Firestore managing auto increment ID [closed] - firebase

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My application will have multiple users and they will be feeding complaints and getting back complaint ID's.
I have created a separate document which stores the latest incremental values, every time a complaint is saved, it firsts gets the maximum number from that document , increments it with + 1 and saves that complaint ID in new complaint document.
Users will be around 8, is this possible that this autoincrement number can be duplicated?
Just in case, attaching screenshot of console and copying my code
get_ticket_id(){
//1. check if the doc exists
var docRef = firebase.firestore().collection('complaints').doc("autoincrement");
docRef.get().then(async doc=> {
if (doc.exists) {
this.ticketnumber = doc.data().number + 1;
await firebase.firestore().collection("complaints").doc("autoincrement").update({
number: this.ticketnumber,
})
.then(async doc=> {
await this.CreateNewComplaint();
})
} else {
Am I following the best practice? Please note: I am not using increment option
const increment = firebase.firestore.FieldValue.increment(1);
number: increment
Is it safer to use increment ?
Edit 1
Use transactions as guided, I am trying to fetch the value of newIncId in a variable but it says, code unreachable on this code of line this.ticketnumber = newIncId; // code uncreable.
var docRef = firebase.firestore().collection('complaints').doc("autoincrement");
firebase.firestore().runTransaction(transaction=> {
return transaction.get(docRef).then(incDoc=> {
//if no value exist, assume it as 0 and increase to 1
var newIncId = (incDoc.data().number || 0) + 1;
transaction.update(docRef, { number: incDoc });
return newIncId;
this.ticketnumber = newIncId; // code uncreable
});
}).then(function(newIncId) {
...//some code
Edit 2
Giving this error:
Function Transaction.update() called with invalid data. Unsupported field value: a custom t object (found in field number)
Attaching screenshot of console

Answer 1

For events like these you should consider Firebase transactions which prevent unwanted behaviours like multiple concurrent overwrites/updates.
final DocumentReference sfDocRef = db.collection("complaints").document("autoincrement");
db.runTransaction(new Transaction.Function<Void>() {
#Override
public Void apply(Transaction transaction) throws FirebaseFirestoreException {
DocumentSnapshot snapshot = transaction.get(sfDocRef);
int newId = snapshot.getInt("number") + 1;
transaction.update(sfDocRef, "number", newPopulation);
// Success
return null;
}
}).addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
Log.d(TAG, "Transaction success!");
}
})
.addOnFailureListener(new OnFailureListener() {
#Override
public void onFailure(#NonNull Exception e) {
Log.w(TAG, "Transaction failure.", e);
}
});
I've copied the code directly from the firebase documentation, so haven't properly tested this.
You could read more about transactions here: https://firebase.google.com/docs/firestore/manage-data/transactions#java

Answer 2

Updated to use transaction and get the new number:
var docRef = firebase.firestore().collection('complaints').doc("autoincrement");
db.runTransaction(function(transaction) {
return transaction.get(docRef).then(function(incDoc) {
//if no value exist, assume it as 0 and increase to 1
var newIncId = (incDoc.data().number || 0) + 1;
transaction.update(docRef, { number: newIncId });
return newIncId;
});
}).then(function(newIncId) {
//`newIncId` This is your new number incremented
//use newIncId here
this.ticketnumber = newIncId;
console.log("New autoincremented number ", newIncId);
}).catch(function(err) {
// Catch block to get any error
console.error(err);
});
See doc https://firebase.google.com/docs/firestore/manage-data/transactions#passing_information_out_of_transactions
Why you're not using number: firebase.firestore.FieldValue.increment(1);?
This use transactions internally. But be aware that firestore document have the write limit of 1/sec. You can use RTDB if you expect to write more than once.