Horton

Re: Offline enabling/disabling of data checksums

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Michael Banck <michael.banck@credativ.de>, Postgres hackers <pgsql-hackers@postgresql.org>, Michael Paquier <michael@paquier.xyz>
Date: 2019-02-03T10:21:09Z
Lists: pgsql-hackers 
Hi,

On 2019-01-09 07:07:17 +0100, Fabien COELHO wrote:
> There is still no documentation.

Michael, are you planning to address this?  It'd also be useful to state
when you just don't agree with things / don't plan to address them.

Given the docs piece hasn't been addressed, and seems uncontroversial,
I'm marking this patch as returned with feedback. Please resubmit once
ready.


> > > Also, the full page is rewritten... would it make sense to only overwrite
> > > the checksum part itself?
> > 
> > So just writing the page header? I find that a bit scary and don't
> > expect much speedup as the OS would write the whole block anyway I
> > guess? I haven't touched that yet.
> 
> Possibly the OS would write its block size, which is not necessary the same
> as postgres page size?

I think it'd be a bad idea to write more granular. Very commonly that'll
turn a write operation into a read-modify-write (although caching will
often prevent that from being a problem here), and it'll be bad for
flash translation layers.

Greetings,

Andres Freund

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/