For automation purposes, I'd like to identify an idempotent pair of command sequences such that I can CREATE SUBSCRIPTION and DROP SUBSCRIPTION without knowing whether a previous attempt to do either operation partly succeeded or not. Specifically, as per Google and the notes in the docs (https://www.postgresql.org/docs/current/logical-replication-subscription.html#LOGICAL-REPLICATION-SUBSCRIPTION-SLOT), sometimes, a simple "DROP REPLICATION" is not enough, and one must do something like this:
ALTER SUBSCRIPTION $SUBSCRIPTION DISABLE; ALTER SUBSCRIPTION $SUBSCRIPTION SET (slot_name = none); DROP SUBSCRIPTION IF EXISTS $SUBSCRIPTION CASCADE;
which of course leaves the slot as the other end, and so when it is to be recreated, "CREATE SUBSCRIPTION" would have to be augmented by "WITH (create_slot=false)".
Let's take it as read that network connectivity between the subscribing end and the publication end is OK. Let's say the DROP sequence looked like this:
try:
DROP SUBSCRIPTION IF EXISTS $SUBSCRIPTION CASCADE;
except e:
# Optionally, check if the exception e relates to a specific set of errors to do with the slot?
ALTER SUBSCRIPTION $SUBSCRIPTION DISABLE; ALTER SUBSCRIPTION $SUBSCRIPTION SET (slot_name = none); DROP SUBSCRIPTION IF EXISTS $SUBSCRIPTION CASCADE;
If the exception path were to be taken, then the next CREATE side would have to look something like this
try:
CREATE SUBSCRIPTION ...
except e:
# Optionally, check if e relates to a pre-existing slot.
CREATE SUBSCRIPTION ... WITH (create_flot=false);
Is that the best that can be done? Is there a better way? I'm happy to use SQL, or PL/SQL as needed.
