'Initializes the "active" columns, i.e., drops those columns and
creates the default indexes.'

def init(self):

    self.db[self.colname_scans].drop()
    self.db[self.colname_hosts].drop()
    self.db[self.colname_oldscans].drop()
    self.db[self.colname_oldhosts].drop()
    self.create_indexes()
