Re: Logical Replication - behavior of ALTER PUBLICATION .. DROP TABLE and ALTER SUBSCRIPTION .. REFRESH PUBLICATION

On Tue, 12 Jan 2021 at 13:39, Amit Kapila wrote:
> On Tue, Jan 12, 2021 at 9:58 AM japin <japinli@hotmail.com> wrote:
>>
>>
>> On Tue, 12 Jan 2021 at 11:37, Amit Kapila wrote:
>> > On Mon, Jan 11, 2021 at 6:51 PM Bharath Rupireddy
>> > <bharath.rupireddyforpostgres@gmail.com> wrote:
>> >>
>> >> Hi,
>> >>
>> >> While providing thoughts on the design in [1], I found a strange
>> >> behaviour with the $subject. The use case is shown below as a sequence
>> >> of steps that need to be run on publisher and subscriber to arrive at
>> >> the strange behaviour.  In step 5, the table is dropped from the
>> >> publication and in step 6, the refresh publication is run on the
>> >> subscriber, from here onwards, the expectation is that no further
>> >> inserts into the publisher table have to be replicated on to the
>> >> subscriber, but the opposite happens i.e. the inserts are still
>> >> replicated to the subscriber. ISTM as a bug. Let me know if I'm
>> >> missing anything.
>> >>
>> >
>> > Did you try to investigate what's going on? Can you please check what
>> > is the behavior if, after step-5, you restart the subscriber and
>> > separately try creating a new subscription (maybe on a different
>> > server) for that publication after step-5 and see if that allows the
>> > relation to be replicated? AFAIU, in AlterSubscription_refresh, we
>> > remove such dropped rels and stop their corresponding apply workers
>> > which should stop the further replication of such relations but that
>> > doesn't seem to be happening in your case.
>>
>> If we restart the subscriber after step-5, it will not replicate the records.
>>
>> As I said in [1], if we don't insert a new data in step-5, it will not
>> replicate the records.
>>
>
> Hmm, but in Bharath's test, it is replicating the Inserts in step-7
> and step-9 as well. Are you seeing something different?
>

Yes, however if we don't Inserts in step-5, the Inserts in step-7 and
step-9 will not replicate.


-- 
Regrads,
Japin Li.
ChengDu WenWu Information Technology Co.,Ltd.