491743c4@mail.gmail.com> To: Robert Haas Cc: "Jonah H. Harris" , Decibel! , Tom Lane , PostgreSQL-development Message-id: <4917EF1C.8010200@sun.com> MIME-version: 1.0 Content-type: text/plain; format=flowed; charset=ISO-8859-1 Content-transfer-encoding: 7BIT References: <491619D2.2090602@sun.com> <29590.1226192897@sss.pgh.pa.us> <36e682920811081835s5b2b07f1uf849b1d058ff80f5@mail.gmail.com> <36e682920811091717g65346b45ie02d1cc3a47d3d4a@mail.gmail.com> <603c8f070811092028r52b523d0o542513d5491743c4@mail.gmail.com> User-Agent: Thunderbird 2.0.0.16 (X11/20080922) X-Archive-Number: 200811/674 X-Sequence-Number: 127386 Robert Haas napsal(a): > Let's suppose, for example, that in 8.5 we decide to change some type > that is presently 16 bits to 32 bits, or 8 bits to 16 bits, etc. This > will make some tuples bigger, and potentially much bigger, but since > it presumably won't be a commonly used data-type, most tuples won't > change at all. However, the worst case scenario for how much free > space you might need to reserve will be very bad, and therefore a > mechanism that allows reserving a fixed amount of free space per page > won't be adequate. The problem with datatypes is different story. It is should be easy to manage this problem with keeping the old datatype definition for "old" tables and for new create new datatype with new OID. You can use ALTER TABLE for converting data from old type to the new one. Zdenek