sqlsrv very slow over network

问题

I'm using sqlsrv (php_pdo_sqlsrv_55_ts.dll and php_sqlsrv_55_ts.dll) in PHP (5.5.12) to connect to a MSSQL 2012 Server over a VPN tunnel. But the transfer rate for large result sets is very slow.

Testing SSMS on the same PC over the same VPN tunnel for this query:

SELECT * 
FROM [Data].[dbo].[Logins]
WHERE date >= '2014-01-27 00:00:00.000' AND date < '2014-01-29 00:00:00.000'

returns about 100,000 rows in 4 seconds. Checking the transfer rate on my firewall/VPN shows 2,500 KB/s (on a 100mbit network) while the query is running.

Using PHP:

sqlsrv_configure('ClientBufferMaxKBSize', 1024*1024);
$dbconnect = "SERVER\\HERE";
$dbconinfo = array("UID" => "user", "PWD" => "pass", "Database" => "Data")
$conn = sqlsrv_connect( $dbconnect, $dbconinfo);
$sql = "
SELECT * 
FROM [dbo].[Logins]
WHERE date >= '2014-01-27 00:00:00.000' AND date < '2014-01-29 00:00:00.000'
";

$options = array();
$options["Scrollable"] = SQLSRV_CURSOR_CLIENT_BUFFERED;
$options["QueryTimeout"] = 30000;     

$stmt = sqlsrv_query( $conn, $sql, array(), $options);

runs 40 seconds and the firewall/VPN shows less than 150 KB/s while the query is running. Task-Manager shows around 5% CPU for the script.

I used SQLSRV_CURSOR_CLIENT_BUFFERED just for testing, because it reads the result in its own buffer without any further PHP code. Fetching each set of data without buffering is just a little bit slower (around 45 seconds).

I also tried a PDO version which lead to the same result.

ConnectionPooling 0 or 1 didn't make any difference either.

Changing server name to DNS vs. IP adress also made no difference.

LogSubsystems -1 and LogSeverity -1 did not show any issues or anything helpful at all.

I even used Wireshark to watch the network traffic but couldn't find any big differences between PHP and SSMS versions. But I don't know too much about networking layers.

Any ideas what might be the issue or what I could try to speed up PHP/sqlsrv would be greatly appreciated.

回答1:

For speed up fetch up to 3 times please use "MultipleActiveResultSets"=>'0' in your sqlsrv_connect connection options.

Ex:

$db = sqlsrv_connect('127.0.0.1', array('Database'=>'dbname','UID'=> 'sa','PWD'=> 'pass',"CharacterSet" =>"UTF-8","ConnectionPooling" => "1"
                    ,"MultipleActiveResultSets"=>'0'

            ));

回答2:

How about replacing

$options["Scrollable"] = SQLSRV_CURSOR_CLIENT_BUFFERED;

with

$options["Scrollable"] = SQLSRV_CURSOR_FORWARD;

回答3:

One of the most common "fixes" for slow sqlsrv operations is to change the scrollable value. I tried this and it didn't help...in fact SQLSRV_CURSOR_CLIENT_BUFFERED caused erratic behavior.

Example:

$stmt = sqlsrv_query( $this->connection,  $sql, array(), array(
                "Scrollable"=>SQLSRV_CURSOR_CLIENT_BUFFERED
));

I believe newer versions of sqlsrv (which I have 4.3.0) already optimize this somewhat and suspect this isn't needed for latest versions.

The second most popular suggestion is to change the connection options...I tried many solutions...and they really didn't help. Again, I think newer sqlsrv drivers have changed the defaults for this.

Example:

    sqlsrv_configure('ClientBufferMaxKBSize', 0);           
$serverName = Config::get('settings.MS_DB_HOST').", 1433"; 
$connectionInfo = array( 
    "Database"=>Config::get('settings.MS_DB_NAME'), 
    "UID"=>Config::get('settings.MS_DB_UID'), 
    "PWD"=>Config::get('settings.MS_DB_PWD'),
    "MultipleActiveResultSets"=>'0',
    "connectionpooling"=>"0",
    "TraceOn"=>"0"
);                  
$this->connection = sqlsrv_connect($serverName, $connectionInfo);

All that said...what finally helped for me was to realize that sqlsrv_connect was my culprit and incredibly slow. For some apps you won't notice this...but in my case I was dealing with code that would constantly reconnect to the database before executing subsequent sql operations. So say this takes a half second to run...if you have 10 different sql statements that each connects on their own "sqlsrv_connect()"...this (for me) could take 5 seconds. The solution was to reuse the connection object from the first instantiation. Once I did this, the performance improvements were dramatic.

Hopefully in the future the sqlsrv library will program something like PHP/MySQL persistent connections and this won't be needed.

来源：https://stackoverflow.com/questions/27553048/sqlsrv-very-slow-over-network

标签

php

sql-server

networking

sqlsrv