从CouchDB中检索分层/嵌套数据

我对couchDB很新,甚至在读完 (latest archive as now deleted) http://wiki.apache.org/couchdb/How_to_store_hierarchical_data (via ‘Store the full path to each node as an attribute in that node’s document’)之后它仍然没有点击.

而不是使用维基中描述的完整路径模式,我希望将子项跟踪为UUID数组,父项作为单个UUID.我倾向于这种模式,所以我可以通过他们在儿童阵列中的位置维持孩子的顺序.

以下是沙发中的一些示例文档,存储桶可以包含存储桶和项目,项目只能包含其他项目. (UUID缩写为清晰)：

{_id: 3944
 name: "top level bucket with two items"
 type: "bucket",
 parent: null
 children: [8989, 4839]
}
{_id: 8989
 name: "second level item with no sub items"
 type: "item"
 parent: 3944
}
{
 _id: 4839
 name: "second level bucket with one item"
 type: "bucket",
 parent: 3944
 children: [5694]
}
{
 _id: 5694
 name: "third level item (has one sub item)"
 type: "item",
 parent: 4839,
 children: [5390]
}
{
 _id: 5390
 name: "fourth level item"
 type: "item"
 parent: 5694
}

是否可以通过map函数中的嵌入文档ID查找文档？

function(doc) {
    if(doc.type == "bucket" || doc.type == "item")
        emit(doc, null); // still working on my key value output structure
        if(doc.children) {
            for(var i in doc.children) {
                // can i look up a document here using ids from the children array?
                doc.children[i]; // psuedo code
                emit(); // the retrieved document would be emitted here
            }
        }
     }
}

在理想的世界中,最终的JSON输出看起来像.

{"_id":3944,
 "name":"top level bucket with two items",
 "type":"bucket",
 "parent":"",
 "children":[
     {"_id":8989, "name":"second level item with no sub items", "type":"item", "parent":3944},
     {"_id": 4839, "name":"second level bucket with one item", "type":"bucket", "parent":3944, "children":[
         {"_id":5694", "name":"third level item (has one sub item)", "type":"item", "parent": 4839, "children":[
             {"_id":5390, "name":"fourth level item", "type":"item", "parent":5694}
         ]}
     ]}
 ]
}

你可以找到一般的讨论 on the CouchDB wiki.

我现在没时间测试它,但是你的地图功能应该类似于：

function(doc) {
    if (doc.type === "bucket" || doc.type === "item")
        emit([ doc._id, -1 ], 1);
        if (doc.children) {
            for (var i = 0, child_id; child_id = doc.children[i]; ++i) {
                emit([ doc._id, i ], { _id: child_id });
            }
        }
    }
}

您应该使用include_docs = true查询它以获取文档,如CouchDB documentation中所述：如果您的map函数发出一个具有{‘_id’：XXX}的对象值,并且您使用include_docs = true参数查询视图,那么CouchDB将获取id为XXX的文档,而不是处理为发出键/值对的文档.

添加startkey = [“3944”]& endkey [“3944”,{}]以仅获取ID为“3944”及其子项的文档.

编辑：有关详细信息,请查看this question.