Date: Thu, 27 Jan 2022 21:46:20 -0800
From: Nathan Bossart <nathandbossart@gmail.com>
To: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	"Bossart, Nathan" <bossartn@amazon.com>,
	Julien Rouhaud <rjuju123@gmail.com>,
	Michael Paquier <michael@paquier.xyz>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Add checkpoint and redo LSN to LogCheckpointEnd log message
Message-ID: <20220128054620.GA654866@nathanxps13>
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On Fri, Jan 28, 2022 at 08:43:36AM +0530, Bharath Rupireddy wrote:
> 2022-01-28 03:06:10.213 UTC [2409486] LOG:  checkpoint starting:
> immediate force wait
> 2022-01-28 03:06:10.257 UTC [2409486] LOG:  checkpoint complete:
> start=0/14D9510, end=0/14D9548; wrote 4 buffers (0.0%); 0 WAL file(s)
> added, 0 removed, 0 recycled; write=0.007 s, sync=0.008 s, total=0.044
> s; sync files=3, longest=0.005 s, average=0.003 s; distance=0 kB,
> estimate=0 kB
> 
> 2022-01-28 03:06:42.254 UTC [2409486] LOG:  checkpoint starting:
> immediate force wait
> 2022-01-28 03:06:42.279 UTC [2409486] LOG:  checkpoint complete:
> start=0/14DBDB8, end=0/14DBDF0; wrote 2 buffers (0.0%); 0 WAL file(s)
> added, 0 removed, 0 recycled; write=0.004 s, sync=0.004 s, total=0.025
> s; sync files=2, longest=0.003 s, average=0.002 s; distance=10 kB,
> estimate=10 kB

I know I voted for "start=%X/%X, end=%X/%X," but looking at this again, I
wonder if it could be misleading.  "start" is the redo location, and "end"
is the location of the checkpoint record, but I could understand why
someone might think that "start" is the location of the previous checkpoint
record and "end" is the redo location of the new one.  I think your
original idea of "lsn=%X/%X, redo lsn=%X/%X" could be a good alternative.

Іn any case, this patch is small and otherwise looks reasonable to me, so I
am going to mark it as ready-for-committer.

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