I have duplicates "email" elements in my Cloud DataStore.
The schema of the entity is:
- ID
- Email
- OtherFields
I would like to find all elements which have the same email address twice or more in the database. Is it possible?
Related
My database is quite simple. A collection and inside, there are documents with user information, including their username.
(I am doing this in flutter and firestore).
What I want is to prevent two users from having the same username.
I am doing this to insert the data.
FirebaseFirestore.instance.collection('users').add({
'username': 'username',
'desc': 'some bio',
'fieldone': 'aaa',
'fieldtwo': 'bbb',
// other user info
});
And to consult the data of a user (by their username).
FirebaseFirestore.instance.collection('users').where('username', isEqualTo: 'username').get();
At the moment I insert the data, what can I do to verify that said username is already in the database?
So if the username already exists, return an error and don't let insert it. And if it doesn't exist yet, it can be inserted.
What query can help me for this?
I am new to firebase. :(. Thanks.
What query can help me for this?
This can't be accomplished by a single query. You will have to take the steps you outlined already in your question. You will have to first query for documents with that username, then only insert a new one if there were none found.
However, you should be aware that there is a race condition here. If two people are trying at the same time to add the same username, it's possible that they both end up adding a document.
The only way to ensure uniqueness in Firestore is using the document ID. You might want to consider using the ID of the document to store the username (or some version of it, like a hash) so that a race condition can never occur, and that you only have one document with that username.
See also:
Firestore unique index or unique constraint?
Cloud Firestore: Enforcing Unique User Names
Unique field in Firestore database + Flutter
firebase rule for unique property in firestore
As you can see, your issue has already been thoroughly discussed on Stack Overflow.
I use Google Firestore for my iOS app built in Swift/SwiftUI and would like to implement the Snapshot listeners feature to my app.
I want to list all documents in debts collection in realtime by using snapshot listeners. Every document in this collection has subcollection debtors, which I want to get in realtime for each debts document as well. Each document in debtors has field userId, which refers to DocumentID in users collection which I would also love to have realtime connection on (for example when user changes his name I would love to see it instantly in the debt entity inside the list). This means I must initialize 2 more snapshot listeners for each document in debts collection. I'm concerned that this is too many opened connections once I have like 100 debts in the list. I can't come up with no idea apart from doing just one time fetches.
Have anyone of you ever dealt with this kind of nested snapshot listeners? Do I have a reason to worry?
This is my Firestore db
Debts
document
- description
- ...
- debtors (subcollection)
- userId
- amount
- ...
Users
document
- name
- profileImage
- email
I uploaded this gist where you can see how I operate with Firestore right now.
https://gist.github.com/michalpuchmertl/6a205a66643c664c46681dc237e0fb5d
If you want to read all debtors documents anywhere in the database with a given value for userId, you can use a collection group query to do so.
In Swift that'd look like:
db.collectionGroup("debtors").whereField("userId", isEqualTo: "uidOfTheUser").getDocuments { (snapshot, error) in
// ...
}
This will read from any collection name debtors. You'll have to add the index for this yourself, and set up the proper security rules. Both of those are documented in the link I included above.
I have the following data as shown in the image.
I want to make sure that the username field is unique. How can I enforce that? Bear in mind that my document id is already unique and I don't want to use my username as the document ID
There is no way to enforce unique values of fields in Firestore. The only uniqueness you can guarantee is the document IDs within a collection, so the solution is to create a new collection where the user names are used as document IDs.
This has been discussed a few times before, so I recommend checking out:
Firestore security rule to check if character username already exists
Check a document field for a specific value in Cloud Firestore
I want to make unique usernames in firebase/firestore, which shows some of the relevant security rules.
Cloud Firestore: Enforcing Unique User Names
Firestore unique index or unique constraint?, a more complete write-up with code and rules samples.
Cloud Firestore: Enforcing Unique User Names
I have a Google Firebase Realtime Database with the following structure:
project
|
- users
|
- uid_1
|
- name
- age
- ...
|
- uid_2
|
- name
- age
- ...
I'm new with Google Firebase. I can read all db-fields from a specific 'uid'. But how can I collect all names from all unsers? I want to make an file-uploader and to assing the file to an existing user, I want to use a dropdown-menu to select the user.
With the way you have this data structured, you're going to have to write code to query everything under "users", iterate the children, and pull the names out of each child.
Realtime Database doesn't offer any sort of SQL-like projection type query that will get you just the vales of certain children. Or to put it another way, you can't do anything like "select name from users". If getting only the name is a common operation for you, you will need to duplicate only the names into another parent node, and query that new node instead.
The Firebase Admin SDK allows retrieving the entire list of users in batches. But max result is 1000.
Or you can denormalizing your data.
So few day ago I moved my apps posts to cloud firestore from realtime database because of the more flexable querying that firestore apparently has. I have been modifying my code to work with firestore as the new database. Now I ran into a problem. How can I retrieve every document within "Posts" collection that has "Likes" collection that contains a specifically named document? I don't know if that makes sense so here's an image showcasing the problem:
I had a working query for firebase realtime database but can't figure out how to do it with firestore. Is it possible or do I have to change the structure of my database? If I do have to change the structure, what would be the most convenient way of getting the same result?
This is currently not possible with collection group queries. You might be tempted to put a filter on the query for FieldPath.documentId() == 'your-doucment-id', but that just isn't supported. FieldPath.documentId() is actually a token that refers to to fully unique document id, which includes the entire path of the document.
The workaround is to store the document ID as a field in the document, and filter on the contents of that field instead. So, if the document had a field called id with the ID of the document, you could query for collectionGroup("Likes").whereEquals('id', 'your-document-id').