Re: 16-bit page checksums for 9.2

On Sat, Dec 24, 2011 at 03:56:58PM +0000, Simon Riggs wrote:
> > Also, as far as I can see this patch usurps the page version field,
> > which I find unacceptably short-sighted.  Do you really think this is
> > the last page layout change we'll ever make?
> 
> No, I don't. I hope and expect the next page layout change to
> reintroduce such a field.
> 
> But since we're agreed now that upgrading is important, changing page
> format isn't likely to be happening until we get an online upgrade
> process. So future changes are much less likely. If they do happen, we
> have some flag bits spare that can be used to indicate later versions.
> It's not the prettiest thing in the world, but it's a small ugliness
> in return for an important feature. If there was a way without that, I
> would have chosen it.

Have you considered the CRC might match a valuid page version number? 
Is that safe?

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + It's impossible for everything to be true. +