Re: Enabling Checksums

On 11/12/12 4:44 AM, Craig Ringer wrote:

> Is it absurd to suggest using another bitmap, like the FSM or visibility
> map, to store information on page checksumming while checksumming is
> enabled but incomplete?

I spent some time thinking about that last week.  One problem with it is 
that the bitmap structure itself has the same issues as every other 
write here--how do we know it's going to disk accurately?  The "put 
'checksum on' bits on the page" idea and "put checksum on bits in a map" 
have the same fundamental issue.  Things might get out of sync in the 
same way, you've just moved the potentially suspicious write to a new place.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com