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How to get all documents on a nested firebase collection

I have a nested subcollection that looks like:
users > user.id > cart > doc.id
And I am trying to get ALL documents on that collection. Here's how I get a single one:
useEffect(() => {
const getStyleProfile = async (user: any) => {
if (user) {
const docRef = doc(db, "users", `${user.uid}`, 'cart', `${1}`);
onSnapshot(docRef, (doc) => {
setStyleProfile(doc.data())
});
}
}
getStyleProfile(user)
}, [user?.uid])
Which returns the first document:
{price: 400, property_id: 1} 'style values'
My question is: how can I return all the documents, no matter the ID?
Any question I've seen doesn't relate to subcollections, so not sure how to get it working, e.g this one

As shown in the documentation, you build a reference to a collection like this:
const usersCollectionRef = collection(db, 'users');
You build a reference to a subcollection in much the same way:
const userCartsCollectionRef = collection(db, 'users', uid, 'carts);
The collection reference is queried exactly the same way no matter how deeply nested it is, as illustrated in the documentation.
const querySnapshot = await getDocs(userCartsCollectionRef);

delete collection firebase in v9

can some one explain how can i delete collection in firebase/firestore using v9 using reactjs
firestore()
.collection('rate')
.get()
.then((querySnapshot) => {
querySnapshot.forEach((doc) => {
doc.ref.delete();
});
this code i am using in v8 i need same thing in v9
const q = query(collection(db, `${udata.id}`));
const querySnapshot = await getDocs(q);
querySnapshot.forEach((doc) => {
// doc.data() is never undefined for query doc snapshots
console.log(doc.data());
});
already try this but this code only read data this can't allow me to delete so can some one tell me how to do it

There's a top-level function deleteDoc() to delete documents in using Modular SDK:
import { collection, query, getDocs, deleteDoc } from 'firebase/firestore';
const q = query(collection(db, `${udata.id}`));
const querySnapshot = await getDocs(q);
const deleteOps = [];
querySnapshot.forEach((doc) => {
deleteOps.push(deleteDoc(doc.ref));
});
Promise.all(deleteOps).then(() => console.log('documents deleted'))

You can use deleteDoc(), as documented here.
deleteDoc() takes a document reference, so you'll need to pass the reference from inside the forEach. In the forEach you're receiving a QueryDocumentSnapshot, so you just need to add a
deleteDoc(doc.ref);

How to get a Subcollection inside a Collection in Firestore Web Version 9 (Modular)?

I was using the chaining mode of the Firestore Web 8, but I'm in the way of updated it to Module 9 and have been a hard time trying to figure out how to get all the content of my subcollection (collection inside my collection).
My older function is like this and works fine:
function getInfo(doc_name) {
let infoDB = db
.collection("collection_name")
.doc(doc_name)
.collection("subcollection_name")
.get();
return alunoHistorico;
}
so with the module way I tried this code
// Initialize Firebase
const app = initializeApp(firebaseConfig);
const db = getFirestore(app);
const docRef = doc(db, "collection_name", "doc_name");
const docSnap = await getDoc(docRef);
if (docSnap.exists()) {
console.log("Document data:", docSnap.data());
} else {
// doc.data() will be undefined in this case
console.log("No such document!");
}
but the function doc() expects a even arguments (not counting the db argument) so if I try to use with 3 arguments like this, I get a error:
const docRef = doc(db, "collection_name", "doc_name", "subcollection_name");
to it work I have to pass the exactly document that is inside the subcollection
const docRef = doc(db, "collection_name", "doc_name", "subcollection_name", "sub_doc");
but it doesn't work for me because I have a list os docs inside the subcollection, that I want o retrieve.
So how can I get all my docs inside my subcollection?
Thanks to anyone who take the time.

You need to use collection() to get a CollectionReference instead of doc() which returns a DocumentReference:
const subColRef = collection(db, "collection_name", "doc_name", "subcollection_name");
// odd number of path segments to get a CollectionReference
// equivalent to:
// .collection("collection_name/doc_name/subcollection_name") in v8
// use getDocs() instead of getDoc() to fetch the collection
const qSnap = getDocs(subColRef)
console.log(qSnap.docs.map(d => ({id: d.id, ...d.data()})))
I wrote a detailed answer on difference between doc() and collection() (in V8 and V9) here:
Firestore: What's the pattern for adding new data in Web v9?

If someone want to get realtime updates of docs inside sub collection using onSnapshot in Modular Firebase V9, you can achieve this like:
import { db } from "./firebase";
import { onSnapshot, collection } from "#firebase/firestore";
let collectionRef = collection(db, "main_collection_id", "doc_id", "sub_collection_id");
onSnapshot(collectionRef, (querySnapshot) => {
querySnapshot.forEach((doc) => {
console.log("Id: ", doc.id, "Data: ", doc.data());
});
});

Firestore Cloud Function empty collection

I have a problem that's bugging me for days. I am trying to create a Firebase Cloud function that reads from the Firestore database.
My Firestore DB looks like this:
Problem is that I cannot list users like this:
db.collection('users').get().then((snapshot) => snapshot.forEach(...));
If I try to do this I get empty response, like there are no users in my users collection.
But I try to access user directly it works:
await db.collection('users/5CZxgu8nmNXu2TgplwOUdOIt8e33/receipts').get()
My complete code:
import * as functions from 'firebase-functions';
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
exports.cat = functions.https.onRequest(async (req, res) => {
const receiptList: any = [];
const db: Firestore = admin.firestore();
const usersRef = await db.collection('users').get();
console.log(usersRef.empty); // Returns true
const receiptsRef = await db
.collection('users/5CZxgu8nmNXu2TgplwOUdOIt8e33/receipts')
.get();
receiptsRef.forEach((receipt: any) => {
console.log(receipt);
receiptList.push(receipt);
// Here I can access data
});
res.send(receiptList);
return '';
});
Does anyone have any idea what I'm doing wrong? Thank you!

Your users collection is actually empty. See how the document IDs are shown in italics? That means there is not actually a document in its place, however, there are subcollections with documents organized underneath them.
When you query a collection, you only get the documents that are immediately within that collection. A query will not pick up documents organized in subcollections. In this respect, queries are said to be "shallow". As you've seen, you need to reach deeper into the subcollection to get its documents.
Bottom line is that the queries you're showing are doing exactly what they're supposed to do.

Thanks again Doug for your help.
I manage to solve my problem. Here is my complete solution.
import * as functions from 'firebase-functions';
import {
Firestore
} from '#google-cloud/firestore';
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);
exports.cat = functions.https.onRequest(async (req, res) => {
const receiptList: any = [];
const db: Firestore = admin.firestore();
const receipts = await db.collectionGroup('receipts').get();
receipts.forEach((doc: any) => {
console.log(doc.id, ' => ', doc.data());
receiptList.push(doc.data());
});
res.send(receiptList);
return '';
});

.get() gets all documents. In your case those documents are empty therefore .get() doesn't consider them.
The simplest solution that I found for this is to replace .get() with .listDocuments(). Now you could read each doc entry like you would a doc.

Query firestore database for document id

I want to query a firestore database for document id. Currently I have the following code:
db.collection('books').where('id', '==', 'fK3ddutEpD2qQqRMXNW5').get()
I don't get a result. But when I query for a different field it works:
db.collection('books').where('genre', '==', 'biography').get()
How is the name of the document id called?

I am a bit late, but there is actually a way to do this
db.collection('books').where(firebase.firestore.FieldPath.documentId(), '==', 'fK3ddutEpD2qQqRMXNW5').get()
This might be useful when you're dealing with firebase security rules and only want to query for the records you're allowed to access.

Try this:
db.collection('books').doc('fK3ddutEpD2qQqRMXNW5').get()
(The first query is looking for an explicit user-set field called 'id', which probably isn't what you want.)

You can use the __name__ key word to use your document ID in a query.
Instead of this db.collection('books').doc('fK3ddutEpD2qQqRMXNW5').get() you can write
db.collection('books').where('__name__', '==' ,'fK3ddutEpD2qQqRMXNW5').get().
In this case you should get an array of length 1 back.
The firebase docs mention this feature in the rules documentation. https://firebase.google.com/docs/reference/rules/rules.firestore.Resource

June, 2021
The new v9 modular sdk is tree-shakeable and results in smaller compiled apps. It is recommended for all new Firestore apps.
import { doc, getDoc } from "firebase/firestore";
const snap = await getDoc(doc(db, 'books', 'fK3ddutEpD2qQqRMXNW5'))
if (snap.exists()) {
console.log(snap.data())
}
else {
console.log("No such document")
}
This is based on the example from the firestore docs
import { doc, getDoc } from "firebase/firestore";
const docRef = doc(db, "cities", "SF");
const docSnap = await getDoc(docRef);
if (docSnap.exists()) {
console.log("Document data:", docSnap.data());
}
else {
// doc.data() will be undefined in this case
console.log("No such document!");
}
You could make this into a helper function
async function getDocument (coll, id) {
const snap = await getDoc(doc(db, coll, id))
if (snap.exists())
return snap.data()
else
return Promise.reject(Error(`No such document: ${coll}.${id}`))
}
getDocument("books", "fK3ddutEpD2qQqRMXNW5")

You can get a document by its id following this pattern:
firebase
.firestore()
.collection("Your collection")
.doc("documentId")
.get()
.then((docRef) => { console.log(docRef.data()) })
.catch((error) => { })

While everyone is telling to use .get(), which is totally reasonable but it's not always the case.
Maybe you want to filter data based on id (using a where query for example).
This is how you do it in Firebase v9 modular SDK:
import {collection, documentId} from 'firebase/firestore'
const booksRef = collection('books')
const q = query(booksRef, where(documentId(), '==', 'fK3ddutEpD2qQqRMXNW5'))

Currently only working way for Cloud Functions if you really need to use this way:
// Import firebase-admin
import * as admin from "firebase-admin";
// Use FieldPath.documentId()
admin.firestore.FieldPath.documentId()
const targetUser = await db.collection("users").where(admin.firestore.FieldPath.documentId() "==", "givenId").get();
Simpler way of this is directly using ID value thru path as there is only one document with given document ID:
const targetUser = await db.doc("users/"+ "givenId").get();
However, you may really need to use it if you are matching given IDs array to the Firebase collection like this:
const admin = require("firebase-admin");
const arr = ["id1", "id2"];
const refArr = arr.map(id => admin.firestore().collection("media").doc(id));
const m = await admin
.firestore()
.collection("media")
.where(admin.firestore.FieldPath.documentId(), "in", refArr)
.get();
This last example is from this discussion

If you are looking for more dynamic queries with a helper function, you can simply try this.
import { db} from '#lib/firebase';
import {query, collection, getDocs ,documentId } from "firebase/firestore";
const getResult = async (_value) => {
const _docId = documentId()
const _query = [{
field: _docID,
operator: '==',
value: _value
}]
// calling function
const result = await getDocumentsByQuery("collectionName", qColl)
console.log("job result: ", result)
}
// can accept multiple query args
const getDocumentsByQuery = async (collectionName, queries) => {
const queryArgs = [];
queries.forEach(q => {
queryArgs.push(
where(q.field, q.operator, q.value)
);
});
const _query = query(collection(db, collectionName), ...queryArgs);
const querySn = await getDocs(_query);
const documents = [];
querySn.forEach(doc => {
documents.push({ id: doc.id, ...doc.data() });
});
return documents[0];
};

From Firestore docs for Get a document.
var docRef = db.collection("cities").doc("SF");
docRef.get().then(function(doc) {
if (doc.exists) {
console.log("Document data:", doc.data());
} else {
// doc.data() will be undefined in this case
console.log("No such document!");
}
}).catch(function(error) {
console.log("Error getting document:", error);
});

This is the first link that came up when I was looking to solve it in the Golang SDK, so I'll add my solution in case anyone else is looking for it:
package main
import (
"context"
"fmt"
"log"
"cloud.google.com/go/firestore"
firebase "firebase.google.com/go/v4"
"google.golang.org/api/option"
)
type (
Car struct {
ID string
Name string `firestore:"name"`
Make string `firestore:"make"`
Price float64 `firestore:"make"`
}
)
func main() {
ctx := context.Background()
// Use a service account
options := option.WithCredentialsFile("PATH/TO/SERVICE/FILE.json")
// Set project id
conf := &firebase.Config{ProjectID: "PROJECT_NAME"}
// Initialize app
app, err := firebase.NewApp(ctx, conf, options)
if err != nil {
log.Fatal(err)
}
// Get firestore client
client, err := app.Firestore(ctx)
if err != nil {
log.Fatal(err)
}
defer client.Close()
collectionRef := client.Collection("CAR_COLLECTION")
// firestore.DocumentID == "__name__"
docSnap, err := collectionRef.Where(firestore.DocumentID, "==", collectionRef.Doc("001")).Get(ctx)
if err != nil {
log.Fatal(err)
}
// Unmarshall item
car := Car{}
docSnap.DataTo(&car)
car.ID = docSnap.Ref.ID
// Print car list
fmt.Println(car)
}

Just to clear confusion here
Remember, You should use async/await to fetch data whether fetching full collection or a single doc.
async function someFunction(){
await db.collection('books').doc('fK3ddutEpD2qQqRMXNW5').get();
}