https://endymecy.gitbooks.io/spark-programming-guide-zh-cn/content/programming-guide/rdds/external-datasets.html
http://dataunion.org/20001.html
https://endymecy.gitbooks.io/spark-programming-guide-zh-cn/content/programming-guide/rdds/external-datasets.html
http://dataunion.org/20001.html