code: public function update($primary_value, $data)
      {
          $data = $this->_do_pre_update($data);
  
          if ($data !== FALSE)
          {
              $result = $this->_database->where($this->primary_key, $primary_value)
                  ->set($data)
                  ->update($this->_table);
  
              $this->trigger('after_update', array($data, $result));
  
              return $result;
          }
          else
          {
              return FALSE;
          }
      }
docs: Updated a record based on the primary value.
  @param $primary_value
  @param $data
  @return bool