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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 28 Jan 2022 12:09:28 +0530
Message-ID: <CALj2ACXWyK9DujhndkuGXb7idjL9wPJfMpzRPpM-DT1LQ6MB=Q@mail.gmail.com>
Subject: Re: Add checkpoint and redo LSN to LogCheckpointEnd log message
To: Nathan Bossart <nathandbossart@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>
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On Fri, Jan 28, 2022 at 11:16 AM Nathan Bossart
<nathandbossart@gmail.com> wrote:
>
> I know I voted for "start=3D%X/%X, end=3D%X/%X," but looking at this agai=
n, 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 checkpoi=
nt
> record and "end" is the redo location of the new one.  I think your
> original idea of "lsn=3D%X/%X, redo lsn=3D%X/%X" could be a good alternat=
ive.
>
> =D0=86n any case, this patch is small and otherwise looks reasonable to m=
e, so I
> am going to mark it as ready-for-committer.

Thanks for your review. In summary, we have these options to choose
checkpoint LSN and last REDO LSN:

1)  "start=3D%X/%X, end=3D%X/%X" (ControlFile->checkPointCopy.redo,
ControlFile->checkPoint)
2)  "lsn=3D%X/%X, redo lsn=3D%X/%X"
3) "location=3D%X/%X, REDO location=3D%X/%X" -- similar to what
pg_controldata and pg_control_checkpoint shows currently.
4) "location=3D%X/%X, REDO start location=3D%X/%X"

I will leave that decision to the committer.

Regards,
Bharath Rupireddy.