I've noticed that after I use a Window function over a DataFrame if I call a
map() with a function, Spark returns a "Task not serializable" Exception
This is my code:
val hc = new org.apache.spark.sql.hive.HiveContext(sc)
import hc.implicits._
import org.apache.spark.sql.expressions.Window
import org.apache.spark.sql.functions._
def f():String = "test"
case class P(name:String,surname:String)
val lag_result = lag($"name",1).over(Window.partitionBy($"surname"))
val lista = List(P("N1","S1"),P("N2","S2"),P("N2","S2"))
val data_frame = hc.createDataFrame(sc.parallelize(lista))
df.withColumn("lag_result", lag_result).map(x => f)
//df.withColumn("lag_result", lag_result).map{case x => def f():String =
"test";f}.collect // This works
And this is the Stack Trace:
org.apache.spark.SparkException: Task not serializable
at
org.apache.spark.util.ClosureCleaner$.ensureSerializable(ClosureCleaner.scala:304)
at
org.apache.spark.util.ClosureCleaner$.org$apache$spark$util$ClosureCleaner$$clean(ClosureCleaner.scala:294)
at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:122)
at org.apache.spark.SparkContext.clean(SparkContext.scala:2055)
at org.apache.spark.rdd.RDD$$anonfun$map$1.apply(RDD.scala:324)
at org.apache.spark.rdd.RDD$$anonfun$map$1.apply(RDD.scala:323)
at
... and more
Caused by: java.io.NotSerializableException: org.apache.spark.sql.Column
Serialization stack:
- object not serializable (class: org.apache.spark.sql.Column, value:
'lag(name,1,null) windowspecdefinition(surname,UnspecifiedFrame))
- field (class:
$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC$$iwC,
name: lag_result, type: class org.apache.spark.sql.Column)
... and more
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