public static <T extends OperatorDesc> Operator<T> getAndMakeChild(
      CompilationOpContext cContext, T conf, RowSchema rwsch) {
    Operator<T> ret = get(cContext, (Class<T>) conf.getClass());
    ret.setConf(conf);
    ret.setSchema(rwsch);
    return ret;
  }
Returns an operator given the conf and a list of parent operators.
ql/src/java/org/apache/hadoop/hive/ql/exec/OperatorFactory.java