Re: Allow GUC settings in CREATE SUBSCRIPTION CONNECTION to take effect

> On Nov 22, 2025, at 22:14, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>
> On Sat, Nov 22, 2025 at 10:31 AM Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>>
>>
>>
>>> On Nov 22, 2025, at 00:14, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>>>
>>> On Fri, Nov 21, 2025 at 6:24 PM Chao Li <li(dot)evan(dot)chao(at)gmail(dot)com> wrote:
>>>> No, what I was thinking is that, we could combine the three set statement into one, like:
>>>>
>>>> ```
>>>> Set a = 1; set b = 2; set c = 3;
>>>> ```
>>>> So that sends a single statement to publisher server, that reduces round-trip from 3 times to one time.
>>>
>>> I see the point about combining the three SET commands to reduce round trips,
>>> but I think the current approach in the patch (i.e., issuing a separate
>>> SET command for each parameter) is sufficient. I still don't think
>>> the additional round trip during replication connection startup is
>>> a real concern. This approach is also consistent with what postgres_fdw
>>> and pg_dump already do.
>>>
>>
>> No problem. I don’t have a strong option here. I just saw you mentioned overhead of round trip and thought to improve. But I agree that overhead is tiny, not a real concern.
>
> Okay, thanks!
>
> I've updated the patch to use lengthof() as you suggested.
> The revised version is attached.
>
> Regards,
>
> --
> Fujii Masao
> <v3-0001-Honor-GUC-settings-specified-in-CREATE-SUBSCRIPTI.patch>

V3 looks good to me.

>> now all user specified options expect the 3 will be kept, will that expose a hold where user badly specifies some option that may break logical replication? If that’s true, then we need to parse user specified options and do some verifications.
>>
>
> Yeah, I agree that if certain GUCs can break logical replication,
> we should enforce "safe" values, just as we currently do for datestyle.
> And if any other GUCs can cause the issue, they could affect
> postgres_fdw etc, so the fix would need to be broader.

Just want to clarify if you mean you will handle this in a future patch?

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