从 Apache Spark SQL split() 函数中获取最后一个元素

问题描述

我想从 Spark SQL split() 函数返回的数组中获取最后一个元素.

I want to get the last element from the Array that return from Spark SQL split() function.

split(4:3-2:3-5:4-6:4-5:2,'-')

我知道它可以通过

split(4:3-2:3-5:4-6:4-5:2,'-')[4]

但是当我不知道 Array 的长度时，我想要另一种方式.请帮帮我.

But i want another way when i don't know the length of the Array .please help me.

推荐答案

您可以使用 UDF 来做到这一点，如下所示:

You could use an UDF to do that, as follow:

val df = sc.parallelize(Seq((1L,"one-last1"), (2L,"two-last2"), (3L,"three-last3"))).toDF("key","Value")
+---+-----------+
|key|Value      |
+---+-----------+
|1  |one-last1  |
|2  |two-last2  |
|3  |three-last3|
+---+-----------+

val get_last = udf((xs: Seq[String]) => Try(xs.last).toOption)

val with_just_last = df.withColumn("Last" , get_last(split(col("Value"), "-")))
+---+-----------+--------+
|key|Value      |Last    |
+---+-----------+--------+
|1  |one-last1  |last1   |
|2  |two-last2  |last2   |
|3  |three-last3|last3   |
+---+-----------+--------+

请记住，SparkSQL 中的 split 函数可以应用于 DataFrame 的列.

Remember that the split function from SparkSQL can be applied to a column of the DataFrame.

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