On Wed, Dec 6, 2023 at 7:20 PM Tomas Vondra <tomas.von...@enterprisedb.com> wrote: > > On 12/6/23 11:19, Amit Kapila wrote: > > On Sun, Dec 3, 2023 at 11:56 PM Tomas Vondra > > <tomas.von...@enterprisedb.com> wrote: > >> > >> On 12/3/23 18:52, Tomas Vondra wrote: > >>> ... > >>> > >> > >> Another idea is that maybe we could somehow inform ReorderBuffer whether > >> the output plugin even is interested in sequences. That'd help with > >> cases where we don't even want/need to replicate sequences, e.g. because > >> the publication does not specify (publish=sequence). > >> > >> What happens now in that case is we call ReorderBufferQueueSequence(), > >> it does the whole dance with starting/aborting the transaction, calls > >> rb->sequence() which just does "meh" and doesn't do anything. Maybe we > >> could just short-circuit this by asking the output plugin somehow. > >> > >> In an extreme case the plugin may not even specify the sequence > >> callbacks, and we're still doing all of this. > >> > > > > We could explore this but I guess it won't solve the problem we are > > facing in cases where all sequences are published and plugin has > > specified the sequence callbacks. I think it would add some overhead > > of this check in positive cases where we decide to anyway do send the > > changes. > > Well, the idea is the check would be very simple (essentially just a > boolean flag somewhere), so not really measurable. > > And if the plugin requests decoding sequences, I guess it's natural it > may have a bit of overhead. It needs to do more things, after all. It > needs to be acceptable, ofc. >
I agree with you that if it can be done cheaply or without a measurable overhead then it would be a good idea and can serve other purposes as well. For example, see discussion [1]. I had more of what the patch in email [1] is doing where it needs to start/stop xact and do so relcache access etc. which seems can add some overhead if done for each change, though I haven't measured so can't be sure. [1] - https://www.postgresql.org/message-id/CAGfChW5Qo2SrjJ7rU9YYtZbRaWv6v-Z8MJn%3DdQNx4uCSqDEOHA%40mail.gmail.com -- With Regards, Amit Kapila.
