def each_prefixed_term prefix
    term = @xapian._dangerous_allterms_begin prefix
    lastTerm = @xapian._dangerous_allterms_end prefix
    until term.equals lastTerm
      yield term.term
      term.next
    end
    nil
  end
def each_prefixed_term prefix
    term = @xapian._dangerous_allterms_begin prefix
    lastTerm = @xapian._dangerous_allterms_end prefix
    until term.equals lastTerm
      yield term.term
      term.next
    end
    nil
  end
Yields each term in the index that starts with prefix