Is it possible to create multiple documents against a collection using Cloud Firestore in the same transaction?
I'm looking at the documentation on batched writes. Unless I'm mistaken (I'm new to Firebase, so could be the case) these examples are meant to demonstrate 'batched writes' but the examples only show a single field being updated.
Yes. Batched writes can work for both updating a single field on multiple documents, or creating a bunch of documents at once.
Follow this link to see a similar case i had which i solved. It talked about a collection with its documents being automatically created when a document is created. You will get an idea on how to solve your issue from it.
The link is thus: When collection is created, the documents are added to it at once
I hope it helps.
Related
I have just published an app that uses Firestore as a backend.
I want to change how the data is structured;
for example if some documents are stored in subcollections like 'PostsCollection/userId/SubcolletionPosts/postIdDocument' I want to move all this last postIdDocument inside the first collection 'PostsCollection'.
Obviously doing so would prevent users of the previous app version from writing and reading the right collection and all data would be lost.
Since I don't know how to approach this issue, I want to ask you what is the best approach that also big companies use when changing the data structure of their projects.
So the approach I have used is document versioning. There is an explanation here.
You basically version your documents so when you app reads them, it knows how to update those documents to get them to the desired version. So in your case, you would have no version, and need to get to version 1, which means read the sub-collections to the top collection and remove the sub collection before working with the document.
Yes it is more work, but allows an iterative approach to document changes. And sometimes, a script is written to update to the desired state and new code is deployed 😛. Which usually happens when someone wants it done yesterday. Which with many documents can have it's own issues.
I wanted to get some community consensus on how to achieve the following with the Firebase JS SDK (e.g., in React):
Suppose I have a collection users and I wanted to paginate users that do not have document IDs matching a subset of IDs (O(100-1000)). This subset of excluded IDs is dynamic based on the authenticated user.
It seems the not in query only supports up to 10 entries, so this is out of the question.
It also seems it's not possible to fetch all document IDs and filter on the client side, at least not in the 'firebase' JS SDK.
The only workaround I can think of is to have a document that keeps an array of all users document IDs, pull that document locally and perform the filtering/pagination logic locally. The limitation here is that a document can be at most 1MB, so realistically the single document can store at most O(10K) IDs.
Firestore has a special bunch of methods for pagination which may be useful for you. Those are called "query cursors".
You can use them to define the start point startAt() or startAfter() and to define an end point endAt() or endBefore(). Additionally, if needed, those can be combined with limit method.
I strongly encourage you to check this tutorial. Here you can find a quick video explaining the matter and lot of examples in all popular languages.
I need to create a firestore doc which also has a collection, ideally in a single write operation.
I'm not seeing anything like this in the documentation, so failing that any tips on getting the created doc id and then adding multiple documents to a collection?
Edit: I'm developing in typescript/js
You can use a transaction or batch write to perform atomic operations among multiple documents. In both cases, you need to know all the IDs for all the documents you want to create ahead of time. You don't need to create a document in order for there to be a subcollection. Documents don't actually "contain" subcollection. Subcollections are currently just a technique for organizing your data.
It wasn't really clear from your question, but if your first document requires a generated ID, you can use the example code in the documentation that generates a DocumentReference object, which you can populate later in your transaction or batch.
Since you didn't say which language or system you're working on, I don't know which code sample to show here from the docs, so you'll have to go to the documentation linked here to see how it works. You'll end up using a method called "doc" or "document" on a CollectionReference to generate the DocumentReference with the generated ID.
I am trying to make feed/timeline where a user can follow - Category,Album or another User. Every time a picture is added to Category,Album,User it should appear on the timeline. I am trying to model my database so it requires 1-2 get requests only.
One idea for the solution is fan-out structure, But how do i make the multi-path update in Firestore? How can i update all the followers timelines when someone uploads a photo ?
How do i structure the database when i cant query on sub-collections? Should i just make one collection which contains all user timeline posts as separate documents, which will be ridiculous amount of duplicated data.
Is there any other way instead of fan-out to structure a user timeline ?
But how do I make the multi-path update in Firestore?
The equivalent of Firebase Realtime Database's multi-path updates, are called batched writes in Cloud Firestore. You can read more in the documentation on batches writes.
Flat.
root
pictures
uid-abc123
url:"http://test.com/img1.jpg"
owner:useriduid,
created: 1529333679449
uid-abc1billion
url:"http://test.com/img1billion.jpg"
owner:useriduid,
created: 1529333679300
Querying and security rules are then easy as pie. You can add indexing and it's very scalable.
Re multipath writes, use batched writes.
I am trying to figure out the best way to execute my cloud function for my firestore database, when data is being read.
I have a field on all of my documents with the timestamp of when the document was last used, this is used to delete documents that haven't been used in two days. The deletion is done by another cloud function.
I want to update this field, when the documents is being used AKA read from my db. What would be the best way to do this?
onWrite(), onCreate(), onUpdate() and onDelete() is not an option.
My database is used by a Android App written in Kotlin.
There are no triggers for reading data. That would not be scalable to provide. If you require a last read time, you will have to control access to your database via some middleware component that you write, and have all readers query that instead. It will be responsible for writing the last read time back to the database.
Bear in mind that Firestore documents can only be written about once every second, so if you have a lot of access to a document, you may lose data.