Можете да опитате агрегирането по-долу.
db.editors.aggregate([
{"$lookup":{
"from":"books",
"localField":"_id",
"foreignField":"parentId",
"as":"books"
}},
{"$unwind":"$books"},
{"$match":{"books.type":"sci-fi"}},
{"$group":{
"_id":"$_id",
"name":{"$first":"$name"},
"scores":{"$sum":"$books.score"}
}},
{"$sort":{"scores":-1}},
{"$limit":10}
])
db.editors.aggregate([
{"$lookup":{
"from":"books",
"localField":"_id",
"foreignField":"parentId",
"as":"books"
}},
{"$project":{
"name":1,
"scores":{"$sum":"$books.score"}
}},
{"$sort":{"scores":-1}}
])