You got it! We designed EdgeQL from the first principles of the relational algebra and the set theory, with focus on practicality. There are a lot of similar ideas in Tutorial D, but EdgeQL is not a descendant of it.
btw, do you implement any edgeql-specific optimizations? I know that the db shares most of the code with psql, and its optimizer is okay. But being closer to the math foundation opens up lots of opportunities..!
Not on the planner level. Most of EdgeQL-specific low-level stuff is currently built as an extension with helpers. Our strategy is to upstream as much as possible, including any possible improvements to the planner that benefit EdgeDB.