[英]Spark Scala - rdd distinct nullpointerexception
我正在用 spark 做小步骤,我的练习将 JSON 文件加载到 RDD,select 一列,然后使用 distinct 获取唯一值。 我过滤的列包含多个值(CSV 行),必须拆分。
val sqlContext = spark.sqlContext
import org.apache.spark.sql.hive.HiveContext
val hiveCtx = new HiveContext(sc)
import hiveCtx.implicits._
val bizDF = hiveCtx.jsonFile("/home/xpto/Documents/PersonalProjects/Yelp_P1/yelp_academic_dataset_business.json")
val catRdd = bizDF.select("categories").rdd.flatMap(row => (row.getString(0).split(",").map(_.trim))).distinct
当我运行语句“catRdd.take (10).foreach (println)”时返回异常:
org.apache.spark.SparkException:作业因阶段失败而中止:阶段 234.0 中的任务 0 失败 1 次,最近的失败:阶段 234.0 中的任务 0.0 丢失(TID 682、192.168.0.122,执行程序驱动程序):
java.lang.NullPointerException
at $anonfun$catRdd$1(<console>:39)
at $anonfun$catRdd$1$adapted(<console>:39)
at scala.collection.Iterator$$anon$11.nextCur(Iterator.scala:484)
at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:490)
at scala.collection.Iterator$$anon$10.hasNext(Iterator.scala:458)
at org.apache.spark.util.collection.ExternalSorter.insertAll(ExternalSorter.scala:192)
at org.apache.spark.shuffle.sort.SortShuffleWriter.write(SortShuffleWriter.scala:62)
at org.apache.spark.shuffle.ShuffleWriteProcessor.write(ShuffleWriteProcessor.scala:59)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:99)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:52)
at org.apache.spark.scheduler.Task.run(Task.scala:127)
at org.apache.spark.executor.Executor$TaskRunner.$anonfun$run$3(Executor.scala:446)
at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1377)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:449)
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)
Driver stacktrace:
at org.apache.spark.scheduler.DAGScheduler.failJobAndIndependentStages(DAGScheduler.scala:2059)
at org.apache.spark.scheduler.DAGScheduler.$anonfun$abortStage$2(DAGScheduler.scala:2008)
at org.apache.spark.scheduler.DAGScheduler.$anonfun$abortStage$2$adapted(DAGScheduler.scala:2007)
at scala.collection.mutable.ResizableArray.foreach(ResizableArray.scala:62)
at scala.collection.mutable.ResizableArray.foreach$(ResizableArray.scala:55)
at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:49)
at org.apache.spark.scheduler.DAGScheduler.abortStage(DAGScheduler.scala:2007)
at org.apache.spark.scheduler.DAGScheduler.$anonfun$handleTaskSetFailed$1(DAGScheduler.scala:973)
at org.apache.spark.scheduler.DAGScheduler.$anonfun$handleTaskSetFailed$1$adapted(DAGScheduler.scala:973)
at scala.Option.foreach(Option.scala:407)
at org.apache.spark.scheduler.DAGScheduler.handleTaskSetFailed(DAGScheduler.scala:973)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.doOnReceive(DAGScheduler.scala:2239)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:2188)
at org.apache.spark.scheduler.DAGSchedulerEventProcessLoop.onReceive(DAGScheduler.scala:2177)
at org.apache.spark.util.EventLoop$$anon$1.run(EventLoop.scala:49)
at org.apache.spark.scheduler.DAGScheduler.runJob(DAGScheduler.scala:775)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2099)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2120)
at org.apache.spark.SparkContext.runJob(SparkContext.scala:2139)
at org.apache.spark.rdd.RDD.$anonfun$take$1(RDD.scala:1423)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:151)
at org.apache.spark.rdd.RDDOperationScope$.withScope(RDDOperationScope.scala:112)
at org.apache.spark.rdd.RDD.withScope(RDD.scala:388)
at org.apache.spark.rdd.RDD.take(RDD.scala:1396)
... 48 elided
Caused by: java.lang.NullPointerException
at $anonfun$catRdd$1(<console>:39)
at $anonfun$catRdd$1$adapted(<console>:39)
at scala.collection.Iterator$$anon$11.nextCur(Iterator.scala:484)
at scala.collection.Iterator$$anon$11.hasNext(Iterator.scala:490)
at scala.collection.Iterator$$anon$10.hasNext(Iterator.scala:458)
at org.apache.spark.util.collection.ExternalSorter.insertAll(ExternalSorter.scala:192)
at org.apache.spark.shuffle.sort.SortShuffleWriter.write(SortShuffleWriter.scala:62)
at org.apache.spark.shuffle.ShuffleWriteProcessor.write(ShuffleWriteProcessor.scala:59)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:99)
at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:52)
at org.apache.spark.scheduler.Task.run(Task.scala:127)
at org.apache.spark.executor.Executor$TaskRunner.$anonfun$run$3(Executor.scala:446)
at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1377)
at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:449)
... 3 more
我运行的 spark 版本是 2.12-3.0.1
我找到了适合我要求的解决方案:
import org.apache.spark.sql.functions._
import org.apache.spark.sql.expressions.Window
val v1 = bizDF.withColumn("categories", split(col("categories"), ","))
.select(col("categories")(0).as("description"))
.distinct
.coalesce(1)
.orderBy(asc("description"))
val windowSpec = Window.orderBy("description")
val v2 = v1.withColumn("id",row_number.over(windowSpec))
val v3 = v2.select("id","description")
您的 json 文件有多行,HiveCtx 不支持。 尝试使用 spark session 代替:
val bizDF = spark.read.format("json").option("multiline", "true").load("/home/xpto/Documents/PersonalProjects/Yelp_P1/yelp_academic_dataset_business.json")
val catRdd = bizDF.select("categories").rdd.flatMap(row => (row.getString(0).split(",").map(_.trim))).distinct
catRdd.take(10).foreach(println)
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