Horton

Re: Variable substitution in psql backtick expansion

Fabien COELHO <coelho@cri.ensmp.fr>

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From: Fabien COELHO <coelho@cri.ensmp.fr>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Pavel Stehule <pavel.stehule@gmail.com>, Corey Huinker <corey.huinker@gmail.com>, Daniel Verite <daniel@manitou-mail.org>, PostgreSQL Developers <pgsql-hackers@postgresql.org>
Date: 2017-09-06T16:42:58Z
Lists: pgsql-hackers

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>> Seeing it as is, it calls for having "SERVER_VERSION" as well, but I'm not
>> sure of the better way to get it. I tried with "SELECT VERSION() AS
>> SERVER_VERSION \gset" but varnames are lowerized.
>
> The problem there is you can't get version() without an extra round trip
> to the server --- and an extra logged query --- which people are going to
> complain about.

Here is a PoC that does it through a guc, just like "server_version" (the 
short version) is transmitted, with a fallback if it is not there.

Whether it is worth it is debatable, but I like the symmetry of having
the same informations accessible the same way for client and server sides.

-- 
Fabien.

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.