Re: Remaining Streaming Replication Open Items

On Thu, 2010-04-08 at 09:40 -0400, Robert Haas wrote:
> On Thu, Apr 8, 2010 at 8:00 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> > On Thu, 2010-04-08 at 07:53 -0400, Robert Haas wrote:
> >
> >> > I do. I see no reason to do the latter, ever, so should not be added to
> >> > any TODO.
> >>
> >> Well, stopping recovery earlier would mean fewer locks, which would
> >> mean a better chance for the read-only backends to finish their work
> >> and exit quickly. But I'm not sure how much it's worth worrying
> >> about.
> >
> > The purpose of the lock is to prevent access to objects when they are in
> > inappropriate states for access. If we stopped startup and allowed
> > access, how do we know that things are in sufficiently good state to
> > allow access? We don't. If the Startup process is holding a lock then
> > that is the only safe thing to do. Otherwise we might allow access to a
> > table with a partially built index or other screw ups.
>
> Hmm. Good point. I guess you could really only stop the startup
> process safely when it wasn't holding any locks anyhow - you couldn't
> just kill it and have it release the locks.

... and if it isn't holding any locks at all, there is no reason to kill
Startup first => no TODO item.

--
Simon Riggs www.2ndQuadrant.com