Re: BUG #16914: Regression test of the worker_spi fails if USE_MODULE_DB environment variable is set.

On Fri, Mar 05, 2021 at 12:42:43AM -0500, Tom Lane wrote:
> Yeah, the fact that bgw_main_arg is declared as Datum is really kind
> of a lie, because the only thing that actually works there is a pass
> by value datatype (not that our docs tell you so).

Exactly.

> We could stuff the database name into bgw_extra perhaps, but that
> seems restrictive as well. I wonder if there's a reasonable way to
> pass over a struct of caller-defined size.

Or we could just rely on a custom memory context that dynamic workers
could use to store their data? It could be simpler IMO to just merge
together bgw_main_arg and bgw_extra, then pass down the whole as an
argument of the main routine of the bgworker, say with a buffer of 256
bytes for example. I am not sure that workers really need that much
for themselves at startup out of GUCs, but I may be wrong :)
--
Michael