Re: proposal: psql: show current user in prompt

On Sun, 3 Sept 2023 at 20:58, Pavel Stehule <pavel.stehule@gmail.com> wrote:
> here is an try

Overall it does what I had in mind. Below a few suggestions:

+int
+PQprotocolSubversion(const PGconn *conn)

Ugh, it's quite annoying that the original PQprotocolVersion only
returns the major version and thus we need this new function. It
seems like it would be much nicer if it returned a number similar to
PQserverVersion. I think it might be nicer to change PQprotocolVersion
to do that than to add another function. We could do:

return PG_PROTOCOL_MAJOR(conn->pversion) * 100 +
PG_PROTOCOL_MINOR(conn->pversion);

or even:

if (PG_PROTOCOL_MAJOR(conn->pversion) == 3 && PG_PROTOCOL_MINOR(conn->pversion))
    return 3;
else
    return PG_PROTOCOL_MAJOR(conn->pversion) * 100 +
PG_PROTOCOL_MINOR(conn->pversion);

The second option would be safest backwards compatibility wise, but in
practice you would only get another value than 3 (or 0) when
connecting to pre 7.4 servers. That seems old enough that I don't
think anyone is actually calling this function. **I'd like some
feedback from others on this though.**

+       /* The protocol 3.0 is required */
+       if (PG_PROTOCOL_MAJOR(their_version) == 3)
+           conn->pversion = their_version;

Let's compare against the actual PG_PROTOCOL_EARLIEST and
PG_PROTOCOL_LATEST to determine if the version is supported or not.