嵌套关系 MongoDb [英] Nested Relations MongoDb

问题描述

我需要一些帮助.我有 2 个要关联的 MongoDB 集合.一种用于类别，另一种用于多媒体内容.一个类别可以包含一个多媒体内容和多个 Childs 类别.

通过传递管道执行聚合后，我得到返回格式(见图 1):Category.Media 内的媒体元素和 Category.Childs 内的子类别.我的问题是我不知道如何在子类别中再次插入媒体(见图 2)

我也离开了使用过的管道.

返回结果:

预期结果:

管道:

<预><代码>[{$匹配":{id_site":3，id_parent":空，id_class":空}},{$查找":{"from": "类别","localField": "_id","foreignField": "id_parent","as": "孩子们"}},{$查找":{"from": "媒体","localField": "id_media","foreignField": "_id","as": "媒体"}}]

提前致谢.任何建议表示赞赏.

解决方案

您必须修改第一个 $lookup 以使用 管道(可从 v3.6 获得)

<预><代码>[{$匹配":{id_site":3，id_parent":空，id_class":空}},{$查找":{"from": "类别",让": {"cid": "$_id"},管道":[{$匹配":{"$expr": { $eq: ["$id_parent", "$$cid"] }}},{$查找":{"from": "媒体","localField": "id_media","foreignField": "_id","as": "媒体"}}],"as": "孩子们"}},{$查找":{"from": "媒体","localField": "id_media","foreignField": "_id","as": "媒体"}}]

I need some help. I have 2 MongoDB collections that I want to relate. One is for categories and the other for multimedia content. A category can contain one multimedia content and Many Childs Categories.

After execute aggregation by passing the pipeline I get the Returned Format (See image 1): Media elements inside Category.Media and Child categories inside Category.Childs. My problem is that I don't know how I can insert again Media inside Child Categories (See image 2)

I also leave below the used pipeline.

Returned Result:

Expected Result:

The Pipeline:

[
    {
        "$match": {
            "id_site": 3,
            "id_parent": null,
            "id_class": null
        }
    },
    {
        "$lookup": {
            "from": "categories",
            "localField": "_id",
            "foreignField": "id_parent",
            "as": "Childs"
        }
    },
    {
        "$lookup": {
            "from": "media",
            "localField": "id_media",
            "foreignField": "_id",
            "as": "Media"
        }
    }
]

Thanks in advance. Any suggestion is appreciated.

解决方案

You'll have to modify the first $lookup to use a pipeline (available from v3.6)

[
    {
        "$match": {
            "id_site": 3,
            "id_parent": null,
            "id_class": null
        }
    },
    {
        "$lookup": {
            "from": "categories",
            "let": {
                "cid": "$_id"
            },
            "pipeline": [
                {
                    "$match": {
                        "$expr": { $eq: ["$id_parent", "$$cid"] }
                    }
                },
                {
                    "$lookup": {
                        "from": "media",
                        "localField": "id_media",
                        "foreignField": "_id",
                        "as": "Media"
                    }
                }
            ],
            "as": "Childs"
        }
    },
    {
        "$lookup": {
            "from": "media",
            "localField": "id_media",
            "foreignField": "_id",
            "as": "Media"
        }
    }
]

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