三重加入CouchDB？ [英] Triple join in CouchDB?

问题描述

我有三种类型的文档：

1. 问题


2. 用户-包含源字段


3. 答案-包含相应的问题ID和用户ID

每个问题均由多个答案回答用户和每个用户仅回答一次每个问题。我想为每个问题查找源 source1的用户回答了多少个答案。

Each questions is answered by multiple users and each user answers each question only once. I want to find for every question how many answers are there answered by users of source "source1".

推荐答案

我认为您可以使用以下方法（使用链接的文档）来获得所需的内容。

I think that the nearer that you can arrive to what you want is the following (using Linked documents).

假设您有

{ "_id": "user1", "source": "source1" },
{ "_id": "user2", "source": "source2" },
{ "_id": "answer1", "question": "question1", "user": "user1" },
{ "_id": "answer2", "question": "question1", "user": "user2" }

，然后定义以下视图

function(doc) {
  if (doc.question) {
    emit(doc.question, {_id: doc.user});
  }
}

然后，如果您使用key = question1 ，并使用include_docs = true
，它将向您显示问题1的所有答案以及所有用户信息，而您只需要选择那些带有source = source1的答案。

Then if you query that view with key="question1" and with include_docs=true it will show you all the answers to question1 with all the user information, and you will only have to select those with source = "source1".

例如，使用先前的值将返回：

For example, with the previous values it will return:

{"total_rows":2,"offset":0,"rows":[
{"id":"answer1","key":"question1","value":{"_id":"user1"},"doc":{"_id":"user1","_rev":"1-c99dc8987841c25c72081a84252793a0","source":"source1"}},
{"id":"answer2","key":"question1","value":{"_id":"user2"},"doc":{"_id":"user2","_rev":"1-0d44e9f4d3806fb932b1b4fcb1e1507b","source":"source2"}}
]}

但是AFAIK，您无法在视图的地图功能中使用其他文档中的信息。

But AFAIK, what you cannot do in the map function of a view is to use information from other documents.

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