mongodb - 使用 $nin 条件根据字段过滤数组中的元素

Question

我有一个如下所示的 mongo 文档；

{
    "_id": "123",
    "name": "ABC",
    "elements": {
        "_id": "123",
        "minorElements": [
            [
                {
                    "id": "xyz1",
                    "name": "xyz1"
                }, {
                    "id": "xyz2",
                    "name": "xyz2"
                }, {
                    "id": "xyz3",
                    "name": "xyz3"
                }
            ],
            [
                {
                    "id": "xyz1",
                    "name": "xyz1"
                }, {
                    "id": "xyz3",
                    "name": "xyz3"
                }, {
                    "id": "xyz5",
                    "name": "xyz5"
                }
            ]
        ]
    }
}

“elements.minorElements”是一个数组数组。

如何编写 mongo 聚合以从“elements.minorElements”中删除“id”不在“xyz1”和“xyz2”中的对象？

预期输出:

{
    "_id": "123",
    "name": "ABC",
    "elements": {
        "_id": "123",
        "minorElements": [
            [{
                    "id": "xyz1",
                    "name": "xyz1"
                }, {
                    "id": "xyz2",
                    "name": "xyz2"
                }
            ],
            [{
                    "id": "xyz1",
                    "name": "xyz1"
                }
            ]
        ]
    }
}

样本有效载荷 https://mongoplayground.net/p/9RjC6GzSQDQ

Answer 1

您需要 $map用于外部阵列和 $filter对于内部数组:

db.collection.aggregate([
    {
        $addFields: {
            "elements.minorElements": {
                $map: {
                    input: "$elements.minorElements",
                    as: "me",
                    in: {
                        $filter: {
                            input: "$$me",
                            cond: {
                                $in: [ "$$this.id", [ "xyz1", "xyz2" ] ]
                            } 
                        }
                    }
                }
            }
        }
    }
])

Mongo Playground