Re: [multithreading] extension compatibility

On Wed Jun 5, 2024 at 3:56 PM CDT, Robert Haas wrote:
> On Wed, Jun 5, 2024 at 4:32 PM Tristan Partin <tristan(at)partin(dot)io> wrote:
> > Not entirely sure how I feel about the approach you've taken, but here
> > is a patch that Heikki and I put together for extension compatibility.
> > It's not a build time solution, but a runtime solution. Instead of
> > PG_MODULE_MAGIC, extensions would use PG_MAGIC_MODULE_REENTRANT. There
> > is a GUC called `multithreaded` which controls the variable
> > IsMultithreaded. We operated under the assumption that being able to
> > toggle multithreading and multi-processing without recompiling has
> > value.
>
> That's interesting, because I thought Heikki was against having a
> runtime toggle.
>
> I don't think PG_MODULE_MAGIC_REENTRANT is a good syntax. It all looks
> great as long as we only ever need the PG_MODULE_MAGIC line to signal
> one bit of information, but as soon as you get to two bits it's pretty
> questionable, and anything more than two bits is insane. If we want to
> do something with the PG_MODULE_MAGIC line, I think it should involve
> options-passing of some form rather than just having an alternate
> macro name.

I agree that this method doesn't lend itself to future extensibility.

--
Tristan Partin
https://tristan.partin.io