MIME-Version: 1.0
References: <ahm_4eOKkkKJ3Gds@nathan>
 <CAOYmi+msZYr=NhBmf-Tg3h3ZHoQjMzp-50ByFqo2A8XDKd-eHQ@mail.gmail.com>
In-Reply-To: 
 <CAOYmi+msZYr=NhBmf-Tg3h3ZHoQjMzp-50ByFqo2A8XDKd-eHQ@mail.gmail.com>
From: Jelte Fennema-Nio <postgres@jeltef.nl>
Date: Fri, 5 Jun 2026 11:34:14 +0200
Message-ID: 
 <CAGECzQQCKSogfz=Dqkf-+1GA13yATMu34CMU9Yqo13KXgmkW8Q@mail.gmail.com>
Subject: Re: alert clients when prepared statements are deallocated
To: Jacob Champion <jacob.champion@enterprisedb.com>
Cc: Nathan Bossart <nathandbossart@gmail.com>, pgsql-hackers@postgresql.org
Content-Type: text/plain; charset="UTF-8"
Archived-At: 
 <https://www.postgresql.org/message-id/CAGECzQQCKSogfz%3DDqkf-%2B1GA13yATMu34CMU9Yqo13KXgmkW8Q%40mail.gmail.com>
Precedence: bulk

On Fri, 29 May 2026 at 19:07, Jacob Champion
<jacob.champion@enterprisedb.com> wrote:
> - let drivers pin protocol-level prepared statements so that
> application-level DISCARD doesn't touch them
> - explicitly separate client and middleware contexts or streams from each other
> - rebuild discarded prepared statements opportunistically on a failure

I think I like option 2 best (and after that 1). I'm often annoyed
that our application layer and protocol layer is so intertwined, so
any attempt to separate them is a welcome addition in my opinion.

One approach would be to:
1. add an optional additional text field to the Parse message as a
kind of "namespace" for prepared statements. Leaving this field out or
set to the empty string, would create an "application-level" prepared
statement. Setting it to anything else would create a protocol-level
prepared statement within that namespace. This would allow libpq to
create its own prepared statements, without conflicting with
protocol-level statements created by client libraries like psycopopg.
2. Application-level DISCARD/DEALLOCATE would not clean up these
namespaced protocol level prepared statements
3. Add a protocol-level version of DEALLOCATE ALL and DISCARD ALL
which also clean up all the protocol-level prepared statements
4. Add a protocol-level message to deallocate all prepared statements
in a certain schema.