StackOverflowError on RDD.union

[Thomas Kwan]

I am trying to combine multiple RDDs into 1 RDD, and I am using the union
function. I wonder if anyone has seen StackOverflowError as follows:

Exception in thread "main" java.lang.StackOverflowError
        at org.apache.spark.rdd.RDD.partitions(RDD.scala:203)
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:66)
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:66)
        at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
        at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
        at
scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
        at
scala.collection.mutable.WrappedArray.foreach(WrappedArray.scala:34)
        at
scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
        at scala.collection.AbstractTraversable.map(Traversable.scala:105)
        at org.apache.spark.rdd.UnionRDD.getPartitions(UnionRDD.scala:66)
        at
org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:205)
        at
org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:203)
        at scala.Option.getOrElse(Option.scala:120)
        at org.apache.spark.rdd.RDD.partitions(RDD.scala:203)
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:66)
        at org.apache.spark.rdd.UnionRDD$$anonfun$1.apply(UnionRDD.scala:66)
        at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
        at
scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
        at
scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
        at
scala.collection.mutable.WrappedArray.foreach(WrappedArray.scala:34)
        at
scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
        at scala.collection.AbstractTraversable.map(Traversable.scala:105)
        at org.apache.spark.rdd.UnionRDD.getPartitions(UnionRDD.scala:66)
        at
org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:205)
        at
org.apache.spark.rdd.RDD$$anonfun$partitions$2.apply(RDD.scala:203)
        at scala.Option.getOrElse(Option.scala:120)
       ....