我可以为每个数据库创建多个集合吗？ [英] Can I create multiple collections per database?

问题描述

从mongo切换到pouchdb（使用Cloudant），我喜欢每个用户一个数据库的概念，但是有没有办法为每个数据库创建多个集合/表？

Switching from mongo to pouchdb (with Cloudant), i like the "one database per user" concept, but is there a way to create multiple collections/tables per database ?

示例

- Peter  
        - History
        - Settings
        - Friends
- John
        - History
        - Settings
        - Friends

etc ...

推荐答案

Couchdb没有集合的概念。但是，将文档的类型标识符与Couchdb视图结合使用，可以达到类似的结果。

Couchdb does not have the concept of collections. However, you can achieve similar results using type identifiers on your documents in conjunction with Couchdb views.

类型标识符

将文档保存在Couchdb中时，添加一个用于指定类型的字段。例如，您将这样存储一个朋友：

When you save a document in Couchdb add a field that specifies the type. For example, you would store a friend like so:

{
  _id: "XXXX",
  type: "Friend",
  first_name: "John",
  ...
}

您将这样存储历史记录：

And you would store history like this:

{
  _id: "XXXX",
  type: "History",
  url: "http://www.google.com",
  ...
}

这两个文档都在同一个数据库中，如果您查询了该数据库中的所有文档，那么您将同时收到这两个文档。

Both of these documents would be in the same database, and if you queried all documents on that database then you would receive both.

视图

您可以创建按类型过滤的视图，然后直接查询这些视图。例如，创建一个视图来检索这样的朋友（在Cloudant中，您可以去添加新的设计文档，您可以直接复制并粘贴它）：

You can create views that filter on type and then query those views directly. For example, create a view to retrieve friends like so (in Cloudant you can go to add new Design Document and you can copy and paste this directly):

{
  "_id" : "_design/friends",
  "views" : {
    "all" : {
      "map" : "function(doc){ if (doc.type && doc.type == 'Friend') { emit(doc._id, doc._rev)}}"
    }
  }
}

让我们扩展地图功能：

function(doc) {
  if (doc.type && doc.type == "Friend") {
    emit(doc._id, doc._rev);
  }
}

基本上，此地图功能是说仅将文档关联到该视图具有== Friend类型。现在，我们可以查询此视图，并且只会返回朋友：

Essentially this map function is saying to only associate documents to this view that have type == "Friend". Now, we can query this view and only friends will be returned:

http://SERVER/DATABASE/_design/friends/_view/all

其中朋友 =名称设计文档和 all =视图名称。将 SERVER 替换为服务器，将 DATABASE 替换为数据库名称。

Where friends = name of the design document and all = name of the view. Replace SERVER with your server and DATABASE with your database name.

您可以在此处找到有关视图的更多信息：

You can find more information about views here:

https：/ /wiki.apache.org/couchdb/Introduction_to_CouchDB_views

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