I am working on online noticeboard app. I have a collection called notices and there is notices with expires date. i want to move them to another collection after the expiration. How can I do it?
There is no server-side "move" operation in Cloud Firestore. You'll have to read the document, write a copy to its new location, and then delete the original.
If you want to do this atomically, you can do all of these in a transaction.
Also see:
How to move a firestore document from cloud functions?
Related
I'm confused when I read firebase document says that :
Deleting a document does not delete its subcollections!
but this isn't the normal in the firebase console now, I can see when I delete a doc from the console all subcollections that belong to it also gone.
on the other side, the firebase emulator doesn't delete the subcollection and just remove any existing fields on the doc and keep the subcollections in place
I think 🤔 they was referring to giving end user the permission to delete data directly in your app and think it will be a more secure way if they delete data from the app through a Callable function that can be call recursively
Hope this help clearly your doubt
I have a single page web application and I have NOT enabled offline persistence.
A component in this application has subscribed to a document using the onSnapshot function and recieves updates.
An other component in the same application instance reads the same document using the get function. Will firebase provide the same instance of the document, which is already loaded in the subscription? Or will it do a new request to the server?
A third component in the same application instance subscribes to the same document. Will this trigger new requests to the server?
What about reading and subscribing collections?
What about subscribing to a collection which is already subscribed, but the second subscription is called after narrowing results with the where function? Will Firestore reuse the already loaded complete collection and filter in my client instance? Or will it make server requests?
As a rule, Firestore does maintain a local cache, mostly for latency/response, not for cost savings. That said, if a document can be read from the cache, it will be, saving the read. I wouldn't try to "design" it in, however; memory limits and other considerations mean you don't really know what's in the cache or not, and shouldn't know.
IF this performance/cost is important to you, it's better to combine Firestore with something like Redux (which I do) to maintain local "sets" of documents to reduce round-trip calls, and Listeners to keep Redux current.
yes. Firebase stores documents and collections in cache memory. when you are offline you can access cache copy of data. also you can manage cache copy of documents and collections.
read this offical docs for more info
https://firebase.google.com/docs/firestore/manage-data/enable-offline
I have an app that has 50k - 60k document reads a day and I can't afford another plan now, so I'm looking for a way to optimize reads, getting less reads possible I can.
The database has 4 collections with some subcollections, I think I might have around 1000 documents in the whole server.
It is there anyway: I can read documents from cloud Firestore (first time the user opens the app) and store on the Firestore cache, after that, make the app only load data from Firestore cache, and if there is a new document(s), it reads these documents only, store to the cache, and keep reading from the cache?
The app could only load data from cache (using the parameter "source") and never directly from Firestore, if possible.
Firestore.instance.collection("images").getDocuments(source: Source.cache);
Is is there anyway: I can read documents from cloud Firestore (first time the user opens the app) and store on the Firestore cache
That's the default behavior. According to the official documentation regarding Firestore offline persistence:
For Android and iOS, offline persistence is enabled by default. To disable persistence, set the PersistenceEnabled option to false.
For the web, offline persistence is disabled by default. To enable persistence, call the enablePersistence method. Cloud Firestore's cache isn't automatically cleared between sessions. Consequently, if your web app handles sensitive information, make sure to ask the user if they're on a trusted device before enabling persistence.
So there is nothing special that you need to do. Once you open a stream on one of your collections, the data is added to the cache.
after that, make the app only load data from Firestore cache, and if there is a new document(s), it reads these documents only, stores to the cache, and keeps reading from the cache?
That's again the default behavior, but this work as long as the documents in your database are not changed. If a document in the database is changed, you'll be charged with a document read for each document. The mechanism is the same.
Besides that, you can tell Firestore to read data only from the cache if needed, as explained in the answer from the following post:
How to cache Firebase data in Flutter?
I'm new to firebase and I want to add it to my vuejs project.
But I'm wondering. Is the a way I can perform a transaction that creates user using the auth() and use the uid to create a user using firestore() and use the uid as a name to upload an image using storage(). However, the whole operation should revert, should any fail.
There are no cross-product transactions available for Firebase products. Of the three products you mentioned, only Firestore has transactions, and they are limited to documents within a single database.
What you will have to do is check for errors each step of the way, and undo any previous changes if something fails.
https://firebase.google.com/docs/firestore says:
Like Realtime Database, Cloud Firestore uses data synchronization to update data on any connected device.
I'm trying to figure out what this "data synchronization" consists of.
https://firebase.google.com/docs/firestore/manage-data/enable-offline says:
When persistence is enabled, Cloud Firestore caches every document received from the backend for offline access.
Does Cloud Firestore update that cache whenever changes happen in the back end?
For example, if I have a certain document in my cache, does the document
update (a) automatically when that document is changed in the back end or
(b) whenever I do a query that uses that document, and I happen to be online
at the time?
UPDATE
I'm going to restate my last paragraph, because it's been misunderstood by
at least one person.
Imagine the following scenario:
I have a smartphone. To make things easy, assume the smartphone
is online all the time.
Installed on this smartphone is a mobile app that contains the Firestore SDK.
The app has enabled the Firestore cache.
The cache contains, say, 1000 documents.
Now my question is: if one of these documents changes in the cloud (not on
the smartphone), under what circumstances will the Firestore SDK update the
document in the cache? Will it (a) update the document automatically, soon
after the change on the cloud, or (b) update the document the next time the
mobile app does a query that uses the document?
Both of the highlighted paragraphs are in my opinion straightforward explanations, and to answer your questions:
Does Firestore update that cache whenever changes happen in the back end?
Yes, if you are offline and some documents are changed, once you are back online, you get all changed documents and vice versa, if you change some documents locally (in your cache), when you're back online, all changed documents are sent to the Firebase servers.
If you have a query that returns 10 documents, it means that you are in sync with 10 documents, which basically means that if of those 10 documents is changed, your listener is triggered only for that change.
does the document update (a) automatically when that document is changed in the back end
Yes, first of all in your cache and once you are back online, also on Firebase servers.
whenever I do a query that uses that document, and I happen to be online at the time?
Whenever you are online and a document is changed, you are notified in realtime.
Edit:
if one of these documents changes in the cloud (not on the smartphone), under what circumstances will the Firestore SDK update the document in the cache? Will it (a) update the document automatically, soon after the change on the cloud, or (b) update the document the next time the mobile app does a query that uses the document?
As long as you are in sync with those documents, it happens in the second moment the document is changed. What I mean through in sync is, that you are using in your code a get() call to get those documents or if you are listening in realtime for documents changes. Simply creating a reference to a document or a query without using a listener, you aren't notified in any way.
update the document the next time the mobile app does a query that uses the document?
Is not correct since you are online and in sync with the documents, the listener is triggered instantly.
Edit2:
In short, a listener is called everytime a change in a document occurs. "Next time the app does the query" is not correct sentence because when you create a query and attach a listener, you are always in sync with the database and when a document is changed you are immediately notified. It is not like, the documents are chainging in the database and when I query (at some point of time), I get the changes, no, you are always notified as the changes occur. That's the beauty of a realtime database, to be notified as the changes are happening :)
If you have the local cache enabled, Firestore automatically stores any documents it receives in that local cache.
This only happens when your app is requesting the documents by calling get() or onSnapshot. Firestore does not automatically request the documents on your behalf. So if your app doesn't request the document, the cache will not be updates.