mikeholler commented on a change in pull request #7897: [FLINK-11817] Uses
aggregate function in DataStream API Tutorial
URL: https://github.com/apache/flink/pull/7897#discussion_r262546713
##########
File path: docs/tutorials/datastream_api.md
##########
@@ -240,13 +255,28 @@ public class WikipediaAnalysis {
DataStream<Tuple2<String, Long>> result = keyedEdits
.timeWindow(Time.seconds(5))
- .fold(new Tuple2<>("", 0L), new FoldFunction<WikipediaEditEvent,
Tuple2<String, Long>>() {
+ .aggregate(new AggregateFunction<WikipediaEditEvent, Tuple2<String,
Long>, 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;
- }
+ public Tuple2<String, Long> createAccumulator() {
+ return new Tuple2<>("", 0L);
+ }
+
+ @Override
+ public Tuple2<String, Long> add(WikipediaEditEvent value,
Tuple2<String, Long> accumulator) {
+ accumulator.f0 = value.getUser();
+ accumulator.f1 += value.getByteDiff();
+ return accumulator;
+ }
+
+ @Override
+ public Tuple2<String, Long> getResult(Tuple2<String, Long> accumulator)
{
+ return accumulator;
+ }
+
+ @Override
+ public Tuple2<String, Long> merge(Tuple2<String, Long> a,
Tuple2<String, Long> b) {
Review comment:
Why isn't `b` used here?
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