db={MindMap:[{"_id":"Yg5uGI3Iy0","data":{"id":"root","topic":"Main topic","expanded":true},"theme":"orange","_p_author":"_User$zqPzSKD7EM","_created_at":{"$date":{"$numberLong":"1658497264836"}},"_updated_at":{"$date":{"$numberLong":"1661334292749"}}},],MindmapView:[{"_id":"qWR6HVIcvT","startViewDate":{"$date":{"$numberLong":"1658669095261"}},"_p_user":"_User$VnrxG9gABO","_p_mindmap":"MindMap$Yg5uGI3Iy0","_created_at":{"$date":{"$numberLong":"1658669095274"}},"_updated_at":{"$date":{"$numberLong":"1658669095274"}}}]}

db.MindmapView.aggregate([{$group:{_id:{day:{$dateToString:{format:"%Y-%m-%d",date:"$startViewDate"}},mindmapId:{$substr:["$_p_mindmap",8,-1]}},watchTime:{$sum:{$dateDiff:{startDate:"$_created_at",endDate:"$_updated_at",unit:"second"}}},uniqueCount:{$addToSet:"$_p_user"}}},{$project:{_id:1,total:{$size:"$uniqueCount"},watchTime:1}},{$lookup:{from:"MindMap",localField:"_id.mindmapId",foreignField:"_id",as:"author"}},{$set:{author:{$first:"$author._p_author"}}}])