It’s possible I’m not understanding proper use of firestore sdk set() method. My understanding is that if a document id does not exist it will perform a “create”. If it does it will perform an “update” to the existing document and overwrite unless merge=True is included. That’s not what I’m seeing however.

I have the following firestore db structure:

Investment (collection)
  News (subcollection)

These are my current rules:

rules_version = '2';
service cloud.firestore {
  
  function isUpdateToActivityField() {
    return request.resource.data.diff(resource.data).affectedKeys().hasOnly(['activity']);
  }

  match /databases/{database}/documents {
    match /Investment/{iid} {
      allow read: if request.auth != null;
      allow update: if request.auth != null && isUpdateToActivityField();
      allow create: if request.auth != null;
      
      match /News/{nid} {
        allow read: if request.auth != null;
        allow create: if request.auth != null;
      }
    }
  }
}

If I manually modify fields in news items and then perform an update it will overwrite my records reverting the text.

This is how I’m using the set() method.

        product_ref = client.collection("Investment").document(self.symbol)
        batch = client.batch()
        for n in news:
            ndict = n.to_dict()
            new_news_ref = product_ref.collection("News").document(ndict.pop("uuid"))
            batch.set(new_news_ref, ndict, merge=True)
        batch.commit()

My goal is just to have the rules prevent a create or update if the record is already there without having to check in code. I’ve even tried changing the create rule to:

allow create: if request.auth != null && !exists(/databases/$(database)/documents/Investment/$(iid)/News/$(nid))

No luck however.

Am I going about this incorrectly?