CouchDB:链接引用不同文档类型数组的文档

Question

对于CouchDB,我是新手.我来自.NET SQL Server世界.

在通过CouchDB浏览权威指南时,我觉得"这太棒了".现在我正在测试我学到的一些东西,希望在现实世界中实现它.

几周前我刚刚注册了Cloudant帐户,并开始使用它进行一些测试/学习.

在弄乱链接文档时,背后的整个理论看起来很简单,也是互联网上的海峡前沿例子.我想从具有不同链接文档数组的文档中检索某些信息,这些文档本身具有链接文档数组.就像连接到多对多关系表的多SQL Server一样.你会看到下面的代码.希望这是有道理的.

以此SQL查询为例.假设每个表中只有一个条目,我们应该返回一条记录,其中包含具有给定sku的鞋子的所有细节.但如果我们有多种鞋码,我们就不得不再写一些代码了.

select ci.sku
        ,sc.color
        ,ss.size
        ,si.url
from CatalogItem ci
    join ShoeImages si
        on ci.sku = si.sku
        and ci.sku = '656F-PINSEC12'
    join ShoeSizes ss
        on ci.sku = ss.sku
    join ShoeColors sc
        on ci.sku = sc.sku

我希望CouchDB通过SKU返回以下JSON,网址为https://username.cloudant.com/test/_design/catalogue/_view/item-details?include_docs=true&key=%22656F-PINSEC12%22

{
   "_id": "689fe6982f4d604541db67ee4050a535",
   "_rev": "5-64b5ddd751c51aadfcef1962c2c99c16",
   "type": "catalogue-item",
   "sku": "656F-PINSEC12",
   "upc": "8549875231",
   "shoe-colors": 
   [
        {
            "color": "black/houndstooth"
            "shoe-sizes": 
            [
                {
                    "size": 5,
                    "IsSizeAvailable": true
                },
                {
                    "size": 6,
                    "IsSizeAvailable": true
                },
                {
                    "size": 7,
                    "IsSizeAvailable": true
                },
                {
                    "size": 8,
                    "IsSizeAvailable": true
                },
                {
                    "size": 9,
                    "IsSizeAvailable": true
                },
                {
                    "size": 10,
                    "IsSizeAvailable": true
                },
                {
                    "size": 11,
                    "IsSizeAvailable": true
                },
                {
                    "size": 12,
                    "IsSizeAvailable": true
                },
                {
                    "size": 13,
                    "IsSizeAvailable": true
                },
                {
                    "size": 14,
                    "IsSizeAvailable": true
                }
            ],
            "shoe-images": 
            [
                {
                    "full-images": 
                    [
                        "http://www.someurl.com/full/656F-PINSEC12.jpg"
                    ],
                    "thumbnail-images": 
                    [
                        "http://www.someurl.com/thumb/656F-PINSEC12.jpg"
                    ]
                }
            ]
        }
    ]
}

给出以下文档和map/reduce:

//--catalog item
{
   "_id": "689fe6982f4d604541db67ee4050a535",
   "_rev": "5-64b5ddd751c51aadfcef1962c2c99c16",
   "type": "catalogue-item",
   "sku": "656F-PINSEC12",
   "upc": "8549875231",
   "shoe-colors": [
       {
           "_id": "bbbb92c3d61ed9f4f0e8111fb20fcf43",
           "shoe-images": [
               {
                   "_id": "7b547bae4ac911c6f05b97eba6cb355a"
               }
           ],
           "shoe-sizes": [
               {
                   "_id": "12b6289d558d7ceb5bef725091666ce5"
               }
           ]
       }
   ]
}

//--shoe images
{
   "_id": "7b547bae4ac911c6f05b97eba6cb355a",
   "_rev": "4-4fde0cac1b4b8afc618bbba5b6669193",
   "type": "shoe-images",
   "sku": "656F-PINSEC12",
   "color": "Black/Houndstoot",
   "full-images": [
       "http://www.someurl.com/full/656F-PINSEC12.jpg"
   ],
   "thumbnail-images": [
       "http://www.someurl.com/thumb/656F-PINSEC12.jpg"
   ]
}

//--shoe color
{
   "_id": "bbbb92c3d61ed9f4f0e8111fb20fcf43",
   "_rev": "2-e5d07c00a0261c231dd2be9b26a6c0dc",
   "type": "shoe-color",
   "sku": "656F-PINSEC12",
   "color": "black/houndstooth"
}

//--shoe sizes
{
   "_id": "12b6289d558d7ceb5bef725091666ce5",
   "_rev": "2-192df709f9de1ef27e9e5f4404863bcc",
   "type": "shoe-sizes",
   "sku": "656F-PINSEC12",
   "shoe-color": "black/houndstooth",
   "shoe-sizes": [
       {
           "size": 5,
           "IsSizeAvailable": true
       },
       {
           "size": 6,
           "IsSizeAvailable": true
       },
       {
           "size": 7,
           "IsSizeAvailable": true
       },
       {
           "size": 8,
           "IsSizeAvailable": true
       },
       {
           "size": 9,
           "IsSizeAvailable": true
       },
       {
           "size": 10,
           "IsSizeAvailable": true
       },
       {
           "size": 11,
           "IsSizeAvailable": true
       },
       {
           "size": 12,
           "IsSizeAvailable": true
       },
       {
           "size": 13,
           "IsSizeAvailable": true
       },
       {
           "size": 14,
           "IsSizeAvailable": true
       }
   ]
}

//--map/reduce
{
   "_id": "_design/catalog",
   "_rev": "4-de5baf04b485768de12d78e5a0e5aa5e",
   "views": {
       "item": {
           "map": "function(doc) 
                {
                  if (doc.type === 'catalog-item') 
                  {
                    emit([doc.sku, doc], null);
                    if (doc.shoe-colors) 
                    {
                      for (var sc in doc.shoe-colors) 
                      {
                        emit([doc.sku, Number(sc)+1], {_id: doc.shoe-colors[sc]._id});
                        for (var si in doc.shoe-colors[sc].shoe-images) 
                        {
                            emit([doc.sku, Number(si)+1], {_id: doc.shoe-colors[sc].shoe-images[si]._id});
                        }
                        for (var sz in doc.shoe-colors[sc].shoe-sizes) 
                        {
                            emit([doc.sku, Number(sz)+1], {_id: doc.shoe-colors[sc].shoe-sizes[sz]._id});
                        }
                      }
                    }
                  }
                }"
       }
   }
}

可能有更好的方法来实现这一点,但我想看看是否有可能拥有一个包含链接文档数组的文档,这些文档也包含一系列链接文档.但是我的map/reduce没有返回任何东西.它返回的全部是:

{"total_rows":0,"offset":0,"rows":[

]}

我猜测有人不会将所有信息存储在单个文档中,因为我们添加新的显示大小或将鞋号标记为不可用,这意味着必须将所有先前的值传递给CouchDB更新一个字段.

希望我的问题有道理Oo__oO

Answer 1

这方面的诀窍是远离JOIN的思考.链接文档为您提供了一种技术,可以根据另一种文档的属性对一种类型的文档进 这可以使用两个功能的组合:

1. CouchDB允许您在查询视图时指定include_docs = true以返回索引文档以及视图结果.
2. 您可以通过在视图结果中指定_id属性来告诉CouchDB返回任何文档.请注意,您仍然只能为每个结果返回一个文档.

举个例子,假设你有文件

{
     "_id": "111",
     "type", "shoe",
     "sku": "656F-PINSEC12",
     "shoe-color": "black/houndstooth",
     "imageId": "222"
}

和

{
     "_id": "222",
     "type": "image",
     "full-images": ["http://www.someurl.com/full/656F-PINSEC12.jpg"]
     "thumbnail-images": ["http://www.someurl.com/thumb/656F-PINSEC12.jpg"]
}

然后你可以使用map函数索引SKU的图像:

function(doc) {
     if(doc.type === "shoe") {
         emit(doc.sku, {_id: doc.imageId });
     }
}

同样重要的是要意识到map函数仅对保存的原始文档进行操作.

我认为在您的示例中,"目录项"和"鞋色"文档是多余的.你可以定义一个地图功能来索引SKU的"鞋子图像"和"鞋子尺寸"文件,例如

function(doc) {
    if(doc.SKU) {
        emit(doc.SKU, null);
    }
}

假设这被分配给视图"item-details",您的查询:

https://username.cloudant.com/test/_design/catalogue/_view/item-details?include_docs=true&key=%22656F-PINSEC12%22

应该回来

{
   "total_rows":2,
   "offset":0,
   "rows":
   [
       {
          "id":"7b547bae4ac911c6f05b97eba6cb355a",
          "key":"656F-PINSEC12",
          "value":null,
          "doc":{
             "_id": "7b547bae4ac911c6f05b97eba6cb355a",
             "_rev": "4-4fde0cac1b4b8afc618bbba5b6669193",
             "type": "shoe-images",
             "sku": "656F-PINSEC12",
             "color": "Black/Houndstoot",
             "full-images": [
                 "http://www.someurl.com/full/656F-PINSEC12.jpg"
             ],
             "thumbnail-images": [
                  "http://www.someurl.com/thumb/656F-PINSEC12.jpg"
             ]
          }
      },
      {
          "id":"12b6289d558d7ceb5bef725091666ce5",
          "key":"656F-PINSEC12",
          "value":null
          "doc":{
            "_id": "12b6289d558d7ceb5bef725091666ce5",
           "_rev": "2-192df709f9de1ef27e9e5f4404863bcc",
           "type": "shoe-sizes",
           "sku": "656F-PINSEC12",
           "shoe-color": "black/houndstooth",
           "shoe-sizes": [
               {
                   "size": 5,
                   "IsSizeAvailable": true
               },
               {
                   "size": 6,
                   "IsSizeAvailable": true
               },
               {
                   "size": 7,
                   "IsSizeAvailable": true
               },
               {
                   "size": 8,
                   "IsSizeAvailable": true
               },
               {
                   "size": 9,
                   "IsSizeAvailable": true
               },
               {
                   "size": 10,
                   "IsSizeAvailable": true
               },
               {
                   "size": 11,
                   "IsSizeAvailable": true
               },
               {
                   "size": 12,
                   "IsSizeAvailable": true
               },
               {
                   "size": 13,
                   "IsSizeAvailable": true
               },
               {
                   "size": 14,
                   "IsSizeAvailable": true
               }
           ]

        }       
    ] 
}

如果要将这些结果合并到单个JSON文档中,可以查看使用list函数生成自定义JSON输出.但是,我不确定这会让你受益匪浅.

看起来您通常会使用更精细的数据模型(例如,每个鞋子/尺寸组合可能是单独的文档),并使用地图函数来聚合给定SKU的数据.