Bug: ProductEncoder not working as expected within User Defined Fuction (UDF)
Status: Open | Priority: Major | Resolution: 
Created: 07/Aug/23 15:39
Affects Version/s: 3.4.0

Hi,

When running the following code in Databricks' notebook:
{code:java}
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.sql.{DataFrame, Dataset, SparkSession}
  
  case class DataRow(field1: String)
  val sparkSession = SparkSession.builder.getOrCreate()
  import sparkSession.implicits._
  val udf1 = udf((x: String) => {
    val testData = Seq(DataRow("test1"), DataRow("test2")).toDF("test") // This is failing at runtime
    3
  })
  val df1 = Seq(DataRow("test1"), DataRow("test2")).toDF("test").withColumn("udf", udf1($"test")) // This is working
  display(df1)
{code}
I get a ScalaReflectionException at runtime:
{code:java}
ScalaReflectionException: class $linedb3da7b2933d4b63a62b3d2a21c675f2141.$read in JavaMirror with com.databricks.backend.daemon.driver.DriverLocal$DriverLocalClassLoader@717115ad of type class com.databricks.backend.daemon.driver.DriverLocal$DriverLocalClassLoader with classpath [] and parent being com.databricks.backend.daemon.driver.ClassLoaders$ReplWrappingClassLoader@1670897 of type class com.databricks.backend.daemon.driver.ClassLoaders$ReplWrappingClassLoader with classpath [<unknown>] and parent being com.databricks.backend.daemon.driver.ClassLoaders$LibraryClassLoader@1a42da0a of type class com.databricks.backend.daemon.driver.ClassLoaders$LibraryClassLoader with classpath [file:/local_disk0/tmp/repl/spark-4071811259476162981-8e526ae9-25fb-4545-8d3f-963a8661cd2b/] and parent being sun.misc.Launcher$AppClassLoader@43ee72e6 of type class sun.misc.Launcher$AppClassLoader with classpath [...] not found. 
at scala.reflect.internal.Mirrors$RootsBase.staticClass(Mirrors.scala:141) 
at scala.reflect.internal.Mirrors$RootsBase.staticClass(Mirrors.scala:29) 
at $linedb3da7b2933d4b63a62b3d2a21c675f2196.$read$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$$$c35395a9233a7197629c985e87dce75$$$$w$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$typecreator6$1.apply(command-2013905963200886:11) 
at scala.reflect.api.TypeTags$WeakTypeTagImpl.tpe$lzycompute(TypeTags.scala:237) 
at scala.reflect.api.TypeTags$WeakTypeTagImpl.tpe(TypeTags.scala:237) 
at org.apache.spark.sql.catalyst.ScalaReflection$.encoderFor(ScalaReflection.scala:848) 
at org.apache.spark.sql.catalyst.encoders.ExpressionEncoder$.apply(ExpressionEncoder.scala:55) 
at org.apache.spark.sql.Encoders$.product(Encoders.scala:312) 
at org.apache.spark.sql.LowPrioritySQLImplicits.newProductEncoder(SQLImplicits.scala:302) 
at org.apache.spark.sql.LowPrioritySQLImplicits.newProductEncoder$(SQLImplicits.scala:302) 
at org.apache.spark.sql.SQLImplicits.newProductEncoder(SQLImplicits.scala:34) 
at $linedb3da7b2933d4b63a62b3d2a21c675f2196.$read$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$$$c35395a9233a7197629c985e87dce75$$$$w$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw.$anonfun$udf1$1(command-2013905963200886:11) {code}
Declaring the case class within the UDF:
{code:java}
import org.apache.spark.{SparkConf, SparkContext}
import org.apache.spark.sql.{DataFrame, Dataset, SparkSession}
 
  case class DataRow(field1: String)
  val sparkSession = SparkSession.builder.getOrCreate()
  import sparkSession.implicits._  
  val udf1 = udf((x: String) => {
    case class DataRow(field1: String)
    val testData = Seq(DataRow("test1"), DataRow("test2")).toDF("test") // This is failing at runtime
    3
  })  
  val df1 = Seq(DataRow("test1"), DataRow("test2")).toDF("test").withColumn("udf", udf1($"test")) // This is working
  display(df1) {code}
I get a different error
{code:java}
error: value toDF is not a member of Seq[DataRow] val testData = Seq(DataRow("test1"), DataRow("test2")).toDF("test"){code}

Questions:
* Is this an expected behaviour or a bug?

Thanks.

Thanks.