Re: issue with synchronized_standby_slots

Fujii Masao <masao.fujii@gmail.com>

From: Fujii Masao <masao.fujii@gmail.com>

To: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>

Cc: Amit Kapila <amit.kapila16@gmail.com>, Alexander Kukushkin <cyberdemn@gmail.com>, Fabrice Chapuis <fabrice636861@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>

Date: 2025-09-09T08:07:18Z

Lists: pgsql-hackers

Commits

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Fix GUC check_hook validation for synchronized_standby_slots.
- e0dc4bbfb885 19 (unreleased) landed
- b45a8d7d8b30 18.1 landed
- 0024f5a1022e 17.7 landed
Make invalid primary_slot_name follow standard GUC error reporting.
- f33e60a53a9c 19 (unreleased) cited

On Tue, Sep 9, 2025 at 2:39 PM Zhijie Hou (Fujitsu)
<houzj.fnst@fujitsu.com> wrote:
> I agree. For synchronized_standby_slots, I think it is acceptable to report only
> parsing errors, because slots could be dropped even after validating the slot
> existence during GUC loading. Additionally, we would report WARNINGs for
> non-existent slots during the wait function anyway (e.g., in
> StandbySlotsHaveCaughtup()).

+1, to also address the issue I reported upthread.

As I understand it, only the walsender and the slot sync worker actually
use synchronized_standby_slots. But in the current code, all processes check
for slot existence via the GUC check hook, which wastes cycles. The proposed
change would eliminate that overhead.

Regards,

-- 
Fujii Masao