尝试在PostgreSQL和Codeigniter中获取最后一个USERID时，“未实现跨数据库引用”

I have a table and I'm use UUID type for the USERID field, I generate it with uuid_generate_v4(). I trying to get the last USERID that insert in my table. I,m use CodeIgniter and PostgreSQL.

this is my code

$array = array('some data');
$this->db->set('"USERID"', 'uuid_generate_v4()', FALSE);
$this->db->set('"INPUTDATE"', 'CURRENT_TIMESTAMP', FALSE);
$this->db->insert('rbac."MSTPENGGUNA"',$array);
$id = $this->db->insert_id('rbac."MSTPENGGUNA"."USERID"');
echo "<pre>";
var_dump($id);
echo "</pre>";

that code return error cross-database references are not implemented: "rbac.MSTPENGGUNA.USERID" LINE 1: SELECT CURRVAL('rbac."MSTPENGGUNA"."USERID"') AS ins_id ^

rbac is schema and "MSTPENGGUNA" is table.

I had use manual query with RETURNING USERID but it made more error in my query.

Anyone can help me ?