On Mon, Jan 25, 2021 at 3:38 PM Bharath Rupireddy <bharath.rupireddyforpostg...@gmail.com> wrote: > > On Mon, Jan 25, 2021 at 3:07 PM Dilip Kumar <dilipbal...@gmail.com> wrote: > > > > So basically, the create subscription will throw an error if the > > > > publication does not exist. So will you throw an error if we try to > > > > drop the publication which is subscribed by some subscription? I mean > > > > basically, you are creating a dependency that if you are creating a > > > > subscription then there must be a publication that is not completely > > > > insane but then we will have to disallow dropping the publication as > > > > well. Am I missing something? > > > > > > Do you mean DROP PUBLICATION non_existent_publication;? > > > > > > Or > > > > > > Do you mean when we drop publications from a subscription? > > > > I mean it doesn’t seem right to disallow to create the subscription if > > the publisher doesn't exist, and my reasoning was even though the > > publisher exists while creating the subscription you might drop it > > later right?. So basically, now also we can create the same scenario > > that a subscription may exist for the publication which does not > > exist. > > Yes, the above scenario can be created even now. If a publication is > dropped in the publisher system, then it will not replicate/publish > the changes for that publication (publication_invalidation_cb, > rel_sync_cache_publication_cb, LoadPublications in > get_rel_sync_entry), so subscriber doesn't receive them. But the > subscription can still contain that dropped publication in it's list > of publications. > > The patch proposed in this thread, just checks while creation/altering > of the subscription on the subscriber system whether or not the > publication exists on the publisher system. This is one way > dependency. But given the above scenario, there can exist another > dependency i.e. publisher dropping the publisher at any time. So to > make it a complete solution i.e. not allowing non-existent > publications from the list of publications in the subscription, we > need to detect when the publications are dropped in the publisher and > we should, may be on a next connection to the subscriber, also look at > the subscription for that dropped publication, if exists remove it. > But that's an overkill and impractical I feel. Thoughts? > > I also feel the best way to remove the confusion is to document why we > allow creating subscriptions even when the specified publications > don't exist on the publisher system? Thoughts?
Yes, that was my point that there is no point in solving it in some cases and it can exist in other cases. So I am fine with documenting the behavior. -- Regards, Dilip Kumar EnterpriseDB: http://www.enterprisedb.com
