Why FoldFunction deprecated?

[tison]

I just write a code snip like

```

.fold(new Tuple2<>("", 0L), new FoldFunction<WikipediaEditEvent, Tuple2<String, Long>>() {

                    @Override

                    public Tuple2<String, Long> fold(Tuple2<String, Long> acc, WikipediaEditEvent event) {

                        acc.f0 = event.getUser();

                        acc.f1 += event.getByteDiff();

                        return acc;

                    }

                });

```

and replace it using `aggregate()`

```

.aggregate(new AggregateFunction<WikipediaEditEvent, Tuple2<String, Long>, Tuple2<String,Long>>() {

                    @Override

                    public Tuple2<String, Long> createAccumulator() {

                        return new Tuple2<>("", 0L);

                    }

                    @Override

                    public Tuple2<String, Long> add(WikipediaEditEvent event, Tuple2<String, Long> acc) {

                        return new Tuple2<>(event.getUser(), acc.f1 + event.getByteDiff());

                    }

                    @Override

                    public Tuple2<String, Long> getResult(Tuple2<String, Long> acc) {

                        return acc;

                    }

                    @Override

                    public Tuple2<String, Long> merge(Tuple2<String, Long> a, Tuple2<String, Long> b) {

                        return new Tuple2<>(a.f0, a.f1 + b.f1);

                    }

                });

```

It seems I have to write much more code using `aggregate()`

Is there something I miss so that write so much code? Or say, maybe `aggregate()` is expressive, but why `fold()` deprecated? Since `fold` is a general concept people can understand.

[Fabian Hueske-2]

Hi,

FoldFunction was deprecated because it doesn't support partial aggregation.
AggregateFunction is much more expressive, however requires a bit more implementation effort.

In favor of a concise API, FoldFunction was deprecated because it doesn't offer more functionality than AggregateFunction.

You can implement your use case also easily using a MapFunction before the window, that maps WikipediaEditEvent to Tuple2<String, Long> and a ReduceFunction in the window that sums the length field.

Best, Fabian

2018-05-04 23:36 GMT+02:00 陈梓立 <[hidden email]>:

I just write a code snip like

```

.fold(new Tuple2<>("", 0L), new FoldFunction<WikipediaEditEvent, Tuple2<String, Long>>() {

                    @Override

                    public Tuple2<String, Long> fold(Tuple2<String, Long> acc, WikipediaEditEvent event) {

                        acc.f0 = event.getUser();

                        acc.f1 += event.getByteDiff();

                        return acc;

                    }

                });

```

and replace it using `aggregate()`

```

.aggregate(new AggregateFunction<WikipediaEditEvent, Tuple2<String, Long>, Tuple2<String,Long>>() {

                    @Override

                    public Tuple2<String, Long> createAccumulator() {

                        return new Tuple2<>("", 0L);

                    }

                    @Override

                    public Tuple2<String, Long> add(WikipediaEditEvent event, Tuple2<String, Long> acc) {

                        return new Tuple2<>(event.getUser(), acc.f1 + event.getByteDiff());

                    }

                    @Override

                    public Tuple2<String, Long> getResult(Tuple2<String, Long> acc) {

                        return acc;

                    }

                    @Override

                    public Tuple2<String, Long> merge(Tuple2<String, Long> a, Tuple2<String, Long> b) {

                        return new Tuple2<>(a.f0, a.f1 + b.f1);

                    }

                });

```

It seems I have to write much more code using `aggregate()`

Is there something I miss so that write so much code? Or say, maybe `aggregate()` is expressive, but why `fold()` deprecated? Since `fold` is a general concept people can understand.