Re: should we document an example to set multiple libraries in shared_preload_libraries?

On Thu, Dec 9, 2021 at 2:32 AM Maciek Sakrejda <m(dot)sakrejda(at)gmail(dot)com> wrote:
> > Considering the vanishingly small number of actual complaints we've
> > seen about this, that sounds ridiculously over-engineered.
> > A documentation example should be sufficient.
>
> I don't know if this will tip the scales, but I'd like to lodge a
> belated complaint. I've gotten myself in this server-fails-to-start
> situation several times (in development, for what it's worth). The
> syntax (as Bharath pointed out in the original message) is pretty
> picky, there are no guard rails, and if you got there through ALTER
> SYSTEM, you can't fix it with ALTER SYSTEM (because the server isn't
> up). If you go to fix it manually, you get a scary "Do not edit this
> file manually!" warning that you have to know to ignore in this case
> (that's if you find the file after you realize what the fairly generic
> "FATAL: ... No such file or directory" error in the log is telling
> you). Plus you have to get the (different!) quoting syntax right or
> cut your losses and delete the change.

+1. I disagree that trying to detect this kind of problem would be
"ridiculously over-engineered." I don't know whether it can be done
elegantly enough that we'd be happy with it and I don't know whether
it would end up just garden variety over-engineered. But there's
nothing ridiculous about trying to prevent people from putting their
system into a state where it won't start.

(To be clear, I also think updating the documentation is sensible,
without taking a view on exactly what that update should look like.)

--
Robert Haas
EDB: http://www.enterprisedb.com