Question

I am writing a polling app with a Firebase backend. Users answer to yes/no questions and see results. They can t see who answered the question though, only their friends can.

questions
    question1:
        readable
           text: "Do you enjoy Stack Overflow?"
           yes_count: 76
           no_count: 14
        response:
            user1: yes
            user2: no
            ...
            user1000: no

users:
    user1:
        friends:
            user1
            user999

这样做的一个办法是在<条码>上打上<条码>。这可能导致下载数千个不必要的国际数据库。

另一种办法是要求服务器这样做。用户要求让朋友UIDs在座,而后台则进行过滤,并将结果放在用户能够聆听的地方。但这是一个巨大的额外负担,特别是考虑到只要对一个问题有新的答案,支持者必须检查每个用户是否由朋友回答。

我如何在<代码>response node上询问消防基地只让朋友UIDs,而不是每个人都知道?

如果无法做到这一点,用户是否最好进行过滤(和下载数千个不需要的电子数据),或者服务器进行过滤(额外负荷)?

Answer 1

This becomes trivial once you require that friendships are bi-directional, so also store the reverse relationship. E.g.

friends:
    user1:
        user42
        user999
    user42:
        user1
    user999:
        user1

With this bidirectional data structure, if a user posts you can simply load their friend list with /friends/$uid and loop over that. No expensive query needed.

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