Github user rdblue commented on a diff in the pull request: https://github.com/apache/spark/pull/22009#discussion_r208637663 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/DataSourceRDD.scala --- @@ -51,18 +58,19 @@ class DataSourceRDD[T: ClassTag]( valuePrepared } - override def next(): T = { + override def next(): Any = { if (!hasNext) { throw new java.util.NoSuchElementException("End of stream") } valuePrepared = false reader.get() } } - new InterruptibleIterator(context, iter) + // TODO: get rid of this type hack. + new InterruptibleIterator(context, iter.asInstanceOf[Iterator[InternalRow]]) } override def getPreferredLocations(split: Partition): Seq[String] = { - split.asInstanceOf[DataSourceRDDPartition[T]].inputPartition.preferredLocations() + split.asInstanceOf[DataSourceRDDPartition].inputPartition.preferredLocations() --- End diff -- Makes sense. If it's a bug, then the error message should indicate that it's a bug to users instead of throwing a `ClassCastException`. Even if someone goes to the code here, it there's no comment to indicate that it's a Spark bug. I'd prefer something like this: ```scala override def getPreferredLocations(split: Partition): Seq[String] = { split match { case dsp: DataSourceRDDPartition => dsp.inputPartition.preferredLocations case _ => throw new SparkException(s"[BUG] Not a DataSourceRDDPartition: $split") } } ```
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