Add a dummy db_select() method to CI_DB_driver and remove it from drivers that don't have such functionality
diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index d3359e1..594fcce 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -192,10 +192,24 @@
// --------------------------------------------------------------------
/**
+ * Select database
+ *
+ * This is just a dummy method to allow drivers without such
+ * functionality to not declare it, while others will override it.
+ *
+ * @return bool
+ */
+ public function db_select()
+ {
+ return TRUE;
+ }
+
+ // --------------------------------------------------------------------
+
+ /**
* Set client character set
*
* @param string
- * @param string
* @return bool
*/
public function db_set_charset($charset)