Fatal error: Allowed memory size of xxxbytes exhausted

HI,
I am getting this error:

Code:

Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 32 bytes) in /home/mywhdms/public_html/am/system/database/drivers/pdo/pdo_result.php on line 195

I am using CodeIgniter V3 and DB Driver is PDO. Trying to retrieve 25000 records for calculation of values.

My DB Settings are as follows :

Code:

$active_group = 'default';
$query_builder = TRUE;

$db['default'] = array(
       'dsn'=> 'mysql:host=XXXXX;dbname=XXXXXX',
'hostname' => 'localhost',
'username' => 'XXXXX',
'password' => 'XXXXX',
'database' => 'XXXXX',
'dbdriver' => 'pdo',
'dbprefix' => '',
'pconnect' => FALSE,
'db_debug' => TRUE,//FALSE
'cache_on' => FALSE,
'cachedir' => '',
'char_set' => 'utf8',
'dbcollat' => 'utf8_general_ci',
'swap_pre' => '',
'encrypt' => FALSE,
'compress' => FALSE,
'stricton' => FALSE,
'failover' => array(),
'save_queries' => TRUE
);