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.

Solution 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.

Solution 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
    }
});

Solution 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);
};

Solution 4

I used batched writes for this. For example I deleted all documents, where the field "text" is empty:

const emptyMessages = await firestore.collection('messages').where("text", "==", "").get()
const batch = firestore.batch();
emptyMessages.forEach(doc => {
    batch.delete(doc.ref);
});
await batch.commit();

View more solutions

Comments

[Doug Stevenson]

How have you measured the efficiency?

[Michał Wolny]

Haven't measured yet, but isn't performing one query more efficient than performing many (e.g. 100) queries?

[Doug Stevenson]

A delete isn't a query. Until you have evidence to substantiate your claim, I don't think there's anything Stack Overflow can do for you. Don't make assumptions about how the client SDK works.

[Michał Wolny]

Maybe I put a wrong question. It should be: what's the best way to delete many (not all) documents from Cloud Firestore?

[Doug Stevenson]

The API you're given allows you to delete documents individually.

[Jay]

If you asked the wrong question or need to add additional info, please update your question as adding it in the comments may be overlooked.

[Michał Wolny]

Hi Frank, thanks for the answer, but I've optimized my code and deleting documents individually is sufficient.

[Paul Smith]

Deleting them in a batch allows you to implement error handling with a single handler though. It also makes easy to perform actions after all selected documents have been deleted.