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Re: 16-bit page checksums for 9.2

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Kevin Grittner <kevin(dot)grittner(at)wicourts(dot)gov>, david <david(at)fetter(dot)org>, aidan <aidan(at)highrise(dot)ca>, stark <stark(at)mit(dot)edu>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: 16-bit page checksums for 9.2
Date: 2012-03-01 12:41:04
Message-ID: CA+TgmoZLF-CgpeLxYkZ=b+sZqH3AT7JAZo0izD6irF=mY4wbZA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Feb 29, 2012 at 5:52 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Wed, Feb 29, 2012 at 4:34 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Easier for who?  I don't care for the idea of code that has to cope with
>>> two page formats, or before long N page formats, because if we don't
>>> have some mechanism like this then we will never be able to decide that
>>> an old data format is safely dead.
>
>> Huh?  You can drop support for a new page format any time you like.
>> You just decree that version X+1 no longer supports it, and you can't
>> pg_upgrade to it until all traces of the old page format are gone.
>
> And how would a DBA know that?

We'd add a column to pg_class that tracks which page version is in use
for each relation.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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