Re: Transactions involving multiple postgres foreign servers, take 2

At Tue, 20 Oct 2020 02:44:09 +0000, "tsunakawa.takay@fujitsu.com" <tsunakawa.takay@fujitsu.com> wrote in 
> From: Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
> > Using pg_cancel_backend() and pg_terminate_backend() a DBA can cancel
> > running query from any backend or terminate a backend. For either to
> > work the backend needs to be interruptible. IIRC, Robert had made an
> > effort to make postgres_fdw interruptible few years back.
> 
> Yeah, I know those functions.  Sawada-san was talking about Ctrl + C, so I responded accordingly.
> 
> Also, how can the DBA find sessions to run those functions against?  Can he tell if a session is connected to or
runningSQL to a given foreign server?  Can he terminate or cancel all session with one SQL command that are stuck in
accessinga particular foreign server?
 

I don't think the inability to cancel all session at once cannot be a
reason not to not to allow operators to cancel a stuck session.

> Furthermore, FDW is not cancellable in general.  So, I don't see a point in trying hard to make only commit be
cancelable.

I think that it is quite important that operators can cancel any
process that has been stuck for a long time. Furthermore, postgres_fdw
is more likely to be stuck since network is involved so the usefulness
of that feature would be higher.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center