code: func NewLongLongFieldDescriptor(nullable NullableColumn) FieldDescriptor {
  	return newFixedLengthFieldDescriptor(
  		mysql_proto.FieldType_LONGLONG,
  		nullable,
  		8,
  		func(b []byte) interface{} { return LittleEndian.Uint64(b) })
  }
docs: // This returns a field descriptor for FieldType_LONGLONG (i.e., Field_longlong)