猫鼬加入两个集合并在两个属性中获取引用数据

debugcn 发表于 Dev

玛丽

我正在做一个简单的关注好友功能。

请在下面查看我的代码：

以下架构：

{
 "userId": { type: String },
 "followers": [{ "followerId": type: String }],
 "followings": [{ "followingId": type: String }], 
}

用户架构：

{
 "fullName": { type: String } 
}

注意：用户8具有1个关注者和2个关注。

现在，我的预期输出应该是这样的：

        "userId": 8,
        "followers": [
            {
                "followerId": 4,
                "fullName": "Rose Marriott",
            },
            {
                "followerId": 5,
                "fullName": "James Naismith",
            }
        ],
        "followings": [
            {
                "followingId": 1,
                "fullName": "Russell Oakham",
            },
            {
                "followingId": 5,
                "fullName": "James Naismith",
            }
        ]

这是我到目前为止尝试过的：

 db.followings.aggregate([
 { $unwind: "$followers" },
    {
        $lookup: {
            from: "users",
            localField: "followers.followerId",
            foreignField: "_id",
            as: "users"
        }
    },
    { 
        $addFields: 
        { 
            users: { $arrayElemAt: ["$users", 0] },
        },
    },
    { $unwind: "$followings" },
    {
        $lookup: {
          from: "users",
          localField: "followings.followingId",
          foreignField: "_id",
          as: "users2"
        }
    },
    { 
        $addFields: 
        { 
            users2: { $arrayElemAt: ["$users2", 0] },
        },
    },
    { $match: {"userId": mongoose.Types.ObjectId(userId) } },
    {
        $group: {
            _id: "$_id",
            userId: { $first: "$userId" },
            followers: {
                $push: {
                    followerId: "$followers.followerId",
                    fullName: "$users.fullName",
                }
            },
            followings: {
                $push: {
                    followingId: "$followings.followingId",
                    fullName: "$users2.fullName",
                }
            }
        }
      }
  ]);

但是我有2个关注者和2个关注者。我想知道是什么导致了这个问题。感谢任何帮助。谢谢！

土生的

你可以试试，

$addFields制作一个称为userIdsform的唯一数组arrayfollowers和followings，$setUnion以获得唯一的ID，
$lookup 与用户集合
$project 显示字段，
- followers获取fullName，$ map以迭代循环followers并followerId使用$reduce和从用户数组中获取名称$cond
- followings获取fullName，$ map以迭代循环followings并followingId使用$reduce和从用户数组中获取名称$cond

db.followings.aggregate([
  {
    $addFields: {
      userIds: {
        $setUnion: [
          {
            $map: {
              input: "$followers",
              in: "$$this.followerId"
            }
          },
          {
            $map: {
              input: "$followings",
              in: "$$this.followingId"
            }
          }
        ]
      }
    }
  },
  {
    $lookup: {
      from: "users",
      localField: "userIds",
      foreignField: "_id",
      as: "users"
    }
  },
  {
    $project: {
      userId: 1,
      followers: {
        $map: {
          input: "$followers",
          as: "f",
          in: {
            $mergeObjects: [
              "$$f",
              {
                fullName: {
                  $reduce: {
                    input: "$users",
                    initialValue: "",
                    in: {
                      $cond: [
                        { $eq: ["$$this._id", "$$f.followerId"] },
                        "$$this.fullName",
                        "$$value"
                      ]
                    }
                  }
                }
              }
            ]
          }
        }
      },
      followings: {
        $map: {
          input: "$followings",
          as: "f",
          in: {
            $mergeObjects: [
              "$$f",
              {
                fullName: {
                  $reduce: {
                    input: "$users",
                    initialValue: "",
                    in: {
                      $cond: [
                        { $eq: ["$$this._id", "$$f.followingId"] },
                        "$$this.fullName",
                        "$$value"
                      ]
                    }
                  }
                }
              }
            ]
          }
        }
      }
    }
  }
])

操场

本文收集自互联网，转载请注明来源。

如有侵权，请联系[email protected] 删除。