Date: Fri, 9 Oct 2020 11:59:02 -0700
From: Andres Freund <andres@anarazel.de>
To: Dave Cramer <davecramer@postgres.rocks>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: dynamic result sets support in extended query protocol
Message-ID: <20201009185902.2hrednanwa7dxout@alap3.anarazel.de>
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Hi,

On 2020-10-09 14:49:11 -0400, Dave Cramer wrote:
> On Fri, 9 Oct 2020 at 14:46, Andres Freund <andres@anarazel.de> wrote:
> > > (I suspect what would be more useful in practice is to designate
> > > output formats per data type.)
> >
> > Yea, that'd be *really* useful. It sucks that we basically require
> > multiple round trips to make realistic use of the binary data for the
> > few types where it's a huge win (e.g. bytea).
> >
> 
> Yes!!! Ideally in the startup message.

I don't think startup is a good choice. For one, it's size limited. But
more importantly, before having successfully established a connection,
there's really no way the driver can know which types it should list as
to be sent in binary (consider e.g. some postgis types, which'd greatly
benefit from being sent in binary, but also just version dependent
stuff).

The hard part around this really is whether and how to deal with changes
in type definitions. From types just being created - comparatively
simple - to extensions being dropped and recreated, with oids
potentially being reused.

Greetings,

Andres Freund