Flink Interval Join 实现左外连接

Flink 的 interval join 操作可以实现左外连接，可以使用一个自定义函数实现。下面是一个示例代码：

val leftDataStream: DataStream[(String, Int)] = ...
val rightDataStream: DataStream[(String, Double)] = ...

val joinedStream = leftDataStream
  .intervalJoin(rightDataStream)
  .between(Time.seconds(-10), Time.seconds(10))
  .process(new MyJoinFunction())

class MyJoinFunction extends ProcessJoinFunction[(String, Int), (String, Double), (String, Int, Double)] {
  override def processElement(left: (String, Int), right: (String, Double), ctx: ProcessJoinFunction[(String, Int), (String, Double), (String, Int, Double)]#Context, out: Collector[(String, Int, Double)]): Unit = {
    if (right != null) {
      out.collect((left._1, left._2, right._2))
    } else {
      out.collect((left._1, left._2, 0.0))
    }
  }
}

在上面的代码中，我们使用了一个ProcessJoinFunction来处理 join 操作。如果右侧数据流中没有匹配到相应的记录，我们将其值设为 0.0，并将其作为左外连接的结果输出。