IKnowledgeSyncProvider::ProcessChangeBatch

Processes a set of changes by detecting conflicts and applying changes to the item store.

HRESULT ProcessChangeBatch(
  CONFLICT_RESOLUTION_POLICY resolutionPolicy,
  ISyncChangeBatch * pSourceChangeBatch,
  IUnknown * pUnkDataRetriever,
  ISyncCallback * pCallback,
  SYNC_SESSION_STATISTICS * pSyncSessionStatistics);

Parameters

• resolutionPolicy
  [in] The conflict resolution policy to use when this method applies changes.

• pSourceChangeBatch
  [in] A batch of changes from the source provider to be applied locally.

• pUnkDataRetriever
  [in] An object that can be used to retrieve change data. It can be an ISynchronousDataRetriever object or a provider-specific object.

• pCallback
  [in] An object that receives event notifications during change application.

• pSyncSessionStatistics
  [in, out] Tracks change statistics. For a provider that uses custom change application, this object must be updated with the results of the change application.

Return Value

• S_OK

• Provider-determined error codes

Remarks

When a source change contains change unit changes, the destination provider must determine which, if any, change unit versions to include in the batch of destination versions that is sent to the change applier. This decision depends on the kind of change from the source provider and whether the item is marked as deleted on the destination replica. For more information, see Synchronizing Change Units.

Example

The following examples show how to implement ProcessChangeBatch. The first example shows how to create an ISynchronousNotifyingChangeApplier object and call ISynchronousNotifyingChangeApplier::ApplyChanges to apply changes to the destination replica. The second example implements the m_pMetadataMgr->GetItemBatchVersions method used in the first example. This method enumerates the changes contained in the source change batch and creates a corresponding list of destination versions by using an IDestinationChangeVersionsBuilder object.

STDMETHODIMP CXMLProvider::ProcessChangeBatch(
    CONFLICT_RESOLUTION_POLICY resolutionPolicy,
    ISyncChangeBatch * pSourceChangeBatch,
    IUnknown * pUnkDataRetriever,
    ISyncCallback * pCallback,
    SYNC_SESSION_STATISTICS * pSyncSessionStatistics)
{
    HRESULT hr = E_UNEXPECTED;

    if (NULL == pSourceChangeBatch || NULL == pUnkDataRetriever || NULL == pSyncSessionStatistics)
    {
        hr = E_POINTER;
    }
    else
    {
        IEnumSyncChanges* pDestinationChangeEnum = NULL;

        _ASSERT(NULL != m_pMetadataMgr);

        // Obtain the local (destination) versions for the items in the source change batch.
        hr = m_pMetadataMgr->GetItemBatchVersions(pSourceChangeBatch, &pDestinationChangeEnum);
        if (SUCCEEDED(hr))
        {
            IProviderSyncServices* pProviderSvc = NULL;
            hr = GetProviderSyncServices(&c_idParams, &pProviderSvc);
            if (SUCCEEDED(hr))
            {
                // Create a standard change applier from Sync Framework.
                ISynchronousNotifyingChangeApplier* pChangeApplier = NULL;
                hr = pProviderSvc->CreateChangeApplier(IID_ISynchronousNotifyingChangeApplier,
                    (void**)&pChangeApplier);
                if (SUCCEEDED(hr))
                {
                    ISyncKnowledge* pDestinationKnowledge = NULL;
                    hr = m_pMetadataMgr->GetKnowledge(&pDestinationKnowledge);
                    if (SUCCEEDED(hr))
                    {
                        // Have the change applier process the change batch and apply changes.
                        // This method will call the change applier target methods to save
                        // changes and conflicts.  It will also pass the data retriever
                        // interface to the change applier target so it can retrieve item data.
                        hr = pChangeApplier->ApplyChanges(resolutionPolicy, pSourceChangeBatch, 
                            pUnkDataRetriever, pDestinationChangeEnum, pDestinationKnowledge, 
                            NULL, this, m_pSessionState, pCallback);
                        
                        pDestinationKnowledge->Release();
                    }

                    pChangeApplier->Release();
                }

                pProviderSvc->Release();
            }

            pDestinationChangeEnum->Release();
        }
    }

    return hr;
}

STDMETHODIMP CMetadataMgr::GetItemBatchVersions(
    ISyncChangeBatch * pRemoteSyncChangeBatch,
    IEnumSyncChanges ** ppLocalVersionsEnum)
{
    HRESULT hr = E_UNEXPECTED;

    if (NULL == pRemoteSyncChangeBatch || NULL == ppLocalVersionsEnum)
    {
        hr = E_POINTER;
    }
    else
    {
        IProviderSyncServices* pProvSvc;
        hr = GetProviderSyncServices(&c_idParams, &pProvSvc);
        if (SUCCEEDED(hr))
        {
            IDestinationChangeVersionsBuilder* pDestChangeBuilder = NULL;
            hr = pProvSvc->CreateDestinationChangeVersionsBuilder(&pDestChangeBuilder);
            if (SUCCEEDED(hr))
            {
                IEnumSyncChanges* pRemoteEnum = NULL;
                hr = pRemoteSyncChangeBatch->GetChangeEnumerator(&pRemoteEnum);
                if (SUCCEEDED(hr))
                {
                    ULONG cFetched;

                    ISyncChange* pChange;
                    SYNC_GID gidItem;
                    DWORD cbID = sizeof(gidItem);
                    DWORD dwFlags;
                    SYNC_VERSION verCurrent;
                    SYNC_VERSION verCreation;
                    HRESULT hrEnum = S_OK;
                    while (S_OK == hrEnum && SUCCEEDED(hr))
                    {
                        pChange = NULL;
                        hrEnum = pRemoteEnum->Next(1, &pChange, &cFetched);
                        if (S_OK == hrEnum)
                        {
                            hr = pChange->GetRootItemId((BYTE*)&gidItem, &cbID);
                            if (SUCCEEDED(hr))
                            {
                                // Try to find the item in the local (destination) metadata.
                                IItemMetadata* pItem = NULL;
                                hr = FindItemMetadataByGlobalId((BYTE*)&gidItem, &pItem);
                                if (S_OK == hr)
                                {
                                    // S_OK means the item exists in our local store.
                                    // Extract its version and tombstone information.
                                    dwFlags = 0;

                                    BOOL fTombstone = FALSE;
                                    hr = pItem->GetIsDeleted(&fTombstone);
                                    if (SUCCEEDED(hr))
                                    {
                                        if (fTombstone)
                                        {
                                            dwFlags = SYNC_CHANGE_FLAG_DELETED;
                                        }
                                    }

                                    if (SUCCEEDED(hr))
                                    {
                                        hr = pItem->GetChangeVersion(&verCurrent);
                                        if (SUCCEEDED(hr))
                                        {
                                            hr = pItem->GetCreationVersion(&verCreation);                                            
                                        }
                                    }

                                    pItem->Release();
                                }
                                else if (S_FALSE == hr)
                                {
                                    // S_FALSE means this item does not exist in our local store.
                                    // Set versions to 0 and flag it as a new item.
                                    verCurrent.dwLastUpdatingReplicaKey = 0;
                                    verCurrent.ullTickCount = 0;
                                    verCreation.dwLastUpdatingReplicaKey = 0;
                                    verCreation.ullTickCount = 0;
                                    dwFlags = SYNC_CHANGE_FLAG_DOES_NOT_EXIST;
                                }

                                if (SUCCEEDED(hr))
                                {
                                    // Add the item to the batch of destination versions.
                                    GUID guidReplicaID = GUID_NULL;
                                    ULONG cbID = sizeof(guidReplicaID);
                                    hr = GetReplicaId((BYTE*)&guidReplicaID, &cbID);
                                    if (SUCCEEDED(hr))
                                    {
                                        hr = pDestChangeBuilder->AddItemMetadata((BYTE*)&guidReplicaID,
                                            (BYTE*)&gidItem, &verCurrent, &verCreation, dwFlags, NULL);
                                    }
                                }
                            }

                            pChange->Release();
                        }
                    }

                    if (FAILED(hrEnum))
                    {
                        hr = hrEnum;                    
                    }

                    pRemoteEnum->Release();                
                }

                if (SUCCEEDED(hr))
                {
                    hr = pDestChangeBuilder->GetChangeEnumerator(ppLocalVersionsEnum);               
                }

                pDestChangeBuilder->Release();
            }

            pProvSvc->Release();        
        }
    }

    return hr;
}

See Also

Reference

IKnowledgeSyncProvider Interface
CONFLICT_RESOLUTION_POLICY Enumeration