Re: RFC: Logging plan of the running query

On Mon, Feb 19, 2024 at 11:53 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Fri, Feb 16, 2024 at 12:29 AM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > If we went with something like tht approach, I think we'd have to do something
> > like redirecting node->ExecProcNode to a wrapper, presumably from within a
> > CFI. That wrapper could then implement the explain support, without slowing
> > down the normal execution path.
>
> That's an annoying complication; maybe there's some better way to
> handle this. But I think we need to do something different than what
> the patch does currently because...
>
> > > It's really hard for me to accept that the heavyweight lock problem
> > > for which the patch contains a workaround is the only one that exists.
> > > I can't see any reason why that should be true.
> >
> > I suspect you're right.
>
> ...I think the current approach is just plain dead, because of this
> issue. We can't take an approach that creates an unbounded number of
> unclear reentrancy issues and then insert hacks one by one to cure
> them (or hack around them, more to the point) as they're discovered.
>
> The premise has to be that we only allow logging the query plan at
> points where we know it's safe, rather than, as at present, allowing
> it in places that are unsafe and then trying to compensate with code
> elsewhere. That's not likely to ever be as stable as we want
> PostgreSQL to be.

This is potentially a bit of a wild idea, but I wonder if having some
kind of argument to CHECK_FOR_INTERRUPTS() signifying we're in
"normal" as opposed to "critical" (using that word differently than
the existing critical sections) would be worth it.

Regards,
James Coleman