Message-ID: <f8872ac0c3fbb9256cd7fc9f7563de61fd80f64f.camel@cybertec.at>
Subject: Re: values of column source in pg_settings
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: "David G. Johnston" <david.g.johnston@gmail.com>, "msalais@msym.fr"
	 <msalais@msym.fr>
Cc: "pgsql-admin@lists.postgresql.org" <pgsql-admin@lists.postgresql.org>
Date: Wed, 10 Sep 2025 23:35:45 +0200
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References: <04f101dc2288$121b2de0$365189a0$@msym.fr>
	 <CAKFQuwbuCSqXH=n-9DY7-J0ss90f1+rF1pb+g8jCoZG5g2dhvA@mail.gmail.com>
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On Wed, 2025-09-10 at 12:39 -0700, David G. Johnston wrote:
> > postgres# select name, source from pg_settings where source like 'envir=
on%';
> > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 name=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
 |=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 =C2=A0source=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=20
> > -----------------+----------------------
> > =C2=A0max_stack_depth | environment variable
> > =C2=A0
> > What is the meaning of =E2=80=98environment_variable=E2=80=99 here?
>=20
> Operating system and/or shell variable.=C2=A0 Established in the parent p=
rocess=E2=80=99s environment before starting the server.

Almost.  "src/backend/utils/misc/guc.c" has this comment:

    /*
     * rlimit isn't exactly an "environment variable", but it behaves about
     * the same.  If we can identify the platform stack depth rlimit, incre=
ase
     * default stack depth setting up to whatever is safe (but at most 2MB)=
.
     * Report the value's source as PGC_S_DYNAMIC_DEFAULT if it's 2MB, or a=
s
     * PGC_S_ENV_VAR if it's reflecting the rlimit limit.
     */

Looking at the code, you seem to get "environment variable" if "ulimit -s"
is less than 2560 and "default" when it is bigger...

Yours,
Laurenz Albe