Re: Reserving GUC prefixes from a non-preloaded DB extension is not always enforced

On Thu, 2024-06-13 at 12:26 -0700, Narek Galstyan wrote:
> I am an extension developer. I use `MarkGUCPrefixReserved` to reserve GUC prefixes,
> which my extension uses to help avoid accidentally misspelled config-file entries.
>
> However, since the reservation happens in `_PG_init()` and `_PG_init()` is not
> called until the first use of an API exposed by my extension, misspelled config-file
> entries that get executed before the extension is loaded will not throw an error.
>
> I'd expect GUC variables reserved by an extension to live more permanently in
> Postgres catalogs (e.g., in pg_settings). 
> So, even when the extension binary is not loaded, Postgres would know which prefixes
> are reserved and which GUC settings must be allowed (similar to how Postgres knows
> in pg_extension which extensions are enabled, even when the corresponding extension
> binary has not been loaded).
>
> > 1. Would you consider the proposed behavior an improvement?

Not really.

If I wanted to avoid that problem, I'd put the extension in "shared_preload_libraries",
so that _PG_init() is executed when the server starts.

Yours,
Laurenz Albe