Примерный алгоритм настройки поисковых индексов для разных сайтов

function BeforeIndexHandler($arFields){
   if($arFields["MODULE_ID"] == "iblock"){
      if($arFields["PARAM2"]==4 && $arFields['SITE_ID'][1]=='s2'){
         CModule::IncludeModule("search");
         CModule::IncludeModule("iblock");
         //AddMessage2Log($arFields);
         $arFields['SITE_ID']=array('s1');
         
         $res = CIBlockElement::GetList(Array(), array('IBLOCK_ID'=>$arFields["PARAM2"], 'ID'=>$arFields["ITEM_ID"]), false, array("nPageSize"=>1), Array('IBLOCK_ID', 'ID', 'PROPERTY_NAME_ENG', 'PROPERTY_PREVIEW_TEXT_ENG', 'IBLOCK_CODE'));
         if($ob = $res->GetNext()){
            CSearch::Index(
               $ob['IBLOCK_ID'],
               $ob['ID'],
               Array(
                  "DATE_CHANGE"=>$arFields["LAST_MODIFIED"],
                  "TITLE"=>$ob['~PROPERTY_NAME_ENG_VALUE'],
                  "SITE_ID"=>array('s2'),
                  "PARAM1"=>$arFields["PARAM1"],
                  "PARAM2"=>$arFields["PARAM2"],
                  "PERMISSIONS"=>$arFields["PERMISSIONS"],
                  "URL"=>'/eng/'.$ob['IBLOCK_CODE'].'/'.$ob['ID'].'/',
                  "BODY"=>$ob['~PROPERTY_PREVIEW_TEXT_ENG_VALUE']['TEXT'],
                  "TAGS"=>$arFields["TAGS"],
               ),
               false
            );
         }
      }
   }
   return $arFields;
}