title: Giving input to mappers in MapReduce
body: <p>I was just going through the word count example in MapReduce. The map function is very straightforward. Is there a higher level function that decides what part of the file go to what mapper?
  Suppose you are relying on a function (such as SHA1) that relies on the input of the entire file, is there any to tell the framework not to split files?</p>