Editorials

Backwards Compatibility

by Ben Taylor

Backwards Compatibility
Backwards Compatibility is the mirror image of the problem introduced yesterday. The problem we have with Forward Compatibility is the ability to use new features, and emulate those features using creative techniques in older versions that do not support the new features. This goal is often not possible for one reason or another.
An example of Forward or Cross Version compatibility is writing your own user defined compression function using SQL CLR for versions of SQL Server not supporting compression natively.

Backwards compatibility is the opposite. What do you do when features formerly supported in SQL Server are deprecated, but you have software requiring those features. In this case, the solution is the same as Backwards Compatibility. In the newer software you have the option of rolling your own implementation of the deprecated feature if it is possible. Otherwise, your only other options are to discontinue using that feature altogether, or branch your code.

Here is a poor example, but one I can think up quickly. SQL Server 2000 was the last version of SQL Server shipping with system tables such as SYSOBJECTS, SYSCOLUMNS, SYSINDEXES, etc. These system view tables were deprecated with the release of SQL Server 2005. They remain today in SQL Server 2008 R2. I have not looked at SQL Server 2012. Perhaps one of our readers may already know.

If you had software written depending on these tables (something that you really don’t want to admit…they have been deprecated for 4 releases now) you could always try to write your own views emulating the contents of the previous ones.

The better option would be to use the new techniques, and emulate them in the older release of SQL Server so that your dependent software can remain current, and still support older versions of SQL Server.

Have any of you found issues of Backward or Forward Compatibility you have had to resolve in SQL Server 2008R2 or SQL Server 2012? Share your experience by sending an Email to btaylor@sswug.org.

Cheers,

Ben

$$SWYNK$$

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Author: Ben TaylorBen is a Relational Database veteran starting in the early eighties on DEC Vax database systems such as Bloom and Harvest. He has specialized in SQL engines for more than two decades, with a primary focus on Microsoft SQL Server. Ben has worked with small and large databases for both OLAP and OLTP working on systems for many industries such as Medical (Medical Claims and Eligibility Warehouse, HMO Provider Management, Enrollment), Financial (credit card processing, mortgage, stock portfolio management), Manufacturing (Assembly Line and Product Assemblies), Sales, Auto Auctions and more.