var items = [];
var preIDs = [];
for (var i = 0; i < Count; i++) {
                queryStr.id = { $nin: preIDs};
                r = Math.floor(Math.random() * rCount);

		var query = Item.find(queryStr);
                query.limit(1);
                query.skip(r);
                query.exec(function (err, results) {
                    items.push(results);
                    preIDs.push(results.id);
                });