Hive OOM error when running a query with tez as execution engine

Question

when I am running the following query, I am getting the error below.

insert overwrite table mybug select row_number() over (order by clickstream_key) as key, clickstream_key as data from mytest;

It is launching around 2 mapper tasks and 240 reducer tasks and the job is going smooth and fast upto 239 tasks, it is taking 3 hrs to do do 4 task attempts and then the job is failing. Table mytest contains 2 billion records with one column "clickstream_key".

2016-07-24 09:54:37,918 [ERROR] [TezChild] |tez.TezProcessor|: java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:3181)
at java.util.ArrayList.grow(ArrayList.java:261)
at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:235)
at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:227)
at java.util.ArrayList.add(ArrayList.java:458)
at org.apache.hadoop.hive.ql.udf.generic.GenericUDAFRowNumber$RowNumberBuffer.incr(GenericUDAFRowNumber.java:73)
at org.apache.hadoop.hive.ql.udf.generic.GenericUDAFRowNumber$GenericUDAFRowNumberEvaluator.iterate(GenericUDAFRowNumber.java:102)
at org.apache.hadoop.hive.ql.udf.generic.GenericUDAFEvaluator.aggregate(GenericUDAFEvaluator.java:185)
at org.apache.hadoop.hive.ql.udf.ptf.WindowingTableFunction.evaluateWindowFunction(WindowingTableFunction.java:164)
at org.apache.hadoop.hive.ql.udf.ptf.WindowingTableFunction.iterator(WindowingTableFunction.java:580)
at org.apache.hadoop.hive.ql.exec.PTFOperator$PTFInvocation.finishPartition(PTFOperator.java:340)
at org.apache.hadoop.hive.ql.exec.PTFOperator.closeOp(PTFOperator.java:95)
at org.apache.hadoop.hive.ql.exec.Operator.close(Operator.java:617)
at org.apache.hadoop.hive.ql.exec.Operator.close(Operator.java:631)
at org.apache.hadoop.hive.ql.exec.tez.ReduceRecordProcessor.close(ReduceRecordProcessor.java:290)
at org.apache.hadoop.hive.ql.exec.tez.TezProcessor.initializeAndRunProcessor(TezProcessor.java:164)
at org.apache.hadoop.hive.ql.exec.tez.TezProcessor.run(TezProcessor.java:139)
at org.apache.tez.runtime.LogicalIOProcessorRuntimeTask.run(LogicalIOProcessorRuntimeTask.java:344)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable$1.run(TezTaskRunner.java:181)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable$1.run(TezTaskRunner.java:172)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1709)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable.callInternal(TezTaskRunner.java:172)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable.callInternal(TezTaskRunner.java:168)
at org.apache.tez.common.CallableWithNdc.call(CallableWithNdc.java:36)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
2016-07-24 09:54:37,920 [INFO] [TezChild] |task.TezTaskRunner|: Encounted an error while executing task: attempt_1469365079244_0001_1_01_000000_0
java.lang.RuntimeException: java.lang.OutOfMemoryError: Java heap space
at org.apache.hadoop.hive.ql.exec.tez.TezProcessor.initializeAndRunProcessor(TezProcessor.java:173)
at org.apache.hadoop.hive.ql.exec.tez.TezProcessor.run(TezProcessor.java:139)
at org.apache.tez.runtime.LogicalIOProcessorRuntimeTask.run(LogicalIOProcessorRuntimeTask.java:344)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable$1.run(TezTaskRunner.java:181)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable$1.run(TezTaskRunner.java:172)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:422)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1709)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable.callInternal(TezTaskRunner.java:172)
at org.apache.tez.runtime.task.TezTaskRunner$TaskRunnerCallable.callInternal(TezTaskRunner.java:168)
at org.apache.tez.common.CallableWithNdc.call(CallableWithNdc.java:36)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.OutOfMemoryError: Java heap space
at java.util.Arrays.copyOf(Arrays.java:3181)
at java.util.ArrayList.grow(ArrayList.java:261)
at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:235)
at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:227)
at java.util.ArrayList.add(ArrayList.java:458)
at org.apache.hadoop.hive.ql.udf.generic.GenericUDAFRowNumber$RowNumberBuffer.incr(GenericUDAFRowNumber.java:73)

I tried increasing data node heap, reducer heap, mapper heap, hive.tez.java.opts but none of them worked. Any leads on this would be highly appreciated. The error says java heap space, which java heap space does it mean ?