@Marius: I didn't mean that you should implement it in RDJ. It was intended as a quick and dirty hack for particular case. I'm not sure if splitting will work, because you still have to store found artist names as variables and "feat" separator can differ.
Few examples from my DB: "Alex Barck
Feat. Jonatan Bäckelie", "Boris Dlugosch
ft. Róisín Murphy", "Riton
feat Meleka". Besides, there are those cases where one artists name match part in other name (e.g. '%Queen%' will match 'Queens of Stone Age'). There are also some other variations with "vs" like "DJ Fresh
VS Diplo
Feat. Dominique Young Unique" for mashups. It woulb be easier if only MySQL supported splitting strings using regex.
I assume that HMC will understand how to use the code based on following:
I do dev work myself on the web site, PHP and also working on Java/Android so I know it can be done probably without to much effort to just ignore the featured artist when importing into the database.
That aside, this kind of separation could be implemented by storing main artists name as separate field in songs table and using that for timestamp updates. The main artists name could be parsed using regex from filename/ID3 tag when importing tracks. The name could be user-editable in track editor.