Re: [HACKERS] Variable substitution in psql backtick expansion

Fabien COELHO <coelho@cri.ensmp.fr> writes:
>> OK, but if human-friendly display is the use-case then it ought to
>> duplicate what psql itself would print in, eg, the startup message about
>> server version mismatch.  The v4 patch does not, in particular it neglects
>> PQparameterStatus(pset.db, "server_version").  This would result in
>> printing, eg, "11.0" when the user would likely rather see "11devel".

> I understand that you would prefer VERSION_NAME to show something like
>    "11devel, server 9.6.4"

No, that's not what I said.  I'm just complaining that as the patch stands
it will set SERVER_NAME to "11.0", where I think it should say "11devel"
(as of today).

> In summary, my prefered option is to have:
>    CLIENT_VERSION "PostgreSQL 11devel on ..."
>    CLIENT_VERSION_NAME "11devel"
>    CLIENT_VERSION_NUM 110000

I don't think we want to drop :VERSION; that would accomplish little
beyond breaking existing scripts.  Plausible choices include duplicating
it, like:
  VERSION "PostgreSQL 11devel on ..."  CLIENT_VERSION "PostgreSQL 11devel on ..."  CLIENT_VERSION_NAME "11devel"
CLIENT_VERSION_NUM110000
 

or just ignoring the discrepancy:
  VERSION "PostgreSQL 11devel on ..."  CLIENT_VERSION_NAME "11devel"  CLIENT_VERSION_NUM 110000

or just leaving "CLIENT" implicit for all of these variables:
  VERSION "PostgreSQL 11devel on ..."  VERSION_NAME "11devel"  VERSION_NUM 110000

Robert seems to prefer the last of those, and that'd be fine with me.
(Note that CLIENT is ambiguous anyway: does it mean psql itself, or
libpq?)

>    SERVER_VERSION_NAME "9.6.4"
>    SERVER_VERSION_NUM 090604

I'm on board with this, except I don't think we should have any leading
zero in the numeric form.  There are contexts where somebody might think
that means octal.
        regards, tom lane