Re: pg_basebackup --create-slot-if-not-exists?

On Wednesday, September 21, 2022, Ashwin Agrawal <ashwinstar(at)gmail(dot)com>
wrote:

> Currently, pg_basebackup has
> --create-slot option to create slot if not already exists or
> --slot to use existing slot
>
> Which means it needs knowledge on if the slot with the given name already
> exists or not before invoking the command. If pg_basebackup --create-slot
> <> command fails for some reason after creating the slot. Re-triggering the
> same command fails with ERROR slot already exists. Either then need to
> delete the slot and retrigger Or need to add a check before retriggering
> the command to check if the slot exists and based on the same alter the
> command to avoid passing --create-slot option. This poses
> inconvenience while automating on top of pg_basebackup. As checking for
> slot presence before invoking pg_basebackup unnecessarily involves issuing
> separate SQL commands. Would be really helpful for such scenarios if
> similar to CREATE TABLE, pg_basebackup can have IF NOT EXISTS kind of
> semantic. (Seems the limitation most likely is coming from CREATE
> REPLICATION SLOT protocol itself), Thoughts?
>

What’s the use case for automating pg_basebackup with a named replication
slot created by the pg_basebackup command? Why can you not leverage a
temporary replication slot (i.e., omit —slot). ISTM the create option is
basically obsolete now.

David J.