Hello,
I ran into a NPE today, which seems to be my fault, but I'm wondering if
there anythig that could be done to make the error more clear.
What I did it is:
'C = FOREACH B GENERATE group, (int)AVG(A.v) as statsavg;'
The problem here is the AVG ran into some null values and returned null. And
consequently the cast failed with a NPE.
This is the stacktrace
2010-02-09 11:14:36,444 [Thread-85] WARN
org.apache.hadoop.mapred.LocalJobRunner - job_local_0006
java.lang.NullPointerException
at org.apache.pig.builtin.IntAvg.getValue(IntAvg.java:282)
at org.apache.pig.builtin.IntAvg.getValue(IntAvg.java:39)
at
org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:208)
at
org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POUserFunc.getNext(POUserFunc.java:281)
at
org.apache.pig.backend.hadoop.executionengine.physicalLayer.expressionOperators.POCast.getNext(POCast.java:182)
at
org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.processPlan(POForEach.java:352)
at
org.apache.pig.backend.hadoop.executionengine.physicalLayer.relationalOperators.POForEach.getNext(POForEach.java:277)
at
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapReduce$Reduce.runPipeline(PigMapReduce.java:423)
at
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapReduce$Reduce.processOnePackageOutput(PigMapReduce.java:391)
at
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapReduce$Reduce.reduce(PigMapReduce.java:371)
at
org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.PigMapReduce$Reduce.reduce(PigMapReduce.java:239)
at
org.apache.hadoop.mapred.ReduceTask.runOldReducer(ReduceTask.java:463)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:411)
at
org.apache.hadoop.mapred.LocalJobRunner$Job.run(LocalJobRunner.java:215)
Now, because I'm not well aware how this works, I did not realize that the
cast throws the NPE and not the computation of the average function on null
values provided by the data set.
I initially thought this was a bug in Pig.
I know the NPE is all on me, but is there anything you can do to improve the
error message
thanks,
alex
