SparkSql - 加入查询执行抛出“对象不是声明类的实例”

Posted 2023-04-15

【中文标题】SparkSql - 加入查询执行抛出“对象不是声明类的实例”

【英文标题】：SparkSql - Join Query execution throws 'object is not an instance of declaring class'

【发布时间】：2017-03-27 08:32:53

【问题描述】：

我正在对SparkSession 执行查询，它会抛出Object is not an instance of declaring class，下面是之后的代码

Dataset<Row> results = spark.sql("SELECT t1.someCol FROM table1 t1 join table2 t2 on t1.someCol=t2.someCol");
    results.count();

异常发生在方法count()期间

我还观察到如果查询是简单的select col from table1，它运行良好，但上面的连接查询会导致错误。

我正在使用 Spark 2.1 并在下面创建 SparkSession

SparkSession.builder().appName("Spark SQL").config(mysparkConf).getOrCreate();

更多堆栈跟踪如下：-

Driver stacktrace:
    at org.apache.spark.scheduler.DAGScheduler.org$apache$spark$scheduler$DAGScheduler$$failJobAndIndependentStages(DAGScheduler.scala:1435)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1423)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$abortStage$1.apply(DAGScheduler.scala:1422)
    at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
    at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
    at org.apache.spark.scheduler.DAGScheduler.abortStage(DAGScheduler.scala:1422)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:802)
    at org.apache.spark.scheduler.DAGScheduler$$anonfun$handleTaskSetFailed$1.apply(DAGScheduler.scala:802)
    at scala.Option.foreach(Option.scala:257)
    at org.apache.spark.scheduler.DAGScheduler.handleTaskSetFailed(DAGScheduler.scala:802)
    at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.doOnReceive(DAGScheduler.scala:1650)
    at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1605)
    at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:1594)
    at org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:48)
    at org.apache.spark.scheduler.DAGScheduler.runJob(DAGScheduler.scala:628)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1918)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1931)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1944)
    at org.apache.spark.SparkContext.runJob(SparkContext.scala:1958)
    at org.apache.spark.rdd.RDD$$anonfun$collect$1.apply(RDD.scala:935)
    at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
    at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
    at org.apache.spark.rdd.RDD.withScope(RDD.scala:362)
    at org.apache.spark.rdd.RDD.collect(RDD.scala:934)
    at org.apache.spark.sql.execution.SparkPlan.executeCollect(SparkPlan.scala:275)
    at org.apache.spark.sql.Dataset$$anonfun$org$apache$spark$sql$Dataset$$execute$1$1.apply(Dataset.scala:2371)
    at org.apache.spark.sql.execution.SQLExecution$.withNewExecutionId(SQLExecution.scala:57)
    at org.apache.spark.sql.Dataset.withNewExecutionId(Dataset.scala:2765)
    at org.apache.spark.sql.Dataset.org$apache$spark$sql$Dataset$$execute$1(Dataset.scala:2370)
    at org.apache.spark.sql.Dataset.org$apache$spark$sql$Dataset$$collect(Dataset.scala:2377)
    at org.apache.spark.sql.Dataset$$anonfun$count$1.apply(Dataset.scala:2405)
    at org.apache.spark.sql.Dataset$$anonfun$count$1.apply(Dataset.scala:2404)
    at org.apache.spark.sql.Dataset.withCallback(Dataset.scala:2778)
    at org.apache.spark.sql.Dataset.count(Dataset.scala:2404)
    at com.citi.eq.ioi.engine.OrderMatchingEngine.main(OrderMatchingEngine.java:85)
Caused by: java.lang.IllegalArgumentException: object is not an instance of declaring class
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.apache.spark.sql.SQLContext$$anonfun$beansToRows$1$$anonfun$apply$1.apply(SQLContext.scala:1113)
    at org.apache.spark.sql.SQLContext$$anonfun$beansToRows$1$$anonfun$apply$1.apply(SQLContext.scala:1113)

【参考方案1】：

当您没有特定领域的类型时，不要使用数据集。而是使用 DataFrame，即 Dataset 的无类型视图。

数据集是特定领域对象的强类型集合，可以使用函数或关系操作并行转换。每个 Dataset 还有一个称为 DataFrame 的无类型视图，它是一个 Dataset of Row。

你可以参考这个： https://spark.apache.org/docs/latest/api/scala/index.html#org.apache.spark.sql.Dataset

【讨论】：

能否请您提供任何示例来执行此操作，因为我在 SparkSession 中找不到任何方法来创建 DataFrame，它们仅生成 DataSet！