Hugo Kornelis

SQL Server 2025 was announced in November 2024, went in public preview in May 2025, and will probably be released at the time of this conference. Join execution plan expert Hugo Kornelis as he takes an in-depth look at some of the new features that affect query performance and execution plans.

Have you ever wanted to know exactly how SQL Server stores data for temporary structures, such as for instance the spooled data in a Table Spool or Index Spool operator? No?

For troubleshooting slow queries, looking at the execution plan is a good starting point. But sometimes, just looking at the plan does not help. Sometimes you need to dig deeper. In this full-day pre-con session, you will learn everything you need to be take your understanding of execution plans to the next level. For almost every operator you can encounter in an execution plan, we will look at the inner workings, and look at properties that can affect their performance. We will also look at how operators in a plan interact with and affect each other. Aside from explaining all of the common operators, we will also touch on several operators that were introduced or modified in the newer versions of SQL Server. In short: After this pre-con, you will be better prepared to look at execution plans, find the spot where it hurts, and then rewrite your query to get a faster execution plan. If you have seen some execution plans but feel you need to bring your understanding to the next level, then this pre-con is for you.

SQL Server 2025 was announced in November 2024, and will probably be in preview, or perhaps already released, at the time of this conference. Join execution plan expert Hugo Kornelis as he takes an in-depth look at all the new features that affect query performance and execution plans.

The SQL Server Query Optimizer makes its plan choices based on estimated rowcounts. If those estimates are wrong, the optimizer will very likely produce a poor plan.

SQL Server 2025 was announced in November 2024, and will probably be in preview, or perhaps already released, at the time of this conference. Join execution plan expert Hugo Kornelis as he takes an in-depth look at all the new features that affect query performance and execution plans.

SQL (the language) is not a third generation language, where the developer tells the computer every step it needs to take. It is a declarative language that specifies the required results.

Sometimes, a close approximation is good enough. And sometimes, a close approximation is a lot faster. Microsoft has introduced “Approximate Query Processing” (the APPROX_COUNT_DISTINCT and APPROX_PERCENTILE functions) to give you exactly that benefit when you don't need exact answers. But do you have a good response when you propose to use this function and your manager asks you to explain how they work first? Or is your only option to claim "black magic by smart Microsoft engineers"? The algorithms used are not a secret. HyperLogLog and KLL Sketch. And now you most likely know exactly as much as you already knew before. And when you google for those terms ... you end up with a headache. Time to join me for a session where I explain the black magic in the simplest possible terms, so that you can then explain it to your manager!

SQL (the language) is not a third generation language, where the developer tells the computer every step it needs to take. It is a declarative language that specifies the required results.

Do you believe the myths that “Third Normal Form is good enough”, or that “Higher Normal Forms are hard to understand”? Do you believe the people who claim that these statements are myths? Or do you prefer to form your own opinion? If you take database design seriously, you cannot afford to miss this session. You will get a clear and easy to understand overview of all the higher Normal Forms: what they are, how to check if they are met, and what consequences their violations can have. This will arm you with the knowledge to reject the myths about higher Normal Forms. But, more important: it will make you a better designer!

SQL (the language) is not a third generation language, where the developer tells the computer every step it needs to take. It is a declarative language that specifies the required results.

An execution plan is in many ways similar to an organization. And the operators are like the employees, trying hard (and sometimes even succeeding) to work together effectively. Managing people, or execution plans, is easier if you know their idiosyncrasies. In this Lightning Talk, I will highlight a few of my favorite empl...eehrmm, operators; and tell you what you need to know in order to manage them effectively.

You know the Hash Match operator. You know it requires a lot of memory. And you also know that it sometimes needs more memory than it has, in which case it spills to tempdb and is slow. But do you know EXACTLY what happens under the cover in the case of a hash spill? Or does you knowledge stop at "it gets slow"? Unless you work for Microsoft on the SQL Server engineering team, there really is no need to know the internals of a hash spill. But that doesn't mean you can't be curious! Would you like to waste some time to learn about dynamic role reversal, grace hash join, bail-out, bit-vector filtering, and more, then join this sessions!

SQL (the language) is not a third generation language, where the developer tells the computer every step it needs to take. It is a declarative language that specifies the required results.

As announced in September 2018, SQL Server 2019 expands the "adaptive query processing" features of SQL 2017 and relabels them as "intelligent query processing".

As announced in September 2018, SQL Server 2019 expands the "adaptive query processing" features of SQL 2017 and relabels them as "intelligent query processing".

As announced in September 2018, SQL Server 2019 expands the "adaptive query processing" features of SQL 2017 and relabels them as "intelligent query processing". This name now covers many features, such as batch mode on rowstore, memory grant feedback, interleaved execution, adaptive joins, deferred compilation, and approximate query processing. In this high-paced session, we will look at all these features and cover some use cases where they might help - or hurt! - you.