Re: Cross-backend signals and administration (Was: Re: pg_terminate_backend for same-role)

Magnus Hagander <magnus(at)hagander(dot)net> writes:
> I wasn't aware that was the reason there. I think it was the general
> "leftovers" from previous times. When we first created
> pg_terminate_backend() there was a general thought that it might not
> be safe to just SIGTERM a backend to make it quit.

Not just "might not be safe" - it was demonstrably buggy in the
beginning.

> A bunch of fixes
> were put in place to make it more safe, but I'm not sure anybody
> actually declared it fully safe.

We never did, we only said we didn't know of more bugs.

> I'm not sure - perhaps we're past that worry these days?

I'm not. I still wouldn't trust SIGTERMing an individual backend in a
production database. It'll probably work, but what if it doesn't?
Best-case scenario is you'll need to do a panic shutdown to clear the
stuck lock or whatever that the backend left behind. (Once you've
diagnosed the problem, that is.) Now, in a case where the alternative
is a database shutdown anyway, you might as well try it. But it's the
kind of tool you only want to hand to responsible adults, which is why
it's superuser-only at the moment. I'm not sure we should be
encouraging people to fire that weapon indiscriminately.

regards, tom lane