[HIVE-11216] UDF GenericUDFMapKeys throws NPE when a null map value is passed in

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.2.0
• Fix Version/s: 1.0.2, 1.2.2, 1.3.0, 2.0.0
• Component/s: UDF
• Assignee: Yibing Shi
• Reporter: Yibing Shi
• Created: 09/Jul/15 10:10
• Updated: 16/Feb/16 23:51
• Resolved: 16/Jul/15 18:47

Description

We can reproduce the problem as below:

hive> show create table map_txt;
OK
CREATE  TABLE `map_txt`(
  `id` int,
  `content` map<int,string>)
ROW FORMAT SERDE
  'org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe'
STORED AS INPUTFORMAT
  'org.apache.hadoop.mapred.TextInputFormat'
OUTPUTFORMAT
  'org.apache.hadoop.hive.ql.io.HiveIgnoreKeyTextOutputFormat'
...
Time taken: 0.233 seconds, Fetched: 18 row(s)
hive> select * from map_txt;
OK
1       NULL
Time taken: 0.679 seconds, Fetched: 1 row(s)
hive> select id, map_keys(content) from map_txt;
....
Error during job, obtaining debugging information...
Examining task ID: task_1435534231122_0025_m_000000 (and more) from job job_1435534231122_0025

Task with the most failures(4):
-----
Task ID:
  task_1435534231122_0025_m_000000

URL:
  http://host-10-17-80-40.coe.cloudera.com:8088/taskdetails.jsp?jobid=job_1435534231122_0025&tipid=task_1435534231122_0025_m_000000
-----
Diagnostic Messages for this Task:
Error: java.lang.RuntimeException: org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime Error while processing row {"id":1,"content":null}
        at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:198)
        at org.apache.hadoop.mapred.MapRunner.run(MapRunner.java:54)
        at org.apache.hadoop.mapred.MapTask.runOldMapper(MapTask.java:450)
        at org.apache.hadoop.mapred.MapTask.run(MapTask.java:343)
        at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:168)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:422)
        at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1642)
        at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:163)
Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Hive Runtime Error while processing row {"id":1,"content":null}
        at org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:559)
        at org.apache.hadoop.hive.ql.exec.mr.ExecMapper.map(ExecMapper.java:180)
        ... 8 more
Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: Error evaluating map_keys(content)
        at org.apache.hadoop.hive.ql.exec.SelectOperator.processOp(SelectOperator.java:84)
        at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:796)
        at org.apache.hadoop.hive.ql.exec.TableScanOperator.processOp(TableScanOperator.java:92)
        at org.apache.hadoop.hive.ql.exec.Operator.forward(Operator.java:796)
        at org.apache.hadoop.hive.ql.exec.MapOperator.process(MapOperator.java:549)
        ... 9 more
Caused by: java.lang.NullPointerException
        at org.apache.hadoop.hive.ql.udf.generic.GenericUDFMapKeys.evaluate(GenericUDFMapKeys.java:64)
        at org.apache.hadoop.hive.ql.exec.ExprNodeGenericFuncEvaluator._evaluate(ExprNodeGenericFuncEvaluator.java:166)
        at org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator.evaluate(ExprNodeEvaluator.java:77)
        at org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator.evaluate(ExprNodeEvaluator.java:65)
        at org.apache.hadoop.hive.ql.exec.SelectOperator.processOp(SelectOperator.java:79)
        ... 13 more


FAILED: Execution Error, return code 2 from org.apache.hadoop.hive.ql.exec.mr.MapRedTask
MapReduce Jobs Launched:
Stage-Stage-1: Map: 1   HDFS Read: 0 HDFS Write: 0 FAIL
hive>

The error is as below (in mappers):

Caused by: java.lang.NullPointerException
        at org.apache.hadoop.hive.ql.udf.generic.GenericUDFMapKeys.evaluate(GenericUDFMapKeys.java:64)
        at org.apache.hadoop.hive.ql.exec.ExprNodeGenericFuncEvaluator._evaluate(ExprNodeGenericFuncEvaluator.java:166)
        at org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator.evaluate(ExprNodeEvaluator.java:77)
        at org.apache.hadoop.hive.ql.exec.ExprNodeEvaluator.evaluate(ExprNodeEvaluator.java:65)
        at org.apache.hadoop.hive.ql.exec.KeyWrapperFactory$ListKeyWrapper.getNewKey(KeyWrapperFactory.java:113)
        at org.apache.hadoop.hive.ql.exec.GroupByOperator.processOp(GroupByOperator.java:778)
        ... 17 more

Looking at the source code:

  public Object evaluate(DeferredObject[] arguments) throws HiveException {
    retArray.clear();
    Object mapObj = arguments[0].get();
    retArray.addAll(mapOI.getMap(mapObj).keySet());
    return retArray;
  }

It is obvious that we will have a NPE when a NULL map value is passed in