.. change::
    :tags: bug, orm
    :tickets: 7463

    Fixed performance regression which appeared at least in version 1.3 if not
    earlier (sometime after 1.0) where the loading of deferred columns, those
    explicitly mapped with :func:`_orm.defer` as opposed to non-deferred
    columns that were expired, from a joined inheritance subclass would not use
    the "optimized" query which only queried the immediate table that contains
    the unloaded columns, instead running a full ORM query which would emit a
    JOIN for all base tables, which is not necessary when only loading columns
    from the subclass.

