Re: [HACKERS] Logical replication in the same cluster

On 2017-05-01 11:22:47 -0700, Peter Geoghegan wrote:
> On Fri, Apr 28, 2017 at 9:28 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> > On Thu, Apr 27, 2017 at 4:08 AM, Petr Jelinek
> > <petr.jelinek@2ndquadrant.com> wrote:
> >> Back when writing the original patch set, I was also playing with the
> >> idea of having CREATE SUBSCRIPTION do multiple committed steps in
> >> similar fashion to CREATE INDEX CONCURRENTLY but that leaves mess behind
> >> on failure which also wasn't very popular outcome.
> 
> There is no inherent reason why the CREATE INDEX CONCURRENTLY style of
> using multiple transactions makes it necessary to leave a mess behind
> in the event of an error or hard crash. Is someone going to get around
> to fixing the problem for CREATE INDEX CONCURRENTLY (e.g., having
> extra steps to drop the useless index during recovery)? IIRC, this was
> always the plan.

Doing catalog changes in recovery is frought with problems. Essentially
requires starting one worker per database, before allowing access.

- Andres