function (collection,field,oldValue,newValue)
{
  var index=0;
  collection="pagango."+collection;
  var cursor = db[collection].find();
  while (cursor.hasNext()) {
      var x = cursor.next();
      if(!x[field]) {continue;}
      x[field]=x[field].replace(oldValue,newValue);
      db[collection].update({_id : x._id}, x);
      index++;
   }
   var date=new Date();
   return index+" items replace."+date.getHours()+":"+date.getMinutes()
}