public int compareTo(BoundarySpec other) {
      int c = direction.compareTo(other.getDirection());
      if (c != 0) {
        return c;
      }

      // Valid range is "range/rows between 10 preceding and 2 preceding" for preceding case
      return this.direction == Direction.PRECEDING ? other.amt - amt : amt - other.amt;
    }
Returns true for bounded non-current frames.
@return
ql/src/java/org/apache/hadoop/hive/ql/parse/WindowingSpec.java