java - 按时间和分数对帖子进行排序的 Firestore 查询

Question

我正在尝试使用以下代码按时间和业力对热门帖子进行排序:

FirebaseFirestore.getInstance().collection("topics")
    .orderBy("time", com.google.firebase.firestore.Query.Direction.DESCENDING)
    .whereGreaterThanOrEqualTo("time",(System.currentTimeMillis() % 1000)-1000*60*60*24*7)
    .orderBy("karma", com.google.firebase.firestore.Query.Direction.DESCENDING).startAfter(currentDoc).limit(10).get()
                .addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                    @Override
                    public void onSuccess(QuerySnapshot documentSnapshots) {
                        for (DocumentSnapshot d : documentSnapshots.getDocuments()){
                            Topic topic = new Topic();
                            topic.setId(d.getId());
                            topic.setUsername(d.getString("username"));
                            topic.setCaption(d.getString("caption"));
                            topic.setPic(d.getString("pic"));
                            topic.setTime(d.getLong("time"));
                            topic.setType(d.getString("type"));
                            topic.setImage(d.getString("image"));
                            topics.add(topic);
                            if (topics.size()==documentSnapshots.size()){
                                currentDoc = d;
                                adapter.updateList(topics);
                                loading.setVisibility(View.GONE);
                            }
                        }

                    }
                }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                e.printStackTrace();
            }
        });

我在 Firestore 中添加了索引。但它不起作用。

我的意思是它显示的是 7 天前的帖子。但它不是按业力排序的。它显示了按时间排序的 7 天前的帖子。如果我从查询中删除 orderBy("time")。它正在崩溃。

需要帮助:(

Answer 1

查询词的顺序很重要。要解决此问题，请像这样更改顺序:

FirebaseFirestore.getInstance().collection("topics")
    .orderBy("karma", com.google.firebase.firestore.Query.Direction.DESCENDING)
    .orderBy("time", com.google.firebase.firestore.Query.Direction.DESCENDING)
    .startAfter(currentDoc).limit(10).get().addOnSuccessListener(/* ... */);

只要您使用的是 index，它就可以工作.

如您所见，我已从查询中删除了以下代码行:

.whereGreaterThanOrEqualTo("time",(System.currentTimeMillis() % 1000)-1000*60*60*24*7)

因为根据关于 Order and limit data with Cloud Firestore 的官方文档你不能:

Range filter and first orderBy on different fields.

另一种方法是使用:

FirebaseFirestore.getInstance().collection("topics")
    .orderBy("time", com.google.firebase.firestore.Query.Direction.DESCENDING)
    .whereGreaterThanOrEqualTo("time",(System.currentTimeMillis() % 1000)-1000*60*60*24*7)
    .startAfter(currentDoc).limit(10).get().addOnSuccessListener(/* ... */);

如您所见，orderBy 和 whereGreaterThanOrEqualTo 都用于同一属性。