Question

抱歉，我的英语不好......

如何使用mongoose查找子匹配？

我的查询是

categorys.aggregate([{
            "$sort": {
                "order": 1,
                "id": 1
            }
        },

        {
            "$lookup": {
                "localField": "id",
                "from": "categorys",
                "foreignField": "parentId",
                "as": "child"
            }
        },
        {
            "$match": {
                see: true,
                depth: 1
            }
        }
    ]).exec(function(err, Categorys)

是结果

{
    "_id": "596e237c414f2137b0c4e9c2",
    "id": 3,
    "name": "DB",
    "address": "DB",
    "parentId": 0,
    "depth": 1,
    "see": true,
    "__v": 0,
    "child": [{
            "_id": "596e24701e1bd30dc415b894",
            "id": 5,
            "name": "Mongodb",
            "address": "Mongodb",
            "parentId": 3,
            "depth": 2,
            "see": true,
            "__v": 0
        },
        {
            "_id": "596e24821e1bd30dc415b895",
            "id": 6,
            "name": "mssql",
            "address": "mssql",
            "parentId": 3,
            "depth": 2,
            "see": false,
            "__v": 0
        }
    ]
}]

我看不到mssql的结果（参见：false）匹配怎么样？救救我！

Answer 1

如果要在$filter数组中匹配，可以在$project阶段使用child。像吼叫一样。

categorys.aggregate([
  {
    "$sort": {
      "order": 1,
      "id": 1
    }
  },
  {
    "$lookup": {
      "localField": "id",
      "from": "categorys",
      "foreignField": "parentId",
      "as": "child"
    }
  },
  {
    $project: {
      name: 1,
      address: 1,
      // ... as you need 
      child: {
        $filter: {
          input: "$child",
          as: "item",
          cond: {
            $and: [
              {$eq: ["$$item.see", true]},
              {$eq: ["$$item.depth", 2]}
            ]
          }
        }
      }
    }
  }
])

N.B：如果你想对"depth":1,"see":true,之类的父字段使用匹配条件，那么你应该在$match之前使用$lookup阶段

categorys.aggregate([
  {$match:{//parent field match condition first}},
  {$sort:{}},
  {$lookup:{}},
  {$project:{//for child}}
]);

如何使用mongoose查找子匹配？

1 个答案: