Re: 16-bit page checksums for 9.2

On Wed, Jan 4, 2012 at 3:13 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> On Wed, Jan 4, 2012 at 1:31 PM, Stephen Frost <sfrost@snowman.net> wrote:
>> Simon, all,
>>
>> * Simon Riggs (simon@2ndQuadrant.com) wrote:
>>> (1) report all errors on a page, including errors that don't change
>>> PostgreSQL data. This involves checksumming long strings of zeroes,
>>> which the checksum algorithm can't tell apart from long strings of
>>> ones.
>>
>> Do we actually know when/where it's supposed to be all zeros, and hence
>> could we check for that explicitly?  If we know what it's supposed to
>> be, in order to be consistent with other information, I could certainly
>> see value in actually checking that.
>
> Yes, we can. Excellent suggestion, will implement.

No, we can't.

I discover that non-all-zeroes holes are fairly common, just not very frequent.

That may or may not be a problem, but not something to be dealt with
here and now.

--
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services