Actualice una fila, pero inserte si la fila no existe en codeigniter

Primero seleccione todos los image_id de la tabla.

$data = $this->db->select(`image_id`)->get($this->table_name)->result_array();

Lista image_id en una matriz.

$image_ids=array();

foreach($data as $key => $value):

$image_ids[$key]=$value[`image_id`];

endforeach;

$update = array(
   array('image_id' => 1, 'name' => 'Party Gustav'),
   array('image_id' => 2, 'name' => 'Peter'),
   array('image_id' => 3, 'name' => 'Lisa')
)

Compruebe si existen image_ids:

$update_query= $this->db->where_in(`image_ids`,$image_ids)
               ->get($this->table_name)->result();

if($update_query->num_rows() > 0):

  $this->db->update_batch($update,$this->table_name);//update if ids exist
else
   $this->db->insert_batch($update,$this->table_name);//insert if does not exist
endif;