对于复杂的数据类型，比如IP和GeoPoint，只是在elasticsearch中有效，用spark读取时会转换成常用的String类型。
Geo types. It is worth mentioning that rich data types available only in Elasticsearch, such asGeoPoint or GeoShape are supported by converting their structure into the primitives available in the table above. For example, based on its storage a geo_point might be returned as a String or aTraversable.