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: Michael Paquier <michael@paquier.xyz>
Cc: Michael Banck <michael.banck@credativ.de>, Postgres hackers <pgsql-hackers@postgresql.org>
Date: 2019-03-13T06:18:32Z
Lists: pgsql-hackers 
Bonjour Michaël,

> Yes, that would be nice, for now I have focused.  For pg_resetwal yes
> we could do it easily.  Would you like to send a patch?

I probably can do that before next Monday. I'll prioritize reviewing the 
latest instance of this patch, though.

>> This seem contradictory to me: you want to disable checksum, and they are
>> already disabled, so nothing is needed. How does that qualifies as a
>> "failed" operation?
>
> If the operation is automated, then a proper reaction can be done if
> multiple attempts are done.  Of course, I am fine to tune things one
> way or the other depending on the opinion of the crowd here.  From the
> opinions gathered, I can see that (Michael * 2) prefer failing with
> exit(1), while (Fabien * 1) would like to just do exit(0).

Yep, that sums it up:-).

>> Indeed. I do not immediately see the use case where no syncing would be a
>> good idea. I can see why it would be a bad idea. So I'm not sure of the
>> concept.
>
> To leverage the buildfarm effort I think this one is worth it.  Or we
> finish to fsync the data folder a couple of times, which would make
> the small-ish buildfarm machines suffer more than they need.

Ok for the particular use-case, provided that the documentation is very 
clear about the risks, which is the case, so fine with me wrt to the 
feature.

-- 
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/