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

I think intuitively, this facility ought to work like client_encoding.
There, the client declares its capabilities, and the server has to
format the output according to the client's capabilities.  That works,
and it also works through connection poolers.  (It is a GUC.)  If we can
model it like that as closely as possible, then we have a chance of
getting it working reliably.  Notably, the value space for
client_encoding is a globally known fixed list of strings.  We need to
figure out what is the right way to globally identify types, like either
by fully-qualified name, by base name, some combination, how does it
work with extensions, or do we need a new mechanism like UUIDs.  I think
that is something we need to work out, no matter which protocol
mechanism we end up using.