Re: Request for comment on setting binary format output per session

On Mon, Apr 3, 2023 at 11:29 AM Dave Cramer <davecramer(at)gmail(dot)com> wrote:

> > participating clients to receive GUC configured format. I do not
>
>> > think that libpq's result format being able to be overridden by GUC
>>> > is a good idea at all, the library has to to participate, and I
>>> > think can be made to so so without adjusting the interface (say, by
>>> > resultFormat = 3).
>>>
>>> Interesting idea. I suppose you'd need to specify 3 for all result
>>> columns? That is a protocol change, but wouldn't "break" older clients.
>>> The newer clients would need to make sure that they're connecting to
>>> v16+, so using the protocol version alone wouldn't be enough. Hmm.
>>>
>>
>>
> So this only works with extended protocol and not simple queries.
> Again, as Peter mentioned it's already easy enough to confuse psql using
> binary cursors so
> it makes sense to fix psql either way.
>
> If you use resultFormat (3) I think you'd still end up doing the Describe
> (which we are trying to avoid) to make sure you could receive all the
> columns in binary.
>

Can you elaborate on why Describe would have to be passed? Agreed that
would be a dealbreaker if so. If you pass a 3 sending it in, the you'd be
checking PQfformat on data coming back as 0/1, or at least that's be smart
since you're indicating the server is able to address the format. This
addresses the concern libpq clients currently passing resultfomat zero
could not have that decision overridden by the server which I also think is
a dealbreaker. There might be other reasons why a describe message may be
forced however.

merlin