if g has an in predicate and joining to a non-constant s or o, do not count extra cardinality for the different gs in the list.  Assume 1 value just like for g = const.  else will have exponential error and will end up preferring cartesian products and other nonsense to the right plan
when placing a dfe record all the setps (oby,gby) between the use of the value and its computation.  The dfe is added as a gby/oby dependent.  when placing predicates that are imported into a dt and these contain subqs e.g. col = scalar subq where the scalar subq is independent of the dt being placed, then disable subq caching.  If kept caching on but placed the subq before the dt the subq would be generated twice because renamed once when importing into the dt