Date: Thu, 20 Jan 2022 12:00:29 +0900 (JST)
Message-Id: <20220120.120029.1092463916382268628.horikyota.ntt@gmail.com>
To: bossartn@amazon.com
Cc: bharath.rupireddyforpostgres@gmail.com, rjuju123@gmail.com,
 michael@paquier.xyz, pgsql-hackers@lists.postgresql.org
Subject: Re: Add checkpoint and redo LSN to LogCheckpointEnd log message
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
In-Reply-To: <BDAE2BB3-2F37-4B7C-A053-874250A47C21@amazon.com>
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At Thu, 20 Jan 2022 00:36:32 +0000, "Bossart, Nathan" <bossartn@amazon.com> wrote in 
> On 1/3/22, 5:52 PM, "Kyotaro Horiguchi" <horikyota.ntt@gmail.com> wrote:
> > It seems to me "LSN" or just "location" is more confusing or
> > mysterious than "REDO LSN" for the average user. If we want to avoid
> > being technically too detailed, we would use just "start LSN=%X/%X,
> > end LSN=%X/%X".  And it is equivalent to "WAL range=[%X/%X, %X/%X]"..
> 
> My first instinct was that this should stay aligned with
> pg_controldata, but that would mean using "location=%X/%X, REDO
> location=%X/%X," which doesn't seem terribly descriptive.  IIUC the
> "checkpoint location" is the LSN of the WAL record for the checkpoint,
> and the "checkpoint's REDO location" is the LSN where checkpoint
> creation began (i.e., what you must retain for crash recovery).  My
> vote is for "start=%X/%X, end=%X/%X."

+1. Works for me.  %X/%X itself expresses it is an LSN.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center