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

Dave Cramer <davecramer@gmail.com> writes:
> On Mon, 20 Mar 2023 at 13:05, Jeff Davis <pgsql@j-davis.com> wrote:
>> 2. Easy to confuse psql:
>> 
>> CREATE TABLE a(d date, t timestamptz);
>> SET format_binary='25,1082,1184';
>> SELECT * FROM a;
>> d | t
>> ---+---
>> ! |
>> (1 row)
>> 
>> Well I'm guessing psql doesn't know how to read date or timestamptz in
>> binary. This is not a failing of the code.

What it is is a strong suggestion that controlling this via a GUC is
not a great choice.  There are many inappropriate (wrong abstraction
level) ways to change a GUC and thereby break a client that's not
expecting binary output.  I think Jeff's suggestion that we should
treat this as a protocol extension might be a good idea.

If I recall the protocol-extension design correctly, such a setting
could only be set at session start, which could be annoying --- at the
very least we'd have to tolerate entries for unrecognized data types,
since clients couldn't be expected to have checked the list against
the current server in advance.

            regards, tom lane