My project based on Node, GraphQl (apollo), MongoDb.
I have basic entity Product:
type Product {
id: ObjectId
name: String
bestPrice: Number
annualSavings: Number
...
}
bestPrice and annualSavings are calculated in base on separate resolvers:
const bestPriceResolver = (product, args, context) => {
return getBestPrice(context.dataStore)
}
const annualSavingsResolver = (product, args, context) => {
const bestPrice = getBestPrice(context.dataStore);
return getAnnualSavings = getAnnualSavings(bestPrice);
}
composeResolvers ({
bestPrice: bestPriceResolver,
annualSavings: annualSavingsResolver,
})
Each resolver goes to database and fetch data for bestPrice. And with this approach I go to dadabase twice to fetch same data (bestPrice). Is it possible to do it once?
Yes, by using dataloader (https://github.com/graphql/dataloader). It's a generic utility which provides batching of requests (and also caching per request).
Throughout request you can collect all ids of some entity that you need, and then you can execute only one query with provided ids.
General idea is that you create new instance of loader for each request and store it in context. Then, instead of calling getBestPrice, you call loader's .load() or .prime() method, which basically collects all ids throughout request. Dataloader returns new function, which should be similar to getBestPrice, but instead of making one query per id, you'll need to provide an array of ids in query, and map responses according to order of ids provided. Dataloader will do the rest :)
Dataloader helps a lot with GraphQL optimizations, since GraphQL queries can often be very heavy.
YouTube provides tons of useful tutorials.
Related
Does Bookshelf.js provide a method to find a model by it's related model?
I have create the two models Order and OrderStatus. Now, I want to fetch an Order model by it's status. Unfortunately, this approach isn't working anymore, as the load method expects a string or string array now.
const order = await new Order().load({"orderStatus": q => q.where({"userId": userId, "status": 10})});
I've found a library called "bookshelf-eloquent" that adds this functionality. However, I'm using Typescript and this library doesn't provide any type declaration.
This code works, but TypeScript indicates that the property whereHas doesn't exist.
const order = await new Order()
.whereHas("orderStatus", q => q.where({"userId": userId, "status": 10}))
.get()
Either the Bookshelf.js developers have added a new method I haven't seen yet, or I need to have a type declaration file for the bookshelf-eloquent library. Otherwise, I can't use it.
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'm having issues retrieving an entity from Google Datastore. Here's my code:
async function pushTaskIdToCurrentSession(taskId){
console.log(`Attempting to add ${taskId} to current Session: ${cloudDataStoreCurrentSession}`);
const transaction = datastore.transaction();
const taskKey = datastore.key(['Session', cloudDataStoreCurrentSession]);
try {
await transaction.run();
const [task] = await transaction.get(taskKey);
let sessionTasks = task.session_tasks;
sessionTasks.push(taskId);
task.session_tasks = sessionTasks;
transaction.save({
key: taskKey,
data: task,
});
transaction.commit();
console.log(`Task ${taskId} added to current Session successfully.`);
} catch (err) {
console.error('ERROR:', err);
transaction.rollback();
}
}
taskId is a string id of another entity that I want to store in an array of a property called session_tasks.
But it doesn't get that far. After this line:
const [task] = await transaction.get(taskKey);
The error is that task is undefined:
ERROR: TypeError: Cannot read property 'session_tasks' of undefined
at pushTaskIdToCurrentSession
Anything immediately obvious from this code?
UPDATE:
Using this instead:
const task = await transaction.get(taskKey).catch(console.error);
Gets me a task object, but it seems to be creating a new entity on the datastore:
I also get this error:
(node:19936) UnhandledPromiseRejectionWarning: Error: Unsupported field value, undefined, was provided.
at Object.encodeValue (/Users/.../node_modules/#google-cloud/datastore/build/src/entity.js:387:15)
This suggests the array is unsupported?
The issue here is that Datastore supports two kinds of IDs.
IDs that start with name= are custom IDs. And they are treated as strings
IDs that start with id= are numeric auto-generated IDs and are treated as integers
When you tried to updated the value in the Datastore, the cloudDataStoreCurrentSession was treated as a string. Since Datastore couldn't find an already created entity key with that custom name, it created it and added name= to specify that it is a custom name. So you have to pass cloudDataStoreCurrentSession as integer to save the data properly.
If I understand correctly, you are trying to load an Array List of Strings from Datastore, using a specific Entity Kind and Entity Key. Then you add one more Task and updated the value of the Datastore for the specific Entity Kind and Entity Key.
I have create the same case scenario as yours and done a little bit of coding myself. In this GitHub code you will find my example that does the following:
Goes to Datastore Entity Kind Session.
Retrieves all the data from Entity Key id=5639456635748352 (e.g.).
Get's the Array List from key: session_tasks.
Adds the new task that passed from the function's arguments.
Performs the transaction to Datastore and updates the values.
All steps are logged in the code and there are a lot of comments explaining exactly how the code works. Also there are two examples of currentSessionID. One for custom names and other one for automatically generated IDs. You can test the code to understand the usage of it and modify it according to your needs.
I am using Cloud Function to send a notification to mobile device. I have two collection in Firestore clientDetail and clientPersonalDetail. I have clientID same in both of the collection but the date is stored in clientDetail and name is stored in clientPersonal.
Take a look:
ClientDetail -- startDate
-- clientID
.......
ClientPersonalDetail -- name
-- clientID
.........
Here is My full Code:
exports.sendDailyNotifications = functions.https.onRequest( (request, response) => {
var getApplicants = getApplicantList();
console.log('getApplicants', getApplicants);
cors(request, response, () => {
admin
.firestore()
.collection("clientDetails")
//.where("clientID", "==", "wOqkjYYz3t7qQzHJ1kgu")
.get()
.then(querySnapshot => {
const promises = [];
querySnapshot.forEach(doc => {
let clientObject = {};
clientObject.clientID = doc.data().clientID;
clientObject.monthlyInstallment = doc.data().monthlyInstallment;
promises.push(clientObject);
});
return Promise.all(promises);
}) //below code for notification
.then(results => {
response.send(results);
results.forEach(user => {
//sendNotification(user);
});
return "";
})
.catch(error => {
console.log(error);
response.status(500).send(error);
});
});
}
);
Above function is showing an object like this
{clienId:xxxxxxxxx, startDate:23/1/2019}
But I need ClientID not name to show in notification so I'll have to join to clientPersonal collection in order to get name using clientID.
What should do ?
How can I create another function which solely return name by passing clientID as argument, and waits until it returns the name .
Can Anybody please Help.?
But I need ClientID not name to show in notification so I'll have to join to clientPersonal collection in order to get name using clientID. What should do ?
Unfortunately, there is no JOIN clause in Firestore. Queries in Firestore are shallow. This means that they only get items from the collection that the query is run against. There is no way to get documents from two top-level collection in a single query. Firestore doesn't support queries across different collections in one go. A single query may only use properties of documents in a single collection.
How can I create another function which solely return name by passing clientID as argument, and waits until it returns the name.
So the most simple solution I can think of is to first query the database to get the clientID. Once you have this id, make another database call (inside the callback), so you can get the corresponding name.
Another solution would be to add the name of the user as a new property under ClientDetail so you can query the database only once. This practice is called denormalization and is a common practice when it comes to Firebase. If you are new to NoQSL databases, I recommend you see this video, Denormalization is normal with the Firebase Database for a better understanding. It is for Firebase realtime database but same rules apply to Cloud Firestore.
Also, when you are duplicating data, there is one thing that need to keep in mind. In the same way you are adding data, you need to maintain it. With other words, if you want to update/detele an item, you need to do it in every place that it exists.
The "easier" solution would probably be the duplication of data. This is quite common in NoSQL world.
More precisely you would add in your documents in the ClientDetail collection the value of the client name.
You can use two extra functions in this occasion to have your code clear. One function that will read all the documents form the collection ClientDetail and instead of getting all the fields, will get only the ClientID. Then call the other function, that will be scanning all the documents in collection ClientPersonalDetail and retrieve only the part with the ClientID. Compare if those two match and then do any operations there if they do so.
You can refer to Get started with Cloud Firestore documentation on how to create, add and load documents from Firestore.
Your package,json should look something like this:
{
"name": "sample-http",
"version": "0.0.1",
"dependencies": {
"firebase-admin": "^6.5.1"
}
}
I have did a little bit of coding myself and here is my example code in GitHub. By deploying this Function, will scan all the documents form one Collection and compare the ClientID from the documents in the other collection. When it will find a match it will log a message otherwise it will log a message of not matching IDs. You can use the idea of how this function operates and use it in your code.
I have been working with the google cloud library, and I can successfully save data in DataStore, specifically from my particle electron device (Used their tutorial here https://docs.particle.io/tutorials/integrations/google-cloud-platform/)
The problem I am now having is retrieving the data again.
I am using this code, but it is not returning anything
function getData(){
var data = [];
const query = datastore.createQuery('ParticleEvent').order('created');
datastore.runQuery(query).then(results => {
const event = results[0];
console.log(results);
event.forEach(data => data.push(data.data));
});
console.log(data)
}
But each time it is returning empty specifically returning this :
[ [], { moreResults: 'NO_MORE_RESULTS', endCursor: 'CgA=' } ]
, and I can't figure out why because I have multiple entities saved in this Datastore.
Thanks
In the tutorial.js from the repo mentioned in the tutorial I see the ParticleEvent entities are created using this data:
var obj = {
gc_pub_sub_id: message.id,
device_id: message.attributes.device_id,
event: message.attributes.event,
data: message.data,
published_at: message.attributes.published_at
}
This means the entities don't have a created property. I suspect that ordering the query by such property name is the reason for which the query doesn't return results. From Datastore Queries (emphasis mine):
The results include all entities that have at least one value for
every property named in the filters and sort orders, and whose
property values meet all the specified filter criteria.
I'd try ordering the query by published_at instead, that appears to be the property with a meaning closest to created.