@Override
  protected void initializeChildren(Configuration hconf) throws HiveException {
    state = State.INIT;
    LOG.info("Operator " + id + " " + getName() + " initialized");
    if (childOperators == null || childOperators.isEmpty()) {
      return;
    }
    LOG.info("Initializing children of " + id + " " + getName());
    childOperatorsArray[0].initialize(hconf, outputObjectInspectors);
    if (reporter != null) {
      childOperatorsArray[0].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/MuxOperator.java