OLE DB Provider Development - Encapsulating a Service Provider

"OLE DB provider development" refers to the process of creating a software component, called an OLE DB provider, which enables applications to access data from a specific data source by implementing the OLE DB standard interfaces

1. OLE DB PROVIDER
DEVELOPMENT
Arun Seetharaman
Computer Call
January 20, 1999

2. AGENDA
•Universal Data Access
•What is an OLE DB provider?
•Creating an OLE DB provider with the OLE DB Provider
Templates
•Extending the provider
•Questions and answers

3. Data
access
Universal Data Access

4. WHAT IS AN OLE DB
DATA PROVIDER?
•Implements core OLE DB interfaces
•Common interfaces to native functionality
•Does not require data to look like a relational
database
•Implements extended OLE DB interfaces to
expose native extended functionality

5. SCENARIOS
•Relational Data
•ODBC Driver exists, No OLE DB Provider
•You App uses ADO to talk to OLE DB Provider for ODBC ,
which talks to the ODBC driver
◆Relational Data
⚫OLE DB Provider exists
⚫You App uses ADO to talk to OLE DB Provider

6. SCENARIOS
•Data in Exchange Server
•OLE DB Provider exists, No Query Engine
•You App uses ADO to talk to MS Exchange OLE DB Provider,
calls upon a Query Processor component to handle querying
◆Data in NT File System
⚫OLE DB Provider over Microsoft Index Server
⚫You App uses ADO to talk to OLE DB Provider

7. WHY WRITE A PROVIDER?
•To participate in Universal Data Access:
⚫Take advantage of ADO to provide C/C++,
Java, Visual Basic
®
, IIS and OLE
Automation programmers easy access to
your data
⚫Expose your data to SQL Server, Access,
Excel, and third-party consumers
⚫Add power to your data through common
Query Processor, Cursor, Notification, and
Remoting components
⚫Participate in heterogeneous joins

8. PROVIDER TEMPLATE SUPPORT
•You could implement a bunch
of interfaces
•OLE DB Provider Templates
•Implements 20 of the most common OLE DB interfaces
•New option in ATL Object Wizard
•Minimal providers ready to go
in ten minutes

9. PROVIDER TEMPLATE SUPPORT
•Implements data source, session, command, and rowset
objects
•Implements all mandatory interfaces
•Minimal case:
•Developer changes PROVIDER_COLUMN_MAP and Execute()
•Significant case:
•Developer adds in additional objects
and interfaces

10. CreateSession()
Session
IDBCreateCommand
IOpenRowset
Execute()
Rowset
Rowset
OpenRowset()
Command
ICommand
CreateCommand()
OLE DB PROVIDER STRUCTURE
Data Source
IDBCreateSession

11. PROPERTIES
•Can be set Objectwise
•Defines Object specific behaviour
•Type, Value, Read/Write attribute
•Property Sets
•Properties with the same GUID
•Many are Pre-defined in OLEDB
•Provider can define custom properties

12. GUID : PropertySet A
Count: 3
Pointer :
DBPROPSET Array
ID: Property 1
Value : Value1
ID: Property 2
Value : Value2
ID: Property 1
Value : Value1
GUID : PropertySet A
Count: 3
Pointer :
DBPROPIDSET Array
Property 1
Property 2
Property 3
DBPROPID Arrays

13. DATA SOURCE INTERFACES
•IDBProperties
•Sets properties used in initialization
•Returns information about
provider's capabilities
•Data Source Properties
Data Source Name, Version, Threading Model
•Initialization Properties
User ID, Password, Locale ID, Timeout

14. DATA SOURCE INTERFACES
•IDBInitialize
•Connects to the provider
•State Change to ‘Initialized’
◆ IDBCreateSession
⚫Gets a session object
◆ IPersist
⚫Returns your CLSID
⚫To persist Connection Information

15. SESSION INTERFACES
•IGetDataSource
•Returns parent datasource
•ISessionProperties
•Sets properties on session
Transaction Isolation Levels Supported in Auto-Commit Mode

16. SESSION INTERFACES
•IOpenRowset
•To Work directly with Table
•No overhead of Query Language support
◆IDBCreateCommand (Optional)
⚫Only if you support commands

17. COMMAND INTERFACES
•ICommandProperties
•Set properties for open rowset
◆ ICommandText
⚫ Set and execute command

18. COMMAND INTERFACES
•IAccessor
•Defines how parameters are read
•Binds each column or parameter to Consumer’s buffer
◆IColumnsInfo
⚫Provides metadata about Columns

19. ROWSET OBJECT
People
Name Address Papers Picture Voice
David
Mike
Monica
NY
CA
DC
...
IStream
IRowset
IDraw IPlay

20. ROWSET OBJECT
•Universal abstraction for tabular data
•Base data, query results,
computed data, schema…
◆ Rows can contain COM objects
◆Efficient, streamlined access to large objects

21. ROWSET OBJECT
•Rowset data can be shared
⚫Multiple Consumers
⚫Multiple Components
⚫Notifications
⚫Deferred/Immediate Updates

22. ROWSET INTERFACES
•IColumnsInfo
•Describes the columns of the rowset
◆IAccessor
⚫Defines how consumer reads data
◆ IRowsetInfo
⚫Returns rowset properties
 Updatability, Bookmarks ...
⚫Interface Support
 Find, Conversions ...

23. ROWSET INTERFACES
•IRowset
•GetNextRows retrieves row handles
•GetData reads data from row handles
◆ IConvertType
⚫Use the Data Conversion library

24. CREATING AN OLE DB PROVIDER
•Run the OLE DB Provider Wizard
•Generates COM objects for data source, session,
command, and rowset
•Modify and extend code

25. class CAgentMan
{
public:
TCHAR szCommand[256];
TCHAR szText[256];

BEGIN_PROVIDER_COLUMN_MAP(CAgentMan)
PROVIDER_COLUMN_ENTRY(“Field1”, 1, szCommand)
PROVIDER_COLUMN_ENTRY(“Field2”, 2, szText)
END_PROVIDER_COLUMN_MAP()
};
MODIFY DATA STRUCTURE
•Represents one row of data
•Contains data members and meta -data

26. HRESULT Execute(DBPARAMS * pParams, LONG* pcRowsAffected)
{
...
}
MODIFY EXECUTE IN ROWSET
•Command is stored in m_strCommandText
•Create instances of your
data structure
•Place instances in m_rgRowData
•Set pcRowsAffected

27. DEMO
•Creating a minimal provider
•Run Provider Wizard
•Modify data structure
•Modify PROVIDER_COLUMN_MAP
•Modify Execute()

28. EXTENDING THE PROVIDER
•Schema rowsets
•Properties
•Add in validation routines
•Add additional OLE DB interfaces

29. CONFORMANCE TESTS
•Generic OLE DB tests that:
•Verify conformance to minimum level
•Test correctness of exposed interfaces
•Based on sample test suites
in OLE DB SDK
•Provide a performance benchmark
•Include ADO acceptance tests

30. SUMMARY
•Writing a provider gives you…
•C/C++, OLE Automation, Java,
and scripting access to your data through ADO
•Exposure to Microsoft
®
and third-party tools, products, and
components