db={shifts:[{"_id":ObjectId("60c5c5524b9058e49d295a75"),"name":"Morning","timeZone":"Asia/Karachi",},{"_id":ObjectId("60de1b64c85070b4a9729722"),"name":"Night","timeZone":"Asia/Karachi",},{"_id":ObjectId("60de1b64c85070b4a9799999"),"name":"Temp Shift","timeZone":"Asia/Karachi",}],users:[{"_id":ObjectId("65d7372605af15ece6508b69"),"shiftId":ObjectId("60de1b64c85070b4a9729722"),"name":"Albert Eienstein",},{"_id":ObjectId("60d7372605af15ece6508b69"),"shiftId":ObjectId("60c5c5524b9058e49d295a75"),"name":"Elon Musk",}],temporaryShifts:[{"_id":ObjectId("60c5c5524b9058e49d295a79"),"userId":ObjectId("65d7372605af15ece6508b69"),"shiftId":ObjectId("60de1b64c85070b4a9799999"),"type":"temporary","date":"2020-02-01"},{"_id":ObjectId("60e019790566e561720d93f1"),"userId":ObjectId("65d7372605af15ece6508b69"),"shiftId":ObjectId("60de1b64c85070b4a9799999"),"type":"temporary","date":"2020-02-03"},{"_id":ObjectId("60de1b64c85070b4a9729722"),"userId":ObjectId("65d7372605af15ece6508b69"),"shiftId":ObjectId("60de1b64c85070b4a9799999"),"type":"temporary","date":"2020-02-05"},]}

db.users.aggregate([{$limit:1},{"$addFields":{"startDate":ISODate("2020-02-01"),"endDate":ISODate("2020-02-05")}},{"$addFields":{"dateRange":{"$range":[0,{$add:[{$divide:[{$subtract:["$endDate","$startDate"]},86400000]},1]}]}}},{"$addFields":{"dateRange":{$map:{input:"$dateRange",as:"increment",in:{"$add":["$startDate",{"$multiply":["$$increment",86400000]}]}}}}},{"$unwind":"$dateRange"},{"$project":{"name":1,"shiftId":1,"dateCursor":"$dateRange"}},{"$lookup":{"from":"temporaryShifts","let":{dateCursor:"$dateCursor",shiftId:"$shiftId"},"pipeline":[{"$addFields":{"parsedDate":{"$dateFromString":{"dateString":"$date","format":"%Y-%m-%d"}}}},{$match:{$expr:{$and:[{$eq:["$$dateCursor","$parsedDate"]}]}}}],"as":"temporaryShiftsLookup"}},{"$unwind":{path:"$temporaryShiftsLookup",preserveNullAndEmptyArrays:true}},{$project:{shiftId:1,type:{"$ifNull":["$temporaryShiftsLookup.type","permanent"]},date:"$dateCursor"}}])