As you can see in the image, whenever I try to update(not replace) a field with a new value, it duplicates the data, and adds up on top of the duplicate. What is causing this issue?

Whenever a user posts, I need to add the post id to an existing array of post ids.

hierarchy:

users - collection - document(emblem(String), photo(String), postIds(String[])...)

mDb = FirebaseFirestore.getInstance();

        // remove old ids
        Map<String, Object> oldIds = new HashMap<>();
        oldIds.put("posts", _oldPostList);

        // add new ids
        Map<String, Object> newIds = new HashMap<>();
        _oldPostList.add(_newValue);
        newIds.put("posts", _oldPostList);

        String docId = FirebaseAuth.getInstance().getCurrentUser().getEmail();

        DocumentReference docRef = mDb.collection("users").document(docId);

        docRef.update("posts", FieldValue.arrayRemove(oldIds)).addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void unused) {
                docRef.update("posts", FieldValue.arrayUnion(newIds)).addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void unused) {
                        sendBroadcast(_context, _action, true, null);
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        sendBroadcast(_context, _action, false, null);
                    }
                });
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                sendBroadcast(_context, _action, false, null);
            }
        });

CodePudding user response：