I have an RDD with the elements of different types, and I want to count them by their types, for example, the code below will work correctly.
scala> val rdd = sc.parallelize(List(1, 2.0, "abc"))
rdd: org.apache.spark.rdd.RDD[Any] = ParallelCollectionRDD[0] at parallelize at <console>:24
scala> rdd.filter{case z:Int => true; case _ => false}.count
res0: Long = 1
scala> rdd.filter{case z:String => true; case _ => false}.count
res1: Long = 1
Now what if the elements are of user-defined types, the code below won't work as expected.
scala> class TypeA extends Serializable // this is the base class
defined class TypeA
scala> case class TypeB(id:Long) extends TypeA // derived class 1
defined class TypeB
scala> case class TypeC(name:String) extends TypeA // derived class 2
defined class TypeC
scala> val rdd1 = sc.parallelize(List(TypeB(123), TypeC("jack"), TypeB(456))) // create an rdd with different types of elements
rdd1: org.apache.spark.rdd.RDD[TypeA with Product] = ParallelCollectionRDD[3] at parallelize at <console>:29
scala> rdd1.count // total size is correct
res2: Long = 3
scala> rdd1.filter{case z:TypeB => true; case _ => false}.count // what the hell?
res3: Long = 0
scala> rdd1.filter{case z:TypeC => true; case _ => false}.count // again ?
res4: Long = 0
scala> rdd1.filter{case z:TypeA => true; case _ => false}.count // only works for the base class?
res5: Long = 3
Did I miss anything here? Help please!
This looks like a variation of Spark-1199
and is likely a REPL bug.
This yields expected behavior when running locally inside IDEA:
import org.apache.spark.SparkContext
class TypeA extends Serializable
case class TypeB(id:Long) extends TypeA
case class TypeC(name:String) extends TypeA
val sc = new SparkContext("local[*]", "swe")
val rdd = sc.parallelize(List(TypeB(12), TypeC("Hsa")))
rdd.filter { case x: TypeB => true; case _ => false }.count()
Yields:
import org.apache.spark.SparkContext
defined class TypeA
defined class TypeB
defined class TypeC
sc: org.apache.spark.SparkContext = org.apache.spark.SparkContext@10a1410d
rdd: org.apache.spark.rdd.RDD[TypeA with Product] = ParallelCollectionRDD[0] at parallelize at <console>:18
[Stage 0:>....... (0 + 0) / 4]
res0: Long = 1
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