On Wed, Jun 5, 2024 at 3:17 PM Bharath Rupireddy <bharath.rupireddyforpostg...@gmail.com> wrote: > > On Tue, Jun 4, 2024 at 5:40 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > Even if we decode it periodically (say each time we decode the > > checkpoint record) then also we need to send the entire set of > > sequences at shutdown. This is because the sequences may have changed > > from the last time we sent them. > > Agree. How about decoding and sending only the sequences that are > changed from the last time when they were sent? I know it requires a > bit of tracking and more work, but all I'm looking for is to reduce > the amount of work that walsenders need to do during the shutdown. >
I see your point but going towards tracking the changed sequences sounds like moving towards what we do for incremental backups unless we can invent some other smart way. > Having said that, I like the idea of letting the user sync the > sequences via ALTER SUBSCRIPTION command and not weave the logic into > the shutdown checkpoint path. As Peter Eisentraut said here > https://www.postgresql.org/message-id/42e5cb35-4aeb-4f58-8091-90619c7c3ecc%40eisentraut.org, > this can be a good starting point to get going. > Agreed. > > > I can imagine a case where there are tens > > > of thousands of sequences in a production server, and surely decoding > > > and sending them just during the shutdown can take a lot of time > > > hampering the overall server uptime. > > > > It is possible but we will send only the sequences that belong to > > publications for which walsender is supposed to send the required > > data. > > Right, but what if all the publication tables can have tens of > thousands of sequences. > In such cases we have no option but to send all the sequences. > > Now, we can also imagine providing option 2 (Alter Subscription > > ... Replicate Sequences) so that users can replicate sequences before > > shutdown and then disable the subscriptions so that there won't be a > > corresponding walsender. > > As stated above, I like this idea to start with. > +1. -- With Regards, Amit Kapila.
