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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Fri, 24 Dec 2021 17:54:02 +0530
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Subject: Re: Add checkpoint and redo LSN to LogCheckpointEnd log message
To: Michael Paquier <michael@paquier.xyz>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Fri, Dec 24, 2021 at 5:42 PM Michael Paquier <michael@paquier.xyz> wrote:
>
> On Fri, Dec 24, 2021 at 02:51:34PM +0900, Kyotaro Horiguchi wrote:
> > I thougt about something like the following, but your proposal may be
> > clearer.
>
> +    "LSN=%X/%X, REDO LSN=%X/%X",
> This could be rather confusing for the average user, even if I agree
> that this is some information that only an advanced user could
> understand.  Could it be possible to define those fields in a more
> deterministic way?  For one, it is hard to understand the relationship
> between both fields without looking at the code, particulary if both
> share the same value.  It is at least rather..  Well, mostly, easy to
> guess what each other field means in this context, which is not the
> case of what you are proposing here.  One idea could be use also
> "start point" for REDO, for example.

How about "location=%X/%X, REDO start location=%X/%X"? The entire log
message can look like below:

2021-12-24 12:20:19.140 UTC [1977834] LOG:  checkpoint
complete:location=%X/%X, REDO start location=%X/%X; wrote 7 buffers
(0.0%); 0 WAL file(s) added, 0 removed, 0 recycled; write=0.005 s,
sync=0.007 s, total=0.192 s; sync files=5, longest=0.005 s,
average=0.002 s; distance=293 kB, estimate=56584 kB

Another variant:
2021-12-24 12:20:19.140 UTC [1977834] LOG:  checkpoint completed at
location=%X/%X with REDO start location=%X/%X: wrote 7 buffers (0.0%);
0 WAL file(s) added, 0 removed, 0 recycled; write=0.005 s, sync=0.007
s, total=0.192 s; sync files=5, longest=0.005 s, average=0.002 s;
distance=293 kB, estimate=56584 kB
2021-12-24 12:20:19.140 UTC [1977834] LOG:  restartpoint completed at
location=%X/%X with REDO start location=%X/%X: wrote 7 buffers (0.0%);
0 WAL file(s) added, 0 removed, 0 recycled; write=0.005 s, sync=0.007
s, total=0.192 s; sync files=5, longest=0.005 s, average=0.002 s;
distance=293 kB, estimate=56584 kB

Thoughts?

Regards,
Bharath Rupireddy.