Re: values of column source in pg_settings

On Wed, 2025-09-10 at 12:39 -0700, David G. Johnston wrote:
> > postgres# select name, source from pg_settings where source like 'environ%';
> >       name       |        source      
> > -----------------+----------------------
> >  max_stack_depth | environment variable
> >  
> > What is the meaning of ‘environment_variable’ here?
>
> Operating system and/or shell variable.  Established in the parent process’s 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, increase
     * 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 as
     * 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