[{_id:"C12",title:"blouse",price:15,units_sold:100,retail_price:30,ad_boost:1,rate_count:34,rating:4},{_id:"C10",title:"loose floral blouse",price:15,units_sold:100,retail_price:30,ad_boost:1,rate_count:34,rating:4}]

db.collection.aggregate([{$group:{_id:{price:"$price",units_sold:"$units_sold",retail_price:"$retail_price",ad_boost:"$ad_boost",rate_count:"$rate_count",rating:"$rating"},duplicate_ids:{$push:{_id:"$_id",title:"$title"}}}}])