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From "Ryan Shih (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-320) Issuing queries with COUNT(DISTINCT) on a column that may contain null values hits a NPE
Date Wed, 04 Mar 2009 02:50:56 GMT
Issuing queries with COUNT(DISTINCT) on a column that may contain null values hits a NPE
----------------------------------------------------------------------------------------

                 Key: HIVE-320
                 URL: https://issues.apache.org/jira/browse/HIVE-320
             Project: Hadoop Hive
          Issue Type: Bug
          Components: Query Processor
    Affects Versions: 0.2.0
            Reporter: Ryan Shih
            Priority: Minor


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



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