สอบถามเรื่อง codeigniter จะเชื่อมต่อ 2 โฮส database 2 ชนิดยังครับ

$db['default']['hostname'] = 'xx.x.xx.xx';
$db['default']['username'] = 'xxxx';   
$db['default']['password'] = 'xxxx';
$db['default']['database'] = 'xxx';
$db['default']['dbdriver'] = 'postgre';
$db['default']['dbprefix'] = '';
$db['default']['pconnect'] = TRUE;
$db['default']['db_debug'] = TRUE;
$db['default']['cache_on'] = FALSE;
$db['default']['cachedir'] = '';
$db['default']['char_set'] = 'utf8';
$db['default']['dbcollat'] = 'utf8_general_ci';
$db['default']['swap_pre'] = '';
$db['default']['autoinit'] = TRUE;
$db['default']['stricton'] = FALSE;
//////////
$db['sqlserver']['hostname'] = 'xx.x.xx.xx';
$db['sqlserver']['username'] = 'xxxx';   
$db['sqlserver']['password'] = 'xxxx';
$db['sqlserver']['database'] = 'xxx';
$db['sqlserver']['dbdriver'] = 'sqlsrv';
$db['sqlserver']['dbprefix'] = '';
$db['sqlserver']['pconnect'] = TRUE;
$db['sqlserver']['db_debug'] = TRUE;
$db['sqlserver']['cache_on'] = FALSE;
$db['sqlserver']['cachedir'] = '';
$db['sqlserver']['char_set'] = 'utf8';
$db['sqlserver']['dbcollat'] = 'utf8_general_ci';
$db['sqlserver']['swap_pre'] = '';
$db['sqlserver']['autoinit'] = TRUE;
$db['sqlserver']['stricton'] = FALSE;