public function checkPrimaryKey()
    {
        if (($retval = $this->checkPrimaryConstraint())) {
            if ($this->is_translation) {
                $this->table_field_id = NABU_LANG_FIELD_ID;
            } else {
                $keys = $this->getStorageDescriptor()->getPrimaryConstraintFieldNames();
                $size = count($keys);
                if ($size > 0) {
                    $this->table_field_id = $keys[$size - 1];
                } else {
                    $this->table_field_id = null;
                    $this->is_translation = false;
                }
            }
        } else {
            $this->table_field_id = null;
            $this->is_translation = false;
        }

        return $retval;
    }