Javascript 在Mongo视图中求和并输出总计

在我的mongDB后端中，我有一个视图，在多个聚合阶段之后，输出如下所示的信息：

{ 
    "_id" : 25k3ejfjyi32132f9z3,
    "customer_id" : 15cgrd582950jj493g5,
    "openBalance": 24,
    // other data...
},
{ 
    "_id" : 35g6ejfjfj32132f8s4, 
    "customer_id" : 23gtrd684563jj494f4
    "openBalance": 20,
    // other data...
}

{ 
    "_id" : 25k3ejfjyi32132f9z3,
    "customer_id" : 15cgrd582950jj493g5,
    "openBalance": 24,
    // other data...
},
{ 
    "_id" : 35g6ejfjfj32132f8s4, 
    "customer_id" : 23gtrd684563jj494f4
    "openBalance": 20,
    // other data...
},
"totalOpenBalance": 44

作为最后一步，我需要做的是合计所有记录的所有“openBalance”金额，并将该数字和其他数据一起输出到一个新字段中。因此，换句话说，基于上述数据，我想在标题为

totalOpenBalance

的a字段中返回

44

有没有办法在mongo视图中处理此聚合逻辑？我不知道该怎么做，因为我不想为返回的每个记录添加一个字段，而是基于记录总数返回一个值？它看起来像这样：

{ 
    "_id" : 25k3ejfjyi32132f9z3,
    "customer_id" : 15cgrd582950jj493g5,
    "openBalance": 24,
    // other data...
},
{ 
    "_id" : 35g6ejfjfj32132f8s4, 
    "customer_id" : 23gtrd684563jj494f4
    "openBalance": 20,
    // other data...
}

{ 
    "_id" : 25k3ejfjyi32132f9z3,
    "customer_id" : 15cgrd582950jj493g5,
    "openBalance": 24,
    // other data...
},
{ 
    "_id" : 35g6ejfjfj32132f8s4, 
    "customer_id" : 23gtrd684563jj494f4
    "openBalance": 20,
    // other data...
},
"totalOpenBalance": 44

---

如果将以下代码添加到管道的末尾

$group: {
    _id: null, // do not really group but throw all documents into the same bucket
    documents: { $push: "$$ROOT" }, // push each encountered document into the group
    totalOpenBalance: { $sum: "$openBalance" } // sum up all "openBalance" values
}

您将得到一些您可能能够使用的东西：

{
    "_id" : null,
    "documents" : [ 
        {
            "_id" : 25k3ejfjyi32132f9z3,
            "customer_id" : 15cgrd582950jj493g5,
            "openBalance" : 24
        }, 
        {
            "_id" : 35g6ejfjfj32132f8s4,
            "customer_id" : 23gtrd684563jj494f4,
            "openBalance" : 20
        }
    ],
    "totalOpenBalance" : 44
}

如果你想彻底疯掉，我不推荐你这么做，那就继续读下去。通过添加以下阶段

{
    $group: {
        _id: null, // do not really group but throw all documents into the same bucket
        documents: { $push: "$$ROOT" }, // push each encountered document into the group
        totalOpenBalance: { $sum: "$openBalance" } // sum up all "openBalance" values
    }
}, {
    $project: {
        "_id": 0, // remove the "_id" field
        "documents": { $concatArrays: [ "$documents", [ { "totalOpenBalance": "$totalOpenBalance" } ] ] } // append a magic subdocument to the the existing documents
    }
}, {
    $unwind: "$documents" // just so we can flatten the resulting array into separate documents
}, {
    $replaceRoot: {
        newRoot: "$documents" // and move the content of our documents field to the root
    }
}

你得到的正是你想要的：

{
    "_id" : 25k3ejfjyi32132f9z3,
    "customer_id" : 15cgrd582950jj493g5,
    "openBalance" : 24
},
{
    "_id" : 35g6ejfjfj32132f8s4,
    "customer_id" : 23gtrd684563jj494f4,
    "openBalance" : 20
},
{
    "totalOpenBalance" : 44
}

---

但是，如果您在管道的末尾添加以下代码，这可能只是一种过激行为…

$group: {
    _id: null, // do not really group but throw all documents into the same bucket
    documents: { $push: "$$ROOT" }, // push each encountered document into the group
    totalOpenBalance: { $sum: "$openBalance" } // sum up all "openBalance" values
}

您将得到一些您可能能够使用的东西：

{
    "_id" : null,
    "documents" : [ 
        {
            "_id" : 25k3ejfjyi32132f9z3,
            "customer_id" : 15cgrd582950jj493g5,
            "openBalance" : 24
        }, 
        {
            "_id" : 35g6ejfjfj32132f8s4,
            "customer_id" : 23gtrd684563jj494f4,
            "openBalance" : 20
        }
    ],
    "totalOpenBalance" : 44
}

如果你想彻底疯掉，我不推荐你这么做，那就继续读下去。通过添加以下阶段

{
    $group: {
        _id: null, // do not really group but throw all documents into the same bucket
        documents: { $push: "$$ROOT" }, // push each encountered document into the group
        totalOpenBalance: { $sum: "$openBalance" } // sum up all "openBalance" values
    }
}, {
    $project: {
        "_id": 0, // remove the "_id" field
        "documents": { $concatArrays: [ "$documents", [ { "totalOpenBalance": "$totalOpenBalance" } ] ] } // append a magic subdocument to the the existing documents
    }
}, {
    $unwind: "$documents" // just so we can flatten the resulting array into separate documents
}, {
    $replaceRoot: {
        newRoot: "$documents" // and move the content of our documents field to the root
    }
}

你得到的正是你想要的：

{
    "_id" : 25k3ejfjyi32132f9z3,
    "customer_id" : 15cgrd582950jj493g5,
    "openBalance" : 24
},
{
    "_id" : 35g6ejfjfj32132f8s4,
    "customer_id" : 23gtrd684563jj494f4,
    "openBalance" : 20
},
{
    "totalOpenBalance" : 44
}

---

然而，这可能是一种过激的行为……

我在mongo聚合查询中也面临类似的问题。抱歉，使用聚合管道无法做到这一点。相反，您必须在聚合管道的回调中执行此操作。基本上，您必须手动计算该“字段”，并将其添加到响应对象中。我将对此进行调查，谢谢。我的mongo聚合查询也面临类似的问题。抱歉，使用聚合管道无法做到这一点。相反，您必须在聚合管道的回调中执行此操作。基本上，您必须手动计算该“字段”，并将其添加到响应对象中。我会查清楚的，谢谢。这看起来是个好办法。谢谢这个解决方案对我也有帮助！我无法告诉你我搜索这个有多久了，但没有结果。这看起来是一条路要走。谢谢这个解决方案对我也有帮助！我无法告诉你我搜索这个有多久了，但没有结果。