Date: Tue, 12 Apr 2022 09:27:42 -0700
From: Nathan Bossart <nathandbossart@gmail.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: tgl@sss.pgh.pa.us, robertmhaas@gmail.com, pgsql-hackers@postgresql.org
Subject: Re: avoid multiple hard links to same WAL file after a crash
Message-ID: <20220412162742.GB2062175@nathanxps13>
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On Tue, Apr 12, 2022 at 03:46:31PM +0900, Kyotaro Horiguchi wrote:
> At Mon, 11 Apr 2022 09:52:57 -0700, Nathan Bossart <nathandbossart@gmail.com> wrote in 
>> I traced this back a while ago.  I believe the link() was first added in
>> November 2000 as part of f0e37a8.  This even predates WAL recycling, which
>> was added in July 2001 as part of 7d4d5c0.
> 
> f0e37a8 lacks discussion.. It introduced the CHECKPOINT command from
> somwhere out of the ML.. This patch changed XLogFileInit to
> supportusing existent files so that XLogWrite can use the new segment
> provided by checkpoint and still allow XLogWrite to create a new
> segment by itself.

Yeah, I've been unable to find any discussion besides a brief reference to
adding checkpointing [0].

[0] https://postgr.es/m/8F4C99C66D04D4118F580090272A7A23018D85%40sectorbase1.sectorbase.com

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com