Re: basebackup: do not verify checksums on pages written before enabling checksums

From: Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>
To: Daniel Gustafsson <daniel(at)yesql(dot)se>
Cc: Zsolt Parragi <zsolt(dot)parragi(at)percona(dot)com>, Yilin Zhang <jiezhilove(at)126(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: basebackup: do not verify checksums on pages written before enabling checksums
Date: 2026-08-18 12:39:42
Message-ID: aoRSjqimKhpRnRxN@bdtpg
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Hi,

On Tue, Aug 18, 2026 at 11:57:39AM +0200, Daniel Gustafsson wrote:
> > On 18 Aug 2026, at 06:18, Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com> wrote:
>
> > The test does not check that verification resumes while lastChecksumChangeRecPtr
> > is set. Just to be sure, did you skip that on purpose, or did you miss [1]?
>
> Sorry, missed to mention that I skipped it on purpose since I don't really
> foresee it providing much value. That being said, I have been wrong before so
> I ended up adding one in the attached v7 anyway.

Thanks for the update!

I've 2 comments:

=== 1

+ if (hit++ < 5)
+ {
+ if (IS_INJECTION_POINT_ATTACHED("basebackup-fail-checksum-verification"))
+ {

Shouldn't hit be incremented only when the injection point is attached?

=== 2

+ checksum ^= checksum;

That's same as "checksum = 0". That works because 0 is not a valid value but
was the intend to "checksum ^= 1"? to express that we want a different checksum?

Regards,

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

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