private Operator<? extends OperatorDesc> getFinalOp(Operator<? extends OperatorDesc> mergeMapOp) {
    for (Operator<? extends OperatorDesc> childOp : mergeMapOp.getChildOperators()) {
      if ((childOp.getChildOperators() == null) || (childOp.getChildOperators().isEmpty())) {
        return childOp;
      } else {
        return getFinalOp(childOp);
      }
    }
    return null;
  }
Process input from tez LogicalInput and write output - for a map plan
Just pump the records through the query plan.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/MapRecordProcessor.java