Apache Flink：我可以获得窗口函数中键字段的名称吗？

Question

我有一个数据流，有不同的字段，我想通过键来进行聚合计算（计数、平均、..)

stream.keyBy("field1").window().aggregate(AggFunc, WindowFunc)...

stream.keyBy("field2").window().aggregate(AggFunc, WindowFunc)...

stream.keyBy("field3").window().aggregate(AggFunc, WindowFunc)...

-字段1上键控的流

("field1", "field1-val1", 3, window1)
("field1", "field1-val2", 5, window1)

-字段2上键控的流

("field2", "field2-val1", 6, window1)
("field2", "field2-val2", 7, window1)

Answer 1

不，windowfunction不允许访问键字段的名称。但是，您可以向windowfunction的构造函数添加一个参数，并在那里传递字段名。

这将与下面的示例类似

// define window function

public static class MyWindowFunc implements WindowFunction<...> { 
    private final String keyname;

    public MyWindowFunc(String keyname) {
        this.keyname = keyname;
    }    

  ...
}

// use window function

stream.keyBy("field1").window().aggregate(AggFunc, new MyWindowFunc("field1"))...
stream.keyBy("field2").window().aggregate(AggFunc, new MyWindowFunc("field2"))...
stream.keyBy("field3").window().aggregate(AggFunc, new MyWindowFunc("field3"))...