MongoDB-$unwind-如何在$group聚合中展开多个数组

（1） 我已将以下内容添加到集合中：

{ "_id" : 1, "hitsPerOneSecond" : [ 2, 3, 5, 4, 1, 2, 3, 4, 1, 2 ], "startTime" :    ISODate("2012-04-07T10:41:33.380Z"), "returnCodeHits" : { "300" : 5, "200" : 12 }, "xxxServer" : "xxx:8100", "statsSummarizedToSeconds" : 10, "pathStats_xxx_api_get_version" : [ 0.2280779683225852, 0.030849283020361273, 0.9947690473370484 ], "pathStats_xxx_api_get_response" : [ 1.2163705612407407, 1.0602539963494662, 1.4853219936411421 ], "type" : "xxxType", "startTimeStr" : "07-04-2012:10AM" }

{ "_id" : 2, "hitsPerOneSecond" : [ 2, 3, 5, 4, 1, 2, 3, 4, 1, 2 ], "startTime" : ISODate("2012-04-07T10:41:43.380Z"), "returnCodeHits" : { "300" : 5, "200" : 12 }, "xxxServer" : "xxx:8100", "statsSummarizedToSeconds" : 10, "pathStats_xxx_api_get_version" : [ 0.2280779683225852, 0.030849283020361273, 0.9947690473370484 ], "pathStats_xxx_api_get_response" : [ 1.2163705612407407, 1.0602539963494662, 1.4853219936411421 ], "type" : "xxxType", "startTimeStr" : "07-04-2012:10AM" }

（2） 执行以下聚合时：

db.newStats.aggregate({$unwind: "$hitsPerOneSecond"},{$group:{_id:"$startTimeStr", totalHits: {$sum: "$hitsPerOneSecond"}, totalHitsCount: {$sum: 1}, avgHit: {$avg: "$hitsPerOneSecond"}, minHit: {$min:"$hitsPerOneSecond"}, maxHit:{$max: "$hitsPerOneSecond"}}});

（3） 结果正确无误：

{
"result" : [
    {
        "_id" : "07-04-2012:10AM",
        "totalHits" : 54,
        "totalHitsCount" : 20,
        "avgHit" : 2.7,
        "minHit" : 1,
        "maxHit" : 5
    }
],
"ok" : 1

}

（4） 但是，我需要在上面相同的聚合中对“pathStats\u xxx\u api\u get\u response”（来自集合）执行展开，以便在上面相同的结果中有totalResponses、TotalResponseCount、avgResponse、minResponse和maxResponse输出。因此，我的结果应该是这样的：

{
"result" : [
    {
        "_id" : "07-04-2012:10AM",
        "totalHits" : 54,
        "totalHitsCount" : 20,
        "avgHit" : 2.7,
        "minHit" : 1,
        "maxHit" : 5,
                    "totalResponses" : ??
                    "totalResponsesCount": ??
        "avgResponse" : 2.7,
        "minResponse" : 1,
        "maxResponse" : 5
    }
],
"ok" : 1

}

---

不知道如何在相同的聚合中添加更多的$unwind，因为我几乎就要做到了

最简单的解决方案可能是使用两个单独的聚合操作，并在应用程序中组合结果

或者，您可以通过Map Reduce操作执行此操作：

以下map和reduce函数应提供您要查找的结果：

var map = function() {
  var totalHits = this.hitsPerOneSecond.map(function(a,b){return a+b;});
  var totalHitsCount = this.hitsPerOneSecond.length;
  var avgHit = totalHits / totalHitsCount;
  var minHit = Math.min.apply(Math, this.hitsPerOneSecond);
  var maxHit = Math.max.apply(Math, this.hitsPerOneSecond);
  var totalResponses = pathStats_xxx_api_get_response.map(function(a,b){return a+b;});
  var totalResponsesCount = this.pathStats_xxx_api_get_response.length;
  var avgResponse = totalResponses / totalResponsesCount;
  var minResponse = Math.min.apply(Math, this.pathStats_xxx_api_get_response);
  var maxResponse = Math.max.apply(Math, this.pathStats_xxx_api_get_response);
  emit(this.startTimeStr, {
    "totalHits": totalHits,
    "totalHitsCount": totalHitsCount,
    "avgHit": avgHit,
    "minHit": minHit,
    "maxHit": maxHit,
    "totalResponses": totalResponses,
    "totalResponsesCount": totalResponsesCount,
    "avgResponse": avgResponse,
    "maxResponse": maxResponse,
    "minResponse": minResponse
  })
}

var reduce = function(key, values) {
  var output = {
    "totalHits": 0,
    "totalHitsCount": 0,
    "avgHit": 0,
    "minHit": null,
    "maxHit": null,
    "totalResponses": 0,
    "totalResponsesCount": 0,
    "avgResponse": 0,
    "maxResponse": null,
    "minResponse": null
  };
  values.forEach(function(v) {
    output.totalHits += v.totalHits;
    output.totalHitsCount += v.totalHitsCount;
    output.avgHit = output.totalHits / output.totalHitsCount;
    if (output.minHit == null) {
      output.minHit = v.minHit;
    } else {
      if (v.minHit < output.minHit) {
        output.minHit = v.minHit
      }
    }
    if (output.maxHit == null) {
      output.maxHit = v.maxHit;
    } else {
      if (v.maxHit > output.maxHit) {
        output.maxHit = v.maxHit
      }
    }

    output.totalResponses += v.totalResponses;
    output.totalResponsesCount += v.totalResponsesCount;
    output.avgResponse = output.totalResponses / output.totalResponsesCount;
    if (output.minResponse == null) {
      output.minResponse = v.minResponse;
    } else {
      if (v.minResponse < output.minResponse) {
        output.minResponse = v.minResponse
      }
    }
    if (output.maxResponse == null) {
      output.maxResponse = v.maxResponse;
    } else {
      if (v.maxResponse > output.maxResponse) {
        output.maxResponse = v.maxResponse
      }
    }
  });
  return output;
}

> db.newStats.mapReduce(map, reduce, {out:{inline:1}})
{
    "results" : [
        {
            "_id" : "07-04-2012:10AM",
            "value" : {
                "totalHits" : 54,
                "totalHitsCount" : 20,
                "avgHit" : 2.7,
                "minHit" : 1,
                "maxHit" : 5,
                "totalResponses" : 7.523893102462698,
                "totalResponsesCount" : 6,
                "avgResponse" : 1.253982183743783,
                "maxResponse" : 1.4853219936411421,
                "minResponse" : 1.0602539963494662
            }
        }
    ],
    "timeMillis" : 0,
    "counts" : {
        "input" : 2,
        "emit" : 2,
        "reduce" : 1,
        "output" : 1
    },
    "ok" : 1,
}
> 

---

如何

$unwind

多个阵列？您是否多次尝试过

$unwinding

请记住，聚合框架将数组作为输入（请注意，我添加了

[

，

]

）。在数组中，您可以向管道添加任意数量的聚合函数（需要引用），任何步骤的输出都将是下一步的输入

注意：

---

不要忘记，如果您试图在一个不存在的键或一个空数组上

$unwind

，您最终将没有任何文档！这就像乘以

0

我猜。。。因此，对于多个（可能多个）

$unwind

，处理重影的机会会增加：如果所涉及的任何数组为空，则整个文档将丢失，而您的任何

$group

聚合都将一无所获……

这是一个极好的示例。非常感谢。此外，链接到文件是非常感谢。在聚合方面-目标是通过仪表板和pymongo聚合动态统计数据，但我认为map/reduce和使用$group聚合可能仍然相对缓慢？我希望从一个python脚本中聚合60080（相当于1周）的10秒数据统计数据，该脚本已经从apache日志文件中将其整理为10秒统计数据。很高兴提供帮助！我更新了我的答案，并在地图上做了一些注释。不过这是一个重要的问题。。您将如何通过pymongo执行db.newStats.aggregate（{$unwind:$hitsPerOneSecond“}..etc，因为我找不到任何相关文档？我已附加了我的答案以包括pymongo示例。啊哈，对了，newStats是集合的名称。我将其添加为“聚合”：“startTimeStr”想知道.司令部怎么知道我说的是哪一个收藏！干杯。

In [1]: import pymongo

In [2]: conn = pymongo.Connection()

In [3]: db = conn.test

In [4]: result = db.command({"aggregate":"newStats", "pipeline":
                            [{"$unwind": "$hitsPerOneSecond"},
                             {"$group": {"_id":"$startTimeStr", 
                                          "totalHits": {"$sum": 
                                          "$hitsPerOneSecond"}, 
                              "totalHitsCount": {"$sum": 1}, 
                              "avgHit": {"$avg": "$hitsPerOneSecond"}, 
                              "minHit": {"$min":"$hitsPerOneSecond"}, 
                              "maxHit":{"$max": "$hitsPerOneSecond"}}}]})

In [5]: result
Out[5]: 
{u'ok': 1.0,
 u'result': [{u'_id': u'07-04-2012:10AM',
   u'avgHit': 2.7,
   u'maxHit': 5.0,
   u'minHit': 1.0,
   u'totalHits': 54.0,
   u'totalHitsCount': 20}]}

db.newStats.aggregate([
    {$unwind: "$hitsPerOneSecond"},
    {$unwind: "$pathStats_xxx_api_get_response"},

    {$group:{
        _id:"$startTimeStr", 
        totalHits: {$sum: "$hitsPerOneSecond"}, 
        totalHitsCount: {$sum: 1}, 
        avgHit: {$avg: "$hitsPerOneSecond"}, 
        minHit: {$min:"$hitsPerOneSecond"}, 
        maxHit:{$max: "$hitsPerOneSecond"},

        totalResponses: {$sum: "$pathStats_xxx_api_get_response"},
        . . .
     }}
]);