Hi Folks This issue occurs on Hive 0.4 and 0.5. I wanted to wait on opening a JIRA ticket until I ran it by the community first.
I'm testing Hive 0.5 running on Apache Hadoop 0.20.2 which is using IBM Java 6 (32 bit x86 Java SR8 : which can be obtained here - https://www.ibm.com/developerworks/java/jdk/linux/download.html) To recreate this I'm using the pokes table loaded with data from the examples directory, per the tutorial and I run the following in the Hive CLI (bin/hive) : select count(1) from pokes; This works just fine on Sun/Oracle Java 6, but when I change the Hadoop-env to point to IBM Java 6 it fails in the Map with the following exception : Caused by: java.lang.ClassCastException: org.apache.hadoop.hive.serde2.objectinspector.primitive.WritableIntObjectInspector incompatible with org.apache.hadoop.hive.serde2.objectinspector.primitive.LongObjectInspector at org.apache.hadoop.hive.ql.udf.generic.GenericUDAFCount$GenericUDAFCountEvaluator.merge(GenericUDAFCount.java:104) at org.apache.hadoop.hive.ql.udf.generic.GenericUDAFEvaluator.aggregate(GenericUDAFEvaluator.java:113) at org.apache.hadoop.hive.ql.exec.GroupByOperator.updateAggregations(GroupByOperator.java:451) at org.apache.hadoop.hive.ql.exec.GroupByOperator.processHashAggr(GroupByOperator.java:591) at org.apache.hadoop.hive.ql.exec.GroupByOperator.processOp(GroupByOperator.java:500) ... 14 more Note, the line number in GenericUDAFCount here is off by 4 based on a couple of LOG.info calls I added for debugging purposes. The net of it is that it is failing when it attempts to do the following cast in the merge method: (LongObjectInspector)inputOI This is where it gets weird. In SUN Java, this method gets called in the Reducer. In IBM Java, it gets called in the Mapper. If I use EXPLAIN in the Hive CLI, the execution plans are identical regardless of which JRE is being used in Hadoop. In SUN Java, the type for inputOI is a BigInt which is being derived off of a single column schema called _col0_ in the reducer (likely the output tuple of the count result) and casts to a Long with no problem. In IBM Java, this call is happening in the Map and inputOI is being derived off of what appears to be the first column of the Spokes table schema, which is an int and is therefore failing when being cats to a Long. It appears the cast is merely symptomatic of a difference in the execution plans. Debugging from this point, really requires someone who understands HIVE execution plans better than I do. Is there anyone that can help with this issue? This is really easy to replicate. Download the IBM JDK, mod your hadoop env to point to the extracted dir of the IBM JDK and do a select count from any table. Regards Steve Watt
