Why I get type mismatch in scala Spark?

Question

First, I read a text file and turn it into RDD[(String,(String,Float))]:

val data = sc.textFile(dataInputPath);
val dataRDD:RDD[(String,(String,Float))] = data.map{f=> {
      val temp=f.split("//x01");
      (temp(0),(temp(1),temp(2).toInt ) );
      }
    } ;

Then, I run following code to turn my data into Rating type

import org.apache.spark.mllib.recommendation.Rating
val imeiMap = dataRDD.reduceByKey((s1,s2)=>s1).collect().zipWithIndex.toMap;
val docidMap = dataRDD.map( f=>(f._2._1,1)).reduceByKey((s1,s2)=>s1).collect().zipWithIndex.toMap;
val ratings = dataRDD.map{case (imei, (doc_id,rating))=> Rating(imeiMap(imei),docidMap(doc_id),rating)};

But I got an error:

Error:(32, 77) type mismatch;
 found   : String
 required: (String, (String, Float))
    val ratings = dataRDD.map{case (imei, (doc_id,rating))=> Rating(imeiMap(imei),docidMap(doc_id),rating)};

Why this happen? I think that the string have already changed to (String, (String, Float)) .

Answer 1

它与您的dataRDD ，而与imeiMap有关：

imeiMap: scala.collection.immutable.Map[(String, (String, Float)),Int] 

Answer 2

The key of docidMap is not a String, is a Tuple (String, Int)

This is because you have the zipWithIndex before the .toMap method:

With this rdd as input for a quick test:

(String1,( String2,32.0))
(String1,( String2,35.0))



scala> val docidMap = dataRDD.map( f=>(f._2._1,1)).reduceByKey((s1,s2)=>s1).collect().zipWithIndex.toMap;
docidMap: scala.collection.immutable.Map[(String, Int),Int] = Map((" String2",1) -> 0)


val docidMap = dataRDD.map( f=>(f._2._1,1)).reduceByKey((s1,s2)=>s1).collect().toMap;
docidMap: scala.collection.immutable.Map[String,Int] = Map(" String2" -> 1)     

The same will happen with your imeiMap , it seems that you just need to remove the zipWithIndex from there too

val imeiMap = dataRDD.reduceByKey((s1,s2)=>s1).collect.toMap