Horton

Re: Online enabling of checksums

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Michael Banck <michael.banck@credativ.de>, Alvaro Herrera <alvherre@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Daniel Gustafsson <daniel@yesql.se>, Robert Haas <robertmhaas@gmail.com>, Magnus Hagander <magnus@hagander.net>, Andrey Borodin <x4mmm@yandex-team.ru>, Heikki Linnakangas <hlinnaka@iki.fi>, Greg Stark <stark@mit.edu>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-08-01T16:33:48Z
Lists: pgsql-hackers 
Hi,

On 2018-08-01 18:25:48 +0200, Tomas Vondra wrote:
> Sure, if there are issues with this approach, that would make it
> unacceptable. I'm not sure why would it be an issue for replicas (which is
> what you mention elsewhere), considering those don't write data and so can't
> fail to update a checksum?

Standbys compute checksums on writeout as well, no? We compute checksums
not at buffer modification, but at writeout time. And replay just marks
buffers dirty, it doesn't directly write to disk.

Architecturally there'd also be hint bits as a source, but I think we
probably neutered them enough for that not to be a problem during
replay.

And then there's also promotions.

Greetings,

Andres Freund

Commits

  1. Online enabling and disabling of data checksums

  2. Deactive flapping checksum isolation tests.

  3. Add support for coordinating record typmods among parallel workers.