Re: Variable substitution in psql backtick expansion

On Sun, Apr 2, 2017 at 11:16 AM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
wrote:

>
>
> 2017-04-02 13:13 GMT+02:00 Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>:
>
>>
>> Hello Pavel,
>>
>> \echo :VERSION
>>>> PostgreSQL 10devel on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu
>>>> 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609, 64-bit
>>>>
>>>> Probably some :VERSION_NUM would make some sense. See attached PoC
>>>> patch.
>>>> Would it make sense?
>>>>
>>>
>>> Maybe better name for you CLIENT_VERSION_NUM
>>>
>>
>> If it was starting from nothing I would tend to agree with you, but there
>> is already an existing :VERSION variable, so it seemed logical to keep on
>> and create variants with the same prefix.
>
>
> you have true - so VERSION_NUM should be client side version
>
>
>>
>>
>> Can be SERVER_VERSION_NUM taken from connection info?
>>>
>>
>> Probably it could. It seems a little less straightforward than defining a
>> client-side string at compile time. The information is displayed when the
>> connection is established, so the information is there somewhere.
>>
>
> It is not too hard
>
> diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
> index 94a3cfce90..d1ae81646f 100644
> --- a/src/bin/psql/command.c
> +++ b/src/bin/psql/command.c
> @@ -3320,16 +3320,21 @@ checkWin32Codepage(void)
> void
> SyncVariables(void)
> {
> + char buffer[100];
> +
> /* get stuff from connection */
> pset.encoding = PQclientEncoding(pset.db);
> pset.popt.topt.encoding = pset.encoding;
> pset.sversion = PQserverVersion(pset.db);
>
> + snprintf(buffer, 100, "%d", pset.sversion);
> +
> SetVariable(pset.vars, "DBNAME", PQdb(pset.db));
> SetVariable(pset.vars, "USER", PQuser(pset.db));
> SetVariable(pset.vars, "HOST", PQhost(pset.db));
> SetVariable(pset.vars, "PORT", PQport(pset.db));
> SetVariable(pset.vars, "ENCODING", pg_encoding_to_char(pset.encod
> ing));
> + SetVariable(pset.vars, "SVERSION_NUM", buffer);
>
> /* send stuff to it, too */
> PQsetErrorVerbosity(pset.db, pset.verbosity);
>
> Regards
>
> Pavel
>
>
>>
>> psql (10devel, server 9.6.2)
>>
>> --
>> Fabien.
>>
>
>

I'm anxious to help with these patches, but they seem a bit of a moving
target. Happy to jump in and review as soon as we've settled on what should
be done.