How is a media library like WinAmp's implemented?

I wonder because the access times are quite short, even for complex expressions ((playcount = "0" OR lastplay < [1 year ago]) AND rating != "1" AND rating != "2" AND filename N开发者_开发问答OTHAS "Midis & Modules" AND type = "0") so basically it behaves like a map from everything to filename, right? What kind of data structure is utilized to get such a fast access?

Relational database like SQLite, with well-defined indexes on popular fields will handle it easily.