if ($context = $DB->get_record('context', array('contextlevel'=>$contextlevel, 'instanceid'=>$instanceid))) {
$result = $DB->delete_records('role_assignments', array('contextid'=>$context->id)) &&
$DB->delete_records('role_capabilities', array('contextid'=>$context->id)) &&
+ $DB->delete_records('role_names', array('contextid'=>$context->id)) &&
$DB->delete_records('context', array('id'=>$context->id));
// do not mark dirty contexts if parents unknown