@HiveDecimalVersionV2
  public String toFormatString(int formatScale, byte[] scratchBuffer) {
    return
        fastToFormatString(
            formatScale,
            scratchBuffer);
  }
Return a string representation of the decimal using the specified scale.
<p>
This method is designed to ALWAYS SUCCEED (unless the newScale parameter is out of range).
<p>
Is does the equivalent of a setScale(int newScale).  So, more than 38 digits may be returned.
See that method for more details on how this can happen.
<p>
@param formatScale The number of digits after the decimal point
@return The scaled decimal representation string representation.
storage-api/src/java/org/apache/hadoop/hive/common/type/HiveDecimal.java