如何查询以基于一个字段作为用户名获取引用到另一个集合的所有文档

Question

In my Node API and MongoDB, I'm trying to make an endpoint to get all the posts associated with one username of a profile. In my Profile schema, I have a reference to the Post Schema and in my Post schema, I have a reference to the Username from Profile schema. My issue I don't know how to get all the posts for that username. I did similarly but with embedded for the Experience schema but I'm not sure how to do that for the referenced collections.

Post model:

const { Connect } = require("../db");

const reactionSchema = {
    likedBy: {
        type: String,
        unique: true,
        sparse: true
    }
};

const postSchema = {
    text: {
        type: String,
        required: true,
        unique: true,
        sparse: false
    },    
    username: {
        type: Connect.Schema.Types.String,
        ref: "Profile"
    },    
    image: {
        type: String,
        default: "https://via.placeholder.com/150",
        required: false
    },
    createdAt: {
        type: Date,
        default: Date.now,
        required: false
    },    
    updatedAt: {
        type: Date,
        default: Date.now,
        required: false
    },    
    reactions: [reactionSchema],    
    comments: {
        type: Connect.Schema.Types.ObjectId,
        ref: "Comment",
        required: false
    }
};

const collectionName = "post";
const postSchemaModel = Connect.Schema(postSchema);
const Post = Connect.model(collectionName, postSchemaModel);

module.exports = Post;

Profile model:

// Here defining profile model
// Embedded we have the Experience as []
const { Connect } = require("../db");
const { isEmail } = require("validator");

const postSchema = {
    type: Connect.Schema.Types.ObjectId,
    ref: "Post"
};

const experienceSchema = {
    role: {
        type: String,
        required: true
    },
    company: {
        type: String,
        required: true
    },
    startDate: {
        type: Date,
        required: true
    },
    endDate: {
        type: Date,
        required: false
    },
    description: {
        type: String,
        required: false
    },    
    area: {
        type: String,
        required: true
    },
    createdAt: {
        type: Date,
        default: Date.now,
        required: false
    },    
    updatedAt: {
        type: Date,
        default: Date.now,
        required: false
    },    
    username: {
        type: String,
        required: false
    },
    image: {
        type: String,
        required: false,
        default: "https://via.placeholder.com/150"
    }
};

const profileSchema = {
    firstname: {
        type: String,
        required: true
    },   
    surname: {
        type: String,
        required: true
    },    
    email: {
        type: String,
        trim: true,
        lowercase: true,
        unique: true,
        required: [true, "Email is required"],
        validate: {
            validator: string => isEmail(string),
            message: "Provided email is invalid"
        }
    },    
    bio: {
        type: String,
        required: true
    },    
    title: {
        type: String,
        required: true
    },    
    area: {
        type: String,
        required: true
    },    
    imageUrl: {
        type: String,
        required: false,
        default: "https://via.placeholder.com/150"
    },    
    username: {
        type: String,
        required: true,
        unique: true
    },    
    experience: [experienceSchema],
    posts: [postSchema],    
    createdAt: {
        type: Date,
        default: Date.now,
        required: false
    },    
    updatedAt: {
        type: Date,
        default: Date.now,
        required: false
    }
};

const collectionName = "profile";
const profileSchemaModel = Connect.Schema(profileSchema);
const Profile = Connect.model(collectionName, profileSchemaModel);

module.exports = Profile;

I was able to make this for the embedded experience but not sure that correct for referenced collection:

const profileWithExperiences = await Student.aggregate([
  { $match: { username: res.username.username } },
  {
    $unwind: "$experience"
  },
  {
    $match: {
      "experience._id": new ObjectID(req.params.experienceId)
    }
  },
  {
    $project: {
      username: 1,
      experience: 1,
      _id: 0
    }
  }
]);

I would like to see an example for referenced collections as it is confusing me how should I do that

[EDIT] JSON for Profiles and Posts

{
    "_id": ObjectId("5e2c98fc3d785252ce5b5693"),
    "imageUrl": "https://i.pravatar.cc/300",
    "firstname": "Jakos",
    "surname": "Lemi",
    "email": "lemi@email.com",
    "bio": "My bio bio",
    "title": "Senior IT developer",
    "area": "Copenhagen",
    "username": "Jakos",
    "experience": [
        {
            "image": "https://via.placeholder.com/150",
            "_id": ObjectId("5e3975f95fbeec9095ff3d2f"),
            "role": "Developer",
            "company": "Google",
            "startDate": ISODate("2018-11-09T23:00:00.000Z"),
            "endDate": ISODate("2019-01-05T23:00:00.000Z"),
            "area": "Copenhagen",
            "createdAt": ISODate("2020-02-04T13:47:37.167Z"),
            "updatedAt": ISODate("2020-02-04T13:47:37.167Z")
        },
        {
            "image": "https://via.placeholder.com/150",
            "_id": ObjectId("5e3978bf5e399698e20c56d4"),
            "role": "Developer",
            "company": "IBM",
            "startDate": ISODate("2018-11-09T23:00:00.000Z"),
            "endDate": ISODate("2019-01-05T23:00:00.000Z"),
            "area": "Copenhagen",
            "createdAt": ISODate("2020-02-04T13:59:27.412Z"),
            "updatedAt": ISODate("2020-02-04T13:59:27.412Z")
        }
    ],
    "createdAt": ISODate("2020-01-25T19:37:32.727Z"),
    "updatedAt": ISODate("2020-02-04T23:14:37.122Z"),
    "__v": NumberInt("0")
}

Post

{
    "_id": ObjectId("5e3beb639e072afedd19dcef"),
    "username": ObjectId("5e2c98fc3d785252ce5b5693"),
    "image": "https://via.placeholder.com/150",
    "text": "My awesome post",
    "createdAt": ISODate("2020-02-06T10:33:07.22Z"),
    "updatedAt": ISODate("2020-02-06T10:33:07.22Z"),
    "reactions": [ ],
    "__v": NumberInt("0")
}

Output expected:

{
    "username": "Jakos",
    "postsCount": [1],
    "posts": [
        {
        "_id": ObjectId("5e3beb639e072afedd19dcef"),
        "image": "https://via.placeholder.com/150",
        "text": "My awesome post",
        "createdAt": ISODate("2020-02-06T10:33:07.22Z"),
        "updatedAt": ISODate("2020-02-06T10:33:07.22Z"),
        "reactions": [ ],
        "__v": NumberInt("0")
    }
    ]

}

I want to see all the posts related to that username

Answer 1

You can use the $lookup aggregation to join collections.

db.profiles.aggregate([
  {
    $match: {
      username: "Jakos"
    }
  },
  {
    $lookup: {
      from: "posts",   //the name of the posts collection, change this if it is different
      localField: "_id",
      foreignField: "username",
      as: "posts"
    }
  },
  {
    $project: {
      username: 1,
      posts: 1,
      postsCount: {
        $size: "$posts"
      },
      _id: 0
    }
  }
])

Playground

For mongoose it should be like this in your app:

const profileWithExperiences = await Student.aggregate([
  { $match: { username: res.username.username } },
  {
    $unwind: "$experience"
  },
  {
    $lookup: {
      from: "posts", //the name of the posts collection, change this if it is different
      localField: "_id",
      foreignField: "username",
      as: "posts"
    }
  },
  {
    $project: {
      username: 1,
      posts: 1,
      postsCount: {
        $size: "$posts"
      },
      _id: 0
    }
  }
]);

Answer 2

Try to get like this i am getting data from two table with the use of node and mongodb.

var param = {};
    param['user_id']=id;
    var search={ user_id:param.user_id,status: [ 'Pending', 'Accepted' ] };
    var output={};
    output = await JobRequest.find(search); 
    if(output !=0)
    {
            var JSon=await JobRequest.aggregate([
                {$match: { user_id: {$gte:id}}  }, 
                     {
                     "$project": {
                      "employee_id": {
                        "$toObjectId": "$employee_id"
                      }, 
                      "service_id": {
                        "$toObjectId": "$service_id"
                      }, 
                      "createdDate": {
                        "$toString": "$createdDate"
                      }, 
                      "chat_status": {
                        "$toString": "$chat_status"
                      },    
                      "status": {
                        "$toString": "$status"
                      },                      
                      "delivery_address": {
                        "$toString": "$delivery_address"
                      },                 
                      "delivery_lat": {
                        "$toString": "$delivery_lat"
                      },         
                      "delivery_lang": {
                        "$toString": "$delivery_lang"
                      },
                    }
                     },

                     {
                      $lookup:
                         {
                            from: "employees",
                            localField: "employee_id",
                            foreignField: "_id",
                            as: "employee_details"
                        }
                   },
                   {
                      $lookup:
                         {
                            from: "services",
                            localField: "service_id",
                            foreignField: "_id",
                            as: "service_details"
                        }
                   }
               ]);