On Sun, Jan 24, 2021 at 5:54 PM Peter Smith <smithpb2...@gmail.com> wrote: > > 4. > > - /* > > - * To build a slot name for the sync work, we are limited to NAMEDATALEN - > > - * 1 characters. We cut the original slot name to NAMEDATALEN - 28 chars > > - * and append _%u_sync_%u (1 + 10 + 6 + 10 + '\0'). (It's actually the > > - * NAMEDATALEN on the remote that matters, but this scheme will also work > > - * reasonably if that is different.) > > - */ > > - StaticAssertStmt(NAMEDATALEN >= 32, "NAMEDATALEN too small"); /* for > > sanity */ > > - slotname = psprintf("%.*s_%u_sync_%u", > > - NAMEDATALEN - 28, > > - MySubscription->slotname, > > - MySubscription->oid, > > - MyLogicalRepWorker->relid); > > + /* Calculate the name of the tablesync slot. */ > > + slotname = ReplicationSlotNameForTablesync( > > + MySubscription->oid, > > + MyLogicalRepWorker->relid); > > > > What is the reason for changing the slot name calculation? If there is > > any particular reasons, then we can add a comment to indicate why we > > can't include the subscription's slotname in this calculation. > > > > The subscription slot name may be changed (e.g. ALTER SUBSCRIPTION) > and so including the subscription slot name as part of the tablesync > slot name was considered to be: > a) possibly risky/undefined, if the subscription slot_name = NONE > b) confusing, if we end up using 2 different slot names for the same > tablesync (e.g. if the subscription slot name is changed before a sync > worker is re-launched). > And since this subscription slot name part is not necessary for > uniqueness anyway, it was removed from the tablesync slot name to > eliminate those concerns. > > Also, the tablesync slot name calculation was encapsulated as a > separate function because previously (i.e. before v18) it was used by > various other cleanup codes. I still like it better as a function, but > now it is only called from one place so we could put that code back > inline if you prefer it how it was..
It turns out those (a/b) concerns I wrote above are maybe unfounded, because it seems not possible to alter the slot_name = NONE unless the subscription is first DISABLED. So probably I can revert all this tablesync slot name calculation back to how it originally was in the OSS HEAD if you want. ---- Kind Regards, Peter Smith. Fujitsu Australia