Re: Block-level CRC checks

On Thu, Nov 13, 2008 at 09:03:41PM -0300, Alvaro Herrera wrote:
> The first idea that comes to mind is skipping hint bits in the CRC too.
> That does away with a lot of the trouble (PD_UNLOGGED_CHANGE, the
> necessity of WAL-logging hint bits, etc). The problem, again, is that
> the checksumming process becomes page type-specific; but then maybe
> that's the only workable approach.

Which brings back the problem of having to decode the page to checksum
it, so your checksumming code needs to have all sorts of failsafes in
it to stop it going crazy on bad data.

But I understand the problem is that you want to continue in the face
of torn pages, something which is AFAICS ambitious. At least MS-SQL
just blows up on a torn page, havn't found results for other
databases...

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while
> boarding. Thank you for flying nlogn airlines.