Re: [HACKERS] Logical replication in the same cluster

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. I wonder how bad it
> would be if we created all the stuff for subscription but in disabled
> form, then committed, then created slot outside of tx (slot creation is
> not transactional anyway) and then switched the subscription to enabled
> (if needed) in next tx. It would still leave subscription behind on
> failure but a) user would see the failure, b) the subscription would be
> inactive so no active harm from it. We also already prevent running
> CREATE SUBSCRIPTION inside transaction block when automatic slot
> creation is chosen so there is no difference from that perspective.

Sounds like a solid approach.  There's no way to end up with a remote
object without also ending up with a logical object, which seems like
it greatly reduces the chances of confusion and error.

-- 
Robert Haas
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