Re: [PATCH v1] command_tag_format — protocol-level command tag negotiation via _pq_

Hi,

On 2026-03-11 21:22:14 +0000, nik(at)postgres(dot)ai wrote:
> PostgreSQL has had a protocol feature negotiation framework since
> 7.4 (the _pq_ namespace in startup parameters) -- over 20 years --
> but it's never been used in practice.

Wasn't that added in

commit ae65f6066dc
Author: Robert Haas <rhaas(at)postgresql(dot)org>
Date: 2017-11-21 13:56:24 -0500

Provide for forward compatibility with future minor protocol versions.

Previously, any attempt to request a 3.x protocol version other than
3.0 would lead to a hard connection failure, which made the minor
protocol version really no different from the major protocol version
and precluded gentle protocol version breaks. Instead, when the
client requests a 3.x protocol version where x is greater than 0, send
the new NegotiateProtocolVersion message to convey that we support
only 3.0. This makes it possible to introduce new minor protocol
versions without requiring a connection retry when the server is
older.

PG 14 / 2017 is quite a while after 7.4...

>
> legacy - INSERT 0 N (default, fully backward compatible)
> verbose - INSERT tablename N
> fqn - INSERT schema.tablename N

Pretty doubtful this survives the complexity / gain tradeoff.

Separately, doing extra work during command handling isn't free either. We've
spent a decent amount of effort in the past lowering it, see e.g.

commit ac998020802
Author: David Rowley <drowley(at)postgresql(dot)org>
Date: 2022-12-16 10:31:25 +1300

Speed up creation of command completion tags

I'm loathe to add work to every statement.

Greetings,

Andres Freund