Java.lang.IllegalArgumentException: requirement failed: Columns not found in Double

问题

I am working in spark I have many csv files that contain lines, a line looks like that:

2017,16,16,51,1,1,4,-79.6,-101.90,-98.900

It can contain more or less fields, depends on the csv file

Each file corresponds to a cassandra table, where I need to insert all the lines the file contains so what I basically do is get the line, split its elements and put them in a List[Double]

sc.stop
import com.datastax.spark.connector._, org.apache.spark.SparkContext, org.apache.spark.SparkContext._, org.apache.spark.SparkConf


val conf = new SparkConf(true).set("spark.cassandra.connection.host", "localhost")
val sc = new SparkContext(conf)
val nameTable = "artport"
val ligne = "20171,16,165481,51,1,1,4,-79.6000,-101.7000,-98.9000"
val linetoinsert : List[String] = ligne.split(",").toList
var ainserer : Array[Double] = new Array[Double](linetoinsert.length)
for (l <- 0 to linetoinsert.length)yield {ainserer(l) = linetoinsert(l).toDouble}
val liste = ainserer.toList
val rdd = sc.parallelize(liste)
rdd.saveToCassandra("db", nameTable) //db is the name of my keyspace in cassandra

When I run my code I get this error

java.lang.IllegalArgumentException: requirement failed: Columns not found in Double: [collecttime, sbnid, enodebid, rackid, shelfid, slotid, channelid, c373910000, c373910001, c373910002]
  at scala.Predef$.require(Predef.scala:224)
  at com.datastax.spark.connector.mapper.DefaultColumnMapper.columnMapForWriting(DefaultColumnMapper.scala:108)
  at com.datastax.spark.connector.writer.MappedToGettableDataConverter$$anon$1.<init>(MappedToGettableDataConverter.scala:37)
  at com.datastax.spark.connector.writer.MappedToGettableDataConverter$.apply(MappedToGettableDataConverter.scala:28)
  at com.datastax.spark.connector.writer.DefaultRowWriter.<init>(DefaultRowWriter.scala:17)
  at com.datastax.spark.connector.writer.DefaultRowWriter$$anon$1.rowWriter(DefaultRowWriter.scala:31)
  at com.datastax.spark.connector.writer.DefaultRowWriter$$anon$1.rowWriter(DefaultRowWriter.scala:29)
  at com.datastax.spark.connector.writer.TableWriter$.apply(TableWriter.scala:382)
  at com.datastax.spark.connector.RDDFunctions.saveToCassandra(RDDFunctions.scala:35)
  ... 60 elided

I figured out that the insertion works if my RDD was of type :

rdd: org.apache.spark.rdd.RDD[(Double, Double, Double, Double, Double, Double, Double, Double, Double, Double)]

But the one I get from what I am doing is RDD org.apache.spark.rdd.RDD[Double]

I can't use scala Tuple9 for example because I don't know the number of elements my list is going to contain before execution, this solution also doesn't fit my problem because sometimes I have more than 100 columns in my csv and tuple stops at Tuple22

Thanks for your help

回答1:

As @SergGr mentioned Cassandra table has a schema with known columns. So you need to map your Array to Cassandra schema before saving to Cassandra database. You can use Case Class for this. Try the following code, I assume each column in Cassandra table is of type Double.

//create a case class equivalent to your Cassandra table
case class Schema(collecttime: Double,
                  sbnid: Double,
                  enodebid: Double,
                  rackid: Double,
                  shelfid: Double,
                  slotid: Double,
                  channelid: Double,
                  c373910000: Double,
                  c373910001: Double,
                  c373910002: Double)
object test {

  import com.datastax.spark.connector._, org.apache.spark.SparkContext, org.apache.spark.SparkContext._, org.apache.spark.SparkConf

  def main(args: Array[String]): Unit = {
    val conf = new SparkConf(true).set("spark.cassandra.connection.host", "localhost")
    val sc = new SparkContext(conf)
    val nameTable = "artport"
    val ligne = "20171,16,165481,51,1,1,4,-79.6000,-101.7000,-98.9000"
    //parse ligne string Schema case class
    val schema = parseString(ligne)
    //get RDD[Schema]
    val rdd = sc.parallelize(Seq(schema))
    //now you can save this RDD to cassandra
    rdd.saveToCassandra("db", nameTable)
    }


    //function to parse string to Schema case class
    def parseString(s: String): Schema = {
       //get each field from string array
       val Array(collecttime, sbnid, enodebid, rackid, shelfid, slotid,
       channelid, c373910000, c373910001, c373910002, _*) = s.split(",").map(_.toDouble)

       //map those fields to Schema class
       Schema(collecttime,
         sbnid,
         enodebid,
         rackid,
         shelfid,
         slotid,
         channelid,
         c373910000,
         c373910001,
         c373910002)
     }
}

来源：https://stackoverflow.com/questions/48502410/java-lang-illegalargumentexception-requirement-failed-columns-not-found-in-dou