title: Hadoop: can you use a pair of values as "Key"?
body: <p>I am trying to analyze a big crimes statistics data set, the file is about 2 GB in CSV format. There are about 20 columns, but I am interested in only a subset of it: Crime_Type and Crime_in_Year. For example, the crime type "burglary", it happens from 2001 through 2013, every year. I want to have a result that counts the occurrences of burglary in each year. </p>
  
  <p>So I am thinking of having a key , and the value will be the sum of its occurrence in year 2003. Is it possible to have a pair of value as key in hadoop/mapreduce?</p>