Review

I'm lucky to be one of the earlier entries in this ``influential papers'' series because I suspect this particular paper will come up time and again [Ed: I actually received this contribution before Laura's, above. How prescient!]. I believe this paper has influenced me in a different way from most other people---for me it's largely been pedagogical. When I think about the papers that have most influenced me from a research perspective about a half dozen come to mind. When I think about those that have most influenced me from a teaching perspective, this is the one.

My reasons for loving this paper are all over the map: (1) It's 20 years later and we're still using it as a coding spec---we're still building ``Selinger-style'' query optimizers. In Computer Science, especially in systems, that level of endurance is amazing. The paper is worth studying for that reason alone. (2) As a non-optimizer expert, this well-written paper eased me into the topic and convinced me that query optimization is an interesting and relatively clean area, with lots of fun nooks and crannies to explore. What better vehicle for teaching students about systems building and research? (3) This paper, the papers it led me to read, and the people it led me to talk to, convinced me that query optimization should be included in a core advanced database curriculum to much greater depth than it has been covered in the past. The query optimizer is the heart of the DBMS, and Selinger et al. led me to believe that from an educational perspective we should all understand the intricacies that lie there.