[Video] SQL Query Optimization: Why Is It So Hard to Get Right?


The first paper on cost-based query optimization was published in 1979 by Patricia Selinger from IBM Research. This paper laid the basic framework for optimizing relational queries that is still in place today. While there have been many technical enhancements since 1979, query optimizers still fail to pick the best plan when faced with a complex SQL query.

In this talk I will describe the basic mechanisms used by modern query optimizers including plan enumeration, the use of histograms to estimate selective factors, and plan costing. I will also talk about a new approach to query optimization that I believe will revolutionize the optimization of queries in the cloud.

About the presenter – Dr. David DeWitt has positively wowed audiences at the PASS Summit over the years, consistently delivering amazing technical keynote presentations. You can read his bio at LinkedIn, or check out his Wikipedia page, or his past work at the University of Wisconsin. He could talk about pretty much anything, and I’d listen.

Here are the slides, but note that they use animations extensively – for the best effect, download the PowerPoint directly and step through it in presenter mode to see the animations.

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