May 2022
Intermediate to advanced
497 pages
13h 4m
English
Content preview from SQL Server Advanced Troubleshooting and Performance Tuning
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Chapter 4. Inefficient Queries
Inefficient queries exist in every system. They impact performance in many ways, most notably by increasing I/O load, CPU usage, and blocking. It is essential to detect and optimize them.
This chapter discusses inefficient queries and their potential impact on your system, and provides guidelines for detecting them, starting with an approach that uses plan cache–based execution statistics. It also covers Extended Events, SQL Traces, and the Query Store, and ends with a few thoughts on third-party monitoring tools. We will cover strategies for optimizing inefficient queries in subsequent chapters.
The Impact of Inefficient Queries
During my career as a database engineer, I have yet to see a system that wouldn’t benefit from query optimization. I’m sure they exist; after all, no one calls me in to look at perfectly healthy systems. Nevertheless, they are few and far between, and there are always opportunities to improve and optimize.
Not every company prioritizes query optimization, though. It’s a time-consuming and tedious process, and in many cases it’s cheaper, given the benefits of speeding up development and time to market, to throw hardware at the problem than to invest hours in performance tuning.
At some point, however, that approach leads to scalability issues. Poorly optimized queries impact systems from many angles, but perhaps the most obvious is disk performance. If the I/O subsystem cannot keep up with the load of large scans, the performance ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.