I seem to recall reading somewhere that one of the reasons Vista was a "bad" os, was that it originally had much higher more optimistic ambitions to build a sql like file system (i suppose similar to this). It however had issues, and a decision to scrap it delayed the vista project, and reduced the scope of "cool" things it was supposed to deliver.
Yep: https://en.wikipedia.org/wiki/WinFS
I suspect there is an inherent scaling problem with the approach. While it demos well and can be useful in a lab setting, the full scale version ends up being so complex that mere mortals aren't able to comprehend it and end up just losing their files constantly in the morass of schemas and structured accesses.
The talk on the wiki about being able to write an editor that can handle any file type smells of pure insanity to me. An application that can present a usable editing interface for any filetype would be so bloated that it's almost inconceivable to think about a single company writing it. Can you imagine the kind of application that has an interface for manipulating photos, writing reports, tabulating data, programming (all languages), doing CAD, editing textures, composing music, etc...?