Running two mapper on a input file and a reducer for simple hadoop mapreduce jobs

Question

In a simple MapReduce program, there is one input file, that after splitting each line, it will be mapped. But now I want to read each line and after split, the line, map it two times by different keys. reading one line and two maps (two times using context.write). I read: Running two mapper and two reducer for simple hadoop mapreduce jobs That answered: So just put 2 files into your input directories so that you can get 2 mappers running. Now I should to put two same files?

Answer 1

There's no point to read line in mapper, split it and pass somewhere. Process it immediately:

void map(K key, Text value, Context ctx) {
    String k1 = getKey1(value);
    String k2 = getKey2(value);
    map1(k1, value);
    map2(k2, value);
}

void map1(...) { ... }
void map2(...) { ... }