Horton

Re: 16-bit page checksums for 9.2

Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>

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From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
To: Kevin Grittner <Kevin.Grittner@wicourts.gov>
Cc: simon@2ndQuadrant.com, stark@mit.edu, aidan@highrise.ca, pgsql-hackers@postgresql.org
Date: 2011-12-27T20:05:11Z
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