视图中CouchDB的链接文档 [英] CouchDB's Linked Documents in a View

问题描述

我很难理解CouchDB的链接文档功能。

I'm having a hard time getting my head around CouchDB's linked documents feature.

我有两种类型数据存储在单个CouchDB数据库中：

I have two types of data being stored in a single CouchDB database:

{
  "id":"1",
  "type": "track",
  "title": "Bohemian Rhapsody"
}

{
  "id":"2",
  "type": "artist",
  "name": "Queen",
  "tracks": ["1"]
}

我的印象是，我可以像下面这样写一个视图，并发出以下文档：

I'm under the impression that I can write a view like the one below and get the following documents emited:

{
  "id":"2",
  "type": "artist",
  "name": "Queen",
  "tracks": [
    {
      "id":"1",
      "type": "track",
      "title": "Bohemian Rhapsody"
    }
  ]
}

我一直在尝试这种视图，但是它没有按照我期望的方式工作：

I've been trying this view, but it's not working the way I'm expecting:

function(doc) {
  if(doc.type == 'artist') {
    var tracks = [];
    for(var i = 0; i < doc.tracks.length; i++) {
      tracks.push({_id:doc.tracks[i]});
    }

    newdoc = eval(uneval(doc));
    newdoc.tracks = tracks;

    emit(doc._id,newdoc);
  }
}

此处为示例： http://jphastings.iriscouch.com/_utils/database.html?music/_design/test / _view / linked

这并没有返回我希望的-您有什么建议吗？谢谢

This isn't returning what I'd hope - do you have any suggestions? Thanks

推荐答案

好吧，我终于明白了您要做什么，是可以的。这就是方法。

Okay I finally understand what you are trying to do.Yes this is possible.Here is how.

您有2个文档

{
"_id":"anyvalue",
"type": "track",
"title": "Bohemian Rhapsody"
}

{
"_id":"2",
"type": "artist",
"name": "Queen",
"tracks": ["anyvalue"]
}

您做错了的是没有在音轨值（数组中的项）周围加引号。

What you were doing wrong was not having quotes around the value of tracks(the item in the array).

2）引用ID必须是_id才能起作用。区别是值得注意的，因为您可以具有id字段，但仅使用_id来标识文档。

2)The reference id must be _id for this to work.The difference is worth noting since you can have id field but only _id are used to identify documents.

对于结果，您希望此视图足够

For the result you want this view would suffice

function(doc) {
    if (doc.type === 'artist') {
        for (var i in doc.tracks) {
            var id = doc.tracks[i];
            emit(id, { _id: id });
        }
    }
}

您想做什么是在for循环内使用emit函数来发出每个艺术家的曲目的id字段。

What you want to be doing is use an emit function inside the for loop to emit the id field of the 'track' of every artist.

然后，您要使用include_docs =查询长沙发db视图真正的参数。这是您在鸢尾花沙发上创建的数据库的最终结果。

Then you want to query couch db view with the include_docs=true parameter.Here is the final result for the database that you created on iris couch.

http://jphastings.iriscouch.com/music/_design/test/_view/nested?reduce=false&include_docs=true

 {
"total_rows": 3,
"offset": 0,
"rows": [
 {
  "id": "0b86008d8490abf0b7e4f15f0c6a50a7",
  "key": "0b86008d8490abf0b7e4f15f0c6a463b",
  "value": {
    "_id": "0b86008d8490abf0b7e4f15f0c6a463b"
  },
  "doc": {
    "_id": "0b86008d8490abf0b7e4f15f0c6a463b",
    "_rev": "3-7e4ba3bfedd29a07898125c09dd7262e",
    "type": "track",
    "title": "Boheniam Rhapsody"
  }
},
{
  "id": "0b86008d8490abf0b7e4f15f0c6a50a7",
  "key": "0b86008d8490abf0b7e4f15f0c6a5ae2",
  "value": {
    "_id": "0b86008d8490abf0b7e4f15f0c6a5ae2"
  },
  "doc": {
    "_id": "0b86008d8490abf0b7e4f15f0c6a5ae2",
    "_rev": "2-b3989dd37ef4d8ed58516835900b549e",
    "type": "track",
    "title": "Another one bites the dust"
  }
},
{
  "id": "0b86008d8490abf0b7e4f15f0c6a695e",
  "key": "0b86008d8490abf0b7e4f15f0c6a6353",
  "value": {
    "_id": "0b86008d8490abf0b7e4f15f0c6a6353"
  },
  "doc": {
    "_id": "0b86008d8490abf0b7e4f15f0c6a6353",
    "_rev": "2-0383f18c198b813943615d2bf59c212a",
    "type": "track",
    "title": "Stripper Vicar"
  }
 }
]
}

Jason在这篇文章中很好地解释了这一点

Jason explains it wonderfully in this post

做一对多的最佳方法 JOIN在CouchDB中

此链接对于沙发数据库中的实体关系也很有帮助

this link is also helpful for entity relationships in couch db

http://wiki.apache.org/couchdb/EntityRelationship

这篇关于视图中CouchDB的链接文档的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！