Date: Fri, 14 Aug 2026 15:27:44 +0000
From: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
To: Daniel Gustafsson <daniel@yesql.se>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Zsolt Parragi <zsolt.parragi@percona.com>
Subject: Re: Offline data checksum changes can cause incorrect checksum state
 on standbys
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Hi,

On Fri, Aug 14, 2026 at 03:59:06PM +0200, Daniel Gustafsson wrote:
> running a cluster with mismatched data_checksums
> settings across the nodes is not a supported mode of operation, and is already
> documented to not work

Thanks for feedback!

The pre f19c0eccae96 pg_checksums documentation said:

"
When using a replication setup with tools which perform direct copies
of relation file blocks (for example pg_rewind), enabling or disabling
checksums can lead to page corruptions in the shape of incorrect
checksums if the operation is not done consistently across all nodes.
"

I read that as a recommendation to stop and switch all nodes consistently, and
as a warning about direct block-copy tools. That interpretation, together with
the pre f19c0eccae96 behavior, is why v1 proposed keeping offline pg_checksums
changes local. The intention was to preserve the previous behavior, not to
introduce a new supported mode.

I just realized that f19c0eccae96 explicitly changed the "Off-line Enabling of
Checksums" documentation:

"
Data checksums are enabled or disabled at the full cluster level, and cannot
be specified individually for databases or tables.
"

by:

"
Data checksums are enabled or disabled at the full cluster level, and cannot
be specified individually for databases, tables or replicated cluster members.
"

while leaving the pg_checksums documentation quoted above unchanged.

Depending on how the issue will be addressed, it might be worth changing this 
pg_checksums wording too?

Looking forward to seeing your and Zsolt's proposals.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com