I use Mongoose.js and cannot solve problem with 3 level hierarchy document.
There 2 ways to do it.
First - without refs.
C = new Schema({
'title': String,
});
B = new Schema({
'title': String,
'c': [C]
});
A = new Schema({
'title': String,
'b': [B]
});
I need to show C record. How can i populate / find it, knowing only _id of C?
I was try use:
A.findOne({'b.c._id': req.params.c_id}, function(err, a){
console.log(a);
});
But i dont know how to get from returnet a object only c object that i need.
Second if working with refs:
C = new Schema({
'title': String,
});
B = new Schema({
'title': String,
'c': [{ type: Schema.Types.ObjectId, ref: 'C' }]
});
A = new Schema({
'title': String,
'b': [{ type: Schema.Types.ObjectId, ref: 'B' }]
});
How to populate all B, C records to get hierarchy?
I was try to use something like this:
A
.find({})
.populate('b')
.populate('b.c')
.exec(function(err, a){
a.forEach(function(single_a){
console.log('- ' + single_a.title);
single_a.b.forEach(function(single_b){
console.log('-- ' + single_b.title);
single_b.c.forEach(function(single_c){
console.log('--- ' + single_c.title);
});
});
});
});
But it will return undefined for single_c.title. I there way to populate it?
Thanks.
As of Mongoose 3.6 the ability to recursively populate related documents in a query has been added. Here is an example of how you might do it:
UserList.findById(listId)
.populate('refUserListItems')
.exec(function(err, doc){
UserListItem.populate(doc.refUserListItems, {path:'refSuggestion'},
function(err, data){
console.log("User List data: %j", doc);
cb(null, doc);
}
);
});
In this case, I am populating an array of id's in 'refUserListItems' with their referenced documents. The result of the query then gets passed into another populate query that references the field of the original populated document that I want to also populate - 'refSuggestion'.
Note the second (internal) populate - this is where the magic happens. You can continue to nest these populates and tack on more and more documents until you have built your graph the way you need it.
It takes a little time to digest how this is working, but if you work through it, it makes sense.
in Mongoose 4 you can populate multilevel like this (even in different database or instance)
A
.find({})
.populate({
path: 'b',
model: 'B',
populate: {
path: 'c',
model: 'C'
}
})
.exec(function(err, a){});
In Mongoose 4 you can populate documents across multiple levels:
Say you have a User schema which keeps track of the user's friends.
var userSchema = new Schema({
name: String,
friends: [{ type: ObjectId, ref: 'User' }]
});
Firstly populate() lets you get a list of user friends. But what if you also wanted a user's friends of friends? In that case, you can specify a populate option to tell mongoose to populate the friends array of all the user's friends:
User.
findOne({ name: 'Val' }).
populate({
path: 'friends',
// Get friends of friends - populate the 'friends' array for every friend
populate: { path: 'friends' }
});
Taken from: http://mongoosejs.com/docs/populate.html#deep-populate
I'm late to this, but I wrote a Mongoose plugin that makes it extremely simple to perform deep model population. For your example, you can do this to populate b and c:
A.find({}, function (err, docs) {
A.deepPopulate(docs, 'b.c', cb)
}
You can also specify Mongoose populate options for each of the populated paths, like this:
A.deepPopulate(docs, 'b.c', {
b: {
select: 'name'
}
}, cb)
Check out the plugin documentation for more information.
Related
In Mongoose, I have two collections, with one referencing the other. Is it possible to have a find query that selects records based on a value in the other. An example of what I am try to get at (not actual schemas):
const CarModelSchema = new mongoose.Schema({
name: String,
brand: { type: mongoose.Schema.Types.ObjectId, ref: 'CarBrand' }
});
const CarBrandSchema = new mongoose.Schema({
name: String,
country: String
});
I then want to perform a query of the form, without needing to do two queries:
CarModelSchema.find({ 'brand.country': 'GER' });
So far I haven't been able to make this work, so I am wondering whether this can be done in Mongo or whether I am approaching it wrong?
Yes it is possible.
I realize you don't have models for your schemas so add them like this:
const CarModel = mongoose.model('CarModel', CarModelSchema);
const CarBrand = mongoose.model('CarBrand', CarBrandSchema);
Also brands should be defined like this:
brand: [{ type: mongoose.Schema.Types.ObjectId, ref: 'CarBrand' }] //added the brackets
You can then run a find query to filter by country by doing the following:
CarModel.
find(...).
populate({
path: 'brand',
match: { country: { $eq: 'GER' }},
// You can even select the field you want using select like below,
select: 'name -_id',
//Even limit the amount of documents returned in the array
options: { limit: 5 }
}).
exec();
And that should do it, as long as the ObjectIds saved in brands array in the CarModel collection are valid or exist.
Using match in your population will do the work.
CarModel.find()
.populate({
path: 'brand',
model: CarBrandModel,
match: { country: { $eq: 'GER' }},
})
.exec()
Keep in mind you have to define CarModel and CarBrandModel like this:
const CarModel = mongoose.model('CarModel', CarModelSchema)
const CarBrandModel = mongoose.model('CarBrandModel', CarBrandSchema)
Yes, you are doing it wrong.
In CarModelSchema.brand there is not string saved, there is ObjectId saved, therefore you have to find that ObjectId (the reference).
You can do it manually - first finding the CarBrandSchema.find({ 'country': 'GER' }); and then use its ObjectId (=_id), or you can use https://mongoosejs.com/docs/populate.html to populate your CarModel with the CarBrand object.
const userSchema = new Schema(
{
_id: Schema.Types.ObjectId,
name: String,
posts: [{ type: Schema.Types.ObjectId, ref: "Post" }],
following: [{ type: Schema.Types.ObjectId, ref: "User" }]
}
};
I want to extract all the posts from all the Users in the 'following' array, put them into one single array, sort them and then display the first 20. I was wondering if that is possible within the cursor or if I have to load it into memory.
function createFeed(user) {
User.findOne({ name: user })
.populate({
path: "following",
populate: {
path: "posts"
}
})
//put all the posts into one array
.sort(...) //sort by time created
.limit(...) //only get the newest n posts
.exec((err, result) => {
if (err) console.log("error", err);
console.log("result", //sorted tweets array);
});
};
(I don't want to filter all the posts in my 'Posts' collection to check if they are made by the user since that would be a lot more expensive)
You can use distinct query in mongoDB
db.User.distinct('following',{})
If you are trying to filter your populate with a condition, then you should be doing this:
User.findOne({ name: user })
.populate({
path: 'posts',
match: { user: 'XXX' }
})
Even more better would be to query the posts with the user filter condition and then populate user details.
I see that one way we use populate is to put one document from another collection into a "parent" collection. I was just going through this question and I was hoping someone could explain the answer to me better. And show me a practical use. Here is an example from the answer.
var PersonSchema = new mongoose.Schema({
t: String
}, {collection: 'persons'});
var User = mongoose.model('User', PersonSchema.extend({
_id: String,
name: String
}));
var ParentSchema = new mongoose.Schema({
s: String
}, {collection: 'parent'});
var Like = mongoose.model('Like', ParentSchema.extend({
_id: String,
user_id: {
type: String,
ref: 'User'
}
}));
Insert Data into DB,
var user = new User({
t: 't1',
_id: '1234567',
name: 'test'
});
var like = new Like({
s: 's1',
_id: '23456789',
});
user.save(function(err, u){
if(err)
console.log(err);
else {
like.user_id = u._id;
console.log(like);
like.save(function(err) {
if (err)
console.log(err);
else
console.log('save like and user....');
});
}
});
Query by
Like.findOne({}).populate('user_id').exec(function(err, doc) {
if (err)
console.log(err);
else
console.log(doc);
});
And the result is
{ _id: '23456789',
__t: 'Like',
user_id: { _id: '1234567', __t: 'User', t: 't1', name: 'test', __v: 0 },
s: 's1',
__v: 0 }
QUESTION
where does __t: 'User' come from?
I was thinking that using populate() or ref that would separate the collections but it looks like at the end the like collection has the users document in it. I think I wanted to use populate so I could make a document smaller.
3.Also if someone really wanted to help explain this to me I have an example that I have been trying to do and I don't know if I should use populate but if I should it would be great if you show me how. Here is the example.
You have
doctors
patients
information about the practice
There could be like a 1000 doctors and lots of patients for each doctor. and the information will be about their practice(like how many employees they have). so I feel that there should be a separation of concern.(one reason is to prevent a single document for a patient from getting to big). So If we're going with the populate method If you could explain how to set it up for this case. I guess I could have a doctor as a parent and a child refs for patients and another child refs for information about practice. so maybe there should be an array of objectId for the patients and an array for Other information
Q1: where does __t: 'User' come from?
Refer to this link.
mongoose now includes schema inheritance and discriminatorKey functionality that breaks mongoose-schema-extend. mongoose now sets the discriminatorKey schema option to __t by default
Q2: I was thinking that using populate() or ref that would separate the collections but it looks like at the end the like collection has the users document in it. I think I wanted to use populate so I could make a document smaller.
It seems you misunderstand the meaning of Population. There are no joins in MongoDB but sometimes we still want references to documents in other collections. This is where population comes in. Population is the process of automatically replacing the specified paths in the document with document(s) from other collection(s). So populate is not used to make document smaller.
Q3: Doctor, Patient, Practice
Schema could be as following:
var DoctorSchema = new Schema ({
name: String,
// ... other field
});
var PatientSchema = new Schema ({
name: String,
doctor: {type: Schema.ObjectId,
ref: 'Doctor'}
});
var PracticeSchema = new Schema ({
ff: String,
patientId: {type: Schema.ObjectId,
ref: 'Patient'},
doctorId: {type: Schema.ObjectId,
ref: 'Doctor'}
});
As for schema, it is hard to determine which schema is better or not, (with populate or without it). The first thing we should consider is to meet our query requirement, to make the query easy. The design of mongoDB to make the query more efficiently. So our schema should meet it.
I want to recreate the models in database after dropping everything in it.
Mongoose (or Mongo itself )actually recreates the documents but not the indices. So is there a way to reset Mongoose so that it can recreate indices as if running the first time?
The reason why I'm using dropDatabase is because it seems easier while testing. Otherwise I would have to remove all collections one by one.
While not recommended for production use, depending on your scenario, you can add the index property to a field definition to specify you want an index created:
var animalSchema = new Schema({
name: String,
type: String,
tags: { type: [String], index: true } // field level
});
animalSchema.index({ name: 1, type: -1 }); // schema level
Or,
var s = new Schema({ name: { type: String, sparse: true })
Schema.path('name').index({ sparse: true });
Or, you can call ensureIndex on the Model (docs):
Animal.ensureIndexes(function (err) {
if (err) return handleError(err);
});
Just a simple query, for example with a double ref in the model.
Schema / Model
var OrderSchema = new Schema({
user: {
type : Schema.Types.ObjectId,
ref : 'User',
required: true
},
meal: {
type : Schema.Types.ObjectId,
ref : 'Meal',
required: true
},
});
var OrderModel = db.model('Order', OrderSchema);
Query
OrderModel.find()
.populate('user') // works
.populate('meal') // dont works
.exec(function (err, results) {
// callback
});
I already tried something like
.populate('user meal')
.populate(['user', 'meal'])
In fact only one of the populates works.
So, how do is get two populates working ?
You're already using the correct syntax of:
OrderModel.find()
.populate('user')
.populate('meal')
.exec(function (err, results) {
// callback
});
Perhaps the meal ObjectId from the order isn't in the Meals collection?
UPDATE:
This solution remains for the version 3.x of Mongoose http://mongoosejs.com/docs/3.8.x/docs/populate.html but is no longer documented for >= 4.x versions of Mongoose and so the answer from #JohnnyHK is the only valid one for now on.
ORIGINAL POST
If you're using Mongoose >= 3.6, you can pass a space delimited string of the path names to populate:
OrderModel.find()
.populate('user meal')
.exec(function (err, results) {
// callback
});
http://mongoosejs.com/docs/populate.html
This has probably been resolved already, but this is my take on multiple & deep population in Mongodb > 3.6:
OrderModel.find().populate([{
path: 'user',
model: 'User'
}, {
path: 'meal',
model: 'Meal'
}]).exec(function(err, order) {
if(err) throw err;
if(order) {
// execute on order
console.log(order.user.username); // prints user's username
console.log(order.meal.value); // you get the idea
}
});
There are probably other ways to do this, but this makes very readable code for beginners (like me)
The best solution in my opinion is arrays when you are populating more than one foreign field on the same level. My code shows that I have multiple populates for different levels.
const patients = await Patient.find({})
.populate([{
path: 'files',
populate: {
path: 'authorizations',
model: 'Authorization'
},
populate: {
path: 'claims',
model: 'Claim',
options: {
sort: { startDate: 1 }
}
}
}, {
path: 'policies',
model: 'Policy',
populate: {
path: 'vobs',
populate: [{
path: 'benefits'
}, {
path: 'eligibility',
model: 'Eligibility'
}]
}
}]);
As you can see, wherever I needed more than one field of a document populated, I encased the populate key in an array and provided an array of objects, each object having a different path. Most robust and concise way to do it, in my opinion.
You can use array syntax:
let results = await OrderModel.find().populate(['user', 'meal']);
You can also select which properties you want from each populate:
let results = await OrderModel.find().populate([{path: 'user', select: 'firstname'}, {path: 'meal', select: 'name'}]);
Latest mongoose v5.9.15
has ability to take array of populate fields
so you can do,
.populate([ 'field1', 'field2' ])
You can try:
OrderModel.find()
.populate('user')
.populate('meal')
.exec(function (err, results) {
// callback
});
or with array options
OrderModel.find()
.populate([
{
path: "path1",
select: "field",
model: Model1
},
{
path: "path2",
select: "field2",
model: Model2
}
])
.exec(function (err, results) {
// callback
});
In model file do something like:-
doctorid:{
type:Schema.Types.ObjectId, ref:'doctor'
},
clinicid:{
type:Schema.Types.ObjectId, ref:'baseClinic'
}
In js file for adding operator use Something like:-
const clinicObj = await BaseClinic.findOne({clinicId:req.body.clinicid})
const doctorObj = await Doctor.findOne({ doctorId : req.body.doctorid}) ;
**and add data as:-**
const newOperator = new Operator({
clinicid:clinicObj._id,
doctorid: doctorObj._id
});
Now, while populating
apiRoutes.post("/operator-by-id", async (req, res) => {
const id = req.body.id;
const isExist = await Operator.find({ _id: id }).populate(['doctorid','clinicid'])
if (isExist.length > 0) {
res.send(isExist)
} else {
res.send("No operator found");
}
});
i have same problem , but my mistake not in populate , i have an error in Model
if you do this
uncorrected
user: {
type: [Schema.Types.ObjectId],
ref: 'User'
}
correct
user: [{
type: Schema.Types.ObjectId,
ref: 'User'
}]
you must put array around of object like this
To populate multiple fields with array of objects in controller/action function, model of both is already referred in schema of post
post.find({}).populate('user').populate('comments').exec(function (err,posts)
{
if(err)
{
console.log("error in post");
}
return res.render('home',{
h1:"home Page",
posts:posts,
});
});
I think you are trying to the nested population you can visit official docs
User.
findOne({ name: 'Val' }).
populate({
path: 'friends',
// Get friends of friends - populate the 'friends' array for every friend
populate: { path: 'friends' }
});