Chapter 4: The Execution Engine

At its heart, the execution engine is a collection of physical operators that are software components performing the functions of the query processor. Their purpose is to execute your query efficiently. If we look at it from another perspective, the operations implemented by the execution engine define the choices available to the query optimizer when building execution plans. The execution engine and its operators were briefly covered in previous chapters. Now, we’ll cover some of the most used operators, their algorithms, and their costs in greater detail. In this chapter, we will focus on operators related to data access, joins, aggregations, parallelism, and updates, as these are the ones most commonly used in queries, and also the ones that are used more in this book. Of course, many more operators are implemented by the execution engine, and you can find a complete list and description within the official SQL Server 2022 documentation. This...