Re: optimizing pg_upgrade's once-in-each-database steps

I've read and tested through the latest version of this patchset and I think
it's ready to go in.  The one concern I have is that tasks can exit(1) on libpq
errors tearing down perfectly functional connections without graceful shutdown.
Longer term I think it would make sense to add similar exit handler callbacks
to the ones in pg_dump for graceful cleanup of connections.  However, in order
to keep goalposts in clear view I don't think this patch need to have it, but
it would be good to consider once in.

Spotted a small typo in the comments:

+     * nothing to process.  This is primarily intended for the inital step in
s/inital/initial/

--
Daniel Gustafsson