Horton

Re: Online enabling of checksums

x4mmm@yandex-team.ru

View thread View on postgr.es
From: Andrey Borodin <x4mmm@yandex-team.ru>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: Daniel Gustafsson <daniel@yesql.se>, Michael Banck <michael.banck@credativ.de>, Magnus Hagander <magnus@hagander.net>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Robert Haas <robertmhaas@gmail.com>, Greg Stark <stark@mit.edu>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-03-20T09:29:41Z
Lists: pgsql-hackers 
Hi!

> 19 марта 2018 г., в 11:27, Heikki Linnakangas <hlinnaka@iki.fi> написал(а):
> 
> Is there no way to stop the checksum helper once it's started? That seems rather user-unfriendly. I can imagine it being a pretty common mistake to call pg_enable_data_checksums() on a 10 TB cluster, only to realize that you forgot to set the cost limit, and that it's hurting queries too much. At that point, you want to abort.
I've tried to pg_cancel_backend() and it worked.
But only if I cancel "checksum helper launcher" and then "checksum helper worker". If I cancel helper first - it spawns new.

Magnus, Daniel, is it safe to cancel worker or launcher?

BTW, I have some questions on pg_verify_chechsums.
It does not check catalog version. It it true that it will work for any?
Also, pg_verify_chechsums will stop on short reads. But we do not stop on wrong checksum, may be we should not stop on short reads either?

I agree with all of Heikki's comments.

Besides these I have no other questions, patch looks good.

Best regards, Andrey Borodin.

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.