def dropObsoleteMongoResults():
out = []
qset = CollectionReference.objects.all()
referenced = [obj.collection_name for obj in qset]
from sketch.mongowrapper import mongo, default_mongo_db
collections = mongo.getDb(default_mongo_db).collection_names()
for coll in collections:
if coll.startswith("results"):
if coll not in referenced:
out.append(coll)
mongo.dropCollection(default_mongo_db, coll)
return out