Key选择器

方法类型

KeySelector[IN, KEY]
  > getKey(IN): KEY

两个例子

scala version

val sensorData = ...
val byId = sensorData.keyBy(r => r.id)

val input = ...
input.keyBy(value => math.max(value._1, value._2))

java version

DataStream<SensorReading> sensorData = ...
KeyedStream<SensorReading, String> byId = sensorData.keyBy(r -> r.id);

DataStream<Tuple2<Int, Int>> input = ...
input.keyBy(value -> Math.max(value.f0, value.f1));