我正在尝试学习 Spark 中的数据集.我想不通的一件事是如何显示 KeyValueGroupedDataset，因为 show 对它不起作用.另外，KeyValuGroupedDataSet 的 map 等价物是什么?如果有人举一些例子，我将不胜感激.

I am trying to learn datasets in Spark. One thing I can't figure out is how to display a KeyValueGroupedDataset, as show doesn't work for it. Also, what is the equivalent of a map for KeyValuGroupedDataSet? I will appreciate if someone give some examples.

推荐答案

好的，我从给出的示例中得到了这个想法 这里 和 这里.我在下面给出一个我写的简单例子.

OK, I got the idea from examples given here and here. I am giving below a simple example that I've written.

val x = Seq(("a", 36), ("b", 33), ("c", 40), ("a", 38), ("c", 39)).toDS
x: org.apache.spark.sql.Dataset[(String, Int)] = [_1: string, _2: int]

val g = x.groupByKey(_._1)
g: org.apache.spark.sql.KeyValueGroupedDataset[String,(String, Int)] = ...

val z = g.mapGroups{case(k, iter) => (k, iter.map(x => x._2).toArray)}
z: org.apache.spark.sql.Dataset[(String, Array[Int])] = [_1: string, _2: array<int>]

z.show
+---+--------+
| _1|      _2|
+---+--------+
|  c|[40, 39]|
|  b|    [33]|
|  a|[36, 38]|
+---+--------+