CODEWITHSUNDEEP
listscaladataframeapache-sparkscala-collections
user2538559
user2538559

Reputation: 59

Spark dataframe value to Scala List

I have a dataframe with a column having Array:

+----------------------------+
|User    | Color             |
+----------------------------+
|User1   | [Green,Blue,Red]  |
|User2   | [Blue,Red]        |
+----------------------------+

I am trying to filter for User1 and get the list of colors into a Scala List:

val colorsList: List[String] = List("Green","Blue","Red")

Here's what I have tried so far (output is added as comments):

Attempt 1:

val dfTest1 = myDataframe.where("User=='User1'").select("Color").rdd.map(r => r(0)).collect()
println(dfTest1)  //[Ljava.lang.Object;@44022255
for(EachColor<- dfTest1){
  println(EachColor)    //WrappedArray(Green, Blue, Red)
}

Attempt 2:

val dfTest2 = myDataframe.where("User=='User1'").select("Color").collectAsList.get(0).getList(0)
println(dfTest2)  //[Green, Blue, Red]   but type is util.List[Nothing]

Attempt 3:

val dfTest32 = myDataframe.where("User=='User1'").select("Color").rdd.map(r => r(0)).collect.toList 
println(dfTest32)   //List(WrappedArray(Green, Blue, Red))

for(EachColor <- dfTest32){
  println(EachColor) //WrappedArray(Green, Blue, Red)
}

Attempt 4:

val dfTest31 = myDataframe.where("User=='User1'").select("Color").map(r => r.getString(0)).collect.toList    
//Exception : scala.collection.mutable.WrappedArray$ofRef cannot be cast to java.lang.String

Upvotes: 2

Views: 437

Answers (1)

mck
mck

Reputation: 42352

You can try getting as Seq[String] and converting toList:

val colorsList = df.where("User=='User1'")
                   .select("Color")
                   .rdd.map(r => r.getAs[Seq[String]](0))
                   .collect()(0)
                   .toList

Or equivalently

val colorsList = df.where("User=='User1'")
                   .select("Color")
                   .collect()(0)
                   .getAs[Seq[String]](0)
                   .toList

Upvotes: 2

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