Re: [EXTERNAL] Re: Add non-blocking version of PQcancel

On Thu, 28 Mar 2024 at 19:03, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> > It doesn't fail when it's too fast -- it's just that it doesn't cover
> > the case we want to cover.
>
> That's hardly better, because then you think you have test
> coverage but maybe you don't.

Honestly, that seems quite a lot better. Instead of having randomly
failing builds, you have a test that creates coverage 80+% of the
time. And that also seems a lot better than having no coverage at all
(which is what we had for the last 7 years since introduction of
cancellations to postgres_fdw). It would be good to expand the comment
in the test though saying that the test might not always cover the
intended code path, due to timing problems.

> Could we make this test bulletproof by using an injection point?
> If not, I remain of the opinion that we're better off without it.

Possibly, and if so, I agree that would be better than the currently
added test. But I honestly don't feel like spending the time on
creating such a test. And given 7 years have passed without someone
adding any test for this codepath at all, I don't expect anyone else
will either.

If you both feel we're better off without the test, feel free to
remove it. This was just some small missing test coverage that I
noticed while working on this patch, that I thought I'd quickly
address. I don't particularly care a lot about the specific test.