Hve on Spark left join的hashTable问题

● 系统环境说明

Linux环境：centos7.4
EMR：3.0.0
Java：1.8.0_112

● 集群配置

机器数量：50
内存：128G
硬盘：100T
CPU核心数：32C

问题

SQL中使用了LEFT JOIN，在执行过程中遇到以下报错：

java.lang.RuntimeException: Map operator initialization failed: java.lang.ClassCastException: org.apache.hadoop.hive.ql.exec.persistence.HashMapWrapper cannot be cast to org.apache.hadoop.hive.ql.exec.persistence.MapJoinTableContainerDirectAccess
    at org.apache.hadoop.hive.ql.exec.spark.SparkMapRecordHandler.init(SparkMapRecordHandler.java:118)
    at org.apache.hadoop.hive.ql.exec.spark.HiveMapFunction.call(HiveMapFunction.java:55)
    at org.apache.hadoop.hive.ql.exec.spark.HiveMapFunction.call(HiveMapFunction.java:30)
    at org.apache.spark.api.java.JavaRDDLike$$anonfun$fn$7$1.apply(JavaRDDLike.scala:186)
    at org.apache.spark.api.java.JavaRDDLike$$anonfun$fn$7$1.apply(JavaRDDLike.scala:186)
    at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$23.apply(RDD.scala:801)
    at org.apache.spark.rdd.RDD$$anonfun$mapPartitions$1$$anonfun$apply$23.apply(RDD.scala:801)
    at org.apache.spark.rdd.MapPartitionsRDD.compute(MapPartitionsRDD.scala:52)
    at org.apache.spark.rdd.RDD.computeOrReadCheckpoint(RDD.scala:324)
    at org.apache.spark.rdd.RDD.iterator(RDD.scala:288)
    at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:99)
    at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:55)
    at org.apache.spark.scheduler.Task.run(Task.scala:121)
    at org.apache.spark.executor.Executor$TaskRunner$$anonfun$10.apply(Executor.scala:408)
    at org.apache.spark.util.Utils$.tryWithSafeFinally(Utils.scala:1360)
    at org.apache.spark.executor.Executor$TaskRunner.run(Executor.scala:414)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.ClassCastException: org.apache.hadoop.hive.ql.exec.persistence.HashMapWrapper cannot be cast to org.apache.hadoop.hive.ql.exec.persistence.MapJoinTableContainerDirectAccess
    at org.apache.hadoop.hive.ql.exec.vector.mapjoin.optimized.VectorMapJoinOptimizedHashTable.(VectorMapJoinOptimizedHashTable.java:92)
    at org.apache.hadoop.hive.ql.exec.vector.mapjoin.optimized.VectorMapJoinOptimizedHashMultiSet.(VectorMapJoinOptimizedHashMultiSet.java:101)
    at org.apache.hadoop.hive.ql.exec.vector.mapjoin.optimized.VectorMapJoinOptimizedStringHashMultiSet.(VectorMapJoinOptimizedStringHashMultiSet.java:61)
    at org.apache.hadoop.hive.ql.exec.vector.mapjoin.optimized.VectorMapJoinOptimizedCreateHashTable.createHashTable(VectorMapJoinOptimizedCreateHashTable.java:85)
    at org.apache.hadoop.hive.ql.exec.vector.mapjoin.VectorMapJoinCommonOperator.setUpHashTable(VectorMapJoinCommonOperator.java:483)
    at org.apache.hadoop.hive.ql.exec.vector.mapjoin.VectorMapJoinCommonOperator.completeInitializationOp(VectorMapJoinCommonOperator.java:461)
    at org.apache.hadoop.hive.ql.exec.Operator.completeInitialization(Operator.java:470)
    at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:400)
    at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:573)
    at org.apache.hadoop.hive.ql.exec.Operator.initializeChildren(Operator.java:525)
    at org.apache.hadoop.hive.ql.exec.Operator.initialize(Operator.java:386)
    at org.apache.hadoop.hive.ql.exec.spark.SparkMapRecordHandler.init(SparkMapRecordHandler.java:109)
    ... 18 more

问题原因

当hashTable为空时，会发生这种情况。

解决方法

官方说法：

所以将hashtable关闭即可：

set hive.mapjoin.optimized.hashtable=false;

问题解决。