I'm trying to populate a model with related details.
Each product has a user reference.
Currently i'm populating my products with user details:
Product document:
{
_id: 'object_product_id`,
title: 'Product1',
user: 'object_user_id'
}
User document:
{
_id: 'object_user_id`,
username: 'User1'
}
To populate a product i use:
Product.find().populate('user').exec()
The expected is:
{
_id: 'object_product_id`,
title: 'Product1',
user: {
_id: 'object_user_id`,
username: 'User1'
}
}
But if a user document is not present it will be:
{
_id: 'object_product_id`,
title: 'Product1',
user: null
}
Is there a way to populate products with a default value when a user document is not present or to leave the default value of user key that was in product document? Only in context of populate().
I've read the mongoose documentation it is a expected behavior to have a null if a document was not found, also i know that i can do that specific population within the callback of exec()
Something like:
{
user: 'my_custom_default_value'
}
Related
I am working on mongodb with two collection, one collection is user account collection, another collection is teacher collection which stores teacher detailed information.
user account
{
username: { type: "String" },
password: { type: "String" }
}
teacher collection
{
name: { type: "String" },
age: { type: "String" },
job: { type: "String" }
}
I wonder is it possible to assign the teacher _id with the user account _id, if both teacher and user account points to the same person?
I'm trying to update and object inside array in MongoDB.
my model is:
let userSchema = new mongoose.Schema({
userName: {
type: String
},
password: {
type: String
},
history: []
});
And inside history each element is from the next type:
id, array(named ing_array) and boolean field called favorite.
I'm trying to update the favorite field with mongoose with the userName and the id.
I tried to do this query and I didn't succed.
Could some one tell me whats worng?
[object photo]: https://i.stack.imgur.com/2mYpP.png
User.findOneAndUpdate(
{ "userName": user_name, "history.id": id },
{ "$set": { "history.$.favorite": true }}
);
You have to use arrayFilters in this way:
db.collection.update({
"userName": "uname",
"history.id": 1
},
{
"$set": {
"history.$[element].favorite": false
}
},
{
"arrayFilters": [
{
"element.id": 1
}
]
})
Note that update query has the format: update(query, update, options) (Check the docs).
When you do { "userName": user_name, "history.id": id } you are telling mongo "Give me all documents where userName is user_name and array history has an id with value id. This return all history array because it belows to the document.
To update an specific object into the array is neccessary to use arrayFilters to tell mongo which object do you want to update. In this case the object where id is equal to 1. You can use as you want to match wit your requirements.
Example here
Consider I have this document in my MongoDB collection, Workout:
{
_id: ObjectId("60383b491e2a11272c845749") <--- Workout ID
user: ObjectId("5fc7d6b9bbd9473a24d3ab3e") <--- User ID
exercises: [
{
_id: ObjectId("...") <--- Exercise ID
exerciseName: "Bench Press",
sets: [
{
_id: ObjectId("...") <--- Set ID
},
{
_id: ObjectId("...") <--- Set ID
}
]
}
]
}
The Workout object can include many exercise objects in the exercises array and each exercise object can have many set objects in the sets array. I am trying to implement a delete functionality for a certain set. I need to retrieve the workout that the set I want to delete is stored in. I have access to the user's ID (stored in a context), exercise ID and the set ID that I want to delete as parameters for the .findOne() function. However, I'm not sure whether I can traverse through the different levels of arrays and objects within the workout object. This is what I have tried:
const user = checkAuth(context) // Gets logged in user details (id, username)
const exerciseID, setID // Both of these are passed in already and are set to the appropriate values
const workoutLog = Workout.findOne({
user: user.id,
exercises: { _id: exerciseID }
});
This returns an empty array but I am expecting the whole Workout object that contains the set that I want to delete. I would like to omit the exerciseID from this function's parameters and just use the setID but I'm not sure how to traverse through the array of objects to access it's value. Is this possible or should I be going about this another way? Thanks.
When matching against an array, if you specify the query like this:
{ exercises: { _id: exerciseID } }
MongoDB tries to do an exact match on the document. So in this case, MongoDB would only match documents in the exercises array of the exact form { _id: ObjectId("...") }. Because documents in the exercises have other fields, this will never produce a match, even if the _ids are the same.
What you want to do instead is query a field of the documents in the array. The complete query document would then look like this:
{
user: user.id,
"exercises._id": exerciseID
}
You can perform both find and update in one step. Try this:
db.Workout.updateOne(
{
"user": ObjectId("5fc7d6b9bbd9473a24d3ab3e"),
},
{
$pull: {
"exercises.$[exercise].sets": {
"_id": ObjectId("6039709fe0c7d52970d3fa30") // <--- Set ID
}
}
},
{
arrayFilters: [
{
"exercise._id" : ObjectId("6039709fe0c7d52970d3fa2e") // <--- Exercise ID
}
]
}
);
I have the following schema:
var lessonSchema = mongoose.Schema({
_id: mongoose.Schema.Types.ObjectId,
name: String,
students: [{
_id: mongoose.Schema.Types.ObjectId,
attendance: {
type: Boolean,
default: false,
},
}],
});
The students array is an array of students who attended the particular lesson. I want to find a lesson using whether a particular user is present in the students array and then sent only that element of the students array which corresponds to the user making the request, along with all other fields as it is. For example, the query should return:
{
_id: 'objectid',
name: 'lesson-name'
students: [details of just the one student corresponding to req.user._id]
}
I tried using:
Lesson.find({'students._id': String(req.user._id)}, {"students.$": 1})
The query returns the document with just the id and the relevant element from the students array:
{
_id: 'objectid'
students: [details of the one student corresponding to req.user._id]
}
I tried using:
Lesson.find({'students._id': mongoose.Types.ObjectId(req.user._id)})
This returns the document with the details of all the students:
{
_id: 'objectid',
name: 'lesson-name'
students: [array containing details of all the students who attended the lesson]
}
How can I modify the query to return it the way I want?
You can return the name field by adding it to the projection object like this:
Lesson.find({ "students._id": String(req.user._id) }, { "name": 1, "students.$": 1 })
When you add a projection object (2nd parameter to find), the _id field is returned by default, plus whichever fields you set to 1.
Therefore, you were returning just the _id and the desired student but not the name field.
If you want to return all other fields and just limit the array to the matched item then you can make use of $slice in your projection:
Lesson.find({ "students._id": String(req.user._id) }, { "students.$": { $slice: 1 } })
I'm trying to get all documents in a collection based on a subdocument array values. This is my data structure in the collection i'm seeking:
{
_id: ObjectId('...'),
name: "my event",
members:
[
{
_id: ObjectId('...'),
name: "family",
users: [ObjectId('...'),ObjectId('...'),ObjectId('...')]
},
{
_id: ObjectId('...'),
name: "work",
users: [ObjectId('...'),ObjectId('...'),ObjectId('...')]
}
]
}
I should point out that the schema of these objects are defined like so:
Events:
{
name: { type: String },
members: {type: [{ type: ObjectId, ref: 'MemberGroup' }], default:[] }
}
MemberGroup:
{
name: { type: String },
users: [{type: mongoose.Schema.Types.ObjectId, ref: 'User'}]
}
and of course User is just an arbitrary object with an id.
What i'm trying to fetch: i want to retrieve all events which has a specific user id in its member.users field.
i'm not sure if its event possible in a single call but here is what i've tried:
var userId = new mongoose.Schema.ObjectId('57d9503ef10d5ffc08d6b8cc');
events.find({members: { $elemMatch : { users: { $in: [userId]} } }})
this syntax work but return no elements even though i know there are matching elements (using robomongo to visualize the db)
So after a long search in stackoverflow i came across the good answare here:
MongoDB: How to find out if an array field contains an element?
my query changed to the following which gave me my desired result:
var userId = new mongoose.Schema.ObjectId('57d9503ef10d5ffc08d6b8cc');
events.find({}, {members: { $elemMatch : { users: { $eq: userId} } }})
notice the use of the second find parameter to specify the query limit instead of the first one (which is odd)