@Override
  public int hashCode() {
    int result = clusterId !=null ? clusterId.intValue() : 0;
    result = 31 * result + (currentClusterState != null ? currentClusterState.hashCode() : 0);
    return result;
  }
Unidirectional one-to-one association to {@link StackEntity}
ambari-server/src/main/java/org/apache/ambari/server/orm/entities/ClusterStateEntity.java