Firebase模拟WHERE IN [英] Firebase mimicing WHERE IN

问题描述

鉴于下面提供的日期模型，在用户登录并检索其数据之后，他们还可以获得其朋友的列表.

Given the date model provided below, after a user logs in and retrieves their data, they can also get a list of their friends.

但是，为了通过ID现在获得这两个朋友的详细信息 fdb17f3a-7b7d-4aa5-9a0b-b9fb33c349de 和 a96da7b1-7c4e-44bc-b82e-fc75bed52bcd ，目前，最有效的操作似乎只是通过以下方式循环访问网址:

However, in order to now attain details of those two friends by ids fdb17f3a-7b7d-4aa5-9a0b-b9fb33c349de and a96da7b1-7c4e-44bc-b82e-fc75bed52bcd, at present, the most efficiently operation appears to simply be to loop through the urls, in such a way as:

for singleFriendID in allFriendIds

    firebase.com/[my_db_name]/users/{singleFriendID} 

end

但这仍然有其主要局限性，例如，如果您要列出40个朋友的用户名列表，则现在需要对服务器进行40个单独的特定呼叫...

but even that has its major limitations, if say you want a list of usernames of your 40 friends, you now need 40 individual, specific calls, to the server...

如何有效地在Firebase中查找数据，而不是将所有朋友详细信息转储到他们的手机中?

How can I efficiently lookup data within Firebase instead of dumping all the friend details to their phone?

Firebase模式:

Firebase schema:

{  
   "users":{  
      "99e4989b-a046-4c5f-9478-5ebd8bdc3ded":{  
         "email":"[e-mail]",
         "friends":{  
            "fdb17f3a-7b7d-4aa5-9a0b-b9fb33c349de":{  
               "confirmed":true,
               "selfSendRequest":false,
               "timeInvited":"2016-02-21 08:49:31"
            },
            "a96da7b1-7c4e-44bc-b82e-fc75bed52bcd":{  
               "confirmed":true,
               "seldSendRequest":false,
               "timeInvited":"2016-02-21 08:49:31"
            }
         },
         "password":"aPassword",
         "phoneNumber":"16144444444",
         "username":"person2"
      }
      "a96da7b1-7c4e-44bc-b82e-fc75bed52bcd": {
      ...
      ...
   }
}

推荐答案

Loolooii的方法将节省调用次数，并且绝对是有效的方法.

Loolooii's approach will save on the number of calls and is definitely a valid approach.

但是您还假设对Firebase数据库的40次调用很多.如果您花一点时间对此进行衡量，您可能会感到惊讶.

But you're also making the assumption that 40 calls to the Firebase database is a lot. If you take a moment to measure this, you'll probably be surprised.

在传统数据库中，您需要为每个调用往返数据库.

In traditional databases, you do a roundtrip to the database for each call.

client                   server
    --- give me item 1 --->
                             loading
                             item 1
    <-- here is item 1 ----
    --- give me item 2 --->
                             loading
                             item 2
    <-- here is item 2 ----
    --- give me item 3 --->
                             loading
                             item 3
    <-- here is item 3 ----
    --- give me item 4 --->
                             loading
                             item 4
    <-- here is item 4 ----

Firebase用管道传输所有请求.因此，基本上，客户立即连续快速发送对所有项目的请求:

Firebase pipelines all the requests. So essentially the clients immediately send the requests for all items in quick succession:

client                   server
    --- give me item 1 --->
    --- give me item 2 --->
    --- give me item 3 --->
    --- give me item 4 --->
                             loading
                             item 1
                             loading
                             item 2
                             loading
                             item 3
                             loading
                             item 4
    <-- here is item 1 ----
    <-- here is item 2 ----
    <-- here is item 3 ----
    <-- here is item 4 ----

您会发现这要快得多，因为您只需要等待1次往返，再加上加载项目的时间.如果涉及到最后一点，请采用Loolooii的方法.

You'll find that this is much faster, since you're only waiting for 1 roundtrip, plus the time to load the items. If that last bit is concerning, take Loolooii's approach.

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