Voice of the DBA

Tag: software development

  • Defensive Programming

    At SQLServerCentral, we have a book on Defensive Programming in T-SQL. However not a lot of people have read it, or at least they haven’t downloaded it. That’s disappointing, as I think this is an area many of could improve our programming skills. Many of the techniques are simple things, or items to be aware of when writing code in order to make it more robust and reliable.

    I ran across a piece on the Enterprise Craftsmanship blog als covering this topic. That post is geared more towards C# and other OOP languages, but some of the concepts are valid for any software system. Certainly the need to guard against invalid values, especially NULLs is important in much code, and especially important in SQL code. I hope all of you understand the impact of NULLs on aggregates as well as other T-SQL commands, operators, and expressions. If you have any doubt, be sure you read about the impact of NULLs in BOL and perhaps write tests that inject NULLs into your code.

    There are places in our T-SQL constructs where we might want to develop code defensively. Checking parameters, using defaults, and watching out for ambiguous updates, and more. However, the place where I really think we want to be defensive is when we deploy changes to our production systems.

    I’ve written about idempotent code before, and all of you that develop software should be familiar with the concept. Perhaps more importantly, you should practice writing code that is idempotent to ensure that you really can write code this way. While not all deployment code needs to be written this way, there are plenty of cases where we want to include some sort of guard clause to prevent unexpected changes during our deployment.

    I’d encourage you to take a bit of time and examine the idea of programming defensively, practicing some of the techniques and making an evaluation of where this might improve your own code base. Who knows, maybe you can prevent some future bugs by learning a bit more today.

    Steve Jones

  • Moving Fast at Redgate

    One of the pushes at Redgate Software over the last year or so is to move faster. We aim to develop software quicker and get the changes and improvements into the hands of our customers quicker. A new feature doesn’t help anyone if it sits inside of a VCS, undeployed, for months. Customers and clients need to see the software changes.

    There are various ways to achieve this. The SQL Prompt team manages themselves, and being a small group, they have been successful at not only writing code quickly, but releasing often. In fact, they’ve released code to customers over 70 times in the last year. As a result, a few other development groups are looking to work in a similar, lightweight, rapid development manner.

    However, that’s not an appropriate process for all developers. In fact, in most companies I’ve worked in, there is always someone that needs to manage and report on milestones and efforts to build software with some sort of plan. In addition, most products have a wider scope than something like SQL Prompt, which means more developers, more coordination required, and everyone must deal with more friction throughout the process.

    One of our project managers wrote an interesting piece on how he worked to get the SQL Monitor team, one of our larger pieces of software, to meet their goals, and also move to a more rapid development and deployment process. It’s a look at the changes made in process and the adaptations to reality that occurred last year. I found it fascinating to read since I’d see the team dramatically improve the product in a fairly short period of time.

    As with most of the stories about successful software development teams, buy in and support from management, especially project management is important. Without your leadership wanting and being willing to change, little will. Developers have to believe as well, but I suspect that if management truly supports improvement and is willing to change the way they work with developers, the people that write code are usually willing to go along for the ride

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 2.9MB) podcast or subscribe to the feed at iTunes and Mevio .

  • A Buggy Release

    I definitely believe in a DevOps process, though a thoughtful, incremental one. I think this is the best way to develop software, whether you release every day or every year. Yes, you can implement DevOps and release once a year. You just end up tracking, testing, communicating, and being ready for that once a year release. Of course, I bet you don’t release once a year since I’m sure you’ll patch the system at least once.

    One of the core principles of DevOps is to use automation where you can. Remove humans and ensure that repeatability is possible for moving software from one machine to the other. Communicate, test, and then alter your process to work better. This requires the monitoring and input of humans to examine the process, but they shouldn’t be involved in deployments other than approving them. It’s too easy for an individual to make a mistake.

    However, DevOps isn’t a panacea for building better software. Witness the issues at Knight Capital, where they went from having $364mm in assets to losing $460mm in 45 minutes. Mostly because of a problem deployment, where an engineer didn’t deploy code to all the servers in their farm. Certainly a clean deployment to every system might have prevented this, but the reuse of old flags in code is problematic, as is leaving old code around that could be executed.

    In addition to moving to a DevOps mindset, I’d also say that you should be sure that you follow good software development practices as well. Clean out old code (including database code) and be very, very careful about reusing any part of your software, including flags, for a new purpose. It’s far, far too easy to make mistakes here.

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 3.5MB) podcast or subscribe to the feed at iTunes and Mevio .

  • Where’s the Unit Testing?

    I’ve been a proponent of Unit Testing, especially for databases. I’ve given presentations on the topic and advocate the use of techniques to verify your code works, especially over time when the complexity grows, new developers change code, and potentially introduce regressions. I’m not the only one as I saw a question recently from Ben Taylor asking where has unit testing gone?

    I was disappointed that few people have responded to the piece, and I think this is the same response that unit testing in front end application software received a decade or two ago. Few people saw value in testing, preferring to assume developers will code well. Over time, and with some investment, quite a few people have seen the value of unit testing, though I’m not sure it’s the majority yet. In building database software, we’re still woefully behind, preferring to use ad hoc tests that are subject to human frailty (forgetfulness, making mistakes in running tests or not examining results closely).

    I do know a few people that are customers of Redgate and use unit testing extensively in their database code. They definitely spend a lot of effort building unit tests, often having more test code than feature code, but they also have very low rates of complaints and bugs from users. I hope that more people having success will publish details on their unit testing successes and failures, and I’d welcome more pieces at SQLServerCentral on either side of the issue.

    For many people writing in-house applications, especially those installed in one location, perhaps a few bugs aren’t a problem. Maybe the impact is low enough that training developers to write tests and making the investment isn’t valuable enough.  However, for those that have disparate external clients, or maybe install software in many locations, I bet that moving to a more thorough set of repeatable, reliable, non-trivial tests will improve your software quality.

    Steve Jones

    The Voice of the DBA Podcast

    Listen to the MP3 Audio ( 3.2MB) podcast or subscribe to the feed at iTunes and Mevio .