The Database Inside Your Codebase https://feifan.blog/posts/the-database-inside-your-codebase. Querying a code base like a database has been my dream for years. What are the state of the art for this? I had the idea of designing a language that can query itself for a while but nothing concrete yet.

JetBrains IDEs tend to have very good static analysis and refactoring, not sure to what extent the model is exposed to query freely. OpenGrok also has some semantic features. Other than that I think you covered most of it in your article.

the two products that come to mind are Semle's CodeQL and NDepend's CQLinq

It's a built-in feature of Smalltalk systems. And @Tudor Girba's Glamorous Toolkit is extending this approch to other languages.

Our own platform is built on top of a reactive database model, and the builder assets are stored in the db, as is the executable (VM for now, soon to be wasm). This allows the interesting ability to build tools as apps in our builder, and also to have plugins that are themselves apps built using the builder. Furthermore the database is a git meets mongodb style multi versioned log structured thing so you can also access previous states of all entities.