刪除文檔中的父對象 (Remove parent object in document)

問題描述

刪除文檔中的父對象 (Remove parent object in document)

我有一個卡片組列表，每組都有一組卡片對象。我創建了一個管道，它使用所有卡片創建一個新集合。當前它插入卡片對象而不是對象的每個值。

當前管道：

pipeline = [
    {"$match": {"cards": {"$exists": True}}},
    {"$project":  {"cards": 1, "_id": 0} },
    {"$project": {"cards.foreignData": 0, "_id": 0}},
    {"$unwind": "$cards"},
    #{"$set": {"_id": "cards.uuid"}},
    {"$out": "cards" }
]
result = database.card_sets_source.aggregate(pipeline) 

當前輸出如下所示：

_id: <random ID>
cards: Object
  artist: "Artist name",
  ...: "...",
  number: 1

我想要的輸出看起來像這樣：

_id: <random ID>
arstist: "Arist name",
...: "...",
number: 1

我缺少什麼聚合函數？

參考解法

方法 1:

It requires to replace object in root and then out to another collection,

• $replaceRoot to replace cards object in root

</ul>

pipeline = [
    # .... your pipeline stages
    { "$replaceRoot": { "newRoot": "$cards" } },
    {"$out": "cards" }
]

(by In0cenT、turivishal)

參考文件

1. Remove parent object in document (CC BY‑SA 2.5/3.0/4.0)