Ask HN: Database Design Materials?

Hi there! I am about to graduate and have recently become REALLY fascinated with databases, and I'd like to research them further. The problem is that all of my research of "Database Design" leads to something along the lines of "modeling schemas and data".

Does anyone have any good references for someone who is looking to learn about the low-level database functionality (storage, indexing, data structures, etc)?

Any help would be greatly appreciated!