private static void proveEquals(Map<String, Object> m1, Map<String, Object> m2) {
    for (Entry<String, Object> e : m1.entrySet()) {
      String key = e.getKey();
      Object v1 = e.getValue();
      Object v2 = m2.get(key);
      if (v1 == v2) {
        continue;
      }
      if (v1 == null || v2 == null || !v1.equals(v2)) {
        throw new RuntimeException(String.format("equals fails: %s (%s!=%s)", key, v1, v2));
      }
    }
  }
Holds the signature of the operator; the keys are are the methods name marked by {@link Signature}.
ql/src/java/org/apache/hadoop/hive/ql/optimizer/signature/OpSignature.java