Alvaro Herrera <alvhe...@2ndquadrant.com> writes: > Andres Freund wrote: >> I think we should constrain the API to only allow later LSNs than >> currently in the slot, rather than arbitrary ones. That's why I was >> thinking of "forward". I'm not convinced it's a good / safe idea to >> allow arbitrary values to be set.
> Hmm. In terms of safety, it is safe to move the LSN backwards, as long > as the oldest LSN across all slots is not changed -- in other words, the > actual safe limit is the oldest of all slot LSNs, rather than the > current position of the slot being manipulated (which is what you're > saying). True, but you'd need to take some kind of global lock to verify that, whereas "move forward only" would only need to examine/change the one slot. regards, tom lane -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers