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我正在使用 MongoDB 聚合框架来尝试从我们的数据集中收集一些总数。

以下是源数据的示例：

{
    "urn": "urn:content:epi:0001",
    "duration": 3450272,
    "profiles": {
         "low": {
             "mp3": {
                 "size": 8623059425,
                 "url": "0001_low.mp3"
             },
             "oga": {
                 "size": 8623059425,
                 "url": "0001_low.oga"
             },
             "m4a": {
                 "size": 8623059425,
                 "url": "0001_low.m4a"
             }
         },
         "medium": {
             "mp3": {
                 "size": 8623059425,
                 "url": "0001_medium.mp3"
             },
             "oga": {
                 "size": 8623059425,
                 "url": "0001_medium.oga"
             },
             "m4a": {
                 "size": 8623059425,
                 "url": "0001_medium.m4a"
             }
         },
         "high": {
             "mp3": {
                 "size": 8623059425,
                 "url": "0001_high.mp3"
             },
             "oga": {
                 "size": 8623059425,
                 "url": "0001_high.oga"
             },
             "m4a": {
                 "size": 8623059425,
                 "url": "0001_high.m4a"
             }
         }
    }
}

我想要做的是将每个单独的文档/项目分离profile.(low|medium|high).(mp3|oga|m4a)成一个单独的文档/项目以进行聚合，例如：

{
    "_id": null,
    "files": [
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_low.mp3"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_low.oga"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_low.m4a"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_medium.mp3"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_medium.oga"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_medium.m4a"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_high.mp3"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_high.oga"
        },
        {
            "urn": "urn:content:epi:0001",
            "duration": 3450272,
            "size": 8623059425,
            "url": "0001_high.m4a"
        }
    ]
}

使用聚合框架是否可以做到这一点，或者这在 MapReduce 上可以做到吗？

4

1 回答 1

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不，聚合框架的$unwind阶段是将单个集合文档转换为多个管道文档的唯一方法，并且$unwind仅适用于数组，而不是像您这样的子文档。

于 2013-05-30T19:06:36.443 回答