Hi,
While looking at the commit
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=29d0a77fa6606f9c01ba17311fc452dabd3f793d,
I noticed that get_old_cluster_logical_slot_infos gets called for even
template1 and template0 databases. Which means, pg_upgrade executes
queries against the template databases to get replication slot
information. I then realized that postgres allows one to connect to
template1 database (or any other user-defined template databases for
that matter), and create logical replication slots in it. If created,
all the subsequent database creations will end up adding inactive
logical replication slots in the postgres server. This might not be a
problem in production servers as I assume the connections to template
databases are typically restricted. Despite the connection
restrictions, if at all one gets to connect to template databases in
any way, it's pretty much possible to load the postgres server with
inactive replication slots.
This leads me to think why one would need logical replication slots in
template databases at all. Can postgres restrict logical replication
slots creation in template databases? If restricted, it may deviate
from the fundamental principle of template databases in the sense that
everything in the template database must be copied over to the new
database created using it. Is it okay to do this? Am I missing
something here?
Thoughts?
--
Bharath Rupireddy
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com