递归Mongo查找

Question

所以我想找出这个人的合伙人的名字。我的数据如下：

{
    _id: objectId,
    first_name: string,
    last_name: string,
    partners: [objectId]
}

我尝试过这个聚合/查找，但是它返回了不正确的结果。

module.exports.getUserPartners = function( user_id, callback ) {

    const query = [
        {
            $unwind: "$partners"
        },
        {
            $lookup: {
                from: "people",
                localField: "partners",
                foreignField: "_id",
                as: "people_partners"
            }
        },
        {
            $match: { "_id": user_id }
        },
        {
            $project: {
                first_name: 1,
                last_name: 1
            }
        }
    ];
    People.aggregate( query, callback );

}

如果我的数据如下所示：(我将'123‘作为user_id传递)

{
    _id: '123',
    first_name: "bob",
    last_name: "smith",
    partners: ['234','345']
},{
    _id: '234',
    first_name: "sally",
    last_name: "smartypants",
    partners: ['789']
},{
    _id: '345',
    first_name: "martin",
    last_name: "tall",
    partners: []
}

我从上面的聚合查找中得到以下结果：

[{
    _id: '123',
    first_name: "bob",
    last_name: "smith"
},{
    _id: '123',
    first_name: "bob",
    last_name: "smith"
}]

当我期待这些结果时：

[{
    _id: '234',
    first_name: "sally",
    last_name: "smartypants"
},{
    _id: '345',
    first_name: "martin",
    last_name: "tall"
}]

*注-我根据推荐表单docs和本文$unwind添加了https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/#unwind-example

Answer 1

请检查此aggregate查询。看上去很复杂。

db.getCollection('people').aggregate([
         {$match : {  "_id" : "123"} },
        {
   $unwind:
        {
          path:"$partners",
          preserveNullAndEmptyArrays: true
        }
        },
        {
            $lookup: {
                from: "people",
                localField: "partners",
                foreignField: "_id",
                as: "people_partners"
            }
        },
         {
       $unwind:
        {
          path:"$people_partners",
          preserveNullAndEmptyArrays: false
        }
        },
        {
            $project: {
                _id : '$people_partners._id',
                first_name : '$people_partners.first_name',
                last_name : '$people_partners.last_name',

            }
        }
    ])