Michael J. Swart

July 16, 2017

10 Things I Learned While Working At D2L

Filed under: Miscelleaneous SQL,SQLServerPedia Syndication — Michael J. Swart @ 3:49 pm

Today marks my tenth anniversary working for D2L and it also marks ten years since I specialized in databases full time.
I’ve never worked anywhere this long. I always told myself that I’d stick around as long as there were new and interesting challenges to tackle and there’s no end in sight.

Recognition
So I thought I’d compile a list of things I didn’t know in 2007.

1. Database Performance Improvements Are Often Dramatic

A poorly performing database query can run orders of magnitude slower than a tuned query. Compare that to poorly performing application code. Improvements there are usually more modest.

But this can work out. It makes you look like a genius. You get to brag how that report that once took 32 hours now takes 10 minutes. Even though that missing index suggestion in the query plan turned out to be right this time, take the credit, you deserve it.

2. The Community Has Your Back

Speaking of appearing like a genius, here are three resources I still use when solving problems.

3. People Love Pictures With Their Content

I’ve been writing here for nearly ten years. One day, I decided to include an illustration with each blog post. For some reason it makes each post just a little more compelling than a wall of text. Drawing has been a very rewarding hobby for me. I highly recommend it.

4. There Are Dozens of Walkable Lunch Options In Downtown Kitchener

Here are a few of my favorites

  • Kava Bean: Excellent all day breakfast
  • City Cafe: Awesome bagels in the morning.
  • Darlise: You have to hunt for it, but it’s great food
  • Holy Guacamole: Especially if you’re a fan of cilantro

If you’re in town, send me an email. I’ll introduce you to one of these places.

5. Don’t Overestimate Normal Forms

Knowing normal forms is a lot less useful than I thought it would be. Normal forms are an academic way of describing a data model and it’s ability to avoid redundant data. But knowing the difference between the different normal forms has never helped me avoid trouble.

Just use this rule of thumb: Avoid storing values in more than one place. That will get you most of the way. Do it right and you’ll never hear anyone say things like

  • We need a trigger to keep these values in sync
  • We need to write a script to correct bad data

6. “How Do You Know That?”

This is one of my favorite lines. I use it when troubleshooting a technical problem. It’s a line that helps me avoid red-herrings or to maybe find out if that info is coming via telephone game. It’s kind of my version of Missouri’s “you’ve got to show me”. It might go something like this:

Say a colleague says “I/O is slow lately.”

So I’d ask “How do you know?”

They might say something like:

  • “Hinky McUnreliable thought that’s what it was. He told me in the hallway just now”
  • The error log reports 3 instances of I/O taking longer than 15 seconds
  • I measured it on the QA box.

7. Reduce Query Frequency

The impact of a particular procedure or query on a server is simply the frequency of a query multiplied by the cost of that query. To reduce the impact on the server it’s often more valuable to focus on reducing the number of calls to that query in addition to tuning it.

  • Look for duplicate queries. You’d be surprised how often a web page asks for the same information.
  • Cache the results of queries that are cache-able. I rely on this one heavily.
  • Consider techniques like lazy loading. Only request values the moment they’re needed.

8. Schema Drift Is Real

If you have multiple instances of a database then schema will drift over time. In other words, the definition of objects like tables, views and procedures will be out of alignment with what’s expected. The drift is inevitable unless you have an automated process to check for misalignment.

We wrote our own but tools like Redgate’s Schema Compare can help with this kind of effort.

9. Get Ahead Of Trouble

Software will change over time and it requires deliberate attention and maintenance to remain stable. Watch production and look for expensive queries before they impact end users.

When I type it out like that, it seems obvious. But the question really then becomes, how much time do you want to invest in preventative maintenance? My advice would be more.

Not enough time means that your team gets really good practice firefighting urgent problems. I work directly with a dream team of troubleshooters. They’re smart, they’re cool during a crisis and they’re awesome at what they do. Fixing issues can be thrilling at times, but it pulls us away from other projects.

And what do they say about people who can’t remember the past? Sometimes we have to relearn this lesson every few years.

10. D2L Is A Great Employer

D2L values learning of course and that includes employee professional development. They have always supported my blogging and speaking activities and they recognize the benefits of it.

The people I work with are great. I couldn’t ask for a better team.

And we’ve got a decent mission. I’m really glad to be part of a team that works so hard to transform the way the world learns. Thanks D2L!

5 Comments »

  1. Thanks, Michael. It’s been a pleasure reading your blog over the years, and learning along with you. Here’s to as many more years as you can stand 😀

    Comment by Erik Darling — July 16, 2017 @ 5:32 pm

  2. No problem Erik, As you know, the SQL community rocks. Happy to be a part of it (even a small part).

    Comment by Michael J. Swart — July 17, 2017 @ 9:27 am

  3. Congratulations Michael, for 10 years at D2L.

    Yes I have also benefited from your sessions at SQL Pass toronto at Younge and Eglinton library.

    Regards
    Vijay

    Comment by Vijay — July 17, 2017 @ 11:50 am

  4. Thanks for those kind words Vijay!

    Comment by Michael J. Swart — July 18, 2017 @ 8:14 am

  5. #10 sounds amazing. Love it, and would love to have such a support.

    Comment by Jaime — July 24, 2017 @ 5:41 pm

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