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

Jacob Champion <jacob.champion@enterprisedb.com>

From: Jacob Champion <jacob.champion@enterprisedb.com>

To: Jelte Fennema-Nio <postgres@jeltef.nl>

Cc: Heikki Linnakangas <hlinnaka@iki.fi>, Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Jacob Burroughs <jburroughs@instructure.com>, Dave Cramer <davecramer@gmail.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, "Andrey M. Borodin" <x4mmm@yandex-team.ru>, Pavel Stehule <pavel.stehule@gmail.com>, Jeff Davis <pgsql@j-davis.com>, Peter Eisentraut <peter@eisentraut.org>, Daniele Varrazzo <daniele.varrazzo@gmail.com>

Date: 2024-08-20T21:48:19Z

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 Tue, Aug 20, 2024 at 12:55 PM Jelte Fennema-Nio <postgres@jeltef.nl> wrote:
> Another way of describing this guarantee: If a client connects using
> 3.8 and configures no protocol parameters, the client needs to handle
> anything 3.8 specific that the handshake requires (such as longer
> cancel token). But then after that handshake it can choose to send
> only 3.0 packets and expect to receive only 3.0 packets back.

That guarantee (if adopted) would also make it possible for my use
case to proceed correctly, since a libpq client can still speak 3.0
packets on the socket safely. But in that case, PQprotocolVersion
should keep returning 3, because there's an explicit reason to care
about the major version by itself.

--Jacob