CODEWITHSUNDEEP
scalaapache-sparkgenericsapache-spark-datasetapache-spark-encoders
Georg Heiler
Georg Heiler

Reputation: 17676

scala generic encoder for spark case class

How can I get this method to compile. Strangely, sparks implicit are already imported.

def loadDsFromHive[T <: Product](tableName: String, spark: SparkSession): Dataset[T] = {
    import spark.implicits._
    spark.sql(s"SELECT * FROM $tableName").as[T]
  }

This is the error:

Unable to find encoder for type stored in a Dataset.  Primitive types (Int, String, etc) and Product types (case classes) are supported by importing spark.implicits._  Support for serializing other types will be added in future releases.
[error]     spark.sql(s"SELECT * FROM $tableName").as[T]

Upvotes: 6

Views: 8788

Answers (1)

Cyrille Corpet
Cyrille Corpet

Reputation: 5315

According to the source code for org.apache.spark.sql.SQLImplicits, you need the type class TypeTag for your type, in order for the implicit Encoder to exist: 

import scala.reflect.runtime.universe.TypeTag
def loadDsFromHive[T <: Product: TypeTag](tableName: String, spark: SparkSession): Dataset[T] = ...

Upvotes: 18

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