public function getPrimaryKey($table)
    {
        $this->checkTableArgument($table);
        $pks = $this->getPrimaryKeys($table);
        if (count($pks) > 1) {
            $keys = implode(',', $pks);
            throw new Exception\MultiplePrimaryKeyException(__METHOD__ . ". Multiple primary keys found on table '$table':  $keys");
        }
        return $pks[0];
    }