Re: Page Checksums

* David Fetter (david(at)fetter(dot)org) wrote:
> On Mon, Dec 19, 2011 at 09:34:51AM -0500, Robert Haas wrote:
> > On Mon, Dec 19, 2011 at 9:14 AM, Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> > > Fair enough, but, could we distinguish these two cases?  In other words,
> > > would it be possible to detect if a page was torn due to a 'traditional'
> > > crash and not complain in that case, but complain if there's a CRC
> > > failure and it *doesn't* look like a torn page?
> >
> > No.
>
> Would you be so kind as to elucidate this a bit?

I'm guessing, based on some discussion on IRC, that it's because we
don't really 'detect' torn pages today, when it's due to a hint-bit-only
update. With all the trouble due to hint-bit updates, and if they're
written out or not, makes me wish we could just avoid doing hint-bit
only updates to disk somehow.. Or log them when we do them. Both of
those have their own drawbacks, of course.

Thanks,

Stephen