Horton

Re: Offline enabling/disabling of data checksums

Fabien COELHO <coelho@cri.ensmp.fr>

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From: Fabien COELHO <coelho@cri.ensmp.fr>
To: Andres Freund <andres@anarazel.de>
Cc: Michael Banck <michael.banck@credativ.de>, Michael Paquier <michael@paquier.xyz>, Magnus Hagander <magnus@hagander.net>, Sergei Kornilov <sk@zsrv.org>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2019-03-20T06:55:39Z
Lists: pgsql-hackers 
Hallo Andres,

> And you're basically adding it because Fabien doesn't like
> postmaster.pid and wants to invent another lockout mechanism in this
> thread.

I did not suggest to rename the control file, but as it is already done by 
another command it did not look like a bad idea in itself, or at least an 
already used bad idea:-)

I'd be okay with anything that works consistently accross all commands 
that may touch a cluster and are mutually exclusive (postmater, pg_rewind, 
pg_resetwal, pg_upgrade, pg_checksums…), without underlying race 
conditions. It could be locking, a control file state, a special file 
(which one ? what is the procedure to create/remove it safely and avoid 
potential race conditions ?), possibly "postmaster.pid", whatever really.

I'll admit that I'm moderately enthousiastic about "posmaster.pid" because 
it does not do anymore what the file names says, but if it really works 
and is used consistently by all commands, why not. In case of unexpected 
problems, the file will probably have to be removed/fixed by hand. I also 
think that the implemented mechanism should be made available in 
"control_utils.c", not duplicated in every command.

-- 
Fabien.

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/