Horton

Re: Variable substitution in psql backtick expansion

Corey Huinker <corey.huinker@gmail.com>

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From: Corey Huinker <corey.huinker@gmail.com>
To: Fabien COELHO <coelho@cri.ensmp.fr>
Cc: Pavel Stehule <pavel.stehule@gmail.com>, Greg Stark <stark@mit.edu>, Daniel Verite <daniel@manitou-mail.org>, Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Developers <pgsql-hackers@postgresql.org>
Date: 2017-04-11T13:50:34Z
Lists: pgsql-hackers 
On Tue, Apr 11, 2017 at 2:56 AM, Fabien COELHO <coelho@cri.ensmp.fr> wrote:

>
> Hello Pavel,
>
> I think so some local expression evaluation could be - but it should not be
>> placed in \if statement
>>
>
> Why?
>
> \expr issupported :VERSION_NUM >= 10000
>>
>
> Hmmm. Although I do not buy this, it could work as a replacement for \set
> which it seems cannot be upgraded because some people may rely on it to
> just store whatever comes after it in a variable.
>

I have no strong opinion on how expressive expressions should be, but
having a separate \expr (or \setexpr, etc) gives us a green field to
develop them.

Commits

  1. Add psql variables showing server version and psql version.

  2. Reformat psql's --help=variables output.

  3. Remove reinvention of stringify macro.

  4. Allow psql variable substitution to occur in backtick command strings.