What I need to do:
wanting to check the snapshot to see if anyone else has already taken that username. Seeing if the user input is already in use (the title of the document inside 'users')
I'm trying to get a snapshot of each document title, so a snapshot of the collection info. I know I could do something like mapping each value into an array but the username count is massive and I feel like that might affect performance?
Heres what I have:
const snap = firestore().collection('users').onSnapshot(snapshot => {
console.log(snapshot.data())
})
and this returns saying that snapshot.data() is not a function, if I remove .data() its a large mess of everything, I can post it if you would like.
If you want to check whether a document with a specific name as its ID already exists, you can do:
const snap = firestore().collection('users').doc('Tobias').onSnapshot(snapshot => {
console.log(snapshot.exists)
})
So this logs true is a document named Tobias exists, and false otherwise.
Related
I'm working with the following collection and sub-collections in Firestore.
I need to retrieve the list of the documents inside "Schedine", but the following code returns nothing.
const ref1 = await firestore.collection("Schedine").get();
ref1.forEach(doc => {
console.log(doc.id);
});
// expected output: gx8qiytV8Zgs0AJR4swFqTH3T82 , but nothing shown
Instead, if I try to get() the documents inside "in corso", a sub-collection of a document inside "Schedine", it works, with the exact same code:
const ref2 = await firestore.collection("Schedine").doc("gx8qiytV8Zgs0AJR4swFqTH3T822").collection("in corso").get();
ref2.forEach(doc => {
console.log(doc.id);
});
// WORKING
How could I get the list of the documents inside "Schedine"?
If you look carefully, you'll see that the document ID in your screenshot is shown in italics. This means that there's no document gx8qiytV8Zgs0AJR4swFqTH3T822 inside your Schedine collection, and the console just shows that ID so that it can show you the subcollections under it.
Since there's no documents in Schedine, calling get on that collection returns an empty query snapshot. But the path exists, which is why you can access the subcollection once you know the document ID in your second snippet.
There's no API on the collection reference to get such non-existent entities, so the common solution is to create an (empty) document when you also create the subcollection.
Hoi, I would like to check, using React javascript, if a collection in the Firestore already exists, no matter if it's empty or not. I tried:
if (collection(db, ref)) // is always true somehow
Any ideas? Thanks!
You would need to try to fetch from the collection and see if anything is returned:
const snap = await query(collection(db, ref), limit(1));
if (snap.empty) {
// no docs in collection
}
There is no function available in the SDK that can help you can check if a particular collection exists. A collection will start to exist only if it contains at least one document. If a collection doesn't contain any documents, then that collection doesn't exist at all. So that being said, it makes sense to check whether a collection contains or not documents. In code, it should look as simple as:
const snapshot = await query(collection(db, yourRef), limit(1));
if (snapshot.empty) {
//The collection doesn't exist.
}
One thing to mention is that I have used a call to limit(1) because if the collection contains documents, then we limit the results so we can pay only one document read. However, if the collection doesn't exist, there is still one document read that has to be paid. So if the above query yields no resul## Heading ##t, according to the official documentation regarding Firestore pricing, it said that:
Minimum charge for queries
There is a minimum charge of one document read for each query that you perform, even if the query returns no results.
You have to fetch the collection out of the database and check if it has more than 0 documents. Even, if the collection doesn't exist, it will return 0.
const db = firebase.firestore();
db.collection("YOUR COLLECTION NAME").get().then((res) =>{
if(res.size==0){
//Collection does not exist
}else{
//Collection does exist
}
I have a collection
/userFeed
Where I create/delete docs (representing users) when the current user starts following/unfollowing them.
...
/userFeed (C)
/some-followed-user (D)
-date <timestamp>
-interactions <number>
When the user likes a post, the interactions field will be updated. But... what if the user doesn't follow the post owner? Then, I will just need to skip the document update, without necessity of producing failures/errors.
const currentUserFeedRef = firestore
.collection("feeds")
.doc(currentUserId)
.collection("userFeed")
.doc(otherUserId);
const data = {
totalInteractions: admin.firestore.FieldValue.increment(value),
};
const precondition = {
exists: false, // I am trying weird things
};
if (batchOrTransaction) {
return batchOrTransaction.update(
currentUserFeedRef,
data,
precondition
);
}
Is it possible to just "skip the update if the doc doesn't exist"?
Is it possible to just "skip the update if the doc doesn't exist"?
No, not in the way that you're explaining it. Firestore updates don't silently fail.
If you need to know if a document exists before updating it, you should simply read it first and check that it exists. You can do this very easily in a transaction, and you can be sure that the update won't fail due to the document being missing if you check it this way first using the transaction object.
In fact, what you are trying to do is illustrated as the very first example in the documentation.
Sorry for the long title. Visually and more precise, I would like to update the stock value after a payment is made. However, I get stuck after querying the entire document (e.g. the selected one with title sneakers). Is there a way to actually query and update for example the Timberlands stock value to its value -1. Or do you have to get all data from the entire document. Then modify the desired part in javascript and update the entire document?
Here is a little snippet of a solution I came up with so far. However, this approach hurts my soul as it seems very inefficient.
const updateFirebaseStock = (orders) => {
orders.forEach( async (order) => {
try {
collRef = db.doc(`collections/${order.collectionid}`);
doc = await collRef.get();
data = doc.data();
//Here:const newItems = data.items.map(if it's corr name, update value, else just return object), results in desired new Array of objects.
//Then Update entire document by collRef.update({items: newItems})
} catch (error) {
console.error(error)
};
});
}
You don't need to get the document at all for that, all you have to do is use FieldValue.increment(), using your code as a starting point it could look like this:
collRef = db.doc(`collections/${order.collectionid}`);
collRef.update({
Price: firebase.firestore.FieldValue.increment(-1)
});
You can increment/decrement with any numeric value using that function.
I want to return an item with a specific ID and perform an update operation on it. My query gets the right result, but it won't let me update it.
I tried following this tutorial: https://www.youtube.com/watch?v=mYyPbfpoZeM
And read the documentation. Both didn't help. Other threads to the same topic are, well, different.
I have a database of objects which have a unique ID stored as integer.
I have an HTML form to get an ID as user input and the query below to retrieve the according object.
I tried this. The query worked, the update didn't.
db.collection('objects').where('ID','==', ID ).get().then((snapshot) => {
snapshot.docs.forEach( doc => {
console.log('debug');
console.log(doc.data().ID);
})
});
I am still new to firebase and js, so please forgive me if my code is uterly wrong.
I am currently stuck with this:
db.collection('objects').where('ID','==', ID ).get().then((doc) => {
console.table(doc);
});
Which is still not working.
For the second snippet an I currently get an unlegible table in which I can't really find the object I was looking for.
How do I update a single value in a single document?
EDIT: I forgot my implementation attempts of the update function.
I tried doc.update({value:0}) inside the for loop in snippet one which yielded doc.update is not a function. Similarly for doc.data().update(...).
In the second snippet I mainly tried to see what I got returned and ran variations of the above mentioned uodate function. With no success.
I managed to get it to work by studying the part of the firestore documentation that goes more into detail about the actual functions. Somehow it was hard for me to find this.
db.collection("users").where("name", "==", somename).limit(1).get().then(query => {
console.log(query);
const thing = query.docs[0];
console.log(thing.data());
let tmp = thing.data();
tmp.current_game_play = tmp.current_game_play + 1;
console.log(tmp);
thing.ref.update(tmp);
});
So I use where to get a Query object, use get to get a a querySnapshot inside the then promise resolve, use docs[0] to retrieve the first (and only) documentSnapshot and finally ref to get a reference that makes the whole thing updatable later.
try this:
var objectRef= db.collection("objects").doc(ID);
objectRef.update({
value: 0
}).then(function() {
console.log("Document successfully updated!");
}).catch(function(error) {
// The document probably doesn't exist.
console.error("Error updating document: ", error);
});