[{directComputers:[{_id:"6139f794f6a0af371900dbfh",name:"MyComputer_1"},{_id:"6319bd1540b41d1a35717a16",name:"MyComputer_2"}],indirectComputers:[{_id:"6319bd1540b41d1a35717a16",name:"MyComputer_2"},{_id:"61f39f8ae2daa732deff6d90",name:"MyComputer_3"}]}]

db.collection.aggregate([{"$project":{allComputers:{"$reduce":{"input":"$indirectComputers","initialValue":"$directComputers","in":{"$cond":{"if":{"$in":["$$this._id","$$value._id"]},"then":"$$value","else":{"$concatArrays":["$$value",["$$this"]]}}}}}}},{"$unwind":"$allComputers"},{"$replaceRoot":{"newRoot":"$allComputers"}}])