I have a model similar to this one:
{
email: String,
name: String,
role: String,
location: {
country: String,
city: String
},
contacts: {
email: String,
phone: String
}
}
I need to show in my view the entire users information but I wish to include also how many users from a country there are.
Using aggregate I don't know how to get the full user over the groups I create.
So at the moment what I'm doing is this:
User.find({}, function(err, users) {
User.aggregate([
{ $group: { _id: { country: '$location.country' }, count: { $sum: 1 }}}
], function(err, results) {
res.render('home', {
users: users,
countries: results
});
});
});
As you can see I'm using Find and then aggregate to get both the information I need... but I'm pretty sure there is a way to get it using only aggregate but I can not find how to do that...
If you need to accumulate the entire user information for each group, then you need to use the $push operator for accumulation and the $$ROOT system variable to access the entire user info.
User.aggregate([
{$group:{"_id":{"country":"$location.country"},
"users":{$push:"$$ROOT"},
"count":{$sum:1}}}
],callback)
In case you would want to accumulate only specific fields of the user information document, you could just push the required fields like:
User.aggregate([
{$group:{"_id":{"country":"$location.country"},
"users":{$push:{"email":"$email","name":"$name"}},
"count":{$sum:1}}}
],callback)
Related
I am making a polling website. Currently I have two collections Polls and Votes. I am using the aggregation pipeline to get the number of votes for each movie. I am having difficulty wrapping my head around updating the poll based on the vote collection. This is the vote Schema:
poll: objectId
votedMovies: Array
0: Object
id: ObjectId
title: string
This is my poll Schema:
_id: ObjectID
pollType: String
totalVotes: Number
movies: Array
0: Object
id: ObjectID
title: String
votes: Number
So far I have an aggregation pipeline that does the following:
let voteCollection = await db.collection('votes').aggregate([
{
$match: {poll: id}
},
{
$unwind: "$votedMovies"
},
{
$group: {_id: "$votedMovies.id", totalVotes: {$sum: 1}}
}
]).toArray()
That spits out something like this:
[{"_id":10674,"totalVotes":2},
{"_id":99861,"totalVotes":1},
{"_id":299534,"totalVotes":4},
{"_id":637157,"totalVotes":3},
{"_id":24428,"totalVotes":5}]
How do I update the poll document so that it has the current number of votes? Am I on the right track with the aggregation pipeline?
You should be able to update each movie votes with:
for (const vote of voteCollection) {
await db.collection('polls').updateOne(
{
_id: id, // pool id
'movies._id': vote._id,
},
{
'movies.$.votes': vote.totalVotes,
}
);
}
I have a collection of documents, that looks like this:
{
name: String,
phoneNumber: String,
myDate: Date
}
And this is how an actual entry would look like:
{
name: 'John Doe',
phoneNumber: '(402)-123-4444',
myDate: 2020-08-31T08:54:47.000+00:00
}
And I have about 1000 entries in my db. Now I want to change the date field to an array of dates, and I want to modify all the entries in my db to be something like this myDate: [Date]. I want to keep the existing entry from the date field, but move it inside of an array. And I don't want to do it manually, any way I can do this with mongoose?
I tried something like Model.update({}, { $set: { myDate: [] } }), but I don't know what to use inside the array to keep the existing entry, and not to add something else.
I believe this will on one-time activity so I wanna propose two steps answer here,
Step 1. : Change the type of field from the mongo/shell as,
> db.collection.find().forEach(function(individualDocument) {
db.collection.update(
{ _id: individualDocument._id },
{ "$set": { "myDate": [individualDocument.myDate] } }
);
})
Step 2: Update your mongoose model as you tried ,
{
name: String,
phoneNumber: String,
myDate: [Date]
}
OR
myDate: { type: Array, default: [Date] }
I have two mongo collections.
Enrollment:
{UserID: String, CourseID: String, EducatorFlag: boolean}
Courses
{_id: String, courseName: String}
I'm attempting to generate a list of courseNames when given a UserID. This requires me to find all courses that a User is enrolled in. The following function returns just the CourseID of each course a user is in.
var currentCourses = Enrollment.find(
{ UserId: Meteor.userId(), EducatorFlag: false },
{ fields: { CourseID: 1 });
I'm unsure of how to take this cursor, and use each item in it to run another query and build a list from the output. Basically for each CourseID in currentCourses I need to do
var result = []
result += Courses.find({_id: CourseID}, {fields: {_id: 0, courseName: 1}});
The goal is simply to print all the courses that a user is enrolled in.
You have several options:
Use the cursor directly with a .forEach()
Use .fetch() to transform the cursor into an array of objects and then manipulate that.
Get an array of _ids of enrollments with .map() and directly search the courses with mongo's $in
Let's just use the first one for now since it's pretty simple:
let courseNames = [];
Enrollment.find(
{ UserId: Meteor.userId(), EducatorFlag: false },
{ fields: { CourseID: 1 }).forEach((e)=>{
let course = Courses.findOne(e.CourseID, { fields: { courseName: 1 }})
courseNames.push(course.courseName);
});
Note: when selecting fields in a query you can't mix exclusions and inclusions.
Getting an array of _ids and using that with $in is also pretty straightforward:
let courseIdArray = Enrollment.find(
{ UserId: Meteor.userId(), EducatorFlag: false },
{ fields: { CourseID: 1 }).map((e)=>{ return e.CourseID });
let courseNames = Courses.find(
{ _id: { $in: courseIdArray }}).map((c)=>{ return c.courseName });
edited after #enRaiser's answer.
I have a sandbox mongoDB database with a single collection called "hotels", the document-schema of which looks like this:
var roomSchema = new mongoose.Schema({
type: String,
number: Number,
description: String,
photos: [ String ],
price: Number
});
var hotelSchema = new mongoose.Schema({
name: String,
stars: Number,
description: String,
photos: [ String ],
currency: String,
location: {
address: String,
coordinates: [ Number ] /* enforce later validation to have max of two numbers in the array */
},
rooms: [roomSchema],
reviews: [{
name: String,
id: String,
review: String,
rating: Number
}],
services: [ String ]
});
Now, I'd like to have two versions of schema for Hotel, one for a 'deep' data model and the other for a min model.
var hotelMinSchema = new mongoose.Schema({
name: String,
stars: Number,
location: {
address: String,
coordinates: [ Number ]
},
currency: String
})
module.exports = {
full: mongoose.model('hotel', hotelSchema),
min: mongoose.model('hotel', hotelMinSchema)
}
Aparently I'm not supposed to have two models for a collection.. not so sure. I get this error thrown.
OverwriteModelError: Cannot overwrite hotel model once compiled.
I think there should be a work-around for this. Any help or suggestion would be appreciated.
This is totally wrong way of developing any Database. even in MYSQL, I would not have think of this way of designing DB.
Firstly there are duplicate data. You alwayse have to take care of syncing them.
and 2nd, even in your full model there is duplication of comment. the comment info is present in both User ( i.e the commenter and the blogger)
Irrespective of the DB. when ever you think of solution you have to identify the real entities. here in your use case there are only two entity User and comment. So just make two model. not more.(in case of MYSQL, I would say just make two tables User table and comment table.)
Then set up a relation between them. for that in mongoose learn the how to make relation and how to populate that data based on relation. its just like setting up foreign key in MYSQL.
Sorry, I just found this out.
var hotelListPromise = Hotel.find({})
.select('name stars location currency')
.exec((err, hotelData) => {
// my callback stuff here
});
I have models called "Activities" that I am querying for (using Mongoose). Their schema looks like this:
var activitySchema = new mongoose.Schema({
actor: {
type: mongoose.Schema.ObjectId,
ref: 'User',
required: true
},
recipient: {
type: mongoose.Schema.ObjectId,
ref: 'User'
},
timestamp: {
type: Date,
default: Date.now
},
activity: {
type: String,
required: true
},
event: {
type: mongoose.Schema.ObjectId,
ref: 'Event'
},
comment: {
type: mongoose.Schema.ObjectId,
ref: 'Comment'
}
});
When I query for them, I am populating the actor, recipient, event, and comment fields (all the references). After that, I also deep-populate the event field to get event.creator. Here is my code for the query:
var activityPopulateObj = [
{ path: 'event' },
{ path: 'event.creator' },
{ path: 'comment' },
{ path: 'actor' },
{ path: 'recipient' },
{ path: 'event.creator' }
],
eventPopulateObj = {
path: 'event.creator',
model: User
};
Activity.find({ $or: [{recipient: user._id}, {actor: {$in: user.subscriptions}}, {event: {$in: user.attending}}], actor: { $ne: user._id} })
.sort({ _id: -1 })
.populate(activityPopulateObj)
.exec(function(err, retrievedActivities) {
if(err || !retrievedActivities) {
deferred.reject(new Error("No events found."));
}
else {
User.populate(retrievedActivities, eventPopulateObj, function(err, data){
if(err) {
deferred.reject(err.message);
}
else {
deferred.resolve(retrievedActivities);
}
});
}
});
This is already a relatively complex query, but I need to do even more. If it hits the part of the $or statement that says {actor: {$in: user.subscriptions}}, I also need to make sure that the event's privacy field is equal to the string public. I tried using $elemMatch, but since the event has to be populated first, I couldn't query any of its fields. I need to achieve this same goal in multiple other queries, as well.
Is there any way for me to achieve this further filtering like I have described?
The answer is to change your schema.
You've fallen into the trap that many devs have before you when coming into document database development from a history of using relational databases: MongoDB is not a relational database and should not be treated like one.
You need to stop thinking about foreign keys and perfectly normalized data and instead, keep each document as self-contained as possible, thinking about how to best embed relevant associated data within your documents.
This doesn't mean you can't maintain associations as well. It might mean a structure like this, where you embed only necessary details, and query for the full record when needed:
var activitySchema = new mongoose.Schema({
event: {
_id: { type: ObjectId, ref: "Event" },
name: String,
private: String
},
// ... other fields
});
Rethinking your embed strategy will greatly simplify your queries and keep the query count to a minimum. populate will blow your count up quickly, and as your dataset grows this will very likely become a problem.
You can try below aggregation. Look at this answer: https://stackoverflow.com/a/49329687/12729769
And then, you can use fields from $addFields in your query. Like
{score: {$gte: 5}}
but since the event has to be populated first, I couldn't query any of its fields.
No can do. Mongodb cannot do joins. When you make a query, you can work with exactly one collection at a time. And FYI all those mongoose populates are additional, distinct database queries to load those records.
I don't have time to dive into the details of your schema and application, but most likely you will need to denormalize your data and store a copy of whatever event fields you need to join on in the primary collection.