Question

我是mongo的新手，并且在以下方面苦苦挣扎。在我的mongodb数据库中，有3个集合，结构如下。

lv1：

{
    "_id": ObjectId("58650f1abbf1cd8804d0abde"), 
    "name": "lv1_aaa"
}

lv2：

{
    "_id": ObjectId("5ba45de41e78c7eb3fdfbfa6"), 
    "lv1_id": ObjectId("58650f1abbf1cd8804d0abde"), 
    "name": "lv2_bbb"
}

lv3：

{
    "_id": ObjectId("5ba45de41e78c7eb3fdfbfa6"), 
    "lv1_id": ObjectId("58650f1abbf1cd8804d0abde"),
    "lv2_id": ObjectId("58d8c3e1bbf1cd7436117bd6"), 
    "name": "lv3_ccc"
}

如何在下面使用$ lookup获取数据结构

[
    {
        "_id": ObjectId("58650f1abbf1cd8804d0abde"), 
        "name": "lv1_aaa",
        "children": [
            {
                "_id": ObjectId("5ba45de41e78c7eb3fdfbfa6"), 
                "lv1_id": ObjectId("58650f1abbf1cd8804d0abde"), 
                "name": "lv2_bbb",
                "children": [
                    {
                        "_id": ObjectId("5ba45de41e78c7eb3fdfbfa6"), 
                        "lv1_id": ObjectId("58650f1abbf1cd8804d0abde"),
                        "lv2_id": ObjectId("58d8c3e1bbf1cd7436117bd6"), 
                        "name": "lv3_ccc"
                    },
                    ......
                ]
            },
            ......
        ]
    },
    ......
]

任何帮助将不胜感激！

Answer 1

您可以在mongodb 3.6 及更高版本

下尝试以下聚合

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        this.engine = cordovaWebViewEngine; // here xwalk view
    } else {
        this.engine = cordovaWebViewEngine; // here system web view engine
    }
}

mongodb $ lookup 3级嵌套文档

1 个答案: