RE: Initial Schema Sync for Logical Replication

> From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> On Wed, Jul 5, 2023 at 7:45 AM Masahiko Sawada
> <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Mon, Jun 19, 2023 at 5:29 PM Peter Smith <smithpb2250(at)gmail(dot)com>
> wrote:
> > >
> > > Hi,
> > >
> > > Below are my review comments for the PoC patch 0001.
> > >
> > > In addition, the patch needed rebasing, and, after I rebased it
> > > locally in my private environment there were still test failures:
> > > a) The 'make check' tests fail but only in a minor way due to
> > > changes colname
> > > b) the subscription TAP test did not work at all for me -- many errors.
> >
> > Thank you for reviewing the patch.
> >
> > While updating the patch, I realized that the current approach won't
> > work well or at least has the problem with partition tables. If a
> > publication has a partitioned table with publish_via_root = false, the
> > subscriber launches tablesync workers for its partitions so that each
> > tablesync worker copies data of each partition. Similarly, if it has a
> > partition table with publish_via_root = true, the subscriber launches
> > a tablesync worker for the parent table. With the current design,
> > since the tablesync worker is responsible for both schema and data
> > synchronization for the target table, it won't be possible to
> > synchronize both the parent table's schema and partitions' schema.
> >
>
> I think one possibility to make this design work is that when publish_via_root
> is false, then we assume that subscriber already has parent table and then
> the individual tablesync workers can sync the schema of partitions and their
> data.

Since publish_via_partition_root is false by default users have to create parent table by themselves
which I think is not a good user experience.

> And when publish_via_root is true, then the table sync worker is
> responsible to sync parent and child tables along with data. Do you think
> such a mechanism can address the partition table related cases?
>