Sounds interesting, would love to take a look if it's available anywhere.

Unfortunately, it was commercial development, so it's not released. But implementation is relatively easy - it was a sqlite virtual table that (as much as I remember) looked in where condition for dir field, and listed that directory (= returned stat() data). Whole thing was quite interesting, because almost every component was somehow hooked into sqlite (either vith function or virtual table), so one could do pretty interesting things only with SQL.