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From: Anastasia Lubennikova <a.lubennikova@postgrespro.ru>
To: Michael Paquier <michael@paquier.xyz>
Cc: Michael Banck <michael.banck@credativ.de>
Cc: PostgreSQL Development <pgsql-hackers@postgresql.org>
Subject: Re: [patch] Fix checksum verification in base backups for zero page headers
Date: Tue, 27 Oct 2020 22:56:23 +0300
Message-ID: <ce25a60e-bd70-6554-1e8f-7e4dc9f6ce59@postgrespro.ru> (raw)
In-Reply-To: <20201026011315.GA2973@paquier.xyz>
References: <6713b5e9d98c7db1608b43cd57b10be4a08dca67.camel@credativ.de>
	<9489c221-e2ef-e7ad-d921-5ccad71b14de@postgrespro.ru>
	<423deac52479a40624e775e6d2ab41c4e9f5b19f.camel@credativ.de>
	<20201007081852.GC30037@paquier.xyz>
	<608f3476-0598-2514-2c03-e05c7d2b0cbd@postgrespro.ru>
	<20201020062432.GA30362@paquier.xyz>
	<69b38451-e91f-95fc-c3ce-06eb778d36e0@postgrespro.ru>
	<20201022012519.GF1475@paquier.xyz>
	<036235b4-2461-c4b2-a448-7875d943ce1e@postgrespro.ru>
	<20201022230008.GK1475@paquier.xyz>
	<20201026011315.GA2973@paquier.xyz>

On 26.10.2020 04:13, Michael Paquier wrote:
> On Fri, Oct 23, 2020 at 08:00:08AM +0900, Michael Paquier wrote:
>> Yeah, we could try to make the logic a bit more complicated like
>> that.  However, for any code path relying on a page read without any
>> locking insurance, we cannot really have a lot of trust in any of the
>> fields assigned to the page as this could just be random corruption
>> garbage, and the only thing I am ready to trust here a checksum
>> mismatch check, because that's the only field on the page that's
>> linked to its full contents on the 8k page.  This also keeps the code
>> simpler.
> A small update here.  I have extracted the refactored part for
> PageIsVerified() and committed it as that's independently useful.
> This makes the patch proposed here simpler on HEAD, leading to the
> attached.
> --
> Michael

Thank you for committing the first part.

In case you need a second opinion on the remaining patch, it still looks 
good to me.

-- 
Anastasia Lubennikova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company






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  To: pgsql-hackers@postgresql.org
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  Subject: Re: [patch] Fix checksum verification in base backups for zero page headers
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