Date: Fri, 17 Sep 2021 18:22:00 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: "Bossart, Nathan" <bossartn@amazon.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	"andres@anarazel.de" <andres@anarazel.de>,
	"masao.fujii@oss.nttdata.com" <masao.fujii@oss.nttdata.com>,
	"pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>,
	"mengjuan.cmj@alibaba-inc.com" <mengjuan.cmj@alibaba-inc.com>,
	"Jakub.Wartak@tomtom.com" <Jakub.Wartak@tomtom.com>
Subject: Re: prevent immature WAL streaming
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On 2021-Sep-17, Bossart, Nathan wrote:

> > That was the first implementation, a few versions of the patch ago.  An
> > added benefit of a separate WAL record is that you can carry additional
> > data for validation, such as -- as suggested by Andres -- the CRC of the
> > partial data contained in the message that we're skipping.  I didn't
> > implement that, but it should be trivial to add it.
> 
> I see.  IMO feels a bit counterintuitive to validate a partial record
> that you are ignoring anyway, but I suppose it's still valuable to
> know when the WAL is badly broken.  It's not expensive, and it doesn't
> add a ton of complexity, either.

Yeah, we don't have any WAL record history validation other than the
verifying the LSN of the previous record; I suppose in this particular
case you could argue that we shouldn't bother with any validation
either.  But it seems safer to do it.  It doesn't hurt anything anyway.

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/