protected function getUserColumns($sPrefix = '', $aCols = [])
    {
        if ($this->aUserColumns === null) {

            $oDb                = Factory::service('Database');
            $aResult            = $oDb->query('DESCRIBE `' . $this->table . '`')->result();
            $this->aUserColumns = [];

            foreach ($aResult as $oResult) {
                $this->aUserColumns[] = $oResult->Field;
            }
        }

        $aCols = array_merge($aCols, $this->aUserColumns);

        return $this->prepareDbColumns($sPrefix, $aCols);
    }