I presented a talk called "Enterprise Data Validation" at the Hampton Road .NET User Group this evening. The premise was simple. Data validation needs to happen in all the tiers of a modern application but the validation rules should be defined only once to avoid synchronization errors. In this talk, I showed how to extend SQL Server using extended properties to store regular expressions for data validation as column metadata. I also showed how to add a regular expression matcher to SQL Server using the SQL CLR and how to add check constraints to invoke the regular expression parser. Then I built a WCF service to query the validation metadata to make it available in other application tiers. I quickly assembled WCF service host and client showed how you could bring all of the elements together to create a working Enterprise Validation solution.

Download the SQL Scripts (20.06 kb)

I wrote a blog post called How SQL Server Sorts the UNIQUEIDENTIFIER Type and another one called Ordering the SQL UNIQUEIDENTIFIER Type Numerically Correct for Reporting a while back. As a result, I get a lot of e-mails from people struggling with UNIQUEIDENTIFIER values in Microsoft SQL Server. That's cool because I like helping other developers. The mistake that most people make when working with this data type is treating them like strings. However, UNIQUEIDENTIFIERS are absurd looking integers, really big ones. We show them in hexadecimal format to make them more compact which adds to their absurdness, I suppose.

When iterating over a sequence of numbers in Python, the range() function is commonly used. However, the implementation of the range() function in Python 2.x instantiates each element in the sequence before the iteration begins. This is really costly from both memory and CPU perspectives when the desired range of numbers is large. Consider using the xrange() function instead which implements a Python generator to yield each number in the sequence as needed. Using xrange() instead of range() for large iterations can have a big, positive impact on your code. For example, in an application I was working on recently, replacing range() calls with xrange() boosted my performance from ~900,000 transactions per second to over 3,000,000. In Python 3.x, the range() function is supposed to be implemented as a generator but I haven't tested that to be true yet. Let me know if you have.

I spoke at the Charlottesville .NET User Group this week and at the Raleigh Code Camp. I cheated and did the same presentation to both groups. Call me lazy but, in the middle of planning our own Code Camp in Richmond, I really didn't want to prepare two separate talks. I did a talk back at CodeStock 2009 on a similar topic back in June 2009 but it's evolved a lot since then based on my own growth and understanding. You can find the code and slides below.