@Override
  public GenericUDAFEvaluator getEvaluator(TypeInfo[] parameters) throws SemanticException {
    return new GenericUDAFExceptionInVertexEvaluator();
  }
This class implements the UDAF which can throw an exception in arbitrary aggregating vertex
(typically reducer) / task / task attempt.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDAFExceptionInVertex.java