My firebase database has a user profile collection, where all the documents are UIDs, each document has a field called subscriptions which is an array of strings, each string being other UIDs.
I have a second collection for host content, where each document contains fields such as imageurl and caption, essentially posts that user has made.
Is there any way I can use the streamprovider on the host content collection to only show the posts by the UID the current user has a subscription for?
There are no SQL-like joins in Firestore, so your only option here (without changing any data) is to add a new listener on each document in hostconent that matches what's in the profile. There is no way to do this with a single query.
If you want to do this with a single query, you should have a field for each document in hostcontent that identifies which profile it's associated with. Then you can make a single query using that field as a filter to find only the documents for a profile.
Related
My db design is above picture. I wanna create a query which returns user where tags are matched. But i didnt any solution to query.
This is my flutter code:
But it doesnt work. How can i query array of map of document?
The courses is an array and not a map so you cannot use the dot notation to query. If the courses is made a collection (or a sub-collection) on it's own then you would be able to query users easily:
users -> {userId}
(col) (doc)
courses -> {courseId}
(col) (doc)
You would have to include a field userId in each course document which would be used to identify which user owns that course.
await firestore.collection("courses").where("tags", arrayContainsAny: tagKeys)
This will return all courses where the tags array contains at least 1 item in the tagKeys list. If you need exact match i.e. all the tags in tagKeys must be present in Firestore document then you would have to restructure the database as mentioned in this answer.
Fetching all matching documents might not be ideal since you just need user IDs that matches the tags. In that case you can store a field which contains tags from all the courses in a single array field in the user document.
Let's say I have a employees collection where I have one document per employee and I want to keep record of all changes that were made to a single employee doc. I was thinking of the following approach:-
Have a pendingEmployeeWrites collection where client is
only allowed to create documents. Each doc here will have an
employeeId field (this id is generated on client side for new employees).
Cloud function will be invoked whenever such a doc is created and then it validates the data. If valid, the employeeId doc in employees collection is overwritten with this data. Otherwise the pendingEmployeeWrites doc is updated to set isFailed as true. Client app is only allowed to read from employees collection.
Keeping pendingEmployeeWrites as a flat collection instead of a sub-collection allows me to pull all changes made by a user as well as all changes for a particular document. Does this approach make sense or is there a better approach that I should consider?
I'd like my web app router slugs to correspond to my Firestore documents data.
For example:
www.mysite.com/restaurants/burger-king
/restaurants <- Firestore Collection
/restaurants/mcdonalds <- Firestore Document
/restaurants/burger-king <- Firestore Document
This is easy enough, as I can assign the name as a slug-friendly UID in Firestore. The difficulty arises with CRUD functionality. I need to be able to rename my item titles, but Firestore does not permit you to rename indexes, which is the issue I'm facing.
One SO solution I saw was to delete the old record and creates a new one at the updated index. That's problematic for me, because sub-collections would be hard to transfer from the client side.
Are there more elegant solutions?
You don't have to identify a document by its ID. If you're able to ensure uniqueness of a document field value, you could instead query a collection for an ID value in a known field, then use the results of that query to satisfy your REST API. Then, you can change the value of that document field as often as you want, in order to satisfy required changes to the public API.
I'm adding data to cloud Firestore through the Firebase Console. I've added a collection and the corresponding documents and fields. When I click on " ADD DOCUMENT", the new document appears randomly (as far as I can make out) on the document column. I want the newly generated document to appear at the bottom of the document column. The order matters when viewing the data on the app. The data is used in a recycler view. Is this possible?
Cloud Firestore does not order documents in the same way as the RTDB. Auto IDs are not time related. You will need to add a timestamp field and order your data by this field.
You can read about this here.
Important: Unlike "push IDs" in the Firebase Realtime Database, Cloud
Firestore auto-generated IDs do not provide any automatic ordering. If
you want to be able to order your documents by creation date, you
should store a timestamp as a field in the documents.
I used Firestore's "set" method instead of "add" and used a numerical date string; it is automatically adding and listing them in numerical order.
// Swift
let dataToSave: [String: Any] = ["example": "example"]
collectionRef.document(dateString).setData(dataToSave) { (error) in
}
If you use the "add" method, the key will be automatically generated with a random alphanumeric string.
The collection orders everthing alphanumerically, so setting your documents using keys of numbers or letters, exclusively, will allow for an ordered list.
I'm using Firebase Cloud Firestore and can't figure out how to access documents without knowing the specific path. The database structure is users/{user id}/favourites/{favourite id}. There are no fields in users/{user id} only subcollections. Knowing the user id, i can get the favourites for the user, but I can't get a list of users to get everyone's favourites. Here is the code I am trying (Java admin SDK):
db.collection("users").get().get()
which results in an empty Iterable with no DocumentSnapshots.
How can I get a list of the most popular favourites?
EDIT: I've discovered I can get a list of users with no fields if I add a field. Even if I delete it later, it still appears as a document in the collection.
EDIT2: I've discovered that I can create an empty document, so I'm just doing that for now. As a one-off, I can get a list of all users from firebase auth and look up which ones have a favourites collection and just set those to empty documents.