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Re: 16-bit page checksums for 9.2

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>
Cc: simon(at)2ndQuadrant(dot)com, stark(at)mit(dot)edu, aidan(at)highrise(dot)ca, pgsql-hackers(at)postgresql(dot)org
Subject: Re: 16-bit page checksums for 9.2
Date: 2011-12-27 20:05:11
Message-ID: 4EFA24F7.6090007@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On 25.12.2011 15:01, Kevin Grittner wrote:
> I don't believe that.  Double-writing is a technique to avoid torn
> pages, but it requires a checksum to work.  This chicken-and-egg
> problem requires the checksum to be implemented first.

I don't think double-writes require checksums on the data pages 
themselves, just on the copies in the double-write buffers. In the 
double-write buffer, you'll need some extra information per-page anyway, 
like a relfilenode and block number that indicates which page it is in 
the buffer.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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