Question

我正在写一个Scala / spark程序，可以找到员工的最高工资。员工数据在CSV文件中可用，工资列有一个数千个逗号分隔符，并且它有一个$前缀，例如$ 74,628.00。

为了处理这个逗号和美元符号，我在scala中编写了一个解析器函数，它将在＆＃34;，＆＃34;上分割每一行。然后将每列映射到要分配给案例类的各个变量。

我的解析器程序如下所示。在此消除逗号和美元符号我使用replace函数将其替换为空，然后最终将typecase更改为Int。

def ParseEmployee(line: String): Classes.Employee = {
    val fields = line.split(",")
    val Name = fields(0)
    val JOBTITLE = fields(2)
    val DEPARTMENT = fields(3)
    val temp = fields(4)

    temp.replace(",","")//To eliminate the ,
    temp.replace("$","")//To remove the $
    val EMPLOYEEANNUALSALARY = temp.toInt //Type cast the string to Int

    Classes.Employee(Name, JOBTITLE, DEPARTMENT, EMPLOYEEANNUALSALARY)
  }

我的案例类如下所示

case class Employee (Name: String,
                      JOBTITLE: String,
                     DEPARTMENT: String,
                     EMPLOYEEANNUALSALARY: Number,
)

我的spark数据帧sql查询如下所示

val empMaxSalaryValue = sc.sqlContext.sql("Select Max(EMPLOYEEANNUALSALARY) From EMP")
empMaxSalaryValue.show

当我运行此程序时，我得到以下异常

Exception in thread "main" java.lang.UnsupportedOperationException: No Encoder found for Number
- field (class: "java.lang.Number", name: "EMPLOYEEANNUALSALARY")
- root class: "Classes.Employee"
    at org.apache.spark.sql.catalyst.ScalaReflection$.org$apache$spark$sql$catalyst$ScalaReflection$$serializerFor(ScalaReflection.scala:625)
    at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$10.apply(ScalaReflection.scala:619)
    at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$10.apply(ScalaReflection.scala:607)
    at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at scala.collection.TraversableLike$$anonfun$flatMap$1.apply(TraversableLike.scala:241)
    at scala.collection.immutable.List.foreach(List.scala:381)
    at scala.collection.TraversableLike$class.flatMap(TraversableLike.scala:241)
    at scala.collection.immutable.List.flatMap(List.scala:344)
    at org.apache.spark.sql.catalyst.ScalaReflection$.org$apache$spark$sql$catalyst$ScalaReflection$$serializerFor(ScalaReflection.scala:607)
    at org.apache.spark.sql.catalyst.ScalaReflection$.serializerFor(ScalaReflection.scala:438)
    at org.apache.spark.sql.catalyst.encoders.ExpressionEncoder$.apply(ExpressionEncoder.scala:71)
    at org.apache.spark.sql.Encoders$.product(Encoders.scala:275)
    at org.apache.spark.sql.SparkSession.createDataFrame(SparkSession.scala:282)
    at org.apache.spark.sql.SQLContext.createDataFrame(SQLContext.scala:272)
    at CalculateMaximumSalary$.main(CalculateMaximumSalary.scala:27)
    at CalculateMaximumSalary.main(CalculateMaximumSalary.scala)

知道我为什么会收到这个错误吗？我在这里做的错误是什么以及为什么它无法对数字进行类型转换？
有没有更好的方法来解决获得员工最高工资的问题？

Answer 1

Spark SQL仅提供有限数量的Encoders，其目标是具体类。不支持像Number这样的抽象类（可以使用有限的二进制Encoders）。

无论如何转换为Int，只需重新定义该类：

case class Employee (
  Name: String,
  JOBTITLE: String,
  DEPARTMENT: String,
  EMPLOYEEANNUALSALARY: Int
)

Spark错误：线程＆＃34; main＆＃34;中的异常java.lang.UnsupportedOperationException

1 个答案: