Re: Offline enabling/disabling of data checksums

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