On Mon, Sep 25, 2023 at 11:43 AM Michael Paquier <mich...@paquier.xyz> wrote: > > On Mon, Sep 25, 2023 at 10:05:41AM +0530, Amit Kapila wrote: > > I also don't think that this patch has to solve the problem of > > publishers in any way but as per my understanding, if due to some > > reason we are not able to do the upgrade of publishers, this can add > > more steps for users than they have to do now for logical replication > > set up after upgrade. This is because now after restoring the > > subscription rel's and origin, as soon as we start replication after > > creating the slots on the publisher, we will never be able to > > guarantee data consistency. So, they need to drop the entire > > subscription setup including truncating the relations, and then set it > > up from scratch which also means they need to somehow remember or take > > a dump of the current subscription setup. According to me, the key > > point is to have a mechanism to set up slots correctly to allow > > replication (or subscriptions) to work after the upgrade. Without > > that, it appears to me that we are restoring a subscription where it > > can start from some random LSN and can easily lead to data consistency > > issues where it can miss some of the updates. > > Sure, that's assuming that the publisher side is upgraded. >
At some point, user needs to upgrade publisher and subscriber could itself have some publications defined which means the downstream subscribers will have the same problem. > FWIW, my > take is that there's room to move forward with this patch anyway in > favor of cases like rollover upgrades to the subscriber. > > > This is the primary reason why I prioritized to work on the publisher > > side before getting this patch done, otherwise, the solution for this > > patch was relatively clear. I am not sure but I guess this could be > > the reason why originally we left it in the current state, otherwise, > > restoring subscription rel's or origin doesn't seem to be too much of > > an additional effort than what we are doing now. > > By "additional effort", you are referring to what the patch is doing, > with the binary dump of pg_subscription_rel, right? > Yes. -- With Regards, Amit Kapila.
