SQLServerFast

Plansplaining, part 7. The Constant Scan that returns no data

Hugo Kornelis
No Comments
This is part seven of the plansplaining series. Each of these posts takes an execution plan with an interesting pattern, and details exactly how that plan works. In this post we look at a deceptively simple query: a simple SELECT with an ISNULL to show either a row returned or a placeholder value. And yet there is more going on under the covers than one might expect. Sample query The query below can be executed in any version of the AdventureWorks sample database. It returns a code string representing the version number on the 2016 and 2017 versions; on older…
Read More

Plansplaining, part 6. Aggregates with OVER.

Hugo Kornelis
2 Comments
This is the sixth 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.…
Read More

Announcing: The SQL Server Execution Plan Reference

Hugo Kornelis
1 Comment
As some of you might already know, Grant Fritchey is working hard on updating his book on execution plans. The refreshed and much-improved third edition should release “real soon now”. And I happen to be involved in this project, as technical editor. While working on that book, I often ran into interesting and intriguing details in the execution plans. Details that, more often than not, are well beyond the scope of the book. So they will not be included, and rightly so. But it felt like a shame to have that information not available anywhere. Or scattered across the internet…
Read More

T-SQL Tuesday #102: Announcing a new site

Hugo Kornelis
2 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. The May 2018 edition, better known as #102, is hosted by Riley Major (b|t). His challenge for this month: give back to the community. Pick an activity to help the community, explain your choice, and then commit to it. And include an ETA. If ever I saw a scary T-SQL Tuesday challenge, this has to be it.…
Read More

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.…
Read More

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…
Read More

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…
Read More

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.…
Read More

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…
Read More

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.…
Read More

Hugo Kornelis

Married, father of 2 children.

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

Subscribe via Email

Enter your email address to subscribe to this blog and receive notifications of new posts by email.

Archives

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close