title: Core Data relationship breaks on updating DB - Restkit
body: <p>I have two entities 'Parent' and 'Child'. Parent Entity has one-many relationship with Child Entity and child has one-one relationship with parent and "Parent" Entity has an unique id (primary key attribute) which i am mapping each time.</p>
  
  <p>When i call an API, the response is coming like this</p>
  
  <pre><code>{
      "parent": {
          "ss": "1",
          "uid": 200,
          "me": "Successfully Retrieved",
          "pn": 2,
          "cl": [
              {
                  "cid": 1500,
                  "cn": "XYZ"
              },
              {
                  "cid": 1501,
                  "cn": "ABC"
              }
          ]
      }
  }
  </code></pre>
  
  <p>The above response is successfully mapped to DB. i can access by [parent.childs allObjects] which returns two objects.</p>
  
  <p>I have an load more functionality which is calling same api and page number incremented by 1 and i get the response(3 objects)  similar to above one. But when i try to fetch data from DB i get only 3 objects that came on latest response. The relationship for the two object that i mapped earlier becomes empty. so i am not able to access all objects. How can i access all data from DB by relationship.</p>
  
  <p>This is how i am mapping</p>
  
  <pre><code>RKObjectManager *manager = [[RestKit sharedDataManager] objectManager];
          RKEntityMapping *parentMapping = [[MFResponseMapper sharedInstance]parentMapper]; //Primary key is mapping here
          RKEntityMapping *childMapping = [[MFResponseMapper sharedInstance]childMapper]; //Child name and Id is mapping here.
  
          [parentMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"cl"
                                                                                      toKeyPath:@"childs"
                                                                                    withMapping:childMapping]];
  
  
          RKResponseDescriptor *responseDescriptor = [RKResponseDescriptor responseDescriptorWithMapping:parentMapping
                                                                                         pathPattern:nil
                                                                                             keyPath:@"parent"
                                                                                         statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)];
  
          [manager addResponseDescriptor:responseDescriptor];
  </code></pre>
  
  <p>Note: i have delete rule for Parent-Child (one-many) relationship in model.</p>
  
  <p>Thanks</p>