Horton

Re: Offline enabling/disabling of data checksums

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Andres Freund <andres@anarazel.de>
Cc: Michael Banck <michael.banck@credativ.de>, Magnus Hagander <magnus@hagander.net>, Fabien COELHO <coelho@cri.ensmp.fr>, Sergei Kornilov <sk@zsrv.org>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-19T23:09:07Z
Lists: pgsql-hackers 
On Tue, Mar 19, 2019 at 09:47:17AM -0700, Andres Freund wrote:
> I'm not sure it needs to be this patch's responsibility to come up with
> a scheme here at all however. pg_rewind, pg_resetwal, pg_upgrade all
> don't really have a lockout mechanism, and it hasn't caused a ton of
> problems. I think it'd be good to invent something better, but it can't
> be some half assed approach that'll lead to people think their database
> is gone.

Amen.  Take it as you wish, but that's actually what I was mentioning
upthread one week ago where I argued that it is a problem, but not a
problem of this patch and that this problems concerns other tools:
https://www.postgresql.org/message-id/20190313093150.GE2988@paquier.xyz
And then, my position has been overthrown by anybody on this thread.
So I am happy to see somebody chiming in and say the same thing.

Honestly, I think that what I sent last week, with a patch in its
simplest form, would be enough:
https://www.postgresql.org/message-id/20190313021621.GP13812@paquier.xyz

In short, you keep the main feature with:
- No tweaks with postmaster.pid.
- Rely just on the control file indicating an instance shutdown
cleanly.
- No tweaks with the system ID.
- No renaming of the control file.
--
Michael

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/