Extension for kohana 3.2 DB class

db.php

<?php defined('SYSPATH') or die('No direct access allowed.');
/**
 *
 * @author skowron-line
 */
class DB extends Kohana_DB {
    /**
     *
     * @var string cache driver
     */
    public static $_cache_driver = 'file';
    /**
     *
     * @param string $table
     * @param array $values
     * @return object 
     */
    public static function _update($table, $values) 
    {
        return parent::update($table)->set($values);
    }
    /**
     *
     * @param string $table
     * @param array $values
     * @return object 
     */
    public static function _insert($table, $values) 
    {
        return parent::insert($table, array_keys($values))->values(array_values($values));
    }
    /**
     *
     * @param object query to execute
     * @param mixed time to cache
     * @return object 
     */
    public static function _query($sql, $lifetime = null) 
    {
        $type = '';
        $cache = Cache::instance(self::$_cache_driver);
        switch(substr(strtolower($sql), 0, 6))
        {
            /**
             * Dirty way
             */
            case '(selec': 
            case 'select':
                if($lifetime != null)
                {
                    if($result = $cache->get($sql))
                    {
                        return $result;
                    }
                    $result = parent::query(Database::SELECT, $sql)->execute();
                    
                    $cache->set($sql, $result, $lifetime);
                    return $result;
                }
                
                return parent::query(Database::SELECT, $sql)->execute();
            break;
            case 'update':
                $type = Database::UPDATE;
            break;
            case 'delete':
                $type = Database::DELETE;
            break;
            case 'insert':
                list($id) = parent::query(Database::INSERT, $sql)->execute();
                return $id;
            break;
        }

        return parent::query($type, $sql)->execute();
    }
    /**
     *
     * @return boolean
     */
    public static function clear_cache()
    {
        return Cache::instance(self::$_cache_driver)->delete_all();
    }
}

?>