protected boolean areAllParentsInitialized() {
    for (Operator<? extends OperatorDesc> parent : parentOperators) {
      if (parent != null && parent.state != State.INIT) {
        return false;
      }
    }
    return true;
  }
checks whether all parent operators are initialized or not.

@return true if there are no parents or all parents are initialized. false
        otherwise
ql/src/java/org/apache/hadoop/hive/ql/exec/Operator.java