Blog - SQLServerFast

Bad parameter sniffing, what is it and what can you do about it

April 13, 2026

Time for a new video blog. This time, the topic is bad parameter sniffing. And with 43 minutes, the video is a bit longer than what I normally shoot for. What is it? What can you do about it? The video starts with an explanation of two good features: parameter sniffing and plan caching. But those features can interact in an unwanted way, resulting in erratic bad performance. Now we have what I call “bad parameter sniffing”. Starting at approximately 8:30, I then describe the three most common root causes for bad parameter sniffing: equality filters on a column with…

A picture showing a hiking path in a forest.

Home for now

April 9, 2026

Hugo Kornelis

(Warning: This blog post is non-technical but purely personal. In my leukemia diary, I write openly about my current health issues. This blog might be triggering for people who struggle with, or lost dear ones to, cancer and other similar diseases.) In my previous post, I wrote about the ups and downs as I was told I could go home as outpatient, and then developed a fever and had to return to the hospital. Luckily, that situation changed shortly after I published that post. Back home (and now for real) As I wrote in my last blog, after feeling rather…

Insane rollercoaster design from the game Rollercoaster Tycoon

Ups and downs

March 31, 2026

Hugo Kornelis

(Warning: This blog post is non-technical but purely personal. In my leukemia diary, I write openly about my current health issues. This blog might be triggering for people who struggle with, or lost dear ones to, cancer and other similar diseases.) I planned to write this on Saturday, March 28. But I didn’t. It’s already Tuesday, March 31 by now, and I finally started writing. There is a reason for that, and I’ll get to it. But, let’s first start with the post I wanted to write, the post I already had drafted in my head, on Saturday. That post…

To be where I need to be

March 23, 2026

Hugo Kornelis

(Warning: This blog post is non-technical but purely personal. In my leukemia diary, I write openly about my current health issues. This blog might be triggering for people who struggle with, or lost dear ones to, cancer and other similar diseases.) As I write this (Monday 19:00 in Utrecht – I might finish and post it later), I want to be somewhere else. Right at this time, the MVP Summit has just started. Official sessions usually run Tuesday to Thursday, but past years often saw extra sessions on the Monday before or the Friday after. Smaller sessions. Informal. Direct contact…

SQL injection, and how to prevent it

March 16, 2026

Hugo Kornelis

For a change, a video about security, rather than performance and execution plans. Why? Well, that should become clear in my next planned videos. Although I really can’t predict when I’ll be able to record those. What is it? And how to prevent it? In the first approximately 12.5 minutes of the video, I try to explain the concept of what SQL injection is in the most simple and non-technical terms I could come up with. But I also show, in that analogy, what defensive measures do and do not work. And how easy it ultimately is to be safe.…

Back in hospital

March 15, 2026

Hugo Kornelis

(Warning: This blog post is non-technical but purely personal. I write openly about my current health issues. This blog might be triggering for people who struggle with, or lost dear ones to, cancer and other similar diseases.) Time for an update in my leukemia diary. I had planned to write as soon as I was admitted to the hospital. I changed that plan a bit, for reasons I’ll get into later. But I am in hospital now, for a few days already. Awkward communication The last thing I had heard from my hematologist when I wrote the previous blog was…

Return to the diary

March 5, 2026

Hugo Kornelis

(Warning: This blog post is non-technical but purely personal. I write openly about my current health issues. This blog might be triggering for people who struggle with, or lost dear ones to, cancer and other similar diseases.) In September 2022, I was diagnosed with leukemia. I was treated with chemotherapy, I received a stem cell infusion, and then, after a long recovery period, I was clean and I could return to life before I got ill. I wrote about that extensively, in what I called my leukemia diary. The only thing in my life that still reminded me of my…

Optimized Locking part 2: Lock After Qualification

February 26, 2026

Hugo Kornelis

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SQL Server 2025 introduced Optimized Locking. Not one, but two features, sharing a single marketing name. Lock After Qualification (LAQ) One of these two features is Lock After Qualification (LAQ). This feature avoids the scenario where a delete or update is blocked by a locked row that would not qualify. But, like any good thing, there is a price. This video shows the feature, explains how it works, and shows some of the potentially undesired side effects. More of me? Was this useful to you? Do you want to learn more from me? You can click here to see an…

Video training update

February 22, 2026

Hugo Kornelis

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My training videos in the SQLServerFast Execution Plan Video Training are never just a done deal. Whenever there is new information to share, either because Microsoft adds new functionality, or because I discover something I did not know before, I go back and add this new information to the appropriate videos. Any such update always comes free of charge to those who bought access to the videos. Once you have access, you can watch these videos as often as you like. And you will always see the latest and greatest version! So it makes sense to stay updated on those…

Photo of Hugo Kornelis presenting at a conference

Precon, precon, precon

February 15, 2026

Hugo Kornelis

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If you read this blog, then it is very likely that you have an interest in execution plans. And that you want to increase your understanding of execution plans. A great way to really get to the next level is to attend a precon about execution plans, to get a full day of training on this topic. Another option is to purchase access to the SQLServerFast Execution Plan Video Training, currently over 20 hours of video with very extensive and in-depth training on execution plans. The best option is of course to combined the two: attend a precon, and get…

Bad parameter sniffing, what is it and what can you do about it

Home for now

Ups and downs

To be where I need to be

SQL injection, and how to prevent it

Back in hospital

Return to the diary

Optimized Locking part 2: Lock After Qualification

Video training update

Precon, precon, precon

Relating unrelated rows

Snapshot isolation: A threat for integrity? (Part 1)

Snapshot isolation: A threat for integrity? (Part 2)

Snapshot isolation: A threat for integrity? (Part 3)

Fun with ambiguous table names

Snapshot isolation: A threat for integrity? (Part 4)

The prime number challenge – great waste of time!

Just stuff it!

The table scan from hell

The Beatles versus the Stones

Hugo Kornelis

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