Grokbase Groups Hive user June 2010
FAQ
Hello,

I'm getting java.lang.NullPointerException(null) when try to query columns
from an empty table (hive is running on Amazon Elastic MapReduce).


Here is the reproduction:

hive> CREATE EXTERNAL TABLE t1 (
request string
)
PARTITIONED BY (source STRING)
ROW FORMAT DELIMITED FIELDS TERMINATED BY '9'
LOCATION 's3://bucket-name/exception/'
;

hive> select * from t1;
OK
Time taken: 0.078 seconds


hive> select request from t1;
Total MapReduce jobs = 1
Number of reduce tasks is set to 0 since there's no reduce operator
Job Submission failed with exception 'java.lang.NullPointerException(null)'
FAILED: Execution Error, return code 1 from
org.apache.hadoop.hive.ql.exec.ExecDriver


Trying the same queries on an unpartitioned table works:

hive> drop table t1;
OK
hive> CREATE EXTERNAL TABLE t1 (request string)
ROW FORMAT DELIMITED FIELDS TERMINATED BY '9'
LOCATION 's3://bucket-name/exception/';
OK
hive> select * from t1;
OK
hive> select request from t1;
Total MapReduce jobs = 1
Number of reduce tasks is set to 0 since there's no reduce operator
Starting Job = job_201006061250_0038, Tracking URL =
http://ip-10-242-230-112.ec2.internal:9100/jobdetails.jsp?jobid=job_201006061250_0038
Kill Command = /home/hadoop/.versions/0.18/bin/../bin/hadoop job
-Dmapred.job.tracker=ip-10-242-230-112.ec2.internal:9001 -kill
job_201006061250_0038
2010-06-06 07:39:59,006 map = 0%, reduce =0%
2010-06-06 07:40:04,048 map = 100%, reduce =100%
Ended Job = job_201006061250_0038
OK


Can I tune something to make hive not NPE on empty tables or should I open a
bug report?


Thank you,
Maxim.

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postedJun 6, '10 at 7:51p
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