SQLServerFast

Plansplaining, part 5. Bitmaps

Hugo Kornelis
9 Comments
This is the fifth post in the plansplaining series. Each of these blog posts focuses on a sample execution plan that exposes an uncommon and interesting pattern, and details exactly how that plan works. In the first post, I covered each individual step of each operator in great detail, to make sure that everyone understands exactly how operators work in the pull-based execution plans. In this post (and all future installments), I will leave out the details that I now assume to be known to my readers. If you did not read part 1 already, I suggest you start there.…
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The Segment operator, an error in Books Online

Hugo Kornelis
2 Comments
If you are as obsessed with execution plans as I am, you must be familiar with this page in Books Online: Showplan Logical and Physical Operators Reference. I must admit that I have mixed feelings about it. My problem with this page is the confusing way in which it mixes physical operators, logical operations (called logical operators on that page to add to the confusion), and operators that only exist in intermediate phases of query optimization and that we will never see in actual execution plans. But I do like it for presenting all operators that exist, with a short…
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T-SQL Tuesday #101: A few of my favorite tools

Hugo Kornelis
1 Comment
Back in 2009, Adam Machanic (b|t) started an initiative that is still going strong: T-SQL Tuesday. This is a monthly blog party. Every second Tuesday of each month, lots of people blog about the same topic, selected by the host for that month. And now, in the 99th installment, I decided to finally join in! The April 2018 edition is hosted by Jens Vestergaard (b|t). His challenge for this month: write about the tools, other than SSMS and VSDT, that we use for our work. Essential tools The full invitation even includes words such as “essential” tools, and “depend on…
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Plansplaining, part 4. Let’s repartition the streams.

Hugo Kornelis
3 Comments
This is the fourth post in the plansplaining series. Each of these blog posts focuses on a sample execution plan that exposes an uncommon and interesting pattern, and details exactly how that plan works. In the first post, I covered each individual step of each operator in great detail, to make sure that everyone understands exactly how operators work in the pull-based execution plans. In this post (and all future installments), I will leave out the details that I now assume to be known to my readers. If you did not read part 1 already, I suggest you start there.…
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T-SQL Tuesday #100: Looking forward

Hugo Kornelis
1 Comment
The monthly blog party that is known as T-SQL Tuesday has hit 100th episode (and I only missed 98 of them!). In true Olympic fashion, it returns to its roots for its centennial celebration. In other words, our host this month is Adam Machanic (b|t) himself. And even though 100 is a perfectly valid number to look back, he decided that looking ahead is more fun. He asks all bloggers to whip out the crystal ball and predict what our world will look like in another 100 months, when (hopefully) T-SQL Tuesday #200 will be celebrated. Looking ahead I must…
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Plansplaining, part 3. How repeating work saves time

Hugo Kornelis
2 Comments
This is the third post in the plansplaining series. Each of these blog posts focuses on a sample execution plan that exposes an uncommon and interesting pattern, and details exactly how that plan works. In the first post, I covered each individual step of each operator in great detail, to make sure that everyone understands exactly how operators work in the pull-based execution plans. In this post (and all future installments), I will leave out the details that I now assume to be known to my readers. If you did not read part 1 already, I suggest you start there.…
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SSMS hidden gem: Edit Query Text

Hugo Kornelis
3 Comments
When I am tuning a query, I usually start with the query text. I execute it to retrieve an execution plan, and then the fun starts. However, very often I first need to find the specific query (or queries) to tune. There are multiple ways to do this, depending on what monitoring tools and which version of SQL Server the customer uses. In some cases, I at first find only an execution plan. Now I do like to see execution plans when tuning, but I also need to have the query! The old method So here is an example of…
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Execution plans 101: (back to) The basics

Hugo Kornelis
3 Comments
I recently received an email from a reader of this blog. Specifically of the plansplaining posts. He wrote that he enjoyed reading it, but he still had some questions. Those questions made me realize that I made a mistake when I started this series. I dove in at the deep end. I assumed a lot of prior knowledge and experience with reading execution plans, but not every reader has that knowledge and that experience. So I decided that for this one post, I will move from the deep end of the pool to the shallow water. In this post I…
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T-SQL Tuesday #99: Dealer’s Choice

Hugo Kornelis
No Comments
Back in 2009, Adam Machanic (b|t) started an initiative that is still going strong: T-SQL Tuesday. This is a monthly blog party. Every second Tuesday of each month, lots of people blog about the same topic, selected by the host for that month. And now, in the 99th installment, I decided to finally join in! For February 2018, our host Aaron Bertrand (b|t) has elected to give bloggers a choice: either share some of the non-tech things that we are passionate about; or go all Aaron-style and tell the world what we consider the worst T-SQL habits that we really…
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Plansplaining, part 2. Why scan and spool instead of seek?

Hugo Kornelis
4 Comments
This is the second post in the plansplaining series. Each of these blog posts focuses on a sample execution plan and details exactly how that plan works. In the first post, I covered each individual step of each operator in great detail, to make sure that everyone understands exactly how operators work in the pull-based execution plans. In this post (and all future installments), I will leave out the details that I now assume to be known to my readers. If you did not read part 1 already, I suggest you start there. Sample query The query in this post…
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Hugo Kornelis

Married, father of 2 children.

Awarded 13x MVP (2006-2016; 2019-now), in the areas SQL Server and Data Platform.

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