从Firestore中选择随机文档

Question

例如:students是Firestore中的一个集合，我在该集合中有1000名学生，我的要求是在每次调用中随机选择10名学生。

Answer 1

根据Alex的回答，我得到了从Firebase Firestore数据库获取重复记录的提示（特别是对于少量数据）

我在他的问题中遇到了以下问题：

• 它给出的所有记录与随机数未更新时相同。
• 即使我们每次都更新randomnumber，最终列表中也可能有重复的记录。
• 它可能有我们已经显示的重复记录。

    FirebaseFirestore database = FirebaseFirestore.getInstance();
    CollectionReference collection = database.collection(VIDEO_PATH);
    collection.get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
        @Override
        public void onComplete(@NonNull Task<QuerySnapshot> task) {
            if (task.isSuccessful()) {
                List<VideoModel> videoModelList = new ArrayList<>();
                for (DocumentSnapshot document : Objects.requireNonNull(task.getResult())) {
                    VideoModel student = document.toObject(VideoModel.class);
                    videoModelList.add(student);
                }

                /* Get Size of Total Items */
                int size = videoModelList.size();
                /* Random Array List */
                ArrayList<VideoModel> randomVideoModels = new ArrayList<>();
                /* for-loop: It will loop all the data if you want 
                 * RANDOM + UNIQUE data.
                 * */
                for (int i = 0; i < size; i++) {
                    // Getting random number (inside loop just because every time we'll generate new number)
                    int randomNumber = new Random().nextInt(size);

                    VideoModel model = videoModelList.get(randomNumber);

                    // Check with current items whether its same or not
                    // It will helpful when you want to show related items excepting current item
                    if (!model.getTitle().equals(mTitle)) {
                        // Check whether current list is contains same item.
                        // May random number get similar again then its happens
                        if (!randomVideoModels.contains(model))
                            randomVideoModels.add(model);

                        // How many random items you want 
                        // I want 6 items so It will break loop if size will be 6.
                        if (randomVideoModels.size() == 6) break;
                    }
                }

                // Bind adapter
                if (randomVideoModels.size() > 0) {
                    adapter = new RelatedVideoAdapter(VideoPlayerActivity.this, randomVideoModels, VideoPlayerActivity.this);
                    binding.recyclerView.setAdapter(adapter);
                }
            } else {
                Log.d("TAG", "Error getting documents: ", task.getException());
            }
        }
    });