- The "wildcard" loader options, in particular the one set up by

- The "wildcard" loader options, in particular the one set up by
the :func:`.orm.load_only` option to cover all attributes not
explicitly mentioned, now takes into account the superclasses
of a given entity, if that entity is mapped with inheritance mapping,
so that attribute names within the superclasses are also omitted
from the load.  Additionally, the polymorphic discriminator column
is unconditionally included in the list, just in the same way that
primary key columns are, so that even with load_only() set up,
polymorphic loading of subtypes continues to function correctly.
fixes #3287

(cherry picked from commit b63aae2c232f980a47aa2a635c35dfa45390f451)

Conflicts:
	lib/sqlalchemy/orm/mapper.py