Re: Online verification of checksums - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Online verification of checksums
Date
Msg-id CA+TgmobAv2nYJuqdAaV3vcBppwsKYRMziyussSeFTZQ8y2eAzA@mail.gmail.com
Whole thread Raw
In response to Re: Online verification of checksums  (Stephen Frost <sfrost@snowman.net>)
Responses Re: Online verification of checksums
List pgsql-hackers
On Mon, Mar 18, 2019 at 2:38 AM Stephen Frost <sfrost@snowman.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


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