I'm trying to make an Activity log system or history for my docs, so every time a field is modified in a document i want to record or save that so i can see after changes history made on each document.
how i can achieve that ? i don't want to save the full doc on each change and then have tons of duplicated docs, if possible i just want to get the changed field (ex. name: 'john' -> name: 'jack').
i don't want to save the full doc on each change and then have tons of duplicated docs
Once a document has changed it becomes a new document. So you won't have duplicate documents unless you make changes that were previously made. Please also note that in Cloud Firestore there are no field-level permissions or access to a document. It's the entire document, or nothing. So if you want to change a field within a document for example from:
userName = "John"
into
userName = "Jack"
You'll will get the entire document and not only the userName property that has been changed.
Cloud Firestore listeners fire on the document level. There is no way to get triggered with just particular fields in a document.
If you want to get notified only of specific fields, consider adding an extra collection with documents that only contain those fields. This sort of data duplication is quite common in NoSQL solutions such as Firestore and for that, I recommend you see this video, Denormalization is normal with the Firebase Database for a better understanding. It is for Firebase real-time database but same principles apply to Cloud Firestore.
For a database schema you can also take a look at my answer from this post.
The best way to achieve something like this is to store the before and after changes happening to the doc, in a new document, which you can add in a subcollection. The changes are available with cloud functions onUpdate trigger. I have written in depth about this topic on my blog, have a look.
https://blog.emad.in/audit-logs-for-firestore-documents/
You can obtain this by creating a cloud function that triggers on all document updates in all collections:
--trigger-resource=projects/$PROJECT_ID/databases/(default)/documents/{collection_id}/{document_id}
In the cloud function you can obtain all the updated fields and their values through the data object.
Python example:
def main(data, context):
# Extract resource
resource = context.resource
resource_split = resource.split('/')
collection_name = resource_split[-2]
document_id = resource_split[-1]
# Get old fields
data_old_values = data['oldValue']
data_old_values_fields = data_old_values['fields']
# Get updated fields
data_updated_mask = data['updateMask']
data_updated_fields = data_updated_mask['fieldPaths']
# Get new field values
data_new_values = data['value']
data_new_values_fields = data_new_values['fields']
# `data_updated_fields` is a list of the fields that has been changed
# `data_old_values_fields` is a dictionary with the old values of the document
# `data_new_values_fields` is a dictionary with the new values of the document
Related
Im trying to create one stream, that is using multiple documents references that are stored and fetched from Firebase Firestore.
Lets say I have two collection named users and documents. When user is created he gets document with his id in users collection with field named documentsHasAccessTo that is list of references to documents inside documents collection. It is important, that these documents can be located in different sub collections inside documents collection so I dont want to query whole documents and filter it, in order to save Firestore transfer and make it faster I already know paths to documents stored in documentsHasAccessTo field.
So for example, I can have user with data inside users/<user uid> document with documentsHasAccessTo field that stores 3 different document references.
I would like to achieve something like this (untested):
final userId = 'blablakfn1n21n4109';
final usersDocumentRef = FirebaseFirestore.instance.doc('users/$userId');
usersDocumentRef.snapshots().listen((snapshot) {
final references = snapshot.data()['documentsHasAccessTo'] as List<DocumentReference>;
final documentsStream = // create single query stream using all references from list
});
Keep in mind, that it would also be great, if this stream would update query if documentsHasAccessTo changes like in the example above, hence I used snapshots() on usersDocumentReferences rather than single get() fetch.
The more I think about this Im starting to believe this is simple impossible or theres a more simple and clean solution. Im open to anything.
You could use rxdart's switchMap and MergeStream:
usersDocumentRef.snapshots().switchMap((snapshot) {
final references = snapshot.data()['documentsHasAccessTo'] as List<DocumentReference>;
return MergeStream(references.map(ref) => /* do something that creates a stream */));
});
My cloud firestore database has an "orders" collection and in HTML I have a 'save' button to add document(s) into that "orders" collection upon clicking. Now, using add will assign auto-generated ID for each document.
What if I want to customise such ID by timestamp? So that the document created yesterday will be assigned an index as '1', and the following document created will be '2', etc...
What you're trying to do is not compatible with the way Cloud Firestore was designed. Firestore will not assign monotonically increasing numbers for document IDs. This just doesn't scale massively as required by Firestore and would introduce performance bottlenecks.
If you want to be able to sort documents by timestamp, the best strategy is to add a timestamp field to each document, then use that field in an ordered query.
Note that you could try to write a lot of code to get this done the way you want, but you are MUCH better off accepting the random IDs and using fields to filter and order data.
in some case, when you need to save several docs in different collection due to an event occurs, it's better to same all docs with same id in different collections with single firestore server's timestamp. you get the timestamp like below:
const admin = require('firebase-admin')
const ts = admin.firestore.Timestamp.now().toMillis().toString()
by doing this, when you need to read all those docs, you only need to query once to get timestamp, then read all other doc by timestamp directly.
it should be faster than query the timestamp inside document fields for each collections
So this is possible:
const docSnapshot = await firebase.firestore().collection("SOME_COL").doc("SOME_DOC").get();
console.log(docSnapshot.exists);
But it "downloads" the whole document just to check if it exists. And I'm currently working with some havier documents and I have a script where I just need to know if they exist, but I don't need to download them at that time.
Is there a way to check if a document exist without .get() and avoid downloading the document data?
It seems you are using the JavaScript SDK. With this SDK there isn't any way to only get a subset of the fields of a document.
One of the possible solutions is to maintain another collection with documents that have the same IDs than the main collection documents but which only hold a very small dummy field. You could use a set of Cloud Functions to synchronise the two collections (Documents creation/deletion).
On the other hand, with the Firestore REST API, it is possible, with the get method, to define a DocumentMask which defines a "set of field paths on a document" and is "used to restrict a get operation on a document to a subset of its fields". Depending on your exact use case, this can be an interesting and easier solution.
What if some data is already there inside the users collection ?
Would doing this 👇🏻 will delete all the previous data ?
var messageRef = db.collection('users').doc(userID)
.collection('private_user_data').doc(userID);
I want to add new data inside users collection and inside that a doc with 4 fields and one more collection inside that and inside that a doc with four more fields.
The code in your question doesn't read from or write to the database in any way. It merely sets up a reference to a document in the database.
There are few ways to implement this, depending on your exact use-case:
To merge data with an existing document, use the update method.
If the document may or may not exist, you can tell Firestore to merge the new values with the existing data when you call the set method.
If you want to set some fields only if the document doesn't exist yet, and leave them unmodified if the document already exists, you will need to use a transaction. In that case you may also want to make sure your security rules reject modifications to those initial fields.
With your code you don't make any operation on your db.
If you would know use .set(someData) your document would be created with given data if there is no document with given id or the document would be overwritten with the given data if there is a document with the given id.
Please check this post from the Firebase docs for more information.
EDIT
To create a document you have to do something like this:
var messageRef = db.collection('users').doc(userID)
.collection('private_user_data').doc(userID);
messageRef.set({
field1: input1,
field2: input2,
field3: input3,
field4: input4
})
Be aware that messageRef.set() will return a promise. So you have to deal with it. And here I would recommend you one of the tutorials from the Firebase team or one of many from the Internet.
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.