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  1. Spark
  2. SPARK-23025

DataSet with scala.Null causes Exception

    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 2.2.1
    • Fix Version/s: 2.3.0
    • Component/s: SQL
    • Labels:
      None

      Description

      When creating a DataSet over a case class containing a field of type scala.Null, there is an exception thrown. As far as I can see, spark sql would support a Schema(NullType, true), but it fails inside the schemaFor function with a MatchError.
      I would expect spark to return a DataSet with a NullType for that field.

      Minimal Exampe
      case class Foo(foo: Int, bar: Null)
      val ds = Seq(Foo(42, null)).toDS()
      
      Exception
      scala.MatchError: scala.Null (of class scala.reflect.internal.Types$ClassNoArgsTypeRef)
        at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$schemaFor$1.apply(ScalaReflection.scala:713)
        at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$schemaFor$1.apply(ScalaReflection.scala:704)
        at scala.reflect.internal.tpe.TypeConstraints$UndoLog.undo(TypeConstraints.scala:56)
        at org.apache.spark.sql.catalyst.ScalaReflection$class.cleanUpReflectionObjects(ScalaReflection.scala:809)
        at org.apache.spark.sql.catalyst.ScalaReflection$.cleanUpReflectionObjects(ScalaReflection.scala:39)
        at org.apache.spark.sql.catalyst.ScalaReflection$.schemaFor(ScalaReflection.scala:703)
        at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$org$apache$spark$sql$catalyst$ScalaReflection$$deserializerFor$1$$anonfun$9.apply(ScalaReflection.scala:391)
        at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$org$apache$spark$sql$catalyst$ScalaReflection$$deserializerFor$1$$anonfun$9.apply(ScalaReflection.scala:390)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
        at scala.collection.immutable.List.foreach(List.scala:381)
        at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
        at scala.collection.immutable.List.map(List.scala:285)
        at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$org$apache$spark$sql$catalyst$ScalaReflection$$deserializerFor$1.apply(ScalaReflection.scala:390)
        at org.apache.spark.sql.catalyst.ScalaReflection$$anonfun$org$apache$spark$sql$catalyst$ScalaReflection$$deserializerFor$1.apply(ScalaReflection.scala:148)
        at scala.reflect.internal.tpe.TypeConstraints$UndoLog.undo(TypeConstraints.scala:56)
        at org.apache.spark.sql.catalyst.ScalaReflection$class.cleanUpReflectionObjects(ScalaReflection.scala:809)
        at org.apache.spark.sql.catalyst.ScalaReflection$.cleanUpReflectionObjects(ScalaReflection.scala:39)
        at org.apache.spark.sql.catalyst.ScalaReflection$.org$apache$spark$sql$catalyst$ScalaReflection$$deserializerFor(ScalaReflection.scala:148)
        at org.apache.spark.sql.catalyst.ScalaReflection$.deserializerFor(ScalaReflection.scala:136)
        at org.apache.spark.sql.catalyst.encoders.ExpressionEncoder$.apply(ExpressionEncoder.scala:72)
        at org.apache.spark.sql.Encoders$.product(Encoders.scala:275)
        at org.apache.spark.sql.LowPrioritySQLImplicits$class.newProductEncoder(SQLImplicits.scala:233)
        at org.apache.spark.sql.SQLImplicits.newProductEncoder(SQLImplicits.scala:33)
        ... 42 elided 
      
      Background Info

      To handle our data in a type-safe fashion, we have generated AVRO schemas and corresponding scala case classes for our domain data. As some fields only contain null values, this results in fields with scala.Null as a type. Moving our pipeline to DataSets/structured streaming, case classes with Null types begin to give problems, even trough NullType is known to spark SQL.

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            • Assignee:
              mgaido Marco Gaido
              Reporter:
              wabu Daniel Davis
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              • Created:
                Updated:
                Resolved: