How to delete multiple documents from Cloud Firestore?

Question

What's the best way to delete many (not all) documents from Cloud Firestore?

The official documentation contains information regarding deleting one document and all documents: https://firebase.google.com/docs/firestore/manage-data/delete-data.

Answer 1

To delete multiple documents, you can do a single batched write. The WriteBatch class has a delete() method for this purpose.

The performance to between a single BatchedWrite and multiple DocumentReference.delete calls is similar though, see here. As in: I expect both of them to be plenty enough efficient for a case where the user selects documents to be deleted. If you find out that this is not the case, share the code that reproduces the performance problem.

Answer 2

FirebaseFirestore db = FirebaseFirestore.getInstance();

WriteBatch writeBatch = db.batch();

for (int i=0;i<cartList.size();i++){
    DocumentReference documentReference = db.collection("Users").document(cartList.get(i).getProductId());
    writeBatch.delete(documentReference);
}

writeBatch.commit().addOnSuccessListener(new OnSuccessListener<Void>() {
    @Override
    public void onSuccess(Void aVoid) {
        // Do anything here
    }
});

Answer 3

As this is the first result when you search for "how to delete multiple documents on Firestore", I wanted to share a working code snippet that not only does what OP is asking, but also splits your batches into chunks to avoid reaching the limit of 500 commits per batch.

const deleteEmptyMessages = async () => {
  
  const snapshot = await firestore.collection('messages').where('text', '==', '').get();
  const MAX_WRITES_PER_BATCH = 500; /** https://cloud.google.com/firestore/quotas#writes_and_transactions */

  /**
   * `chunk` function splits the array into chunks up to the provided length.
   * You can get it from either:
   * - [Underscore.js](https://underscorejs.org/#chunk)
   * - [lodash](https://lodash.com/docs/4.17.15#chunk)
   * - Or one of [these answers](https://stackoverflow.com/questions/8495687/split-array-into-chunks#comment84212474_8495740)
   */
  const batches = chunk(snapshot.docs, MAX_WRITES_PER_BATCH);
  const commitBatchPromises = [];

  batches.forEach(batch => {
    const writeBatch = firestore.batch();
    batch.forEach(doc => writeBatch.delete(doc.ref));
    commitBatchPromises.push(writeBatch.commit());
  });

  await Promise.all(commitBatchPromises);
};