Horton

Re: Offline enabling/disabling of data checksums

Magnus Hagander <magnus@hagander.net>

View thread View on postgr.es
From: Magnus Hagander <magnus@hagander.net>
To: Michael Banck <michael.banck@credativ.de>
Cc: Sergei Kornilov <sk@zsrv.org>, Michael Paquier <michael@paquier.xyz>, Fabien COELHO <coelho@cri.ensmp.fr>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-13T16:51:59Z
Lists: pgsql-hackers 
On Wed, Mar 13, 2019 at 4:46 PM Michael Banck <michael.banck@credativ.de>
wrote:

> Hi,
>
> Am Mittwoch, den 13.03.2019, 12:24 +0100 schrieb Magnus Hagander:
> > On Wed, Mar 13, 2019 at 11:54 AM Sergei Kornilov <sk@zsrv.org> wrote:
> > > One new question from me: how about replication?
> > > Case: primary+replica, we shut down primary and enable checksum, and
> > > "started streaming WAL from primary" without any issue. I have
> > > master with checksums, but replica without.
> > > Or cluster with checksums, then disable checksums on primary, but
> > > standby think we have checksums.
> >
> > Enabling or disabling the checksums offline on the master quite
> > clearly requires a rebuild of the standby, there is no other way
>
> What about shutting down both and running pg_checksums --enable on the
> standby as well?
>

That sounds pretty fragile to me. But if we can prove that the user has
done things in the right order, sure. But how can we do that in an offline
process? what if the user just quickly restarted the primary note after the
standby had been shut down? We'll need to somehow validate it across the
nodes..
-- 
 Magnus Hagander
 Me: https://www.hagander.net/ <http://www.hagander.net/>
 Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>

Commits

  1. Reorganize Notes section in documentation of pg_checksums

  2. Add option -N/--no-sync to pg_checksums

  3. Add options to enable and disable checksums in pg_checksums

  4. Refactor more code logic to update the control file

  5. Rename pg_verify_checksums to pg_checksums

  6. Fix cross-version compatibility checks of pg_verify_checksums

  7. Add routine able to update the control file to src/common/