Re: BUG #18644: ALTER PUBLICATION ... SET (publish_via_partition_root) wrong/undocumented behavior.

On Fri, Oct 25, 2024 at 2:26 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, Oct 25, 2024 at 6:12 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
> >
> > Hi Kuroda-san,
> >
> > This is only a caution for ALTER of 'publish_via_partition_root', so
> > that should be immediately clear up-front in the first few words of
> > the text.
> >
> > Also, the current explanation appears to give more details about how
> > and why it happens than I felt was necessary. e.g. this is for user
> > documentation, not for a code comment. Basically, I'm wondering if the
> > whole thing could be "dumbed down" a little bit, keeping only the
> > information essential so the users can protect themselves. Maybe
> > something a bit more like below?
> >
> > SUGGESTION
> > <caution>
> > <para>
> > Altering the <literal>publish_via_partition_root</literal> parameter
> > can lead to data loss or duplication at the subscriber because it
> > changes the identity and schema of the published tables.
> > </para>
>
> This appears precise but lacks the key information that the problem
> can happen when a partitioned root table is specified as a replication
> target. So, how about one of the following:
>
> * Altering the <literal>publish_via_partition_root</literal> parameter
> when the partition root table is specified as the replication target
> can lead to data loss or duplication at the subscriber because it
> changes the identity and schema of the published tables.
>
> * Altering the <literal>publish_via_partition_root</literal> parameter
> can lead to data loss or duplication at the subscriber because it
> changes the identity and schema of the published tables. Note this
> happens only when the partition root table is specified as the
> replication target.

+1 for the second one. (but maybe say "a partition root table" instead
of "the partition root table")

>
> > <para>
> > This problem can be avoided by refraining from modifying
> > partition leaf tables
> > after the <command>ALTER PUBLICATION ... SET</command> until the
> > <link linkend="sql-altersubscription"><command>ALTER
> > SUBSCRIPTION ... REFRESH PUBLICATION</command></link>
> > is executed, and by only refreshing using the <literal>copy_data
> > = off</literal> option.
> > </para>
> > </caution>
> >
>
> We can keep this part as you proposed.
>
> --
> With Regards,
> Amit Kapila.