Book Image

SQL Server Query Tuning and Optimization

By : Benjamin Nevarez
Book Image

SQL Server Query Tuning and Optimization

By: Benjamin Nevarez

Overview of this book

SQL Server is a relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications. This book starts by describing the inner workings of the query optimizer, and will enable you to use this knowledge to write better queries and provide the query engine with all the information it needs to produce efficient execution plans. As you progress, you’ll get practical query optimization tips for troubleshooting underperforming queries. The book will also guide you through intelligent query processing and what is new in SQL Server 2022. Query performance topics such as the Query Store, In-Memory OLTP and columnstore indexes are covered as well. By the end of this book, you’ll be able to get the best possible performance for your queries and applications.
Table of Contents (14 chapters)

Degree of parallelism feedback

Based on the same concept as the memory feedback and cardinality estimation feedback features, and also relying on the query store, the degree of parallelism feedback works by identifying parallelism performance problems for repeating queries. The degree of parallelism feedback bases its decisions on the CPU time, the elapsed time, and the parallelism parallel-related waits.

Based on the feedback of recent query executions, the degree of parallelism feedback can automatically change the degree of parallelism and, again, monitor the performance of the query to see whether the change helps. The minimum value for a new query degree of parallelism that the feedback can recommend is 2, meaning the query cannot go to a serial plan. The maximum degree of parallelism is the max degree of parallelism server setting. As suggested, the feedback is persisted as it uses the query store.