DataFrame and DataSet - converting values to <k,v> pair - apache-spark

Question

Sample Input (black coloured text) and Output (red coloured text)
I have a DataFrame (one in black), how can I transform it to one like in red?
(column number, value)
[Image is attached]
val df = spark.read.format("csv").option("inferSchema", "true").option("header", "true").load("file:/home/hduser/Desktop/Demo.csv")
case class Employee(EmpId: String, Experience: Double, Salary: Double)
val ds = df.as[Employee]
I need the solution in both DataFrame and DataSet way.
Thank you in advance! :-)

Answer 1

I believe it's a structure you want when you say pair. check if below code gives your expected output.
With DataFrame:
import spark.sqlContext.implicits._
import org.apache.spark.sql.functions._
val data = Seq(("111",5,50000),("222",6,60000),("333",7,60000))
val df = data.toDF("EmpId","Experience","Salary")
val newdf = df.withColumn("EmpId", struct(lit("1").as("key"),col("EmpId").as("value")))
.withColumn("Experience", struct(lit("2").as("key"),col("Experience").as("value")))
.withColumn("Salary", struct(lit("3").as("key"),col("Salary").as("value")))
.show(false)
output:
+--------+----------+----------+
|EmpId |Experience|Salary |
+--------+----------+----------+
|[1, 111]|[2, 5] |[3, 50000]|
|[1, 222]|[2, 6] |[3, 60000]|
|[1, 333]|[2, 7] |[3, 60000]|
+--------+----------+----------+
With Dataset:
First you need to define case class for new structure otherwise you can't create a dataset
case class Employee2(EmpId: EmpData, Experience: EmpData, Salary: EmpData)
case class EmpData(key: String,value:String)
val ds = df.as[Employee]
val newDS = ds.map(rec=>{
(EmpData("1",rec.EmpId), EmpData("2",rec.Experience.toString),EmpData("3",rec.Salary.toString))
})
val finalDS = newDS.toDF("EmpId","Experience","Salary").as[Employee2]
finalDS.show(false)
Output:
+--------+--------+------------+
|EmpId |Experience|Salary |
+--------+--------+------------+
|[1, 111]|[2, 5] |[3, 50000] |
|[1, 222]|[2, 6] |[3, 60000] |
|[1, 333]|[2, 7] |[3, 60000] |
+--------+--------+------------+
Thanks