Couchdb 使用键连接两个文档

2022-01-13 00:00:00 join mapreduce couchdb javascript relational-algebra

我有两个文档，一个具有树结构，另一个与第一个文档相关.我试图通过 fk 和 pk 加入这两个文档.我无法得到实际结果，它显示所有空值.

I have two documents one with tree structure and the other one relation to the first doc. Im trying to join these two doc`s by fk and pk. I couldnt get the actual results and it displays all null values.

第一个文档

{
   "name": "one",
   "root": {
            "level1" : {
                       "level2" : {
                                 "level3" : {
                                           "itemone": "Randomkey1",
                                           "itemtwo": "Randomkey2
                                          }
                                }
                     }
         },
   "type": "firstdoc"
}

第二个文档

{
    "name"  : "two",
    "mapBy" : "Randomkey1",
    "type"  : "senconddoc
}

我编写了一个 map 函数，它列出了给定级别 1 或 2 或 3 的所有键.现在我想使用密钥加入第一个文档和第二个文档.我尝试了两种方法(第一种:我得到所有(Root，Randomkey)，(docName，Randomkey1)但它没有做任何加入.我正在寻找类似的结果(根，文档名)

I`ve written a map function, which lists all the keys given a level 1 or 2 or 3 . Now I want o join this first doc and second doc using the key. Ive tried two ways (first: Im getting all (Root, Randomkey), (docName, Randomkey1) but it doesnt do any join. Im looking for a result like (Root, docName)

有人可以帮忙解决这个问题

Could someone assist in fixing this

地图

function(doc) {
   if (doc.type === 'firstdoc' || doc.type === 'seconddoc' ) {
      var rootObj = doc.Root;
      for (var level1 in rootObj) {

         var level2Obj = doc.Root[level1];

         for (var level2 in level2Obj) {

           var keys = new Array();
            var level3Obj = level2Obj[level2];

            for (var i in level3Obj) {

                var itemObj = level3Obj[i];

                for (var i in itemObj) {
                    keys.push(itemObj[i]);

                    emit(doc.name, [itemObj[i], 0]);

                     var firstDocName = doc.name;

                    //This is gives null values
                    if (doc.Type === 'senconddoc' && doc.mapBy === itemObj[i]) {

                         emit(firstDocName , doc);
                    }
                }
            }



        }


    }
}

//This just lists keys to me
if (doc.type === 'senconddoc') {

    emit([doc.mapBy, 1] , doc);
}
}

推荐答案

要模拟连接，你必须输出一个带有 _id 的文档，_id 需要指向文档的实际 _id.然后你可以利用 include_docs=true 来拉取相关文档.这里的多对多示例:http://danielwertheim.se/couchdb-多对多关系/

To simulate joins you have to output a doc with an _id in it, the value of the _id needs to point to an actual _id of a document. Then you can make use of include_docs=true to pull in the related documents. Example with many-to-many here: http://danielwertheim.se/couchdb-many-to-many-relations/

如果这不适用，您可以通过首先返回自定义键来进行两步手动连接.然后对所有文档视图进行第二次查询，指定多个键.

If this is not applicable, you can make a two step manual join by first returning custom keys. Then make a second query against the all documents view, with multiple keys specified.

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