code: func NewLongFieldDescriptor(nullable NullableColumn) FieldDescriptor {
  	return newFixedLengthFieldDescriptor(
  		mysql_proto.FieldType_LONG,
  		nullable,
  		4,
  		func(b []byte) interface{} { return uint64(LittleEndian.Uint32(b)) })
  }
docs: // This returns a field descriptor for FieldType_LONG (i.e., Field_long)