Need to make sure the sub-object indexes are cleaned up as well, though
the forgetting of the objects by the base table's index will have released
the elements.  This makes sure that the stale keys are removed from the
sub-object tables, if present.  Sure it slows things down a bit, but I want
the memory to be *clean* after a forget.

Hmmm.  I need a new signature for forget().  I only want to forget sub-objects
for deletions, not updates.
There.  That should do it.  Now to get a clean build.  The code, she be written.