Re: Add new protocol message to change GUCs for usage with future protocol-only GUCs

Jelte Fennema-Nio <me@jeltef.nl>

From: Jelte Fennema-Nio <me@jeltef.nl>

To: Tom Lane <tgl@sss.pgh.pa.us>

Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Dave Cramer <davecramer@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Jacob Burroughs <jburroughs@instructure.com>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>, Pavel Stehule <pavel.stehule@gmail.com>, Jeff Davis <pgsql@j-davis.com>, Peter Eisentraut <peter@eisentraut.org>

Date: 2023-12-29T23:49:40Z

Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

libpq: Add min/max_protocol_version connection options
- 285613c60a7a 18.0 landed
libpq: Handle NegotiateProtocolVersion message differently
- 5070349102af 18.0 landed
Add PQfullProtocolVersion() to surface the precise protocol version.
- cdb6b0fdb0b2 18.0 landed
Do not hardcode PG_PROTOCOL_LATEST in NegotiateProtocolVersion
- 516b87502dc1 18.0 landed
libpq: Handle NegotiateProtocolVersion message
- bbf9c282ce92 16.0 cited
Provide for forward compatibility with future minor protocol versions.
- ae65f6066dc3 11.0 cited

On Fri, 29 Dec 2023 at 19:38, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> > 2. It paves the way for GUCs that can only be set using a protocol
> > message (and not using SET).
>
> This is assuming facts not in evidence.

How about instead of talking about protocol-only GUCs (which are
indeed currently a theoretical concept), we start considering this
patch as a way to modify parameters for protocol extensions. Protocol
extension parameters (starting with _pq_.) can currently only be
configured using the StartupMessage and afterwards there is no way to
modify them.

I believe [1], [2] and [3] from my initial email could all use such
protocol extension parameters, if those parameters could be changed
after the initial startup.