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Subject: Re: Optimize LISTEN/NOTIFY
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: <4b7b49a5-5e1a-44a8-93e0-60457d15cb1d@app.fastmail.com>
Date: Tue, 28 Oct 2025 09:02:57 +0800
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
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To: Joel Jacobson <joel@compiler.org>
Archived-At: 
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> On Oct 27, 2025, at 14:18, Joel Jacobson <joel@compiler.org> wrote:
>=20
> On Mon, Oct 27, 2025, at 02:27, Chao Li wrote:
>>> On Oct 27, 2025, at 07:24, Joel Jacobson <joel@compiler.org> wrote:
>>>=20
>>> Write-up of changes since v20:
>>>=20
>>> Two new fields have been added to QueueBackendStatus:
>>> + QueuePosition advisoryPos; /* safe skip-ahead position */
>>> + bool advancingPos; /* backend is reading the queue */
> ...
>> I did a quick review on v21 only focusing on the =E2=80=9Cdirect =
advancement=E2=80=9D logic.
>>=20
>> In v21, you added advisoryPos and advancingPos which is same as my=20
>> proposed solution. But you missed an important point from mine.
>>=20
> ...
>> =46rom this perspective, we need to add a new field=20
>> adviancingTillPos to QueueBackendStatus. (This field was also missing=20=

>> from my proposed patch).
>=20
> I'm doubtful yet another field is worth the added complexity cost.
>=20
> Before increasing the complexity further, I think we should first
> try to simulate somewhat realistic workloads, to see if we actually
> have a problem first.
>=20
> /Joel
>=20

I don=E2=80=99t think that=E2=80=99s extra complexity, IMO, that just =
ensure =E2=80=9Cdirect advancement=E2=80=9D to be fully functional.

But anyway, we should run some load tests to verify every solution to =
see how much they really improve. Do you already have or plan to work on =
a load test script?

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/