Delphi with SQL Server: OLEDB vs. Native Client drivers

Question

I have been told that SQL Native Client is supposed to be faster than the OLEDB drivers. So I put together a utility to do a load-test between the two - and am getting

Answer 1

• The query execution time tells you how well the database engine (and any schema/query optimization) work well. Here what you use doesn't matter. ODBC/OLEDB/Native whatever just passes the query along to the database and it is executed there
• The time it takes to read from the first record to the last tells you how well the data access layer and your network perfom. Here you time how well data are returned and "cached" on your client. Depending on the data, the network settings may be important. For example if your tables use "large" records, a larger MTU may requires less packets (and less roundtrips) to send them to the client.

Anyway, before looking for a solution, you have to identify the problem. Profile your application, both client side and server side (SQL Server has good tools for that), and find what exactly makes it slower. Then and only then you can look for the correct solution. Maybe the data access layer is not the problem. 20,000 records is a small dataset today, not a large one.

Answer 2

Also, besides the lack of support for the XML data type, Delphi ADO does not recognize columns defined in SQL Server as TIME (DBTYPE_DBTIME2=145) or DATETIMEOFFSET (DBTYPE_DBTIMESTAMPOFFSET=146); trying to use those fields in your application will cause multiple errors like 'Invalid Variant Value' or some controls (like TDBGrid) will simply drop the field entirely.

Seems like the lack of support for DBTYPE_DBTIME2=145 is a bug/QC-issue since there is already ftTime support (it's also not clear to me why SQL Server doesn't return DBTYPE_DBTIME which Delphi does support), the XML and Offset types have no clear TFieldType mapping.

Data Type Support for OLE DB Date/Time Improvements