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...
}
作为最后一步,我需要做的是将所有" openBalance"所有记录的金额,并在新字段中输出该数字以及其他数据。换句话说,根据以上数据,我想在标题为44
的字段中返回totalOpenBalance
。
有没有办法在mongo视图中处理这种聚合逻辑?我不知道该怎么做,因为我不想在返回的每条记录中添加一个字段,而是根据记录的总数返回一个值?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...
},
"totalOpenBalance": 44
答案 0 :(得分:3)
如果您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: "$$ROOT" }, // push each encountered document into the group
totalOpenBalance: { $sum: "$openBalance" } // sum up all "openBalance" values
}
你会得到一些你可以使用的东西:
{
"_id" : null,
"documents" : [
{
"_id" : 25k3ejfjyi32132f9z3,
"customer_id" : 15cgrd582950jj493g5,
"openBalance" : 24
},
{
"_id" : 35g6ejfjfj32132f8s4,
"customer_id" : 23gtrd684563jj494f4,
"openBalance" : 20
}
],
"totalOpenBalance" : 44
}
如果你想完全疯狂,我不会真的推荐,请继续阅读。通过添加以下阶段
{
$group: {
_id: null, // do not really group but throw all documents into the same bucket
documents: { $push: "$$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
}
}
你得到了你所要求的:
{
"_id" : 25k3ejfjyi32132f9z3,
"customer_id" : 15cgrd582950jj493g5,
"openBalance" : 24
},
{
"_id" : 35g6ejfjfj32132f8s4,
"customer_id" : 23gtrd684563jj494f4,
"openBalance" : 20
},
{
"totalOpenBalance" : 44
}
然而,这可能只是一种矫枉过正的行为......