Re: 16-bit page checksums for 9.2

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: simon(at)2ndquadrant(dot)com, ants(dot)aasma(at)eesti(dot)ee, heikki(dot)linnakangas(at)enterprisedb(dot)com, jeff(dot)janes(at)gmail(dot)com, aidan(at)highrise(dot)ca, stark(at)mit(dot)edu, pgsql-hackers(at)postgresql(dot)org
Subject: Re: 16-bit page checksums for 9.2
Date: 2012-01-04 21:25:00
Message-ID: CA+TgmobVny0M5GYUvbs3Kj0BH_BZrwdEFCZJivEkVJm9q5YHaA@mail.gmail.com
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On Wed, Jan 4, 2012 at 3:51 PM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
>> If double writes aren't going to give us anything "for free",
>> maybe that's not the right place to be focusing our
>> efforts...
>
> I'm not sure why it's not enough that they improve performance over
> the alternative.  Making some other feature with obvious overhead
> "free" seems an odd requirement to hang on this.  (Maybe I'm
> misunderstanding you on that point?)

Well, this thread is nominally about checksums, but here we are
talking about double writes, so I thought we were connecting those
features in some way?

Certainly, life is easier if we can develop them completely separately
- but checksums really ought to come with some sort of solution to the
problem of a torn-page with hint bit changes, IMO, and I thought
that's why were thinking so hard about DW just now.

Maybe I'm confused.

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

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