hive join空指针异常的示例分析

小编给大家分享一下hive join空指针异常的示例分析，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！

2015-07-28 10:03:21,557 Stage-2 map = 100%,  reduce = 0%Ended Job = job_1437720498561_1035 with errorsError during job, obtaining debugging information...Examining task ID: task_1437720498561_1035_m_000000 (and more) from job job_1437720498561_1035Task with the most failures(4): -----Task ID:  task_1437720498561_1035_m_000000URL:  http://0.0.0.0:8088/taskdetails.jsp?jobid=job_1437720498561_1035&tipid=task_1437720498561_1035_m_000000-----Diagnostic Messages for this Task:Error: java.lang.RuntimeException: java.lang.NullPointerException        at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:172)        at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:54)        at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:453)        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:343)        at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:163)        at java.security.AccessController.doPrivileged(Native Method)        at javax.security.auth.Subject.doAs(Subject.java:415)        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)        at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:158)Caused by: java.lang.NullPointerException        at org.apache.hadoop.hive.ql.exec.MapJoinOperator.loadHashTable(MapJoinOperator.java:286)        at org.apache.hadoop.hive.ql.exec.MapJoinOperator.cleanUpInputFileChangedOp(MapJoinOperator.java:313)        at org.apache.hadoop.hive.ql.exec.Operator.cleanUpInputFileChanged(Operator.java:1069)        at org.apache.hadoop.hive.ql.exec.Operator.cleanUpInputFileChanged(Operator.java:1073)        at org.apache.hadoop.hive.ql.exec.Operator.cleanUpInputFileChanged(Operator.java:1073)        at org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:501)        at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:163)        ... 8 moreFAILED: Execution Error, return code 2 from org.apache.hadoop.hive.ql.exec.mr.MapRedTask

hive join 操作时若发生NullPointerException，请执行 set hive.auto.convert.join=false;
如设置hive.auto.convert.join的值为true，hive将在表的大小符合设置时自动使用MapJoin

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