I am writing a article about PostgreSQL 11 features. Now I am looking on new option --create-slot option of pg_basebackup command.
I don't understand to use case for this option, because It fails when requested slot already exists. I cannot to imagine use case for this. If I write some scripts, then I prefer the behave like "create if doesn't exist or do nothing".
Any repeated running of script with this option should to fail. Is it required? Why?
The slot is intended to then be used by a replica that was created by pg_basebackup. I think it writes the slot name into recovery.conf; if it doesn't, it should.
So you use a unique slot name for each replica.
I understand so slot should be unique. But same result (unique rep slot) can be done, if it does nothing when slot exists already. This behave is not idempotent.
Maybe I am search problem, where it is not. Just, when I see some "create object" option, I expect any way, how I can enforce "--if-exists", because it was necessary in major cases.