Re: [PoC] pg_upgrade: allow to upgrade publisher node

On Thu, Aug 31, 2023 at 7:56 PM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:

> Thanks for giving comments!

Thanks

> > Some comments in 0002
> >
> > 1.
> > + res = executeQueryOrDie(conn, "SELECT slot_name "
> > + "FROM pg_catalog.pg_replication_slots "
> > + "WHERE slot_type = 'logical' AND "
> > + "temporary IS FALSE;");
> >
> > What is the reason we are ignoring temporary slots here? I think we
> > better explain in the comments.
>
> The temporary slots were expressly ignored while checking because such slots
> cannot exist after the upgrade. Before doing pg_upgrade, both old and new cluster
> must be turned off, and they start/stop several times during the upgrade.
>
> How do you think?

LGTM

>
> > 2.
> > + res = executeQueryOrDie(conn, "SELECT slot_name "
> > + "FROM pg_catalog.pg_replication_slots "
> > + "WHERE slot_type = 'logical' AND "
> > + "temporary IS FALSE;");
> > +
> > + if (PQntuples(res))
> > + pg_fatal("New cluster must not have logical replication slots but
> > found \"%s\"",
> > + PQgetvalue(res, 0, 0));
> >
> > It looks a bit odd to me that first it is fetching all the logical
> > slots from the new cluster and then printing the name of one of the
> > slots. If it is printing the name of the slots then shouldn't it be
> > printing all the slots' names or it should just say that there
> > existing slots on the new cluster without giving any names? And if we
> > are planning for option 2 i.e. not printing the name then better to
> > put LIMIT 1 at the end of the query.
>
> I'm planning to change that the number of slots are reported by using count(*).

Yeah, that seems a better option.

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com