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From: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Date: Tue, 24 Mar 2026 20:23:07 -0700
Message-ID: 
 <CALj2ACVi1OtetQ_xNfvTMCWSFqS0FPvBosj-w4WJR0GyEnMPGA@mail.gmail.com>
Subject: Re: log XLogPrefetch stats at end of recovery
To: Lakshmi N <lakshmin.jhs@gmail.com>
Cc: Jakub Wartak <jakub.wartak@enterprisedb.com>,
 Thomas Munro <thomas.munro@gmail.com>,
	SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com>,
 pgsql-hackers@postgresql.org
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Precedence: bulk

Hi,

On Tue, Mar 24, 2026 at 5:07=E2=80=AFAM Lakshmi N <lakshmin.jhs@gmail.com> =
wrote:
>
>> so instead of like:
>> redo prefetch stats: prefetch=3D%lu, hit=3D%lu, skip_init=3D%lu,
>> skip_new=3D%lu, skip_fpw=3D%lu, skip_rep=3D%lu"
>>
>> something like below ones:
>> redo prefetch stats: done %lu prefetches, %lu hit, %lu zero-initated, ..
>> redo prefetch stats: done %lu prefetches, (%d% hit ratio), %lu
>> zero-initated, .. or something like that
>
> Please find the attached patch with the suggested changes. I referenced [=
1] to log the message as suggested.
>
> 2026-03-24 04:53:15.251 PDT [18898] LOG:  redo prefetch stats: prefetched=
 27 blocks, skipped 22 blocks because they were already in the buffer pool,=
 skipped 17 blocks because they would be zero-initialized, skipped 0 blocks=
 because they didn't exist yet, skipped 28 blocks because a full page image=
 was included in the WAL, skipped 155 blocks because they were already rece=
ntly prefetched.

IMHO, the above looks too verbose. +1 for Jakub's suggestion. Would
something like the below work? I believe the developers looking at
these logs for analysis will have some understanding of what each of
these means.

LOG: redo prefetch stats: prefetched 27, skipped (22 in buffer pool,
17 zero-inited, 0 non-existent, 28 FPI, 155 recently prefetched)

--
Bharath Rupireddy
Amazon Web Services: https://aws.amazon.com