[{"product_id":1212,"name":"sprit","category_id":1234,"category":"drink"},{"product_id":1212,"name":"sprit","category_id":2122,"category":"soda"},{"product_id":1212,"name":"sprit","category_id":2121,"category":"mocktail"},{"product_id":1212,"name":"sprit","category_id":2121,"category":"mocktail"}]

db.collection.aggregate([{$match:{"product_id":1212}},{$group:{_id:"$product_id",name:{$first:"$name"},categogies:{$addToSet:{"category_id":"$category_id","category":"$category"}}}},{$project:{_id:0,product_id:"$_id",name:"$name",categogies:"$categogies"}}])