mongodb count 导致不正确的数量（mongodb count 一个坑）

 public long getCount() {
                String user = "用户名";
                String database = "admin";
                String password = "密码";
                MongoCredential credential = MongoCredential.createCredential(user,database, password.toCharArray());
        
                MongoClientOptions options = MongoClientOptions.builder()
                        .connectionsPerHost(10)
                        .threadsAllowedToBlockForConnectionMultiplier(10)
                        .socketTimeout(20000)
                        .connectTimeout(15000)
                        .maxWaitTime(50000)
                        .build();
        
                MongoClient mongoClient = new MongoClient(new ServerAddress("IP地址", "端口"), Arrays.asList(credential), options);
        
                MongoDatabase mongoDatabase = mongoClient.getDatabase("数据库");
                MongoCollection<Document> collection = mongoDatabase.getCollection("数据表");
        
                final long[] count = new long[1];
                Block<Document> printBlock = new Block<Document>() {
                    @Override
                    public void apply(final Document document) {
                         count[0] = (long) document.get("count");
                    }
                };
                Bson bson = Filters.eq("categories", "Bakery");
                collection.aggregate(
                        Arrays.asList(
                                Aggregates.match(bson),
                                Aggregates.group(null, Accumulators.sum
                                        ("count", 1L))
                        )
                ).forEach(printBlock);
        
                return count[0];
}