OLE DB 2.0 Architecture - Supporting Remote Data Exchange
0 likes5 views
Microsoft OLE DB stands for Object Linking and Embedding Database and provides a standardised way to represent and work with data from different sources, enabling applications to access and manipulate data in a consistent and efficient manner.
OLE DB 2.0 Architecture - Supporting Remote Data Exchange
- 1. OLE DB 2.0 ARCHITECTURE Arun Seetharaman Computer Call January 20, 1999
- 4. AGENDA ➔Review of OLE DB object model • New in OLE DB 2.0 • Connecting to OLE DB data sources • Navigating hierarchical data • OLE DB service components • Questions and answers
- 5. DATA AS A COMMON ABSTRACTION • Common representation of data • Code/knowledge reuse • Tools can access data generically • Generic components can add functionality • Components can combine different types of data ◆ Sharing data ⚫ Reduces memory footprint ⚫ Reduces data movement ⚫ Better component coordination
- 6. TERMINOLOGIES • Data Provider • Software that implements OLEDB Interfaces • Exposes data in a tabular form ◆ Consumer ⚫ Consumes the data ◆ Service Provider ⚫ Consumes data exposed by Data Provider ⚫ Transforms and provides data
- 7. OLE DB DESIGN PHILOSOPHY • Data stores provide interfaces to native functionality • Data store is not required to implement extended functionality ◆ Consumers assume common functionality ⚫ Consumers don't need excess conditional code ◆ “Service components” augment data store's native functionality ⚫ Generic, reusable components provide a guaranteed level of interoperability
- 8. Data source IDBCreateSession Rowset OpenRowset() Rowset Execute() OLE DB OBJECT MODEL ICommand Command CreateCommand() IDBCreateCommand IOpenRowset Session CreateSession()
- 9. AGENDA Review of OLE DB object model ➔New in OLE DB 2.0 ➔Connecting to OLE DB data sources • Navigating hierarchical data • OLE DB service components • Questions and answers
- 10. CONNECTING TO A DATA SOURCE BEFORE 2.0 • Via root enumerator • Passing provider’s CLSID to CoCreateInstance • Hard-code provider CLSIDs • Obtain CLSID via application specific code ◆ Disadvantages: ⚫ No common UI ⚫ No common way to represent or persist connection information
- 11. CONNECTING TO A DATA SOURCE OLE DB 2.0 • OLE DB 2.0 provides common services to connect to data sources: • IDataInitialize • Persists connection strings • Leverages OLE DB services (More on this later…) • IDBPromptInitialize • Uses the data links UI • Manages data source properties and data link (*.UDL) files
- 12. WHAT CAN I DO WITH IDATAINITIALIZE ? • Modify sample consumer to use IDataInitialize • Instantiate the OLE DB initialization service CLSID_MSDAINITIALIZE One simple change to current code • Create a Data Source object via IDataInitialize::CreateDBInstance
- 13. // Create the Initialization Component hr = CoCreateInstance( CLSID_MSDAINITIALIZE, NULL, CLSCTX_INPROC_SERVER, IID_IDataInitialize, (void **)&pIDataInit); if (FAILED(hr)) {… } // Create an instance of the OLE DB provider for Jet hr = pIDataInit->CreateDBInstance( CLSID_JETOLEDB_3_51, NULL, CLSCTX_INPROC_SERVER, NULL, IID_IDBInitialize, (IUnknown**) &pIDBInit); if (FAILED(hr)) {… }
- 14. WHAT ELSE CAN I DO WITH IDATAINITIALIZE? • Given a data source, retrieve a connection string • GetInitializationString • Persist a connection string • WriteStringToStorage
- 15. // Use IDataInitialize::GetInitializationString to return connection string hr = pIDataInit->GetInitializationString( (IUnknown*)pIDBInit, TRUE, &pwszInitString); if (FAILED(hr)) {… } // Use IDataInitialize::WriteStringToStorage to persist connection string hr = pIDataInit->WriteStringToStorage(pwszFileName, pwszInitString, CREATE_ALWAYS); if (FAILED(hr)) {… }
- 16. WHAT ELSE CAN I DO WITH IDATAINITIALIZE? • Persist a connection string • LoadStringFromStorage • Given a connection string, instantiate a data source object • GetDataSource
- 17. //Create the Initialization Component hr = CoCreateInstance( CLSID_MSDAINITIALIZE, NULL, CLSCTX_INPROC_SERVER, IID_IDataInitialize, (void **)&pIDataInit); if (FAILED(hr)) {… } // Read the initialization info from previous example hr = pIDataInit->LoadStringFromStorage(pwszFileName, &pwszInitString); if (FAILED(hr)) {… } // Create a Data Source object using the initialization string hr = pIDataInit->GetDataSource(NULL, CLSCTX_INPROC_SERVER, pwszInitString,IID_IDBInitialize, (IUnknown**) &pIDBInit); if (FAILED(hr)) {… }
- 18. DATA LINKS • Common UI for data sources • Can be used by any application • Reflects properties of the provider • Connection information can be persisted as “Data links” Data links can be used from ADO or OLE DB Invoked from desktop
- 19. IDBPROMPTINITIALIZE • Program access to the Data Links service • PromptDataSource • Opens data link properties dialog • Returns a data link with properties • PromptFileName • Opens Select data link dialog • Returns path to data link (*.UDL) file
- 20. DATA LINKS EXAMPLE • Demonstrate data links UI from Windows® desktop • Data links UI via RowsetViewer • RowsetViewer is available in the data access SDK
- 21. AGENDA Review of OLE DB object model New in OLE DB 2.0 Connecting to OLE DB data sources ➔Navigating hierarchical data • OLE DB service components • Questions and answers
- 22. NAVIGATING HIERARCHICAL DATA • Data is more than just isolated tables • Hierarchies arrange data “nodes” in a tree • Modeling hierarchies in OLE DB
- 23. OLE DB IRowset->GetNextRows(chap1,…) chap1 chap1 IRowset->GetNextRows(chap2,…) chap2 chap2 IRowset->GetNextRows(chap3,…) chap3 chap3 OLE DB ... ... ... ... ... ... ... ... ... ... ... HIERARCHIES VIA CHAPTERS • Efficiently expose hierarchical data through a single rowset per level • Appears as child recordsets in ADO 2.0
- 24. SHAPE EXAMPLE SHAPE {select * from Orders} APPEND({select * from `Order Details`} RELATE OrderID TO OrderID) Orders rowset OLE DB ... ... OLE DB ... ... ... ... Order details rowset chap1 chap2 chap3 ... ... ... ... ... chap1 chap2 chap3
- 25. SHAPE PROVIDER • Constructs hierarchical rowsets from data providers • Driven by Shape data manipulation syntax ◆ Types of Hierarchies ⚫ Appends chapter-valued columns to parent rowset ⚫ Generates parent rowset from child rowset with aggregations ⚫ Parameterised Hierarchies
- 26. SHAPE EXAMPLE • Load shape provider’s data link from storage • Create a command object • Set command text with a shape command • Set any rowset properties on the command • Execute the command to obtain parent rowset
- 27. // Create an instance of the OLE DB Initialization Component hr = CoCreateInstance( CLSID_MSDAINITIALIZE, NULL, CLSCTX_INPROC_SERVER, IID_IDataInitialize, (void **)&pIDataInit); if (FAILED(hr)) { ...} // Read the Data Link file for this example: hr = pIDataInit->LoadStringFromStorage(pwszFileName, &pwszInitString); if (FAILED(hr)) { ...} // Create a Data Source object using the initialization string hr = pIDataInit->GetDataSource(NULL, CLSCTX_INPROC_SERVER, pwszInitString,IID_IDBInitialize, (IUnknown**) &pIDBInit); if (FAILED(hr)) { ...}
- 28. // Create the command object hr = pSession->QueryInterface( IID_IDBCreateCommand,(void **)&pIDBCreateCommand ); if (FAILED(hr)) { ...} hr = pIDBCreateCommand->CreateCommand( NULL, IID_ICommandText, (IUnknown **)&pICommandText); if (FAILED(hr)) { ...} pwsz_CommandText = L"SHAPE{select * from Orders} COMPUTE (SUM(FREIGHT)) as CHAPTER by customerID) "; hr = pICommandText->SetCommandText( guidDialect, pwsz_CommandText); if (FAILED(hr)) { ...}
- 29. NAVIGATING CHAPTERS • IParentRowset::GetChildRowset returns child rowset • IRowset:GetNextRows(hChapter…) returns child rows for that chapter
- 30. AGENDA Review of OLE DB object model New in OLE DB 2.0 Connecting to OLE DB data sources Navigating hierarchical data ➔OLE DB service components • Questions and answers
- 31. SERVICE COMPONENTS • What are service components? • How do they work? • 2.0 service components • Client cursor engine • Resource pooling • How do I use them?
- 32. Service Components make up the difference Minimum provider interfaces Service components OLE DB consumer WHAT ARE SERVICE COMPONENTS? • A bridge between consumer expectation and provider capability
- 33. WHAT ARE SERVICE COMPONENTS? • OLE DB core components that augment a provider’s functionality • Work with existing providers • Without knowledge of the service • Without special logic • Work with consumers • ADO uses them automatically
- 34. SERVICE COMPONENTS • Service component manager • Invokes services as needed • Handles navigation between interfaces implemented by different objects • Provides a common entry point for hooking other services • Consumer calls methods directly OLE DB rowset Provider rowset Service component manager Service component Service component
- 35. 2.0 SERVICE COMPONENTS • Client cursor engine • Scrollable cursors • IRowsetFind implementation • Updateable rowsets over a SQL provider ◆ Resource pooling ⚫ Multiple, homogenous pools ⚫ Caches provider information ⚫ Automatic transaction enlistment in Microsoft Transaction Server
- 36. USING SERVICE COMPONENTS • Invoking service components • Create a data source using IDataInitialize or IDBPromptInitialize • Use ADO • Use the data links UI • Service component manager determines which services to invoke • Applications should request the functionality they want • Via command and rowset properties
- 37. DISABLING SERVICE COMPONENTS • By provider • OLEDB_SERVICES registry entry ◆ By Consumer ⚫ Property control of core services ⚫ “OLE DB Services” String
- 38. CLIENT CURSOR EXAMPLE • Connect to a sample provider • Request backwards scrolling • Re-connect using service components • Demonstrate scrolling
- 39. OLE DB RESOURCE POOLING • Improves performance and scaling • Works with Microsoft Transaction Server • What is pooled? • Initialized data source object Based on connection info • Associated session object • Provides multiple, homogenous pools • Reduces contention • Manages object lifetimes and state changes
- 40. OLE DB POOLING • Application • Calls middle tier object ◆ OLE DB services ⚫ Returns proxy DSO ⚫ Sets initialization properties ⚫ Calls Initialize() ⚫ Caches information ⚫ Sets cached properties ⚫ Calls Initialize() ⚫ Creates a session ⚫ Enlists in transaction ⚫ Does work Windows NT MTS ◆ Middle tier object ⚫ Calls CreateDBInstance() OLE DB services OLE DB ⚫ Creates provider DSO SQL Server DSO Provider DCOM MT O
- 41. OLE DB POOLING • Application • Calls middle tier object ◆ Middle tier object ⚫ Calls CreateDBInstance() ◆ OLE DB services ⚫ Returns proxy DSO ⚫ Sets initialization properties ⚫ Calls Initialize() ⚫ Caches information ⚫ Creates Provider DSO ⚫ Sets cached properties ⚫ Calls Initialize() ⚫ Creates a Session ⚫ Enlists in transaction ⚫ Does work ⚫ Goes away Windows NT MTS OLE DB services OLE DB SQL Server DSO Provider
- 42. OLE DB POOLING Windows NT MTS OLE DB services OLE DB SQL Server DSO Provider HTTP Internet Information Server MT O Web browser ⚫ Calls middle tier object ⚫ Calls CreateDBInstance() ⚫ Returns proxy DSO ⚫ Sets initialization properties ⚫ Calls Initialize() ⚫ Caches information ⚫ Sets cached properties ⚫ Calls Initialize() ⚫ Creates a Session ⚫ Enlists in transaction ⚫ Does work Provider OLE DB DSO Oracle ◆ Creates provider DSO ◆ Middle tier object ◆ OLE DB Services ◆ Web browser
- 43. OLE DB POOLING Windows NT MTS OLE DB services OLE DB SQL Server DSO Provider Web browser ⚫ Calls middle tier object ⚫ Calls CreateDBInstance() ⚫ Returns proxy DSO ⚫ Sets initialization properties ⚫ Calls Initialize() ⚫ Caches information ⚫ Sets cached properties ⚫ Calls Initialize() ⚫ Creates a Session ⚫ Enlists in transaction ⚫ Does work ⚫ Goes away Provider OLE DB DSO Oracle ◆ Creates provider DSO ◆ Middle tier object ◆ OLE DB Services ◆ Web browser
- 44. OLE DB POOLING Windows NT MTS OLE DB services OLE DB SQL Server Provider DSO Web browser Provider DSO Oracle DCOM MT O ◆ Application ⚫ Calls middle tier object ◆ OLE DB Services ⚫ Sets initialization properties ⚫ Calls CreateDBInstance() ⚫ Caches information ⚫ Does work ◆ Middle tier object ⚫ Returns proxy DSO ⚫ Returns DSO from pool DSO ⚫ Calls Initialize()
- 45. OLE DB POOLING Windows NT MTS OLE DB services OLE DB SQL Server Provider DSO Web browser Provider DSO Oracle ◆ Application ⚫ Calls middle tier object ◆ Middle tier object ⚫ Calls CreateDBInstance() ⚫ Sets initialization properties ⚫ Calls Initialize() ⚫ Does work ⚫ Goes away ◆ OLE DB services ⚫ Returns proxy DSO ⚫ Caches information ⚫ Returns DSO from pool
- 46. Windows NT MTS OLE DB services OLE DB SQL Server Provider DSO Web browser Provider DSO Oracle ◆ Application ◆ Middle tier object ◆ OLE DB services OLE DB POOLING
- 47. OLE DB POOLING OLE DB Services MTS Web browser Windows NT OLE DB DSO SQL Server Provider ◆ Application ◆ Middle tier object ◆ OLE DB services ⚫ Oracle connection times out
- 48. OLE DB POOLING OLE DB Services MTS Web browser Windows NT ◆ Application ◆ Middle tier object ◆ OLE DB services ⚫ Oracle connection times out ⚫ SQL Server connection times out
- 49. LEVERAGING OLE DB POOLING • Connect using CreateDBInstance, GetDataSource, or data links UI • Don’t request provider specific interfaces prior to connecting • Don’t request prompting • Don’t uninitialize • Only use one session per connection • …or, just use ADO!
- 50. OLE DB SUMMARY • OLE DB 2.0 improves the architecture for universal data access • Easier access to your data sources • Ability to model hierarchical data • Service components • OLE DB 2.0 service components • Client cursor engine support for scrolling and searching • Resource pooling improves performance and scalability • Leveraging service components is easy