Re: proposal: psql: show current user in prompt

On Fri, 8 Sept 2023 at 21:08, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> ok changed - there is minor problem - almost all PQ functions are of int type, but ProtocolVersion is uint

Your current implementation requires using the PG_PROTOCOL macros to
compare versions. But clients cannot currently use those macros since
they are not exported from libpq-fe.h, only from pqcomm.h which is
then imported by libpq-int.h. (psql/command.c imports pcomm.h
directly, but I don't think we should expect clients to do that). We
could ofcourse export these macros from libpq-fe.h too. But then we'd
need to document those macros too.

> Using different mapping to int can be problematic - can be messy if we cannot use PG_PROTOCOL macro.

I see no big problems returning an unsigned or long from the new
function (even if existing functions all returned int). But I don't
even think that is necessary. Returning the following as an int from
PQprotocolVersionFull would work fine afaict:

return PG_PROTOCOL_MAJOR(version) * 1000 + PG_PROTOCOL_MINOR(version)

This would give us one thousand minor versions for each major version.
This seems fine for all practical purposes. Since postgres only
releases a version once every year, we'd need a protocol bump every
year for one thousand years for that to ever cause any problems. So
I'd prefer this approach over making the PG_PROTOCOL macros a public
interface.