java.util.NoSuchElementException：接下来是空迭代器，同时尝试使用Spark DataFrame从Cassandra检索和遍历数据

Question

我正在尝试使用spark数据框从cassandra检索数据。 以下是用于从cassandra和错误stacktrace检索数据的代码。 请帮助我解决问题。

sparkSession.sql未检索任何数据，“ res”数据框为空。 大多数情况下它找不到任何匹配的记录。

 def getCurrentTrip(s_id1: Long, a_id1: String, summ_typ1: String, summ_dt1:Date, trp_summ_Id1: String): Boolean = {

         var foundtrip = false

         // val selectTripQuery = "select * from ap.ts where service_id = ? and asset_id = ? and summ_typ = ? and summ_dt = ? and trp_summ_id = ?;"



         val df_read2 = sparkSession.read
                             .format("org.apache.spark.sql.cassandra")
                             .option("spark.cassandra.connection.host","host")
                             .option("spark.cassandra.connection.port","9042")
                             .option( "spark.cassandra.auth.username","user")
                             .option("spark.cassandra.auth.password","pass")
                             .option("keyspace","ap")
                             .option("table","ts")
                             .load()


         df_read2.createOrReplaceTempView("query_data2")


         val sqlDate = summ_dt1.getTime()

         var res = sparkSession.sql(s"""select * from query_data2 where s_id=$service_id1 and a_id=$asset_id1 and summ_typ='T' and summ_dt=timestamp($sqlDate) and trp_summ_id=("$trp_summ_Id1")""".stripMargin)
   println("one..")
         res.show()
          println("two...")

       //  val row = res.first()
         if (res.count>0) {
             println ("Found Trip")
             foundtrip = true
          } else {
              println ("Not Found")
              foundtrip = false
          }

      foundtrip

    }

---

18/09/25 19:58:28 ERROR app.ProcessMPacket$: error for processing this event For M-packet
java.util.NoSuchElementException: next on empty iterator
    at scala.collection.Iterator$$anon$2.next(Iterator.scala:39)
    at scala.collection.Iterator$$anon$2.next(Iterator.scala:37)
    at scala.collection.IndexedSeqLike$Elements.next(IndexedSeqLike.scala:63)
    at scala.collection.IterableLike$class.head(IterableLike.scala:107)
    at scala.collection.mutable.ArrayOps$ofRef.scala$collection$IndexedSeqOptimized$$super$head(ArrayOps.scala:186)
    at scala.collection.IndexedSeqOptimized$class.head(IndexedSeqOptimized.scala:126)
    at scala.collection.mutable.ArrayOps$ofRef.head(ArrayOps.scala:186)
    at org.apache.spark.sql.Dataset.head(Dataset.scala:2491)
    at org.apache.spark.sql.Dataset.first(Dataset.scala:2498)
    at com.vzt.afm.hum.dh.util.CassandraUtils$.getDashBoardData(CassandraUtils.scala:165)
    at com.vzt.afm.hum.dh.app.TripAggregation$.updateOdometer(TripAggregation.scala:84)
    at com.vzt.afm.hum.dh.app.ProcessMPacket$$anonfun$1$$anonfun$apply$1.apply(ProcessMPacket.scala:175)
    at com.vzt.afm.hum.dh.app.ProcessMPacket$$anonfun$1$$anonfun$apply$1.apply(ProcessMPacket.scala:129)
    at scala.collection.immutable.List.foreach(List.scala:392)
    at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
    at scala.collection.mutable.ListBuffer.foreach(ListBuffer.scala:45)
    at com.vzt.afm.hum.dh.app.ProcessMPacket$$anonfun$1.apply(ProcessMPacket.scala:129)
    at com.vzt.afm.hum.dh.app.ProcessMPacket$$anonfun$1.apply(ProcessMPacket.scala:75)
    at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$23.apply(RDD.scala:800)
    at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$23.apply(RDD.scala:800)
    at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:38)
    at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
    at org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
    at org.apache.spark.scheduler.ResultTask.runTask(ResultTask.scala:87)
    at org.apache.spark.scheduler.Task.run(Task.scala:109)
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:345)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)