Horton

Re: Offline enabling/disabling of data checksums

Michael Banck <michael.banck@credativ.de>

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From: Michael Banck <michael.banck@credativ.de>
To: Andres Freund <andres@anarazel.de>, Michael Paquier <michael@paquier.xyz>
Cc: Magnus Hagander <magnus@hagander.net>, Fabien COELHO <coelho@cri.ensmp.fr>, Sergei Kornilov <sk@zsrv.org>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-19T15:55:12Z
Lists: pgsql-hackers 
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.


Michael

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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/