Firestore function to track new writes of documents and limit the count of all documents

Question

When using Firestore database and Firestore functions, I am trying to achieve a way to keep documents count of a specific collection limited (For example, I don't want the collection to have more than MAX_COUNT documents).

This is the template of what I want to achieve (a Javascript script in index.js):

exports.docAdded = functions.firestore.document('myCollection/{docID}').onWrite((change, context) => {
 if (!change.before.exists) {
     // New document Created - check total number of documents in myCollection
       //- Delete old documents in case of size>MAX_COUNT
 }
});

Any help is appreciated !

Answer 1

There isn't a function developed yet, that supports the tracking of the number of documents in a collection. However, there are some alternatives and methods that you can give it a try, to help you achieve this limitation goal that you want.

I would recommend you to take a look at the below articles and posts from the Community, that might help you and provide some ideas on how to achieve this.

• FR: Firestore collection count feature #932 - information about a feature request for this to be implemented in the future.
• Cloud Firestore collection count
• How do you force a Firestore client app to maintain a correct document count for a collection?

Let me know if the information helped you!