Explicitly added driver name variable in each DB driver, based on this bug report: #4436
diff --git a/system/database/drivers/odbc/odbc_driver.php b/system/database/drivers/odbc/odbc_driver.php
index 2992880..cc8d334 100644
--- a/system/database/drivers/odbc/odbc_driver.php
+++ b/system/database/drivers/odbc/odbc_driver.php
@@ -30,6 +30,8 @@
  */

 class CI_DB_odbc_driver extends CI_DB {

 

+	var $dbdriver = 'odbc';

+

 	/**

 	 * The syntax to count rows is slightly different across different

 	 * database engines, so this string appears in each driver and is