protected void initializeChildren(Configuration hconf) throws HiveException {
    state = State.INIT;
    LOG.debug("Operator Initialized: {}", this);

    if (CollectionUtils.isEmpty(childOperators)) {
      return;
    }

    LOG.debug("Initializing Children: {}", this);

    for (int i = 0; i < childOperatorsArray.length; i++) {
      childOperatorsArray[i].initialize(hconf, outputObjInspector, childOperatorsTag[i]);
      if (reporter != null) {
        childOperatorsArray[i].setReporter(reporter);
      }
    }
  }
Calls initialize on each of the children with outputObjetInspector as the
output row format.
ql/src/java/org/apache/hadoop/hive/ql/exec/Operator.java