/** @return number of bytes per term, based on the NumericValue.requiredBits() */
 @Override
 public long bytesPerValue(BytesRef term) {
   // Estimate about  about 0.8 (8 / 10) compression ratio for
   // numbers, but at least 4 bytes
   return Math.max(type.requiredBits() / 10, 4);
 }