[HIVE-320] Issuing queries with COUNT(DISTINCT) on a column that may contain null values hits a NPE

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 0.3.0, 0.6.0
• Fix Version/s: 0.3.0
• Component/s: Query Processor
• Hadoop Flags: Reviewed
• Assignee: Namit Jain
• Reporter: Ryan Shih
• Created: 04/Mar/09 02:50
• Updated: 17/Dec/11 00:08
• Resolved: 17/Mar/09 01:14

Description

When issuing a query that may contain a null value, I get a NPE.

E.g. if 'middle_name' potentially holds null values,

select count(distinct middle_name) from people; will fail with the below exception.

Other queries that work with the same input set:
select distinct middle_name from people;
select count(1), middle_name from people group by middle_name;

java.io.IOException: org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.NullPointerException
at org.apache.hadoop.hive.ql.exec.ExecReducer.reduce(ExecReducer.java:169)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:318)
at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:2198)
Caused by: org.apache.hadoop.hive.ql.metadata.HiveException: java.lang.NullPointerException
at org.apache.hadoop.hive.ql.exec.GroupByOperator.process(GroupByOperator.java:424)
at org.apache.hadoop.hive.ql.exec.ExecReducer.reduce(ExecReducer.java:164)
... 2 more
Caused by: java.lang.NullPointerException
at org.apache.hadoop.hive.ql.exec.GroupByOperator.updateAggregations(GroupByOperator.java:376)
at org.apache.hadoop.hive.ql.exec.GroupByOperator.processAggr(GroupByOperator.java:477)
at org.apache.hadoop.hive.ql.exec.GroupByOperator.process(GroupByOperator.java:420)
... 3 more

Issue Links

• duplicates: HIVE-326 [hive] groupby count distinct with nulls has some problems