I have an application in which I manage categories and subcategories.
So each time I delete a category, I have a mongoose middleware that deletes all the subcategories who belong to it.
schema.post('findOneAndDelete',
(category: CategoryDocument) => subcategoryModel.deleteMany({ category: category.id }))
That works fine when I delete just one category, what happens when I delete multiple?
I tried registering a deleteMany middleware like so:
schema.post('deleteMany',
(deletedQueryResult: any) => {})
But the deleteMany middleware just sends to my callback the result of the query (the time it took, number of deleted documents and some internal mongoose/mongodb properties).
Is there anyway I can get the deleted documents or their ids inside a mongoose middleware?
If not what are my other options here?
The deleteMany method returns an object with three fields:
n – number of matched documents
ok – 1 if the operation was successful, else 0
deletedCount – number of deleted documents
This is the same behaviour of the mongodb db.collection.deleteMany method.
I suggest you to add a static method to your model:
// Assign a function to the "statics" object of our schema
categorySchema.statics.deleteManyWithSubs = async function(catIds) {
const deleteQuery = /*your delete query using catIDs*/
const delRes = await this.deleteMany(deleteQuery);
catIds.forEach(id => {
await subcategoryModel.deleteMany({ category: id })
});
return true;
};
// Usage
categoryModel.deleteManyWithSubs(ids)...
Related
So here I Have multiple sub-collections(subjects) in different doc's(grades) and I want to get all the sub-collections(subjects) documents(questions) at once I tried to get them by using Collection group queries the only problem which I am facing in my code sometime it returning all the doc's(questions) but sometimes not what is the issue
this is what i have tried
const getAllQuestions = (request,response)=>{
const subjects = ['Maths','English']
const questionsArray = []
subjects.forEach((subject,index)=>{
db.collectionGroup(subject)
.get()
.then((querySnapshot)=>{
querySnapshot.forEach((doc) => {
questionsArray.push({...doc.data(),id:doc.id})
})
if(index==subjects.length-1){
response.status(200).json({
status:200,
data:questionsArray,
length:questionsArray.length
})
}
})
})
}
If you don't want to get the subcollections from all grades, but only from one of them, you should not use a collection group query but instead specify the entire path to the collection you want to query/read:
db.collection('quizQuesDb/Grade 5/'+subject)
.get()
If you want to perform a query across all collections of a certain name under a specific path, see: CollectionGroupQuery but limit search to subcollections under a particular document
Here's an abbreviated version of the data model for my firestore collections:
// /posts/{postId}
interface Post {
id: string;
lastCommentedAt: Timestamp | null
}
// /posts/{postId}/comments/{commentId}
interface Comment {
id: string;
createdAt: Timestamp;
}
So I have a collection of posts, and within each post is a subcollection of comments.
I want to do the following:
When a comment is created, update the lastCommentedAt field of the parent Post document with the comment's createdAt value
When a comment is deleted, the parent Post's lastCommentedAt field may no longer be valid so we need to get all of the Post's comments and get the most recent comment to update lastCommentedAt.
I see a couple ways to do this:
In my client code, I can do the above logic inside of functions like createComment(post, comment), and deleteComment(post, comment)
Especially in the case of deleting it seems like it is not ideal to require the client to fetch all comments for the post and iterate through them just to delete one
Would I need to use transactions for this since someone could be deleting a comment at the same time someone was creating a new one?
In my cloud functions I could create triggers on /posts/{postId}/comments/{commentId} for create and delete and do this logic on the backend
Is there risk of race conditions here as well? Again maybe I should use a transaction?
The use case for this lastCommentedAt field is that I want to be able to query for posts and sort them by the ones that have recent comments.
Edit: possible implementation for deleteComment using a batched write. Is it actually safe to do a query for documents before the writes though?
async function deleteComment(post, comment) {
const batch = writeBatch(firestore);
const postRef = doc("posts", post.id);
const commentRef = doc("posts", post.id, "comments", comment.id);
const commentsCollection = collection("posts", post.id, "comments");
const recentCommentSnapshot = await getDocs(
query(
commentsCollection,
where("id", "!=", comment.id),
orderBy("createdAt", "desc"),
limit(1)
)
);
let lastCommentedAt = null;
if (recentCommentSnapshot.docs.length > 0) {
lastCommentedAt = recentCommentSnapshot.docs[0].data().createdAt;
}
batch.delete(commentRef);
batch.update(postRef, { lastCommentedAt });
await batch.commit();
}
For adding comments you can use batched writes to ensure the comment is added and the parent document is update with current timestamp.
const batch = db.batch();
const postDocRef = db.collection('posts').doc('postId');
const commentRef = postDocRef.collection("comments").doc();
batch.update(postDocRef, { lastCommentedAt: FieldValue.serverTimestamp() });
batch.set(commentRef, { createdAt: FieldValue.serverTimestamp() });
await batch.commit();
When deleting comments you might have to query the latest comment using createdAt field and then update parent document.
const getLastComment = (postId: string) => {
const postRef = db.collection('posts').doc(postId);
return await postRef.orderBy('createdAt', 'desc').limit(1).get();
}
I'm trying to build an application, using MongoDB and Node.JS. I have 3 models: User, Ride, Participating.
Participating contains a userID and a rideID. It is almost as with a SQL logic: Participating links the two others models.
I'd like to, using a userID, return every Ride thanks to Participating Model
I tried to use a forEach, as the first request returns an array.
router.get('/getAllRide/:userID',function(req,res){
let userID = req.params.userID
let return = []
Participating.find({_idUser: userID })
.then(participating => {
participating.forEach(element => {
Ride.find({_id: element._id})
.exec()
.then(ride => {
retour.push(ride)})
});
res.status(200).json(return)
});
At the end of this code, the array return is empty, while it is supposed to contain every Ride whose _id is in an entity Participating.
OK, there are a couple of issues here:
return is a keyword. You probably shouldn't be using it as a variable name.
Database calls are asynchronous. forEach loops are synchronous. This means that you're immediately going to be returning retour (which looks undefined).
Mongoose has tools to populate nested relationships -- it's best not to do it in application code. Even if you are doing this in application code, it's likely best not to iterate over your results & do new finds -- instead, it's better to construct a single find query that returns all of the new documents you need.
If you did want to do this in application code, you'd want to either use async/await or Promise.all:
const toReturn = [];
const findPromises = participating.map(element => {
return Ride.find({_id: element._id})
.exec()
.then(result => toReturn.push(result)
});
return Promise.all(findPromises).then(() => res.status(200).json(toReturn));
(note: rather than using Promise.all, if you're using Bluebird you could instead use Promise.map.
I am attempting a CRUD app with MEAN stack. I am using mongoose in Express to call to the MongoDB. I am using the FindOne function with a specified parameter, and it's always returning the same (incorrect) document.
I know I am connected to the correct database, since I get a document back from that collection, but it's always the same document, no matter what I pass as the parameter.
module.exports = mongoose.model('Player', playersSchema, 'players'); //in player.js
const Player = require('./model/players');
app.get('/api/player/:id', (req, res) =>{
Player.findOne({id: req.params.playerId},
function(err, player) {
if(err) {
res.json(err);
}
else {
res.json(player);
}
});
});
I have 3 separate "players", with three distinct "playerID" fields (38187361, 35167321, 95821442). I can use Postman to GET the following URL, for example:
http://localhost:3000/api/player/anythingyouWantInHere
and it will return 38187361, the first document. I've been over this website, many tutorials, and the Mongoose documentation and I can't see what I'm doing wrong..
I'd like to eventually find by playerId OR username OR email, but one hurdle at a time...
From the mongoose documentation of findOne, if you pass Id a null or an empty value, it will query db.players.findOne({}) internally which will return first document of the collection everytime you fetch. So make sure you are passing non-empty id here.
Note: conditions is optional, and if conditions is null or undefined,
mongoose will send an empty findOne command to MongoDB, which will
return an arbitrary document. If you're querying by _id, use
findById() instead.
Your route is '/api/player/:id', so the key on the req.params object will be 'id' not 'playerId'.
I don't know what/where/if you're populating the playerId param, but if you update your query to call req.params.id it should actually change the document based on the path as you seem to be wanting to do.
I had the same problem, and it was that the name of column's table was different from the model I had created.
In my model the name of the wrong column was "role" and in my table it was "rol".
How can I know the count of a model that data has been saved? there is a method of Model.count(), but it doesn't seem to work.
var db = mongoose.connect('mongodb://localhost/myApp');
var userSchema = new Schema({name:String,password:String});
userModel =db.model('UserList',userSchema);
var userCount = userModel.count('name');
userCount is an Object, which method called can get a real count?
Thanks
The reason your code doesn't work is because the count function is asynchronous, it doesn't synchronously return a value.
Here's an example of usage:
userModel.count({}, function( err, count){
console.log( "Number of users:", count );
})
The code below works. Note the use of countDocuments.
var mongoose = require('mongoose');
var db = mongoose.connect('mongodb://localhost/myApp');
var userSchema = new mongoose.Schema({name:String,password:String});
var userModel =db.model('userlists',userSchema);
var anand = new userModel({ name: 'anand', password: 'abcd'});
anand.save(function (err, docs) {
if (err) {
console.log('Error');
} else {
userModel.countDocuments({name: 'anand'}, function(err, c) {
console.log('Count is ' + c);
});
}
});
You should give an object as argument
userModel.countDocuments({name: "sam"});
or
userModel.countDocuments({name: "sam"}).exec(); //if you are using promise
or
userModel.countDocuments({}); // if you want to get all counts irrespective of the fields
For the older versions of mongoose, use
userModel.count({name: "sam"});
The collection.count is deprecated, and will be removed in a future version. Use collection.countDocuments or collection.estimatedDocumentCount instead.
userModel.countDocuments(query).exec((err, count) => {
if (err) {
res.send(err);
return;
}
res.json({ count: count });
});
Background for the solution
As stated in the mongoose documentation and in the answer by Benjamin, the method Model.count() is deprecated. Instead of using count(), the alternatives are the following:
Model.countDocuments(filterObject, callback)
Counts how many documents match the filter in a collection. Passing an empty object {} as filter executes a full collection scan. If the collection is large, the following method might be used.
Model.estimatedDocumentCount()
This model method estimates the number of documents in the MongoDB collection. This method is faster than the previous countDocuments(), because it uses collection metadata instead of going through the entire collection. However, as the method name suggests, and depending on db configuration, the result is an estimate as the metadata might not reflect the actual count of documents in a collection at the method execution moment.
Both methods return a mongoose query object, which can be executed in one of the following two ways. Use .exec() if you want to execute a query at a later time.
The solution
Option 1: Pass a callback function
For example, count all documents in a collection using .countDocuments():
someModel.countDocuments({}, function(err, docCount) {
if (err) { return handleError(err) } //handle possible errors
console.log(docCount)
//and do some other fancy stuff
})
Or, count all documents in a collection having a certain name using .countDocuments():
someModel.countDocuments({ name: 'Snow' }, function(err, docCount) {
//see other example
}
Option 2: Use .then()
A mongoose query has .then() so it’s “thenable”. This is for a convenience and query itself is not a promise.
For example, count all documents in a collection using .estimatedDocumentCount():
someModel
.estimatedDocumentCount()
.then(docCount => {
console.log(docCount)
//and do one super neat trick
})
.catch(err => {
//handle possible errors
})
Option 3: Use async/await
When using async/await approach, the recommended way is to use it with .exec() as it provides better stack traces.
const docCount = await someModel.countDocuments({}).exec();
Learning by stackoverflowing,
Using mongoose.js you can count documents,
count all
const count = await Schema.countDocuments();
count specific
const count = await Schema.countDocuments({ key: value });
The highest voted answers here are perfectly fine I just want to add up the use of await so that the functionality asked for can be achieved:
const documentCount = await userModel.count({});
console.log( "Number of users:", documentCount );
It's recommended to use countDocuments() over 'count()' as it will be deprecated going on. So, for now, the perfect code would be:
const documentCount = await userModel.countDocuments({});
console.log( "Number of users:", documentCount );
Model.count() method is deprecated in mongoose version 6.2.0. If you want to count the number of documents in a collection, e.g. count({}), use the estimatedDocumentCount() function instead. Otherwise, use the countDocuments() function instead.
Model.estimatedDocumentCount() Estimates the number of documents in the MongoDB collection. It is Faster than using countDocuments() for large collections because estimatedDocumentCount() uses collection metadata rather than scanning the entire collection.
Example:
const numAdventures = await Adventure.estimatedDocumentCount();
reference : https://mongoosejs.com/docs/api.html#model_Model.estimatedDocumentCount
As said before, your code will not work the way it is. A solution to that would be using a callback function, but if you think it would carry you to a 'Callback hell', you can search for "Promisses".
A possible solution using a callback function:
//DECLARE numberofDocs OUT OF FUNCTIONS
var numberofDocs;
userModel.count({}, setNumberofDocuments); //this search all DOcuments in a Collection
if you want to search the number of documents based on a query, you can do this:
userModel.count({yourQueryGoesHere}, setNumberofDocuments);
setNumberofDocuments is a separeted function :
var setNumberofDocuments = function(err, count){
if(err) return handleError(err);
numberofDocs = count;
};
Now you can get the number of Documents anywhere with a getFunction:
function getNumberofDocs(){
return numberofDocs;
}
var number = getNumberofDocs();
In addition , you use this asynchronous function inside a synchronous one by using a callback, example:
function calculateNumberOfDoc(someParameter, setNumberofDocuments){
userModel.count({}, setNumberofDocuments); //this search all DOcuments in a Collection
setNumberofDocuments(true);
}