如果我在其中使用变量，则实时数据库endAt方法不起作用

Question

"Posts" : {
"-MnLFAlhayTv80FxzUfL" : {
  "description" : "",
  "picture" : "",
  "postKey" : "-M",
  "timeStamp" : 1635682139495,
  "title" : "",
  "userId" : "",
  "userPhoto" : ""
},
"-MnLFzItc050Sn0EtDho" : {
  "description" : "",
  "picture" : "",
  "postKey" : "-M",
  "timeStamp" : 1635682350531,
  "title" : "",
  "userId" : "b",
  "userPhoto" : ""
},

这是我的数据结构。我将使用orderbyChild（timeStamp）.endat（）方法创建一个删除旧帖子的代码，当我只试验长变量如1635682350531 this->>orderbyChild（timeStamp）.endat(1635682350531L)时；当我把l加到1635682350531时，它就可以工作了

if (UId.equals("k")) {
        long tlong = System.currentTimeMillis(); long ttime;
        ttime = tlong - 3*24*60*60*1000;
        StorageReference picRef = FirebaseStorage.getInstance().getReferenceFromUrl(postImage);
        showMessage(String.valueOf(ttime));
        picRef.delete()
                .addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        //image deleted, now delete database
                        DatabaseReference db = FirebaseDatabase.getInstance().getReference();
                        Query queryByTimestamp = db.child("Posts").orderByChild("timeStamp").endAt(ttime);
                        queryByTimestamp.get().addOnCompleteListener(new OnCompleteListener<DataSnapshot>() {
                            @Override
                            public void onComplete(@NonNull Task<DataSnapshot> task) {
                                if (task.isSuccessful()) {
                                    for (DataSnapshot ds : task.getResult().getChildren()) {
                                        ds.getRef().removeValue();
                                        Toast.makeText(PostDetailActivity.this,"게시글이 삭제되었습니다.",Toast.LENGTH_SHORT).show();
                                    }
                                } else {
                                    Log.d("TAG", task.getException().getMessage());
                                    Toast.makeText(PostDetailActivity.this,"게시글이 삭제되지않았습니다.",Toast.LENGTH_SHORT).show();

                                }
                            }
                        });


                    }
                })
                .addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        //failed, can't go further
                        Toast.makeText(PostDetailActivity.this, "" + e.getMessage(), Toast.LENGTH_SHORT).show();
                    }
                });
    }

Answer 1

使用以下查询时：

Query queryByTimestamp = db.child("Posts").orderByChild("timeStamp").endAt(ttime);

需要索引。因此最有可能的是以下log语句：

Log.d("TAG", task.getException().getMessage());

生成以下错误消息：

{
  "rules": {
    "Posts": {
      ".indexOn": "timeStamp",
      ".read": true,
      ".write": true
    }    
  }
}

为了让它起作用。设置此索引后，查询将返回预期结果和以下代码行：

ds.getRef().removeValue();

将从数据库中删除两个子级。