Hi Justin, thanks for your anwer! My question is not so much about "can i drop a certain replication slot", more about "does this publication still have any replication slots?". Or, if you will: "what's the publication for this replication slot?".
I've double checked the views that you suggested, and I found that I can relate the WAL sender processes to replication slots through pg_replication_slots.active_pid . I've also looked into replication origins. But I can't find a link to the publication. And that's what I need to know. Cheers, Willy-Bas On Sun, Apr 6, 2025 at 3:36 PM Justin <zzzzz.g...@gmail.com> wrote: > On Fri, Apr 4, 2025 at 4:58 AM Willy-Bas Loos <willy...@gmail.com> wrote: > >> Hi! >> >> I'm looking for a way to find out if there are still replication slots >> active for a publication before dropping the publication in an automated >> way. The idea is that the publication is thought not to be needed any >> longer, but we want to make sure. >> >> I'm having trouble finding a link between a publication, the >> subscriptions and the replication slots. Especially when you don't want to >> make assumptions about any subscriber nodes, so you are restricted to the >> publisher node. >> >> The best I could find was a query listed in pg_stat_activity that lists >> the slot name and the publication name: >> START_REPLICATION SLOT "my_slot" LOGICAL 5DD1/3E56D360 (proto_version >> '1', publication_names '"my_publication"') >> >> I don't like the idea of using string manipulation on such query strings >> to get the information I need. Postgres must have a way to compose this >> query. >> Can anyone tell me a way to find replication slots that belong to a >> publication? >> >> -- >> Willy-Bas Loos >> > > Hi Willy-Bas, > > Logical replication slots appear in the views pg_stat_replication and > pg_replication_slots. Both views have the information you are looking for, > the difference is pg_stat_replication shows only the active slots. Keep in > mind Temporary Slots only live for the length of the session that created > it; the slot will appear in both views. > > The bigger issue I think you are trying to address is when can a slot be > dropped safely. Once a logical replication slot is dropped there is no > recovery of the slot's lsn position. Probably the best way to decide if a > slot has been abandoned is how far behind it is. The pg_wal_lsn_diff can > be used to figure out how far behind a slot is > > https://www.postgresql.org/docs/13/view-pg-replication-slots.html > > https://www.postgresql.org/docs/13/monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-VIEW > > > https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-ADMIN-BACKUP > > Hope this answers your question > > > Justin > -- Willy-Bas Loos
