public static boolean checkPrefixKeys(List<ExprNodeDesc> childKeys, List<ExprNodeDesc> parentKeys,
      Operator<? extends OperatorDesc> childOp, Operator<? extends OperatorDesc> parentOp)
          throws SemanticException {
    return checkPrefixKeys(childKeys, parentKeys, childOp, parentOp, false);
  }
Checks whether the keys of a parent operator are a prefix of the keys of a
child operator.
@param childKeys keys of the child operator
@param parentKeys keys of the parent operator
@param childOp child operator
@param parentOp parent operator
@return true if the keys are a prefix, false otherwise
@throws SemanticException
ql/src/java/org/apache/hadoop/hive/ql/plan/ExprNodeDescUtils.java