static <A extends Concept> MultiSet<S> nuLike distinctCIFieldValuesOfConcepts_multiSet(Class<A> c, S field) {
  ret distinctCIFieldValuesOfConcepts_multiSet(db_mainConcepts(), c, field);
}

static <A extends Concept> MultiSet<S> distinctCIFieldValuesOfConcepts_multiSet(Concepts concepts, Class<A> c, S field) {
  // indexed
  IFieldIndex<A, S> index = concepts.getCIFieldIndex(c, field);
  if (index != null)
    ret index.allValues_multiSet();

  // table scan
  MultiSet<S> set = ciMultiSet();
  for (A x : concepts.list(c)) set.add((S) getOpt(x, field));
  ret set;
}