public void testGroupedReduceWithSelectorFunctionKey() {
try {
ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
env.setDegreeOfParallelism(8);
DataSet<Tuple2<String, Double>> data = env.readCsvFile("file:///will/never/be/read").types(String.class, Double.class)
.name("source").setParallelism(6);
data
.groupBy(new KeySelector<Tuple2<String,Double>, String>() {
public String getKey(Tuple2<String, Double> value) { return value.f0; }