title: Apache Spark simple join results in cryptic error
body: <p>I have two Datasets which I'm able to query and show() individually. One has 17 records and another has 3.</p>
  
  <pre><code>Dataset&lt;Row&gt; attReader = spark
      .read()
      .format("org.apache.spark.sql.cassandra")
      .option("table", "table_1")
      .load();
  
  Dataset&lt;Row&gt; surReader = spark
      .read()
      .format("org.apache.spark.sql.cassandra")
      .option("table", "table_2")
      .load();
  </code></pre>
  
  <p>When I attempt to join and show them like so:</p>
  
  <pre><code>    Dataset&lt;Row&gt; joined = attReader.join(surReader,
          attReader.col("key_field").equalTo(surReader.col("key_field")), "inner");
      joined.show();
  </code></pre>
  
  <p>I'm sure these fields are correct since I can show the data for the individual Datasets and see them. Join fields are strings.</p>
  
  <p>I get the following exception, which doesn't offer much help:</p>
  
  <pre><code>org.apache.spark.SparkException: Exception thrown in awaitResult: 
      at org.apache.spark.util.ThreadUtils$.awaitResult(ThreadUtils.scala:205)
      at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec.doExecuteBroadcast(BroadcastExchangeExec.scala:136)
      at org.apache.spark.sql.execution.InputAdapter.doExecuteBroadcast(WholeStageCodegenExec.scala:367)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeBroadcast$1.apply(SparkPlan.scala:144)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeBroadcast$1.apply(SparkPlan.scala:140)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
      at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
      at org.apache.spark.sql.execution.SparkPlan.executeBroadcast(SparkPlan.scala:140)
      at org.apache.spark.sql.execution.joins.BroadcastHashJoinExec.prepareBroadcast(BroadcastHashJoinExec.scala:135)
      at org.apache.spark.sql.execution.joins.BroadcastHashJoinExec.codegenInner(BroadcastHashJoinExec.scala:232)
      at org.apache.spark.sql.execution.joins.BroadcastHashJoinExec.doConsume(BroadcastHashJoinExec.scala:102)
      at org.apache.spark.sql.execution.CodegenSupport$class.consume(WholeStageCodegenExec.scala:181)
      at org.apache.spark.sql.execution.FilterExec.consume(basicPhysicalOperators.scala:85)
      at org.apache.spark.sql.execution.FilterExec.doConsume(basicPhysicalOperators.scala:206)
      at org.apache.spark.sql.execution.CodegenSupport$class.consume(WholeStageCodegenExec.scala:181)
      at org.apache.spark.sql.execution.RowDataSourceScanExec.consume(DataSourceScanExec.scala:77)
      at org.apache.spark.sql.execution.RowDataSourceScanExec.doProduce(DataSourceScanExec.scala:125)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:88)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
      at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
      at org.apache.spark.sql.execution.CodegenSupport$class.produce(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.RowDataSourceScanExec.produce(DataSourceScanExec.scala:77)
      at org.apache.spark.sql.execution.FilterExec.doProduce(basicPhysicalOperators.scala:125)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:88)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
      at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
      at org.apache.spark.sql.execution.CodegenSupport$class.produce(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.FilterExec.produce(basicPhysicalOperators.scala:85)
      at org.apache.spark.sql.execution.joins.BroadcastHashJoinExec.doProduce(BroadcastHashJoinExec.scala:97)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:88)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
      at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
      at org.apache.spark.sql.execution.CodegenSupport$class.produce(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.joins.BroadcastHashJoinExec.produce(BroadcastHashJoinExec.scala:39)
      at org.apache.spark.sql.execution.ProjectExec.doProduce(basicPhysicalOperators.scala:45)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:88)
      at org.apache.spark.sql.execution.CodegenSupport$$anonfun$produce$1.apply(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
      at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
      at org.apache.spark.sql.execution.CodegenSupport$class.produce(WholeStageCodegenExec.scala:83)
      at org.apache.spark.sql.execution.ProjectExec.produce(basicPhysicalOperators.scala:35)
      at org.apache.spark.sql.execution.WholeStageCodegenExec.doCodeGen(WholeStageCodegenExec.scala:524)
      at org.apache.spark.sql.execution.WholeStageCodegenExec.doExecute(WholeStageCodegenExec.scala:576)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:131)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$execute$1.apply(SparkPlan.scala:127)
      at org.apache.spark.sql.execution.SparkPlan$$anonfun$executeQuery$1.apply(SparkPlan.scala:155)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
      at org.apache.spark.sql.execution.SparkPlan.executeQuery(SparkPlan.scala:152)
      at org.apache.spark.sql.execution.SparkPlan.execute(SparkPlan.scala:127)
      at org.apache.spark.sql.execution.SparkPlan.getByteArrayRdd(SparkPlan.scala:247)
      at org.apache.spark.sql.execution.SparkPlan.executeTake(SparkPlan.scala:337)
      at org.apache.spark.sql.execution.CollectLimitExec.executeCollect(limit.scala:38)
      at org.apache.spark.sql.Dataset.org$apache$spark$sql$Dataset$$collectFromPlan(Dataset.scala:3278)
      at org.apache.spark.sql.Dataset$$anonfun$head$1.apply(Dataset.scala:2489)
      at org.apache.spark.sql.Dataset$$anonfun$head$1.apply(Dataset.scala:2489)
      at org.apache.spark.sql.Dataset$$anonfun$52.apply(Dataset.scala:3259)
      at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:77)
      at org.apache.spark.sql.Dataset.withAction(Dataset.scala:3258)
      at org.apache.spark.sql.Dataset.head(Dataset.scala:2489)
      at org.apache.spark.sql.Dataset.take(Dataset.scala:2703)
      at org.apache.spark.sql.Dataset.showString(Dataset.scala:254)
      at org.apache.spark.sql.Dataset.show(Dataset.scala:723)
      at org.apache.spark.sql.Dataset.show(Dataset.scala:682)
      at org.apache.spark.sql.Dataset.show(Dataset.scala:691)
      at com.kilonova.CassandraStream.sparkSql(CassandraStream.java:111)
      at com.kilonova.CassandraStream.init(CassandraStream.java:174)
      at com.kilonova.Main.runStream(Main.java:20)
      at com.kilonova.Main.main(Main.java:14)
  Caused by: java.lang.IllegalArgumentException
      at org.apache.xbean.asm5.ClassReader.&lt;init&gt;(Unknown Source)
      at org.apache.xbean.asm5.ClassReader.&lt;init&gt;(Unknown Source)
      at org.apache.xbean.asm5.ClassReader.&lt;init&gt;(Unknown Source)
      at org.apache.spark.util.ClosureCleaner$.getClassReader(ClosureCleaner.scala:46)
      at org.apache.spark.util.FieldAccessFinder$$anon$3$$anonfun$visitMethodInsn$2.apply(ClosureCleaner.scala:449)
      at org.apache.spark.util.FieldAccessFinder$$anon$3$$anonfun$visitMethodInsn$2.apply(ClosureCleaner.scala:432)
      at scala.collection.TraversableLike$WithFilter$$anonfun$foreach$1.apply(TraversableLike.scala:733)
      at scala.collection.mutable.HashMap$$anon$1$$anonfun$foreach$2.apply(HashMap.scala:103)
      at scala.collection.mutable.HashMap$$anon$1$$anonfun$foreach$2.apply(HashMap.scala:103)
      at scala.collection.mutable.HashTable$class.foreachEntry(HashTable.scala:230)
      at scala.collection.mutable.HashMap.foreachEntry(HashMap.scala:40)
      at scala.collection.mutable.HashMap$$anon$1.foreach(HashMap.scala:103)
      at scala.collection.TraversableLike$WithFilter.foreach(TraversableLike.scala:732)
      at org.apache.spark.util.FieldAccessFinder$$anon$3.visitMethodInsn(ClosureCleaner.scala:432)
      at org.apache.xbean.asm5.ClassReader.a(Unknown Source)
      at org.apache.xbean.asm5.ClassReader.b(Unknown Source)
      at org.apache.xbean.asm5.ClassReader.accept(Unknown Source)
      at org.apache.xbean.asm5.ClassReader.accept(Unknown Source)
      at org.apache.spark.util.ClosureCleaner$$anonfun$org$apache$spark$util$ClosureCleaner$$clean$14.apply(ClosureCleaner.scala:262)
      at org.apache.spark.util.ClosureCleaner$$anonfun$org$apache$spark$util$ClosureCleaner$$clean$14.apply(ClosureCleaner.scala:261)
      at scala.collection.immutable.List.foreach(List.scala:381)
      at org.apache.spark.util.ClosureCleaner$.org$apache$spark$util$ClosureCleaner$$clean(ClosureCleaner.scala:261)
      at org.apache.spark.util.ClosureCleaner$.clean(ClosureCleaner.scala:159)
      at org.apache.spark.SparkContext.clean(SparkContext.scala:2299)
      at org.apache.spark.SparkContext.runJob(SparkContext.scala:2073)
      at org.apache.spark.SparkContext.runJob(SparkContext.scala:2099)
      at org.apache.spark.rdd.RDD$$anonfun$collect$1.apply(RDD.scala:945)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
      at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
      at org.apache.spark.rdd.RDD.withScope(RDD.scala:363)
      at org.apache.spark.rdd.RDD.collect(RDD.scala:944)
      at org.apache.spark.sql.execution.SparkPlan.executeCollectIterator(SparkPlan.scala:304)
      at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anonfun$relationFuture$1$$anonfun$apply$1.apply(BroadcastExchangeExec.scala:76)
      at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anonfun$relationFuture$1$$anonfun$apply$1.apply(BroadcastExchangeExec.scala:73)
      at org.apache.spark.sql.execution.SQLExecution$.withExecutionId(SQLExecution.scala:97)
      at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anonfun$relationFuture$1.apply(BroadcastExchangeExec.scala:72)
      at org.apache.spark.sql.execution.exchange.BroadcastExchangeExec$$anonfun$relationFuture$1.apply(BroadcastExchangeExec.scala:72)
      at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
      at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
      at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135)
      at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
      at java.base/java.lang.Thread.run(Thread.java:844)
  </code></pre>