Spark中的扁平化行

Question

我正在使用 scala 对 spark 进行一些测试。我们通常读取需要操作的json文件，如下例：

test.json:

{"a":1,"b":[2,3]}

val test = sqlContext.read.json("test.json")

如何将其转换为以下格式：

{"a":1,"b":2}
{"a":1,"b":3}

Answer 1

你可以使用explode函数：

scala> import org.apache.spark.sql.functions.explode
import org.apache.spark.sql.functions.explode


scala> val test = sqlContext.read.json(sc.parallelize(Seq("""{"a":1,"b":[2,3]}""")))
test: org.apache.spark.sql.DataFrame = [a: bigint, b: array<bigint>]

scala> test.printSchema
root
 |-- a: long (nullable = true)
 |-- b: array (nullable = true)
 |    |-- element: long (containsNull = true)

scala> val flattened = test.withColumn("b", explode($"b"))
flattened: org.apache.spark.sql.DataFrame = [a: bigint, b: bigint]

scala> flattened.printSchema
root
 |-- a: long (nullable = true)
 |-- b: long (nullable = true)

scala> flattened.show
+---+---+
|  a|  b|
+---+---+
|  1|  2|
|  1|  3|
+---+---+