Genre radio playlist generation

gistfile1.txt

select artist_id, track_id from (
	select att.track_id, att.artist_id, tag.tag_count as tag_weight, rank() over 
	(partition by att.artist_id order by (random()*(110 - rank + (play_count/3))) desc) as artist_rank from library.artisttoptrackplaycount att
	inner join (
		select toptag.artist_id, sum(tag_count) as tag_count from (
 			select artist_id, max(tag_count) as tag_count from music.artisttoptag att
			inner join music.tag t on att.tag_id = t.id
			where coalesce(t.corrected_id, t.id) in (
				select id from music.tag where tag_name in ('riot grrrl', 'punk')
			) group by artist_id, coalesce(t.corrected_id, t.id)
		) toptag group by artist_id
	) tag on tag.artist_id = att.artist_id
) ranked_tracks
where ranked_tracks.artist_rank <= 3
order by random() * ranked_tracks.tag_weight * ranked_tracks.tag_weight desc
limit 20;