insert data di postgres

saya ingin membuat data insert di CI, menggunakan databse mysql itu aman" saya ttapi ketika saya pindah mengginakan database pgadmin4/postgres muncul error seperti ini

error.PNG

adakah yg tau solusinya...

kode programnya gini, ini modelnya

<?php
class M_barang extends CI_Model{

	public function getdata($key)
		{
			$this->db->where('barang_id');
			$hasil = pg_query("SELECT * FROM tbl_barang");
			return $hasil;
		}

		public function getupdate($key,$data)
		{
			$this->db->where('barang_id',$key);
			$this->db->update('tbl_barang',$data);
		}

		public function getinsert($data)
		{
			$this->db->insert('tbl_barang',$data);
		}

		public function getdelete($key)
		{
			$this->db->where('barang_id',$key);
			$this->db->delete('tbl_barang');
		}

ini controller

<?php
defined('BASEPATH') OR exit('No direct script access allowed');
class Barang extends CI_Controller {
    function __construct(){
        parent::__construct();
        $this->load->model('M_barang');
    }

    public function index(){
        $data['content'] ='v_barang';
        $data['query'] = $this->db->get('tbl_barang');
        $this->load->view('welcome_message',$data);
    }

    public function simpan_barang(){

        $key = $this->input->post('barang_id');
            $data['barang_id']      = $this->input->post('barang_id');
            $data['nama_barang']   = $this->input->post('nama_barang');
            $data['barang_satuan']    = $this->input->post('barang_satuan');
            $data['harga_barang']        = $this->input->post('harga_barang');

            $this->load->model('M_barang');
            $query =$this->M_barang->getdata($key);
            if ($query->num_rows() > 0) {
                $this->M_barang->getupdate($key,$data);
            }else{
                $this->M_barang->getinsert($data);
            }
            redirect('barang');
    }
}