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

Dear Amit,

Thanks for giving comment. New version will be available in the upcoming post.

> + 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 slot, but
> found \"%s\"",
> + PQgetvalue(res, 0, 0));
> +
> + PQclear(res);
> +
> + nslots = count_logical_slots(&old_cluster);
> +
> + /*
> + * Do additional checks when the logical replication slots have on the old
> + * cluster.
> + */
> + if (nslots)
> 
> Shouldn't these checks be reversed? I mean it would be better to test
> the presence of slots on the new cluster if there is any slot present
> on the old cluster.

Hmm, I think the later part is meaningful only when the old cluster has logical
slots. To sum up, any checking should be done when the
count_logical_slots(&old_cluster) > 0, right? Fixed like that.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED