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From: Hannu Krosing <hannuk@google.com>
Date: Thu, 15 Jan 2026 22:06:23 +0100
Message-ID: <CAMT0RQRFa43CAf773LaDUvBYmZtwcNfdQSAzpBUtdJ+EiHH=kQ@mail.gmail.com>
Subject: Re: Proposal to allow setting cursor options on Portals
To: Dave Cramer <davecramer@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, 
	Jelte Fennema-Nio <postgres@jeltef.nl>, Jacob Champion <jacob.champion@enterprisedb.com>, 
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Heikki Linnakangas <hlinnaka@iki.fi>
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Precedence: bulk

First, let me say that I very much support getting this into the wire proto=
col.

As for ways to extend the protocol, I have been myself working on
another patch + extension where one can return extra info in
ReadyForQuery message

The first things to add are
* CommitLSN so we can make use of ability to WAIT FOR LSN on replica
and two connection-pooling helpers
* a flag telling that there are HOLD CURSORS
* a flag telling that there are temp tables

This extra feedback is enabled by setting a flag, so no flag --
nothing to confuse the client.
The extras themselves are uniform (length, tag, data) so client can
ignore any tag they do not recognize.

On Thu, Jan 15, 2026 at 8:11=E2=80=AFPM Dave Cramer <davecramer@gmail.com> =
wrote:
>
>
> On Thu, 15 Jan 2026 at 14:00, Robert Haas <robertmhaas@gmail.com> wrote:
>>
...
>> I think what I like least about this proposal is the feeling that
>> we're about to embark on a long slippery slope of changing the
>> protocol a little bit in every new PG version. The cancel key thing is
>> a small change, look here's another. If we just keep doing that, we'll
>> end up with either a lot of minor version bumps or a lot of
>> extensions. I don't foresee a good outcome either way. This is a
>> widely used, widely adopted protocol. The idea that we can just start
>> tweaking it a little bit every year and have nothing bad happened
>> seems wild, regardless of how we do the tweaking.

I think "tweaking ait  little bit" and only whhere needed is exactly
the right approach, if it can be cleanly isolated.

My approach to protocol extension modulation *is* the ability to
enable different parts of the protocol individually.

For example the protocol extension to allow cursor/portal flags could
be implemented this way

Client has to set a flag to PROTOCOL_PORTAL_OPTIONS=3Dtrue to tell the
server that new protocol messages are coming
- If flag setting fails, client will not send the new protocol messages
- If flag setting succeeds, then it is ok to send the new messages
corresponding to the flag.

This way the extra packets are disconnected from protocol version and
can be enabled/disabled individually and per connection

And it also lets one cleanly backport the change as needed without
affecting anything else.

> This leaves us with an all or nothing solution, which practically means w=
e do nothing, since we have to wait until we have a sufficient backlog of
> changes or features to change the protocol. I see that as untenable, unle=
ss you are now advocating for using extensions for everything ?
>
> Dave