Re: Re: Postgres Parameters

I found that PostgreSQL 15.3 doesn't support the pg_stat_checkpointer view. We can use pg_stat_bgwriter instead. The SQL is as follows:
SELECT
checkpoints_timed AS num_timed, -- Checkpoints triggered by timeout
checkpoints_req AS num_requested, -- Checkpoints triggered by requests (like when WAL space is tight)
round(
(checkpoints_req::numeric / NULLIF(checkpoints_timed + checkpoints_req, 0)) * 100,
2
) AS requested_pct -- % of checkpoints that were request-triggered
FROM pg_stat_bgwriter;

From: Sam Stearns
Date: 2025-11-11 23:24
To: Fabrice Chapuis; Laurenz Albe; Ron Johnson
CC: Pgsql-admin; Henry Ashu
Subject: Re: Postgres Parameters
Awesome stuff. Thank you, everyone!

Sam

On Tue, Nov 11, 2025 at 3:19 AM Fabrice Chapuis <fabrice636861(at)gmail(dot)com> wrote:
Hi, You could also use this query, if the ratio is low, that means there is no pressure on wal size and you can keep the max_wal_size value as it is. SELECT num_timed, num_requested, round((num_requested: : numeric / NULLIF(num_timed + num_requested,
ZjQcmQRYFpfptBannerStart
This Message Is From an Untrusted Sender
You have not previously corresponded with this sender.

ZjQcmQRYFpfptBannerEnd
Hi,

You could also use this query, if the ratio is low, that means there is no pressure on wal size and you can keep the max_wal_size value as it is.

SELECT
num_timed,
num_requested,
round((num_requested::numeric / NULLIF(num_timed + num_requested, 0)) * 100, 2)
AS requested_pct
FROM pg_stat_checkpointer;
+-----------+---------------+---------------+
| num_timed | num_requested | requested_pct |
+-----------+---------------+---------------+
| 3502 | 146 | 4.00 |
+-----------+---------------+---------------+
(1 row)

Regards,

Fabrice

On Tue, Nov 11, 2025 at 12:28 AM Sam Stearns <sam(dot)stearns(at)dat(dot)com> wrote:
Howdy,

Could someone advise on how to determine the correct settings for the following, please?:

checkpoint_timeout
max_wal_size

Thank you,

Sam

--
Samuel Stearns
Team Lead - Database
c: 971 762 6879 | o: 971 762 6879 | DAT.com

--
Samuel Stearns
Team Lead - Database
c: 971 762 6879 | o: 971 762 6879 | DAT.com