Schema schema = new Schema("schema", fields);
// Define a FieldSelector to select only columns 1, 4, 6
// 0 is the first column
FieldSelector selector = new FieldSelector(1, 4, 6);
TupleMRBuilder builder = new TupleMRBuilder(conf);
builder.addIntermediateSchema(schema);
builder.setGroupByFields("floatField"); // but we don't care, really
// Define the Input Format and the Output Format!