我从这里看到了这段漂亮的代码，我把它贴在下面：

import org.apache.spark.sql.{DataFrame, SparkSession}
import org.apache.spark.sql.functions._
import org.apache.spark.sql.types._
import scala.annotation.tailrec
import scala.util.Try

implicit class DFHelpers(df: DataFrame) {
    def columns = {
      val dfColumns = df.columns.map(_.toLowerCase)
      df.schema.fields.flatMap { data =>
        data match {
          case column if column.dataType.isInstanceOf[StructType] => {
            column.dataType.asInstanceOf[StructType].fields.map { field =>
              val columnName = column.name
              val fieldName = field.name
              col(s"${columnName}.${fieldName}").as(s"${columnName}_${fieldName}")
            }.toList
          }
          case column => List(col(s"${column.name}"))
        }
      }
    }

    def flatten: DataFrame = {
      val empty = df.schema.filter(_.dataType.isInstanceOf[StructType]).isEmpty
      empty match {
        case false =>
          df.select(columns: _*).flatten
        case _ => df
      }
    }
    def explodeColumns = {
      @tailrec
      def columns(cdf: DataFrame):DataFrame = cdf.schema.fields.filter(_.dataType.typeName == "array") match {
        case c if !c.isEmpty => columns(c.foldLeft(cdf)((dfa,field) => {
          dfa.withColumn(field.name,explode_outer(col(s"${field.name}"))).flatten
        }))
        case _ => cdf
      }
      columns(df.flatten)
    }
}

// Exiting paste mode, now interpreting.

import org.apache.spark.sql.{DataFrame, SparkSession}
import org.apache.spark.sql.functions._
import org.apache.spark.sql.types._
import scala.annotation.tailrec
import scala.util.Try
defined class DFHelpers

但是，除了一个特定的列之外，有没有一种方法可以展平所有的内容（代码是这样做的）？例如，如果我有：

scala> df.printSchema
root
 |-- stackoverflow: array (nullable = true)
 |    |-- element: struct (containsNull = true)
 |    |    |-- tag: struct (nullable = true)
 |    |    |    |-- author: string (nullable = true)
 |    |    |    |-- frameworks: array (nullable = true)
 |    |    |    |    |-- element: struct (containsNull = true)
 |    |    |    |    |    |-- id: long (nullable = true)
 |    |    |    |    |    |-- name: string (nullable = true)
 |    |    |    |-- id: long (nullable = true)
 |    |    |    |-- name: string (nullable = true)
 |-- category: array (nullable = true)

除了“类别”之外，有没有办法把所有的东西（它已经做到了）都扁平化？