和Hadoop交互的四种方法：
1. Native Libraries
2. Hive
3. Pig
4. Cascading
At a high level, people use the native Hadoop libraries to achieve the
greatest performance and have the most fine-grained control. Pig is somewhere
between the very SQL-like, database language provided by Hive and the very
Java-like programming language provided by Cascading. - See more at:
http://blog.gopivotal.com/pivotal/products/hadoop-101-programming-mapreduce-
with-native-libraries-hive-pig-and-cascading#sthash.h7JxtIq3.dpuf
At a high level, people use the native Hadoop libraries to achieve the
greatest performance and have the most fine-grained control. Pig is somewhere
between the very SQL-like, database language provided by Hive and the very
Java-like programming language provided by Cascading.