Horton

Re: Offline enabling/disabling of data checksums

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Michael Banck <michael.banck@credativ.de>
Cc: Michael Paquier <michael@paquier.xyz>, Magnus Hagander <magnus@hagander.net>, Fabien COELHO <coelho@cri.ensmp.fr>, Sergei Kornilov <sk@zsrv.org>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-19T16:00:37Z
Lists: pgsql-hackers 
On 2019-03-19 16:55:12 +0100, Michael Banck wrote:
> Hi,
> 
> Am Dienstag, den 19.03.2019, 08:36 -0700 schrieb Andres Freund:
> > On 2019-03-18 17:13:01 +0900, Michael Paquier wrote:
> > > +/*
> > > + * Locations of persistent and temporary control files.  The control
> > > + * file gets renamed into a temporary location when enabling checksums
> > > + * to prevent a parallel startup of Postgres.
> > > + */
> > > +#define CONTROL_FILE_PATH		"global/pg_control"
> > > +#define CONTROL_FILE_PATH_TEMP	CONTROL_FILE_PATH ".pg_checksums_in_progress"
> > 
> > I think this should be outright rejected. Again, you're making the
> > control file into something it isn't. And there's no buyin for this as
> > far as I can tell outside of Fabien and you. For crying out loud, if the
> > server crashes during this YOU'VE CORRUPTED THE CLUSTER.
> 
> The cluster is supposed to be offline during this.  This is just an
> additional precaution so that nobody starts it during the operation -
> similar to how pg_upgrade disables the old data directory.

I don't see how that matters. Afterwards the cluster needs low level
surgery to be recovered. That's a) undocumented b) likely to be done
wrongly.  This is completely unacceptable *AND UNNECESSARY*.

Greetings,

Andres Freund

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/