記一次mongodb聚合查詢

　　先說一下場景，產品中用到了簡單的表單構造器，開始提供了一系列的控件，例如單行文本框、多行文本框、單選、複選、時間等，以後你能夠拖拽控件本身組裝你想要的表單……網上有不少的表單構造器，這裏就不細說了，可能功能有多有少，可是原理相似。由於這種表單的這種實現方式，咱們不僅僅要存儲表單的真實數據，還要存儲對應表單的配置數據來渲染表單的樣子。這裏不細說配置相關的事情，細說一下表單數據的存儲和查詢。

　　對於一條記錄有不少共有屬性：主鍵ID、建立用戶ID、建立時間、表單ID（用於讀取表單配置）等一些業務數據，這裏着重說一下表單ID也就是下面演示中提到的TableCode,咱們這種存儲方式能夠將業務上的多種表都存儲在如今的一張表中，因此必需要一個字段來區分這條記錄存儲的具體是什麼信息，以方便在查詢時找到具體的數據；還有一些就是具體的表單項了。咱們採用的是Mongodb存儲，不用想確定是複雜結構了，數組或者鍵值對對象……也不知道什麼緣由了，咱們採用的是數組，這裏記做FormItems，FormItems列中存儲着全部的表單項，具體的看一下數據庫的存儲結構：

{
    "_id" : "1",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-02-07",
    "FormItems" : [ 
        {
            "key" : "CarBrand",
            "value" : "紅旗"
        }, 
        {
            "key" : "VehicleType",
            "value" : "H7"
        }, 
        {
            "key" : "CarNum",
            "value" : "京A00001"
        }, 
        {
            "key" : "PurchaseDate",
            "value" : "2019-01-01"
        }
    ],
    "TableCode" : "CarInfo" 
}

　　上面看到是一個縮減版的結構（爲了方便演示），簡單的介紹一下：TableCode-表單名稱，FormItems數組中存儲着全部的表單項，key原本是惟一值，這裏僅僅爲了演示因此如此，value就是具體的表單項的值了。查詢演示用到了三張表，第一張表如上，車輛信息表：車牌子、車型、牌照、購買日期等；車輛維修表：車輛ID、花費、內容；出車記錄表：車輛ID、收入、里程、備註。首先插入一些數據：

try{
    db.t1.insertMany([{
        "_id": "1",
        "CreateUserName": "ddz1",
        "CreateDate": "2018-02-07",
        "FormItems": [{
            "key": "CarBrand",
            "value": "紅旗"
        },
        {
            "key": "VehicleType",
            "value": "H7"
        },
        {
            "key": "CarNum",
            "value": "京A00001"
        },
        {
            "key": "PurchaseDate",
            "value": "2019-01-01"
        }],
        "TableCode": "CarInfo"
    },{
        "_id": "2",
        "CreateUserName": "ddz1",
        "CreateDate": "2018-02-08",
        "FormItems": [{
            "key": "CarBrand",
            "value": "紅旗"
        },
        {
            "key": "VehicleType",
            "value": "H5"
        },
        {
            "key": "CarNum",
            "value": "京A00002"
        },
        {
            "key": "PurchaseDate",
            "value": "2019-02-01"
        }],
        "TableCode": "CarInfo"
    },{
        "_id": "3",
        "CreateUserName": "ddz1",
        "CreateDate": "2018-02-09",
        "FormItems": [{
            "key": "CarBrand",
            "value": "紅旗"
        },
        {
            "key": "VehicleType",
            "value": "L5"
        },
        {
            "key": "CarNum",
            "value": "京A00003"
        },
        {
            "key": "PurchaseDate",
            "value": "2019-03-01"
        }],
        "TableCode": "CarInfo"
    },
    {
        "_id": "4",
        "CreateUserName": "ddz1",
        "CreateDate": "2018-02-10",
        "FormItems": [{
            "key": "CarBrand",
            "value": "長城"
        },
        {
            "key": "VehicleType",
            "value": "哈弗H6"
        },
        {
            "key": "CarNum",
            "value": "京A00004"
        },
        {
            "key": "PurchaseDate",
            "value": "2018-03-01"
        }],
        "TableCode": "CarInfo"
    },{
        "_id": "5",
        "CreateUserName": "ddz1",
        "CreateDate": "2018-02-09",
        "FormItems": [{
            "key": "CarBrand",
            "value": "長城"
        },
        {
            "key": "VehicleType",
            "value": "哈弗H5"
        },
        {
            "key": "CarNum",
            "value": "京A00005"
        },
        {
            "key": "PurchaseDate",
            "value": "2018-03-01"
        }],
        "TableCode": "CarInfo"
    },{
        "_id": "6",
        "CreateUserName": "ddz1",
        "CreateDate": "2018-03-09",
        "FormItems": [{
            "key": "CarBrand",
            "value": "長城"
        },
        {
            "key": "VehicleType",
            "value": "哈弗H4"
        },
        {
            "key": "CarNum",
            "value": "京A00006"
        },
        {
            "key": "PurchaseDate",
            "value": "2018-03-01"
        }],
        "TableCode": "CarInfo"
    },{
        "_id": "7",
        "CreateUserName": "ddz100",
        "CreateDate": "2018-06-06",
        "FormItems": [{
            "key": "CarId",
            "value": "1"
        },
        {
            "key": "Cost",
            "value": 100
        },
        {
            "key": "Contents",
            "value": "噴漆"
        }],
        "TableCode": "MaintenanceRecord"
    },{
        "_id": "8",
        "CreateUserName": "ddz100",
        "CreateDate": "2018-08-06",
        "FormItems": [{
            "key": "CarId",
            "value": "1"
        },
        {
            "key": "Cost",
            "value": 25
        },
        {
            "key": "Contents",
            "value": "洗車"
        }],
        "TableCode": "MaintenanceRecord"
    },{
        "_id": "9",
        "CreateUserName": "ddz101",
        "CreateDate": "2018-06-03",
        "FormItems": [{
            "key": "CarId",
            "value": "2"
        },
        {
            "key": "Cost",
            "value": 1560
        },
        {
            "key": "Contents",
            "value": "換輪胎"
        }],
        "TableCode": "MaintenanceRecord"
    },{
        "_id": "10",
        "CreateUserName": "ddz102",
        "CreateDate": "2018-06-26",
        "FormItems": [{
            "key": "CarId",
            "value": "3"
        },
        {
            "key": "Cost",
            "value": 36
        },
        {
            "key": "Contents",
            "value": "爆胎"
        }],
        "TableCode": "MaintenanceRecord"
    },{
        "_id": "11",
        "CreateUserName": "ddz103",
        "CreateDate": "2018-09-08",
        "FormItems": [{
            "key": "CarId",
            "value": "3"
        },
        {
            "key": "Cost",
            "value": 1630
        },
        {
            "key": "Contents",
            "value": "換加速器"
        }],
        "TableCode": "MaintenanceRecord"
    },{
        "_id": "12",
        "CreateUserName": "ddz10",
        "CreateDate": "2018-06-06",
        "FormItems": [{
            "key": "CarId",
            "value": "1"
        },
        {
            "key": "Income",
            "value": 106
        },
        {
            "key": "Mileage",
            "value": 50
        },
        {
            "key": "Remarks",
            "value": "123"
        }],
        "TableCode": "DispatchRecord"
    },{
        "_id": "13",
        "CreateUserName": "ddz11",
        "CreateDate": "2018-06-16",
        "FormItems": [{
            "key": "CarId",
            "value": "1"
        },
        {
            "key": "Income",
            "value": 250
        },
        {
            "key": "Mileage",
            "value": 100
        },
        {
            "key": "Remarks",
            "value": "123"
        }],
        "TableCode": "DispatchRecord"
    },{
        "_id": "14",
        "CreateUserName": "ddz12",
        "CreateDate": "2018-06-16",
        "FormItems": [{
            "key": "CarId",
            "value": "2"
        },
        {
            "key": "Income",
            "value": 1000
        },
        {
            "key": "Mileage",
            "value": 630
        },
        {
            "key": "Remarks",
            "value": "2345sfgfg"
        }],
        "TableCode": "DispatchRecord"
    },{
        "_id": "15",
        "CreateUserName": "ddz12",
        "CreateDate": "2018-08-16",
        "FormItems": [{
            "key": "CarId",
            "value": "3"
        },
        {
            "key": "Income",
            "value": 1213
        },
        {
            "key": "Mileage",
            "value": 569
        },
        {
            "key": "Remarks",
            "value": "12asdfasdfasdf3"
        }],
        "TableCode": "DispatchRecord"
    }]);
}catch(e){
    print(e);
}

View Code

　　這種存儲方式有必定的好處，可是弊端也很明顯：查詢、排序等很費勁，若是服務器端以這樣的方式返回客戶端，客戶端還得解析FormItems，很是不友好（感受本身在給本身找麻煩）……因此我就想看看能不能在全部的查詢操做以前，首先處理一下數據，將FormItems中的表單項都提到文檔的最外層和公共字段一個層次，以後在進行查詢排序彷佛就簡單點了，爲了實現這個目標真是廢了九牛二虎之力，道路至關坎坷，經歷的時間也很長，不過最終好在找到一個例子解決了咱們的問題：https://jira.mongodb.org/browse/SERVER-5947 。在此表示感謝，很是感謝……在這以後又遇到了一個問題就是：在關聯查詢時mongodb的處理方式是將全部的相關聯的數據存儲在一個屬性中，由於咱們全部的「表」都存在這一個表中，因此關聯的也是這一張表，也就是關聯本身查詢，結果獲得關聯的數據仍是沒有處理以前的樣子，相同的數據最後的結構都不同，都很差意思返回客戶端，這個問題比以前的問題更費勁……不知道度過了多少天，個人一個同事說弄出來了，我就有點……因此我也想嘗試一下，最後廢了半天勁兒終於弄出來，不知道和同事弄的同樣不同，這裏只能吐槽mongodb你怎麼能這樣……看一下代碼：

db.getCollection('t1').aggregate([
    {$addFields:
        {
            FormValueObj:{
                $arrayToObject:{
                    $map:
                     {
                       input: "$FormItems",
                       as: "field",
                       in: ["$$field.key","$$field.value"]
                     }
                }
            }
        }
    },
    {
        $addFields:{
            "FormValueObj._id":"$_id",
            "FormValueObj.CreateUserName":"$CreateUserName",
            "FormValueObj.CreateDate":"$CreateDate",
            "FormValueObj.TableCode":"$TableCode"
        }
    },
    {
        $replaceRoot: { newRoot: "$FormValueObj" }
    },
    {
        $lookup:{
           from: "t1",
           localField: "_id",
           foreignField: "FormItems.value",
           as: "RelationData1"
        }
    },
    {
        $addFields:{
            RelationData1:{
                 $map:
                 {
                    input: "$RelationData1",
                    as: "tr",
                    in: {
                        $arrayToObject:{
                            $map:
                             {
                               input:{ 
                                   $concatArrays: [ 
                                   [
                                        {key:"_id",value:"$$tr._id"},
                                        {key:"CreateUserName",value:"$$tr.CreateUserName"},
                                        {key:"CreateDate",value:"$$tr.CreateDate"},
                                        {key:"TableCode",value:"$$tr.TableCode"},
                                   ], 
                                   "$$tr.FormItems" ] 
                               },
                               as: "field",
                               in: ["$$field.key","$$field.value"]
                             }
                        }
                    }
                 }
            }
        }
    }
])

查詢語句

/* 1 */
{
    "CarBrand" : "紅旗",
    "VehicleType" : "H7",
    "CarNum" : "京A00001",
    "PurchaseDate" : "2019-01-01",
    "_id" : "1",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-02-07",
    "TableCode" : "CarInfo",
    "RelationData1" : [ 
        {
            "_id" : "7",
            "CreateUserName" : "ddz100",
            "CreateDate" : "2018-06-06",
            "TableCode" : "MaintenanceRecord",
            "CarId" : "1",
            "Cost" : 100.0,
            "Contents" : "噴漆"
        }, 
        {
            "_id" : "8",
            "CreateUserName" : "ddz100",
            "CreateDate" : "2018-08-06",
            "TableCode" : "MaintenanceRecord",
            "CarId" : "1",
            "Cost" : 25.0,
            "Contents" : "洗車"
        }, 
        {
            "_id" : "12",
            "CreateUserName" : "ddz10",
            "CreateDate" : "2018-06-06",
            "TableCode" : "DispatchRecord",
            "CarId" : "1",
            "Income" : 106.0,
            "Mileage" : 50.0,
            "Remarks" : "123"
        }, 
        {
            "_id" : "13",
            "CreateUserName" : "ddz11",
            "CreateDate" : "2018-06-16",
            "TableCode" : "DispatchRecord",
            "CarId" : "1",
            "Income" : 250.0,
            "Mileage" : 100.0,
            "Remarks" : "123"
        }
    ]
}

/* 2 */
{
    "CarBrand" : "紅旗",
    "VehicleType" : "H5",
    "CarNum" : "京A00002",
    "PurchaseDate" : "2019-02-01",
    "_id" : "2",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-02-08",
    "TableCode" : "CarInfo",
    "RelationData1" : [ 
        {
            "_id" : "9",
            "CreateUserName" : "ddz101",
            "CreateDate" : "2018-06-03",
            "TableCode" : "MaintenanceRecord",
            "CarId" : "2",
            "Cost" : 1560.0,
            "Contents" : "換輪胎"
        }, 
        {
            "_id" : "14",
            "CreateUserName" : "ddz12",
            "CreateDate" : "2018-06-16",
            "TableCode" : "DispatchRecord",
            "CarId" : "2",
            "Income" : 1000.0,
            "Mileage" : 630.0,
            "Remarks" : "2345sfgfg"
        }
    ]
}

/* 3 */
{
    "CarBrand" : "紅旗",
    "VehicleType" : "L5",
    "CarNum" : "京A00003",
    "PurchaseDate" : "2019-03-01",
    "_id" : "3",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-02-09",
    "TableCode" : "CarInfo",
    "RelationData1" : [ 
        {
            "_id" : "10",
            "CreateUserName" : "ddz102",
            "CreateDate" : "2018-06-26",
            "TableCode" : "MaintenanceRecord",
            "CarId" : "3",
            "Cost" : 36.0,
            "Contents" : "爆胎"
        }, 
        {
            "_id" : "11",
            "CreateUserName" : "ddz103",
            "CreateDate" : "2018-09-08",
            "TableCode" : "MaintenanceRecord",
            "CarId" : "3",
            "Cost" : 1630.0,
            "Contents" : "換加速器"
        }, 
        {
            "_id" : "15",
            "CreateUserName" : "ddz12",
            "CreateDate" : "2018-08-16",
            "TableCode" : "DispatchRecord",
            "CarId" : "3",
            "Income" : 1213.0,
            "Mileage" : 569.0,
            "Remarks" : "12asdfasdfasdf3"
        }
    ]
}

/* 4 */
{
    "CarBrand" : "長城",
    "VehicleType" : "哈弗H6",
    "CarNum" : "京A00004",
    "PurchaseDate" : "2018-03-01",
    "_id" : "4",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-02-10",
    "TableCode" : "CarInfo",
    "RelationData1" : []
}

/* 5 */
{
    "CarBrand" : "長城",
    "VehicleType" : "哈弗H5",
    "CarNum" : "京A00005",
    "PurchaseDate" : "2018-03-01",
    "_id" : "5",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-02-09",
    "TableCode" : "CarInfo",
    "RelationData1" : []
}

/* 6 */
{
    "CarBrand" : "長城",
    "VehicleType" : "哈弗H4",
    "CarNum" : "京A00006",
    "PurchaseDate" : "2018-03-01",
    "_id" : "6",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-03-09",
    "TableCode" : "CarInfo",
    "RelationData1" : []
}

/* 7 */
{
    "CarId" : "1",
    "Cost" : 100.0,
    "Contents" : "噴漆",
    "_id" : "7",
    "CreateUserName" : "ddz100",
    "CreateDate" : "2018-06-06",
    "TableCode" : "MaintenanceRecord",
    "RelationData1" : []
}

/* 8 */
{
    "CarId" : "1",
    "Cost" : 25.0,
    "Contents" : "洗車",
    "_id" : "8",
    "CreateUserName" : "ddz100",
    "CreateDate" : "2018-08-06",
    "TableCode" : "MaintenanceRecord",
    "RelationData1" : []
}

/* 9 */
{
    "CarId" : "2",
    "Cost" : 1560.0,
    "Contents" : "換輪胎",
    "_id" : "9",
    "CreateUserName" : "ddz101",
    "CreateDate" : "2018-06-03",
    "TableCode" : "MaintenanceRecord",
    "RelationData1" : []
}

/* 10 */
{
    "CarId" : "3",
    "Cost" : 36.0,
    "Contents" : "爆胎",
    "_id" : "10",
    "CreateUserName" : "ddz102",
    "CreateDate" : "2018-06-26",
    "TableCode" : "MaintenanceRecord",
    "RelationData1" : []
}

/* 11 */
{
    "CarId" : "3",
    "Cost" : 1630.0,
    "Contents" : "換加速器",
    "_id" : "11",
    "CreateUserName" : "ddz103",
    "CreateDate" : "2018-09-08",
    "TableCode" : "MaintenanceRecord",
    "RelationData1" : []
}

/* 12 */
{
    "CarId" : "1",
    "Income" : 106.0,
    "Mileage" : 50.0,
    "Remarks" : "123",
    "_id" : "12",
    "CreateUserName" : "ddz10",
    "CreateDate" : "2018-06-06",
    "TableCode" : "DispatchRecord",
    "RelationData1" : []
}

/* 13 */
{
    "CarId" : "1",
    "Income" : 250.0,
    "Mileage" : 100.0,
    "Remarks" : "123",
    "_id" : "13",
    "CreateUserName" : "ddz11",
    "CreateDate" : "2018-06-16",
    "TableCode" : "DispatchRecord",
    "RelationData1" : []
}

/* 14 */
{
    "CarId" : "2",
    "Income" : 1000.0,
    "Mileage" : 630.0,
    "Remarks" : "2345sfgfg",
    "_id" : "14",
    "CreateUserName" : "ddz12",
    "CreateDate" : "2018-06-16",
    "TableCode" : "DispatchRecord",
    "RelationData1" : []
}

/* 15 */
{
    "CarId" : "3",
    "Income" : 1213.0,
    "Mileage" : 569.0,
    "Remarks" : "12asdfasdfasdf3",
    "_id" : "15",
    "CreateUserName" : "ddz12",
    "CreateDate" : "2018-08-16",
    "TableCode" : "DispatchRecord",
    "RelationData1" : []
}

查詢結果

　　你可能看到了查詢語句太長了，這仍是最基本的，幸虧3.4以後提供了視圖的功能，咱們能夠建立一個視圖，弄成咱們想要的樣子：

db.createView("t1view","t1",[
    {$addFields:
        {
            FormValueObj:{
                $arrayToObject:{
                    $map:
                     {
                       input: "$FormItems",
                       as: "field",
                       in: ["$$field.key","$$field.value"]
                     }
                }
            }
        }
    },
    {
        $addFields:{
            "FormValueObj._id":"$_id",
            "FormValueObj.CreateUserName":"$CreateUserName",
            "FormValueObj.CreateDate":"$CreateDate",
            "FormValueObj.TableCode":"$TableCode"
        }
    },
    {
        $replaceRoot: { newRoot: "$FormValueObj" }
    }
])

建立視圖

　　以後咱們就是在視圖中查詢了

db.getCollection('t1view').aggregate([
    {$match:{_id:"1"}},
    {
        $lookup:{
           from: "t1view",
           localField: "_id",
           foreignField: "CarId",
           as: "RelationData1"
        }
    }
])

視圖查詢

/* 1 */
{
    "CarBrand" : "紅旗",
    "VehicleType" : "H7",
    "CarNum" : "京A00001",
    "PurchaseDate" : "2019-01-01",
    "_id" : "1",
    "CreateUserName" : "ddz1",
    "CreateDate" : "2018-02-07",
    "TableCode" : "CarInfo",
    "RelationData1" : [ 
        {
            "CarId" : "1",
            "Cost" : 100.0,
            "Contents" : "噴漆",
            "_id" : "7",
            "CreateUserName" : "ddz100",
            "CreateDate" : "2018-06-06",
            "TableCode" : "MaintenanceRecord"
        }, 
        {
            "CarId" : "1",
            "Cost" : 25.0,
            "Contents" : "洗車",
            "_id" : "8",
            "CreateUserName" : "ddz100",
            "CreateDate" : "2018-08-06",
            "TableCode" : "MaintenanceRecord"
        }, 
        {
            "CarId" : "1",
            "Income" : 106.0,
            "Mileage" : 50.0,
            "Remarks" : "123",
            "_id" : "12",
            "CreateUserName" : "ddz10",
            "CreateDate" : "2018-06-06",
            "TableCode" : "DispatchRecord"
        }, 
        {
            "CarId" : "1",
            "Income" : 250.0,
            "Mileage" : 100.0,
            "Remarks" : "123",
            "_id" : "13",
            "CreateUserName" : "ddz11",
            "CreateDate" : "2018-06-16",
            "TableCode" : "DispatchRecord"
        }
    ]
}

視圖查詢結果

　　這樣在操做就簡單多了，還避免了上面的第二個問題,😓😓😓，不知道你有沒有發現一個問題，在上面的查詢結果中「RelationData1」中冗餘了車輛維護表和車輛出車記錄的全部相關記錄，這不是咱們想要的，咱們想要的是RelationData1是相關的「車輛維護記錄」，RelationData2是相關的「車輛出車記錄」，出現這種問題的緣由是關聯查詢時，關聯的表不容許過濾，3.4版本以前就這樣了，不知道大神們有沒有好的辦法，我只能用升級來解決了，3.6以後就能夠了……

　　暫時就記到這裏吧！有時間在補充。