Develop Reference

MongooseError: Query was already executed:

I'm trying to update the document but the error says the query has already been executed.
MongooseError: Query was already executed: footballs.updateOne({ date: 'January 4' }, {})
app.post('/api/bookslot', async (req, res) => {
console.log(req.body);
try {
const token = req.headers['x-access-token'];
const decoded = jwt.verify(token, 'secret123');
const email = decoded.email;
const user = await UserModel.findOne({ email: email });
let sportname = req.body.selectedSport.toLowerCase();
const time = req.body.slotTime;
const seats = req.body.availableSeats - 1;
if (!sportname.endsWith('s')) {
sportname = sportname.concat('s');
}
const NewSlotModel = mongoose.model(sportname, slotSchema);
var update = {};
update[time] = seats - 1;
console.log(update);
const a = await NewSlotModel.updateOne(
{ date: req.body.slotDate },
{ $set: update },
function (err, success) {
if (err) return handleError(err);
}
);
return res.json({ status: 'ok' });
} catch (e) {
console.log(e);
res.json({ status: 'error' });
}
});
where am I going wrong?

You are using both async/await and callbacks in your code, causing mongoose to throw an error.
The actual effect of using them both is exactly the error type that you are receiving:
Query was already executed
Mongoose v6 does not allow duplicate queries.
Mongoose no longer allows executing the same query object twice. If
you do, you'll get a Query was already executed error. Executing the
same query instance twice is typically indicative of mixing callbacks
and promises, but if you need to execute the same query twice, you can
call Query#clone() to clone the query and re-execute it. See gh-7398
Duplicate Query Execution
To fix the issue, just remove the third argument from the await
NewSlotModel.updateOne
Making it:
const a = await NewSlotModel.updateOne(
{ date: req.body.slotDate },
{ $set: update }
);

Mongoose v6. Don't support callbacks any longer.. check the image.
const productCount = await Product.countDocuments((count) => count) BAD
const productCount = await Product.countDocuments(); GOOD

Asynchronous verification within the .map function

I am developing the backend of an application using Node JS, Sequelize and Postgres database.
When the course is registered, the user must inform which organizations, companies and teachers will be linked to it.
The organization IDs are passed through an array to the backend, I am trying to do a check to make sure that the passed IDs exist.
What I've done so far is this:
const { organizations } = req.body;
const organizationsArray = organizations.map(async (organization) => {
const organizationExists = await Organization.findByPk(organization);
if (!organizationExists) {
return res
.status(400)
.json({ error: `Organization ${organization} does not exists!` });
}
return {
course_id: id,
organization_id: organization,
};
});
await CoursesOrganizations.bulkCreate(organizationsArray);
This link has the complete controller code, I believe it will facilitate understanding.
When !OrganizationExists is true, I am getting the return that the organization does not exist. The problem is when the organization exists, I am getting the following message error.

The Array.map() is returning an array of promises that you can resolve to an array using Promise.all(). Inside the map you should use throw new Error() to break out of the map - this error will be raised by Promise.all() and you can then catch it and return an error to the client (or swallow it, etc).
This is a corrected version of your pattern, resolving the Promise results.
const { organizations } = req.body;
try {
// use Promise.all to resolve the promises returned by the async callback function
const organizationsArray = await Promise.all(
// this will return an array of promises
organizations.map(async (organization) => {
const organizationExists = await Organization.findByPk(organization, {
attributes: ['id'], // we only need the ID
raw: true, // don't need Instances
});
if (!organizationExists) {
// don't send response inside the map, throw an Error to break out
throw new Error(`Organization ${organization} does not exists!`);
}
// it does exist so return/resolve the value for the promise
return {
course_id: id,
organization_id: organization,
};
})
);
// if we get here there were no errors, create the records
await CoursesOrganizations.bulkCreate(organizationsArray);
// return a success to the client
return res.json({ success: true });
} catch (err) {
// there was an error, return it to the client
return res.status(400).json({ error: err.message });
}
This is a refactored version that will be a bit faster by fetching all the Organizations in one query and then doing the checks/creating the Course inserts.
const { Op } = Sequelize;
const { organizations } = req.body;
try {
// get all Organization matches for the IDs
const organizationsArray = await Organization.findAll({
attributes: ['id'], // we only need the ID
where: {
id: {
[Op.in]: organizations, // WHERE id IN (organizations)
}
},
raw: true, // no need to create Instances
});
// create an array of the IDs we found
const foundIds = organizationsArray.map((org) => org.id);
// check to see if any of the IDs are missing from the results
if (foundIds.length !== organizations.length) {
// Use Array.reduce() to figure out which IDs are missing from the results
const missingIds = organizations.reduce((missingIds, orgId) => {
if (!foundIds.includes(orgId)){
missingIds.push(orgId);
}
return missingIds;
}, []); // initialized to empty array
throw new Error(`Unable to find Organization for: ${missingIds.join(', ')}`);
}
// now create an array of courses to create using the foundIds
const courses = foundIds.map((orgId) => {
return {
course_id: id,
organization_id: orgId,
};
});
// if we get here there were no errors, create the records
await CoursesOrganizations.bulkCreate(courses);
// return a success to the client
return res.json({ success: true });
} catch (err) {
// there was an error, return it to the client
return res.status(400).json({ error: err.message });
}

If you have an array of Ids and you want to check if they exist you should you use the (in) operator, this makes it so that you are hitting the DB only once and getting all the records in one hit (instead of getting them one by one in a loop), after you get these records you can check their lengths to determine if they all exist or not.
const { Op } = require("sequelize");
let foundOrgs = await Organization.findAll({
where: {
id: {
[Op.in]: organizationsArray,
}
}
});

Best practise to combine multiple rest calls to populate 1 graphQL type in apollo-server

I have graphql User type that needs information from multiple REST api's and different servers.
Basic example: get the user firstname from rest domain 1 and get lastname from rest domain 2. Both rest domain have a common "userID" attribute.
A simplefied example of my resolver code atm:
user: async (_source, args, { dataSources }) => {
try {
const datasource1 = await dataSources.RESTAPI1.getUser(args.id);
const datasource2 = await dataSources.RESTAPI2.getUser(args.id);
return { ...datasource1, ...datasource2 };
} catch (error) {
console.log("An error occurred.", error);
}
return [];
}
This works fine for this simplefied version, but I have 2 problems with this solution:
first, IRL there is a lot of logic going into merging the 2 json results. Since some field are shared but have different data (or are empty). So it's like cherry picking both results to create a combined result.
My second problem is that this is still a waterfall method. First get the data from restapi1, when thats done call restapi2. Basicly apollo-server is reintroducing rest-waterfall-fetch graphql tries to solve.
Keeping these 2 problems in mind.. Can I optimise this piece of code or rewrite is for better performance or readability? Or are there any packages that might help with this behavior?
Many thanks!

With regard to performance, if the two calls are independent of one another, you can utilize Promise.all to execute them in parallel:
const [dataSource1,dataSource2] = await Promise.all([
dataSources.RESTAPI1.getUser(args.id),
dataSources.RESTAPI2.getUser(args.id),
])
We normally let GraphQL's default resolver logic do the heavy lifting, but if you're finding that you need to "cherry pick" the data from both calls, you can return something like this in your root resolver:
return { dataSource1, dataSource2 }
and then write resolvers for each field:
const resolvers = {
User: {
someField: ({ dataSource1, dataSource2 }) => {
return dataSource1.a || dataSource2.b
},
someOtherField: ({ dataSource1, dataSource2 }) => {
return someCondition ? dataSource1.foo : dataSource2.bar
},
}
}

Assuming your user resolver returns type User forsake...
type User {
id: ID!
datasource1: RandomType
datasource1: RandomType
}
You can create individual resolvers for each field in type User, this can reduce the complexity of the user Query, to only the requested fields.
query {
user {
id
datasource1 {
...
}
}
}
const resolvers = {
Query: {
user: () => {
return { id: "..." };
}
},
User: {
datasource1: () => { ... },
datasource2: () => { ... } // i wont execute
}
};
datasource1 & datasource2 resolvers will only execute in parallel, after Query.user executes.

For parallel call.
const users = async (_source, args, { dataSources }) => {
try {
const promises = [
dataSources.RESTAPI1,
dataSources.RESTAPI2
].map(({ getUser }) => getUser(args.id));
const data = await Promise.all(promises);
return Object.assign({}, ...data);
} catch (error) {
console.log("An error occurred.", error);
}
return [];
};

Avoid two request at same time in firestore

I created a function to communicate with the firestore database.
First, check if there is something in the relation. If not then add something.
If something already exists then use the data and then delete the entry in the queried relation. But you have to add that in the function(else section). And now the question arises what happens when two users simultaneously perform the function.
Is there a way to put the second user in a queue while the first user is done with the request?
let ref = db.collection('relation1').doc('test').collection('user');
var checkForAdd = ref.get().then(snapshot => {
if(snapshot.size < 1){
db.collection('relation1').doc('test').collection('user').add({
user: 'Test',
createdAt: Date.now()
}).catch(err =>{
console.log(err)
})
}

Cloud Firestore supports atomic operations for reading and writing data. In a set of atomic operations, either all of the operations succeed, or none of them are applied.
https://firebase.google.com/docs/firestore/manage-data/transactions
// Create a reference to the user doc you want to create if it doesn't exist.
const userCollectionRef = db.collection('relation1').doc('test').collection('user');
const userDocRef = userCollectionRef.doc('documentID');
return db.runTransaction(transaction => {
// This code may get re-run multiple times if there are conflicts.
return transaction.get(userDocRef).then(userDoc => {
if (userDoc.exists) {
// If something already exists then use the data and
// then delete the entry in the queried relation.
} else {
transaction.update(userDocRef, {
user: 'Test',
createdAt: Date.now()
});
}
});
}).then(() => {
console.log("Transaction successfully committed!");
}).catch(error => {
console.log("Transaction failed: ", error);
});

push array in const inside .then

I'm trying to push a value inside a const but its in a .then and it's not working do you know how can I do that ?
I get a value in my console.log(newResult) in my if but the data is not pushed in my const newResult in the return
res.status(200).json(newResult);
.then(function (friends) {
if (friends) {
const newResult = [];
friends.forEach((r) => {
if (r.UserID == userFound.id) {
models.User.findOne({
where: {
id: r.idFriend
}
})
.then(function(userFound) {
newResult.push({
id: r.id,
user: {
id: r.User.id,
email: userFound.email,
username: userFound.username
}
});
console.log(newResult)
})
} else
newResult.push({
id: r.id,
user: {
id: r.User.id,
email: r.User.email,
username: r.User.username
}
});
console.log(newResult)
});
res.status(200).json(newResult);
}
}
every test realised return an empty tab when i go in my if condition

It will never work because, you are doing async calls
models.User.findOne inside forEach.
You'll get results on console.log when async call to database for fetching user is complete.
But before this all happens the forEach is done executing and code hits the line res.status(200).json(newResult); and you see no results from your if condition.
Instead of using this approach go for mongoose populate and populate userObject based userID while finding friends this way you won't have to do async call inside the forEach.
Read about mongoose populate at: http://mongoosejs.com/docs/populate.html