I am trying to get all documents where the length of the "users" array is less than 2 and where the userId is not present already. I am doing the following query, but it is not executing correctly. What is the problem and how can I fix it? I just want all documents where there is only one entry in the array "users" and where the array does NOT contain the current userId.
await FirebaseFirestore.instance
.collection('rooms')
.where("users"[0], isNotEqualTo: userId)
.where('users'[1], isEqualTo: null)
.get()
.then((snapshot) async {
// If no empty room is found, create room
if (snapshot.docs.isEmpty) {
print("No empty room found, creating new room");
roomId = await createRoom(userId);
return roomId;
}
You can't query individual array elements in Firestore. You can only check whether an array contains a specific item.
It sounds like your array items have a specific meaning, in which case you should create (nested) fields that indicate/name the roles. For example:
participants: {
creator: "uid1",
receiver: "uid2"
}
With that you can then query the nested fields with dot notation:
.where("participants.creator", "!=", "uid1")
.where("participants.receiver", "==", null)
Keep in mind there that the participants.receiver field still has to exist in the latter case and have a value of null. Firestore can't filter in fields that don't exist.
Related
I'm creating a post that uploads data to Firestore's sub-collection and brings it up to MyBookmark page. It's good to create a sub-collection and upload data simply. And now I'd like to add a 'data duplication prevention' function here.
If the post is already saved in the bookmark, should not upload it.
For this purpose, I would like to check if the post is already in the collection when I press the bookmark button.
IconButton(
onPressed: () async {
//get userModel
UserModelState _userModelstate =
Provider.of<UserModelState>(context, listen: false);
//=========================================
//duplication data test
DocumentReference bookmarkRef = Firestore.instance
.collection(COLLECTION_USERS)
.document(_userModelstate.userModel.userKey)
.collection(COLLECTION_BOOKMARk)
// .where(KEY_BOOKMARK_PRODUCTKEY, isEqualTo: productKey)
.document();
DocumentSnapshot bookmarkSnapshot = await bookmarkRef.get();
//test (return "No exist")
if(bookmarkSnapshot.exists) {
print("Yes exist");
} else {
print("No exist");
}
I tried writing a code to check if there was data in the collection, but it is always printed as "No exist".
How can I confirm the existence of a specific document in collection?
Thank you.
If the productKey is supposed to be unique in the Bookmark collection of the user, consider using the productKey as the document ID. Since document IDs are by definition unique within their collection, using them guarantees unique product keys without you having to write any code for it.
That said, you current code can't work because you call document(). Whenever you call document() without any parameters, it generates a reference to a new unique document. And since you immediately call get() on that reference, the document will (also: by definition) not exist yet.
To check if a document with a specific product ID exist, you will need to run a query:
CollectionReference bookmarksRef = Firestore.instance
.collection(COLLECTION_USERS)
.document(_userModelstate.userModel.userKey)
.collection(COLLECTION_BOOKMARk);
Query bookmarkQuery = bookmarksRef.where(KEY_BOOKMARK_PRODUCTKEY, isEqualTo: productKey);
QuerySnapshot bookmarkSnapshot = await bookmarkQuery.get();
if (bookmarkSnapshot.size > 0) {
print("product key already in use");
}
Hi I am pretty new to Firebase real time database and this is my first project. Sorry if this is a stupid question.
I am saving my data as follows.
firebase database structure:
Now I want to retrieve all parent chat ids on which the student is participating, using the student_id variable.
I tried as per this SO question and this structure database and retrieve data documentation, but its not retrieving values. Anybody have an idea?
I would suggest saving the chatroom IDs your students are in in a separate location. For example:
Path:
“/users/$uid/chatrooms”
Data:
{
0: 350,
1: 423
}
Thus you could retrieve the chat room ids first before getting the chatroom data.
import { initializeApp } from “firebase”;
import { getDatabase, get, set, ref } from “firebase/database”;
const userChatroomIdsRef = ref(db, ‘/users/${uid}/chatrooms‘);
get(userChatroomIdsRef).then(result => {
const chatroomIds = result.val();
if (!(chatroomIds && chatroomIds instanceof Array)) return; // firebase will return null if its an empty array.
const getChatroomInfoPromises = chatroomIds.map(id => get(ref(db, ‘/chat/${id}/${uid}’)).then(result => result.val());
Promise.all(getChatroomInfoPromises).then(chatroomInfoArray => { YOUR LOGIC HERE });
});
Removing/adding students from/to chatrooms would now be simple as you could just change the array of chatroomIds.
const userChatroomIdsRef = ref(db, ‘/users/${uid}/chatrooms‘);
get(userChatroomIdsRef).then(result => {
const oldIds = result.val();
const newChatroomIds = oldIds.filter(id => id !== ID TO DELETE);
return set(userChatroomIdsRef, newChatroomIds)
});
This is of course assuming that you know the uid of your student_id. If you do not know what uid each student_id has, you must must store a reference. I would suggest saving all student info in the “/users/$uid/” directory. Here you could save the studentId so you can programmatically use it.
In all other firebase logic I would try to use the native firebase uid for querying. This will make your life easier.
It’s always good the keep information organized on the database so your logic is simple.
Please check my code for syntax errors; I wrote this on an iPhone.
Future<List<DocumentSnapshot>> finallist() async {
List<DocumentSnapshot> finallist;
Future createList(QuerySnapshot snapshot) async {
List<DocumentSnapshot> listoflocationforsingle = snapshot.documents;
for (DocumentSnapshot u in listoflocationforsingle) {
print('Added ' + u.data['country']);
finallist.add(u);
}
}
finallist.add(u) fails with add on null error.
Exception has occurred.
NoSuchMethodError (NoSuchMethodError: The method 'add' was called on null.
Receiver: null
Tried calling: add(Instance of 'DocumentSnapshot'))
Even tho when I hover over the data in createlist(data), it shows list of QuerySnapshot with the data in my firestore database.
There is no single query that can get data from multiple subcollections. Firestore queries are shallow, and only work with documents within a single collection at a time. If you want data from three subcollections, you will need to be three queries, one for each subcollection.
Oh, my future function actually does it. Just that I needed to add in
List<DocumentSnapshot> finallist = []; // add in the ' = [] '
I am trying to create a query which only selects documents whose reference is equal to a given reference, using Java for Android development. A document which it would match contains the reference for the path "/users/someUser". I am creating the reference like so:
DocumentReference ref = mDatabase.document("users/someUser");
I have also tried:
DocumentReference ref = mDatabase.document("/users/someUser");
Then the query:
Query query = mDatabase.collection("myCollection").whereEqualTo("refField", ref).limit(10);
However, when I run the query and check the task.isSuccessful() in the onComplete method, it's not passing, i.e. it didn't work, whereas when I remove the .whereEqualTo(), it passes and the task's result isn't empty. How can I properly use .whereEqualTo() to check for all documents containing a specific reference?
An example of a document that should match my query would be:
/myCollection/GDpojS5koac2C7YlIqxS which contains the field:
refField: /users/someUser (value of type reference)
And an example of a document that should not match my query would be:
/myCollection/J5ZcVAMYU1nI5XZmh6Bv which contains the field:
refField: /users/wrongUser (value of type reference)
I think you need to add a get() method to run the query and add an onCompletionListener.
Something like this should work:
mDatabase.collection("myCollection")
.whereEqualTo("refField", ref)
.limit(10)
.get()
.addOnCompleteListener({task ->
if(task.isSuccessful){
val result = task.result
})
The above example is in kotlin, but i guess in java it is something similar
You need not to worry about the documents, if you create a query based on your fields then all the documents will be returned in the "QuerySnapshot" object,
for eg,
CollectionReference collectionReference = db.collection(FIRESTORE_USERS);
DocumentReference documentReference = collectionReference.document(userID);
CollectionReference notificationCollection = documentReference.collection(FIRESTORE_NOTIFICATIONS);
notificationCollection.whereEqualTo(USER_TYPE, userType)
.whereGreaterThanOrEqualTo(SEND_AT, calendar.getTime())
.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
#Override
public void onSuccess(QuerySnapshot documentSnapshots) {
List<DocumentSnapshot> snapshotsList = documentSnapshots.getDocuments();
ArrayList<NotificationCollections> notificationCollectionsArrayList = new ArrayList<>();
for (DocumentSnapshot snapshot : snapshotsList) {
// each document having that particular field based on query
}
}});
in the above example I am fetching all those documents which match a particular user id and also having time greater than or equal to supplied time (time will not be used in your case)
I hope this helps...
Happy coding :)
Firestore database image
Hello, I just tried to use Firestore. I had some problem when getting document id.
The question is, I want to get a document id (red box) which has value (blue box) in it.
I use the following query:
collection("mychannel").whereEqualTo("74wRU4xHrcV9oWAXEkKeRNp41c53")
But did not give results.
Thanks!
As in the official documentation:
Although Cloud Firestore can store arrays, it does not support querying array members or updating single array elements.
So there is no way in which you can use the following query:
collection("mychannel").whereEqualTo("74wRU4xHrcV9oWAXEkKeRNp41c53")
If you only want to get the entire userId array you need to iterate over a Map like this:
collection("mychannel").document("1fReXb8pgQvJzFdzpkSy").get().addOnCompleteListener(new OnCompleteListener<DocumentSnapshot>() {
#Override
public void onComplete(#NonNull Task<DocumentSnapshot> task) {
if (task.isSuccessful()) {
DocumentSnapshot document = task.getResult();
if (document.exists()) {
Map<String, Object> map = document.getData();
for (Map.Entry<String, Object> entry : map.entrySet()) {
if (entry.getKey().equals("userId")) {
Log.d("TAG", entry.getValue().toString());
}
}
}
}
}
});
But note, even if userId object is stored in the database as an array, entry.getValue() returns an ArrayList, not an array.
So the output will be:
[74wRU4xHrcV9oWAXEkKeRNp41c53]
A better approach will be if you consider this alternative database structure, where each user id is the key in a map and all values are true:
userId: {
"74wRU4xHrcV9oWAXEkKeRNp41c53": true,
"AdwF...": true,
"YsHs...": true
}
This question is answered here: Firestore: Query by item in array of document
In summary, don't use arrays to store data in Firestore as the query you are trying to do is not available yet (remember it is still in beta). You should use a Map instead.