將行轉換爲MongoDB中的列

Question

相關問題是Efficiently convert rows to columns in sql server。但是答案是針對SQL的。

我想要相同的結果，即將行轉換爲列，而不在MongoDB中彙總任何內容（截至目前爲止）。

集合看起來如下所示。這是Facebook的頁面屬性統計：

 

timestamp | propName | propValue 
-------------------------------- 
1371798000000 | page_fans | 100 
-------------------------------- 
1371798000000 | page_posts | 50 
-------------------------------- 
1371798000000 | page_stories | 25 
-------------------------------- 

我需要回答如下：

 
timestamp | page_fans | page_posts | page_stories 
-------------------------------- 
1371798000000 | 100 | 50 | 25 
-------------------------------- 

的列名是預先確定的。他們不必動態生成。但問題是如何在MongoDB中實現這一點。

我認爲聚合對此目的沒有用處。我需要使用MapReduce嗎？但在這種情況下，我沒有什麼可以減少的我猜？那麼另一個選擇就是可以在代碼中獲取這些值並在編程語言中進行操作。 Java

任何見解都會有所幫助。提前致謝 ：）！！！

EDIT（基於輸入從Schaliasos）：

輸入JSON：

{ 
     "_id" : ObjectId("51cd366644aeac654ecf8f75"), 
     "name" : "page_storytellers", 
     "pageId" : "512f993a44ae78b14a9adb85", 
     "timestamp" : NumberLong("1371798000000"), 
     "value" : NumberLong(30871), 
     "provider" : "Facebook" 
} 
{ 
     "_id" : ObjectId("51cd366644aeac654ecf8f76"), 
     "name" : "page_fans", 
     "pageId" : "512f993a44ae78b14a9adb85", 
     "timestamp" : NumberLong("1371798000000"), 
     "value" : NumberLong(1291509), 
     "provider" : "Facebook" 
} 
{ 
     "_id" : ObjectId("51cd366644aeac654ecf8f77"), 
     "name" : "page_fan_adds", 
     "pageId" : "512f993a44ae78b14a9adb85", 
     "timestamp" : NumberLong("1371798000000"), 
     "value" : NumberLong(2829), 
     "provider" : "Facebook" 
} 

期望輸出JSON：

{ 
     "timestamp" : NumberLong("1371798000000"), 
     "provider" : "Facebook", 
     "page_storytellers" : NumberLong(30871), 
     "page_fans" : NumberLong("1371798000000"), 
     "page_fan_adds" : NumberLong("1371798000000") 
} 

Answer 1

我做了這樣的事情使用聚集。這可以幫助嗎？

db.foo.insert({ timestamp: '1371798000000', propName: 'page_fans', propValue: 100}) 
db.foo.insert({ timestamp: '1371798000000', propName: 'page_posts', propValue: 25}) 
db.foo.insert({ timestamp: '1371798000000', propName: 'page_stories', propValue: 50}) 

db.foo.aggregate({ $group: { _id: '$timestamp', result: { $push: { 'propName': '$propName', 'propValue': '$propValue' } }}}) 

{ 
    "result" : [ 
     { 
      "_id" : "1371798000000", 
      "result" : [ 
       { 
        "propName" : "page_fans", 
        "propValue" : 100 
       }, 
       { 
        "propName" : "page_posts", 
        "propValue" : 50 
       }, 
       { 
        "propName" : "page_stories", 
        "propValue" : 25 
       } 
      ] 
     } 
    ], 
    "ok" : 1 
} 

您可能希望使用$sum運算符。請參閱here

Answer 2

現在，您可以利用新彙總operator $arrayToObject來轉換MongoDB密鑰。該操作符在MongoDB v3.4中可用。4+

例如，給定的示例性數據：

db.foo.insert({ provider: "Facebook", timestamp: '1371798000000', name: 'page_storytellers', value: 20871}) 
db.foo.insert({ provider: "Facebook", timestamp: '1371798000000', name: 'page_fans', value: 1291509}) 
db.foo.insert({ provider: "Facebook", timestamp: '1371798000000', name: 'page_fan_adds', value: 2829}) 
db.foo.insert({ provider: "Google", timestamp: '1371798000000', name: 'page_fan_adds', value: 1000}) 

可以Aggregation Pipeline下面利用：

db.foo.aggregate([ 
    {$group: 
    {_id:{provider:"$provider", timestamp:"$timestamp"}, 
     items:{$addToSet:{name:"$name",value:"$value"}}} 
    }, 
    {$project: 
    {tmp:{$arrayToObject: 
     {$zip:{inputs:["$items.name", "$items.value"]}}}} 
    }, 
    {$addFields: 
    {"tmp.provider":"$_id.provider", 
     "tmp.timestamp":"$_id.timestamp"} 
    }, 
    {$replaceRoot:{newRoot:"$tmp"} 
    } 
]); 

輸出將是：

{ 
    "page_fan_adds": 1000, 
    "provider": "Google", 
    "timestamp": "1371798000000" 
}, 
{ 
    "page_fan_adds": 2829, 
    "page_fans": 1291509, 
    "page_storytellers": 20871, 
    "provider": "Facebook", 
    "timestamp": "1371798000000" 
} 

參見$group ， $project, $addFields， $zip， 和$replaceRoot

Answer 3

示例數據：

db.products.insertMany([ 
 
    { 
 
     "_id":"m1", 
 
     "model":"Model 1", 
 
     "size": "3.5", 
 
     "grade":"B", 
 
     "quantity":1.0 
 
    }, 
 
    { 
 
     "_id":"m2", 
 
     "model":"Model 1", 
 
     "size": "3.5", 
 
     "grade":"A", 
 
     "quantity":2.0 
 
    }, 
 
    { 
 
     "_id":"m3", 
 
     "model":"Model 2", 
 
     "size": "3.5", 
 
     "grade":"A", 
 
     "quantity":3.0 
 
    }, 
 
    { 
 
     "_id":"m4", 
 
     "model":"Model 2", 
 
     "size": "3.5", 
 
     "grade":"A", 
 
     "quantity":4.0 
 
    }, 
 
    { 
 
     "_id":"m5", 
 
     "model":"Model 2", 
 
     "size": "5.5", 
 
     "grade":"C", 
 
     "quantity":3.0 
 
    }, 
 
    { 
 
     "_id":"m6", 
 
     "model":"Model 3", 
 
     "size": "5.5", 
 
     "grade":"B", 
 
     "quantity":10.0 
 
    } 
 
])

查詢：

db.products.aggregate([ 
 
{ $group: { _id: { item: { model: "$model", grade: "$grade" } }, total: { $sum: "$quantity" } } }, 
 
{ $project: { _id: 0, grades: 1, item: "$_id.item", total: 1 } }, 
 
{ $group: { _id: { item: {model: "$item.model"} }, grades: { $addToSet: { name: "$item.grade", sum: "$total" } } } }, 
 
{ $project: { _id: 0, item: "$_id.item", grades: 1 } }, 
 
{ $sort : { item: 1 } }, 
 
]);

個

結果：

所有的

/* 1 */ 
 
{ 
 
    "grades" : [ 
 
     { 
 
      "name" : "A", 
 
      "sum" : 2.0 
 
     }, 
 
     { 
 
      "name" : "B", 
 
      "sum" : 1.0 
 
     } 
 
    ], 
 
    "item" : { 
 
     "model" : "Model 1" 
 
    } 
 
} 
 

 
/* 2 */ 
 
{ 
 
    "grades" : [ 
 
     { 
 
      "name" : "A", 
 
      "sum" : 7.0 
 
     }, 
 
     { 
 
      "name" : "C", 
 
      "sum" : 3.0 
 
     } 
 
    ], 
 
    "item" : { 
 
     "model" : "Model 2" 
 
    } 
 
} 
 

 
/* 3 */ 
 
{ 
 
    "grades" : [ 
 
     { 
 
      "name" : "B", 
 
      "sum" : 10.0 
 
     } 
 
    ], 
 
    "item" : { 
 
     "model" : "Model 3" 
 
    } 
 
}