[{"productId":1,"isVariant":1,"variantId":1,"attributeSet":[{"name":"Capacity","value":"500 GB","id":3},{"name":"Form Factor","value":"5 inch","id":4},{"id":5,"name":"Memory Components","value":"3D NAND"}]},{"productId":3,"isVariant":1,"variantId":1,"attributeSet":[{"name":"Capacity","value":"500 GB","id":3},{"name":"Form Factor","value":"2.5 inch","id":4},{"id":5,"name":"Memory Components","value":"3D NAND"}]}]

db.collection.aggregate([{$unwind:"$attributeSet"},{$group:{_id:"$attributeSet.value",data:{"$addToSet":{productId:"$productId"}}}},{"$project":{_id:0,data:1,attributeValue:"$_id"}}])