Re: Planning incompatibilities for Postgres 10.0

The assumption that we ought to plan expressly for an incompatibility that
essentially discards pg_upgrade seems premature, particularly in advance of
would-be solutions that, in some cases, mightn't actually work.

If pg_upgrade doesn't work, then, at present, the plausible solutions are
to either dump and restore, which might take way too long, or use one of
the logical replication systems (e.g. - Slony, Londiste, or similar, in the
absence of the would-be built-in logical replication).

Unfortunately, there are significant scenarios where none of these work,
particularly for data warehouse-like systems where the database size is so
large that the users cannot afford the disk space to construct a replica.
It sure seems premature to intentionally leave that set of users out in the
cold.