mongodb how to use aggregate like populate
To make it easier i would not change the current pipeline but just add a $group stage to end of it in order to re-structure the data.
{ $group: { _id: "$_id", user: {$first: "$user"}, dream: {$addToSet: "$dream"}, works: {$addToSet: "$works"} }}With that said if you are using Mongo version 3.6+ i do recommend you use the "newer" version of $lookup to re-write your pipeline to be a bit more efficient by avoiding all these $unwind's.