Date: Mon, 31 Oct 2022 08:31:20 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: Maciek Sakrejda <m.sakrejda@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Robert Haas <robertmhaas@gmail.com>,
	"David G. Johnston" <david.g.johnston@gmail.com>,
	Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>,
	Cary Huang <cary.huang@highgo.ca>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: warn if GUC set to an invalid shared library
Message-ID: <20221031133120.GO16921@telsasoft.com>
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On Sun, Oct 30, 2022 at 04:12:33PM -0700, Maciek Sakrejda wrote:
> On Sat, Oct 29, 2022 at 10:40 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
> >
> > On Fri, Sep 02, 2022 at 05:24:58PM -0500, Justin Pryzby wrote:
> > > It caused no issue when I changed:
> > >
> > >                         /* Check that it's acceptable for the indicated parameter */
> > >                         if (!parse_and_validate_value(record, name, value,
> > > -                                                     PGC_S_FILE, ERROR,
> > > +                                                     PGC_S_TEST, ERROR,
> > >                                                       &newval, &newextra))
> > >
> > > I'm not sure where to go from here.
> >
> > I'm hoping for some guidance ; this simple change may be naive, but I'm not
> > sure what a wider change would look like.
> 
> I assume you mean guidance on implementation details here, and not on

ALTER SYSTEM tests the new/proposed setting using PGC_S_FILE ("which is
a lie").

It seems better to address that lie before attempting to change the
behavior of *_preload_libraries.

PGC_S_TEST is a better fit, so my question is whether it's really that
simple ?  

> Also, for what it's worth, I think requiring the libraries to be in
> place before running ALTER SYSTEM does not really seem that onerous. I
> can't really think of use cases it precludes.

Right now, it's allowed to set the GUC before installing the shlib.
That's a supported case (see the 11 month old messages toward the
beginning of this thread).

-- 
Justin