Re: Data is copied twice when specifying both child and parent table in publication

On Thu, Oct 21, 2021 at 2:56 PM Peter Smith <smithpb2250@gmail.com> wrote:
>
> I just wanted to bring to your attention an earlier thread [1] in
> which I had already encountered/reported behaviour that is either
> exactly the same or is closely related to what is being discussed in
> this current thread. If it is different please take that into account
> also.
>
> ------
> [1] https://www.postgresql.org/message-id/CAHut%2BPvJMRB-ZyC80we2kiUFv4cVjmA6jxXpEMhm1rmz%3D1ryeA%40mail.gmail.com
>

Thanks, I was able to reproduce that behavior, which is similar (but
in that case the publish_via_partition_root flag is toggled with the
partitioned table present in the publication, whereas in the case
being discussed the presence of the partitioned table in the
publication is toggled with publish_via_partition_root always true).

What seems to happen internally when a partitioned table is published
is that when publish_via_partition_root=true the subscriber to that
publication is effectively subscribed to the parent partitioned table
but not the child partitions. If publish_via_partition_root is changed
to false and the subscriber refreshes, the partitioned table is
unsubscribed and it subscribes to the partitions. This explains why
data gets "re-copied" when this happens, because then it is
subscribing to a "new" table and copy_data=true by default.


Regards,
Greg Nancarrow
Fujitsu Australia