private static function doSmartUpdate($coords, $pageId)
 {
     $prevCoords = GeoData::getAllCoordinates($pageId, array(), DB_MASTER);
     $add = array();
     $delete = array();
     foreach ($prevCoords as $old) {
         $delete[$old->id] = $old;
     }
     foreach ($coords as $new) {
         $match = false;
         foreach ($delete as $id => $old) {
             if ($new->fullyEqualsTo($old)) {
                 unset($delete[$id]);
                 $match = true;
                 break;
             }
         }
         if (!$match) {
             $add[] = $new->getRow($pageId);
         }
     }
     $dbw = wfGetDB(DB_MASTER);
     if (count($delete)) {
         $dbw->delete('geo_tags', array('gt_id' => array_keys($delete)), __METHOD__);
     }
     if (count($add)) {
         $dbw->insert('geo_tags', $add, __METHOD__);
     }
 }