Codeigniter - prevent added space on the select statement - codeigniter

Question

How to prevent auto fix in the select statement using CodeIgniter 3?
Query that I want: SELECT REPLACE(item, ',', '') AS item (without space)
I tried : $this->db->select("replace(item, ',', '') AS item", FALSE);
Result : SELECT REPLACE(item, ', ', '') AS item (CI added a space in my query)
I read this documentation but it didn't work.
This my real query:
$this->db->select("a.unit_id");
$this->db->select("replace(c.topik, ',', '') AS topik", FALSE); //this my problem (added space which shouldnt)
$this->db->select("COUNT(*) AS jumlah");
$this->db->from('opub_kliping a');
$this->db->join('opub_media b','a.media_id = b.organisasi_id');
$this->db->join('opub_tag c','a.id = c.kliping_id');
if(!empty($data['keyword']))$this->db->where("(a.judul LIKE '%".$data['keyword']."%' OR a.text LIKE '%".$data['keyword']."')");
if(!empty($data['tgl1']))$this->db->where("a.tanggal >=",$data['tgl1']);
if(!empty($data['tgl2']))$this->db->where("a.tanggal <=",$data['tgl2']);
if(!empty($data['unit']))$this->db->where("a.unit_id ",$data['unit']);
if(!empty($data['media']))$this->db->where("a.media_id ",$data['media']);
if(!empty($data['jenis']))$this->db->where("a.jenis_id ",$data['jenis']);
if(!empty($data['tone']))$this->db->where("a.karakter ",$data['tone']);
if(!empty($data['topik']))
{
$qTopik = array();
$expTopik = explode(',', $data['topik']);
foreach($expTopik as $t)
{
if(!empty($t))
{
$qTopik[] = "c.topik LIKE '%$t%'";
}
}
if(!empty($qTopik))
{
$qTopiks = implode(",", $qTopik);
$this->db->where($qTopiks);
}
}
$this->db->where('a.unit_id !=', 0);
$this->db->where('c.topik !=', NULL);
$this->db->where('c.topik !=', '');
$this->db->group_by("a.unit_id");
$this->db->group_by("replace(c.topik, ',', '')", FALSE); //this produce correct query (without adding space)
$this->db->order_by('a.unit_id', 'ASC');
$this->db->order_by('jumlah', 'DESC');
$q= $this->db->get();

Answer 1

i found this after tried some experiment
$this->db->select(array('REPLACE(c.topik', "','", "'') AS topik"), false);
seems little hack maybe. but its work for me
hope will help others

Answer 2

change 4 lines of your query
$this->db->select("a.unit_id,replace(c.topik, ',', '') AS topik,COUNT(*) AS jumlah")->from('opub_kliping a');
$this->db->join('opub_media b','a.media_id = b.organisasi_id');