public function set_identifiers(array $identifiers) {
        if ($this->definition->set_identifiers($identifiers)) {
            // As static acceleration uses input keys and not parsed keys
            // it much be cleared when the identifier set is changed.
            $this->staticaccelerationarray = array();
            if ($this->staticaccelerationsize !== false) {
                $this->staticaccelerationkeys = array();
                $this->staticaccelerationcount = 0;
            }
        }
    }