mongodb'；s聚合查找管道条件集合

当我写查询时，我必须检索所有学校的男生的详细信息，该查询同时检索男生和女生

      let result = await schoolModel.aggregate([
        { $match: { isdeleted: false } },
        { $lookup: {
                localField: "_id", from: "students", foreignField: "schl_id", as: "studentsList" },
        { $project: { "studentsList.isdeleted": 1, "studentsList.gender": 1, "studentsList._id": 1 } },
        { $match: { "studentsList.isdeleted": false, "studentsList.gender": "Male" } }
    ]);

---

在上面的查询中，它没有检查匹配条件，即..，studentsList.isdeleted&gender有人能帮我找出上面查询的错误吗

$lookup返回一个数组，这意味着当您使用匹配查询时，如果数组包含与您的条件匹配的文档，它将返回true

要检索您想要的结果，您有两种选择：

到

studentList

匹配每个文档，然后分组以重新构造结果

使用Mongo的v3.6+的更优雅的方式

它看起来有点像这样：

let result = await schoolModel.aggregate([
        {
            $match: {
                isdeleted: false
            }
        },
        {
            $lookup:
                {
                    from: "students",
                    let: {school_id: "$_id"},
                    pipeline: [
                        {
                            $match:
                                {
                                    $expr:
                                        {
                                            $and:
                                                [
                                                    {$eq: ["$schl_id", "$$school_id"]},
                                                    {$eq: ["$gender", "Male"]},
                                                    {$eq: ["$isdeleted", false]}
                                                ]
                                        }
                                }
                        }
                    ],
                    as: "studentList"
                }
        },
        {
            $match: {
                "studentList.0": {$exists: true}
            }
        }
    ]);