Sqlsrv driver: support for limit and offset on MS SQL server.

[jakubskrz]

Since MS SQL 2012 there is equivalent to LIMIT OFFSET clause in T-SQL.

But it requires to use ORDER BY clause in query, see official docs

To consider:

• add default ORDER BY instead of exception
• throw NotSupportedException when connected to older MSSQL Server version

[milo]

What about older MSSQL? Sqlsrv driver supports MSSQL since version 2005.

[jakubskrz]

On 2005 and 2008 versions this SQL syntax cause an error, so it would be good solution to check database version, like this:

$info = $this->connection->query('SELECT SERVERPROPERTY(\'ProductVersion\') AS version')->fetch();

if ($info->version < 11) { // 11 == SQL Server 2012
    throw new Nette\NotSupportedException('Offset is not supported by this database.');
}

But that doesn't work for me, I'm getting NULL.

[jakubskrz]

Hm, OK, when selecting server version via sql query, it's needed to be manually cast to string.

So this one 43a7fc1 will preserve current behaviour on older MS SQL versions.

[meridius]

How about checking version only once, like this:

    public function applyLimit(& $sql, $limit, $offset)
    {
        static $ver = null;
        if (is_null($ver)) {
            $info = $this->connection->query("SELECT CAST(SERVERPROPERTY('ProductVersion') AS varchar) AS [ver]")->fetch();
            $ver = (int) $info->ver;
        }
        if ($ver < 11) { // 11 == SQL Server 2012

I'd really like to see this merged. Perhaps squashing would help?

[dg]

Is possible to use $connection->getPdo()->getAttribute(\PDO::ATTR_SERVER_VERSION) like in MySqlDriver?

[meridius]

Yes, it is.

    /** @var string */
    private $version;

    public function __construct(Nette\Database\Connection $connection, array $options)
    {
        $this->connection = $connection;
        $this->version = $connection->getPdo()->getAttribute(\PDO::ATTR_SERVER_VERSION);
    }
...
    public function applyLimit(& $sql, $limit, $offset)
    {
        if (version_compare($this->version, 11, '<')) { // < SQL Server 2012

[meridius]

@jakubskrz Could you please incorporate all the mentioned changes and squash all to one commit so it could be merged?

[jakubskrz]

Hi, sorry for delay, I hadn't much time last week.

I've updated my PR with suggested changes and also with changes from this commit b3b6e9b so there is no merge conflict with current head. Looking at #99, I've also removed checking for ORDER BY clause.

But I can't test it right now, as I can't access my dev SQL server (broken VPN :/).

[dg]

Merged, thx 15ccd8b