Re: Online verification of checksums

On Mon, Mar 18, 2019 at 2:38 AM Stephen Frost <sfrost(at)snowman(dot)net> wrote:
> Sure the backend has those facilities since it needs to, but these
> frontend tools *don't* need that to *never* have any false positives, so
> why are we complicating things by saying that this frontend tool and the
> backend have to coordinate?
>
> If there's an explanation of why we can't avoid having false positives
> in the frontend tool, I've yet to see it. I definitely understand that
> we can get partial reads, but a partial read isn't a failure, and
> shouldn't be reported as such.

I think there's some confusion between 'partial read' and 'torn page',
as Michael also said.

It's torn pages that I am concerned about - the server is writing and
we are reading, and we get a mix of old and new content. We have been
quite diligent about protecting ourselves from such risks elsewhere,
and checksum verification should not be held to any lesser standard.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company