SQLSRV improvements

Mainly for performance (issue #2474), but also added a 'scrollable' configuration flag
and auto-detection for SQLSRV_CURSOR_CLIENT_BUFFERED (only available since SQLSRV 3).

3 files changed, 69 insertions, 3 deletions

diff --git a/system/database/drivers/sqlsrv/sqlsrv_driver.php b/system/database/drivers/sqlsrv/sqlsrv_driver.php
index 09e6b8c9a..2759bac0b 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_driver.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_driver.php
@@ -48,6 +48,18 @@ class CI_DB_sqlsrv_driver extends CI_DB {
 	 */
 	public $dbdriver = 'sqlsrv';
 
+	/**
+	 * Scrollable flag
+	 *
+	 * Determines what cursor type to use when executing queries.
+	 *
+	 * FALSE or SQLSRV_CURSOR_FORWARD would increase performance,
+	 * but would disable num_rows() (and possibly insert_id())
+	 *
+	 * @var	mixed
+	 */
+	public $scrollable;
+
 	// --------------------------------------------------------------------
 
 	/**
@@ -70,6 +82,27 @@ class CI_DB_sqlsrv_driver extends CI_DB {
 	// --------------------------------------------------------------------
 
 	/**
+	 * Class constructor
+	 *
+	 * @param	array	$params
+	 * @return	void
+	 */
+	public function __construct($params)
+	{
+		parent::__construct($params);
+
+		// This is only supported as of SQLSRV 3.0
+		if ($this->scrollable === NULL)
+		{
+			$this->scrollable = defined('SQLSRV_CURSOR_CLIENT_BUFFERED')
+				? SQLSRV_CURSOR_CLIENT_BUFFERED
+				: FALSE;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Database connection
 	 *
 	 * @param	bool	$pooling
@@ -154,9 +187,9 @@ class CI_DB_sqlsrv_driver extends CI_DB {
 	 */
 	protected function _execute($sql)
 	{
-		return ($this->is_write_type($sql) && stripos($sql, 'INSERT') === FALSE)
+		return ($this->scrollable === FALSE OR $this->is_write_type($sql))
 			? sqlsrv_query($this->conn_id, $sql)
-			: sqlsrv_query($this->conn_id, $sql, NULL, array('Scrollable' => SQLSRV_CURSOR_STATIC));
+			: sqlsrv_query($this->conn_id, $sql, NULL, array('Scrollable' => $this->scrollable));
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/sqlsrv/sqlsrv_result.php b/system/database/drivers/sqlsrv/sqlsrv_result.php
index 3c8148f1b..ba38f7454 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_result.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_result.php
@@ -39,15 +39,45 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_sqlsrv_result extends CI_DB_result {
 
 	/**
+	 * Scrollable flag
+	 *
+	 * @var	mixed
+	 */
+	public $scrollable;
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Constructor
+	 *
+	 * @param	object	$driver_object
+	 * @return	void
+	 */
+	public function __construct(&$driver_object)
+	{
+		parent::__construct($driver_object);
+
+		$this->scrollable = $driver_object->scrollable;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Number of rows in the result set
 	 *
 	 * @return	int
 	 */
 	public function num_rows()
 	{
+		// sqlsrv_num_rows() doesn't work with the FORWARD and DYNAMIC cursors (FALSE is the same as FORWARD)
+		if ( ! in_array($this->scrollable, array(FALSE, SQLSRV_CURSOR_FORWARD, SQLSRV_CURSOR_DYNAMIC), TRUE))
+		{
+			return parent::num_rows();
+		}
+
 		return is_int($this->num_rows)
 			? $this->num_rows
-			: $this->num_rows = @sqlsrv_num_rows($this->result_id);
+			: $this->num_rows = sqlsrv_num_rows($this->result_id);
 	}
 
 	// --------------------------------------------------------------------
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index c68258e1c..5c01d64af 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -222,6 +222,9 @@ Release Date: Not Released
       - Added port handling support for UNIX-based systems (MSSQL driver).
       - Added *OFFSET* support for SQL Server 2005 and above.
       - Added ``db_set_charset()`` support (MSSQL driver).
+      - Added a *scrollable* property to enable configuration of the cursor to use (SQLSRV driver).
+      - Added support and auto-detection for the ``SQLSRV_CURSOR_CLIENT_BUFFERED`` scrollable cursor flag (SQLSRV driver).
+      - Changed default behavior to not use ``SQLSRV_CURSOR_STATIC`` due to performance issues (SQLSRV driver).
 
    -  Improved support of the Oracle (OCI8) driver, including: