Re: psql: Add command to use extended query protocol

On Mon, Nov 7, 2022 at 9:02 PM Pavel Stehule <pavel.stehule@gmail.com> wrote:

út 8. 11. 2022 v 3:47 odesílatel Corey Huinker <corey.huinker@gmail.com> napsal:

On Mon, Nov 7, 2022 at 4:12 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Corey Huinker <corey.huinker@gmail.com> writes:
> I thought about basically reserving the \$[0-9]+ space as bind variables,
> but it is possible, though unlikely, that users have been naming their
> variables like that.

Don't we already reserve that syntax as Params?  Not sure whether there
would be any conflicts versus Params, but these are definitely not legal
as SQL identifiers.

                        regards, tom lane

I think Pavel was hinting at something like:

\set $1 foo

\set $2 123

UPDATE mytable SET value = $1 WHERE id = $2;

no, I just proposed special syntax for variable usage like bind variable

like

\set var Ahoj

SELECT $var;

Why not extend psql conventions for variable specification?

SELECT :$var$;

Thus:

:var => Ahoj

:'var' => 'Ahoj'

:"var" => "Ahoj"

:$var$ => $n  (n => <Ahoj>)

The downside is it looks like dollar-quoting but isn't actually causing <$Ahoj$> to be produced.  Instead psql would have to substitute $n at that location and internally remember that for this query $1 is the contents of var.

I would keep the \gp meta-command to force extended mode regardless of whether the query itself requires it.

A pset variable to control the default seems reasonable as well.  The implication would be that if you set that pset variable there is no way to have individual commands use simple query mode directly.

David J.