Re: libpq: Bump protocol version to version 3.2 at least until the first/second beta

Hi,

On 2025-11-03 15:46:10 +0100, Jelte Fennema-Nio wrote:
> From 31851ddff8cb40f732aac0bfac364da61ed9fa30 Mon Sep 17 00:00:00 2001
> From: Jelte Fennema-Nio <postgres(at)jeltef(dot)nl>
> Date: Thu, 23 Oct 2025 15:08:52 +0200
> Subject: [PATCH v3 2/2] libpq: Request protocol version 3.9999 to GREASE the
> ecosystem
>
> The main reason that libpq does not request protocol version 3.2 by
> default is because other proxy/server implementations don't implement
> the negotiation. This is a bit of a chicken and egg problem: We don't
> bump the default version that libpq asks, but proxies will only
> implement version negotiation when their users run into issues.

> This patch defines 3.999 as an explicitly unsupported protocol version
> number and _pq_.test_protocol_negotiation as an explicitly unsupported
> protocol extension. It also starts requesting that version and protocol
> extension by default. This change to the default will be reverted before
> we release PG19 release candidates (when exactly to revert before that
> time is TBD). The intent is to stress test the ecosystem for
> servers/middleware that don't support protocol version negotiation, so
> that those servers/middleware can implement the negotiation. This is
> similar to the GREASE[1] mechanism that TLS has.
>
> It's still possible for users to connect to servers that don't support
> protocol negotiation by using max_protocol_version=3.0 in their
> connection string. Only the default connection behaviour is impacted.
>
> [1]: https://www.rfc-editor.org/rfc/rfc8701.html

Won't this mean that it'll be harder to performance comparisons between the
in-development version and other versions? Because there will be negotiation
before we branch of 19, but not after and not in release branches?

Greetings,

Andres Freund