bool Item_sum_bit::clear_as_window()
{
  memset(bit_counters, 0, sizeof(bit_counters));
  num_values_added= 0;
  set_bits_from_counters();
  return 0;
}
bool Item_sum_bit::clear_as_window()
{
  memset(bit_counters, 0, sizeof(bit_counters));
  num_values_added= 0;
  set_bits_from_counters();
  return 0;
}