我想将单独的集合合并为 1 个 json，但嵌套 $lookup 时遇到一些问题。
这是我的示例集合。 收藏包_订阅:
[
{
"_id": "1",
"package_name": "Small",
"package_desc": "AAA",
"package_price": 10
},
{
"_id": "2",
"package_name": "Medium",
"package_desc": "BBB",
"package_price": 20
}
集合Package_modules:
{
"_id" : 1,
"subscription_id" : 1,
"billing_model_id" : 1,
"module_id" : 1,
"created_at" : ISODate("2019-06-17T07:59:43.199Z"),
}
{
"_id" : 2,
"subscription_id" : 1,
"billing_model_id" : 3,
"module_id" : 2,
"created_at" : ISODate("2019-06-17T08:00:37.464Z"),
}
{
"_id" : 3,
"subscription_id" : 2,
"billing_model_id" : 2,
"module_id" : 1,
"created_at" : ISODate("2019-06-17T08:00:56.610Z"),
}
{
"_id" : 4,
"subscription_id" : 2,
"billing_model_id" : 4,
"module_id" : 2,
"created_at" : ISODate("2019-06-17T08:01:29.667Z"),
}
收集模块:
{
"_id" : 1,
"module_name" : "Call",
"status" : "Active",
}
{
"_id" : 2,
"module_name" : "SMS",
"status" : "Active",
}
集合 Billing_models
{
"_id" : 1,
"unit_count" : "Menit",
"counter" : 2000,
},
{
"_id" : 2,
"unit_count" : "Menit",
"counter" : 3000,
}
{
"_id" : 3,
"unit_count" : "SMS",
"counter" : 3000,
},
{
"_id" : 4,
"unit_count" : "SMS",
"counter" : 5000,
}
这是我尝试该问题的代码，但没有达到预期。
Package_subscription
.aggregate([
{
$lookup: {
from: "o_package_modules",
localField: "_id",
foreignField: "subscription_id",
as: "package_modules"
}
},
{
$unwind: {
path: "$package_modules",
preserveNullAndEmptyArrays: true
}
},
{
$lookup: {
from: "o_modules",
localField: "package_modules.module_id",
foreignField: "_id",
as: 'module'
}
},
{
$lookup: {
from: "o_billing_models",
localField: "package_modules.billing_model_id",
foreignField: "_id",
as: 'billing_module'
}
}
])
.exec()
.then((pricing) => {
res.json(pricing)
})
.catch((err) => {
res.send(err)
})
我期望输出是:
[
{
"_id": "1",
"package_name": "Small",
"package_desc": "AAA",
"package_price": 10,
"package_modules": [
{
"_id": 1,
"subscription_id": 1,
"billing_model": {
"_id": 1,
"unit_count": "Menit",
"counter": 2000
},
"module": {
"_id": 1,
"module_name": "Call",
"status": "Active"
},
"created_at": "2019-06-17T07:59:43.199Z",
},
{
"_id": 2,
"subscription_id": 1,
"billing_model": {
"_id": 3,
"unit_count": "SMS",
"counter": 3000
},
"module": {
"_id": 2,
"module_name": "SMS",
"status": "Active"
},
"created_at": "2019-06-17T08:00:37.464Z",
}
]
},
{
"_id": 2,
"package_name": "Medium",
"package_desc": "BBB",
"package_price": 20,
"package_modules": [
{
"_id": 3,
"subscription_id": 2,
"billing_model": {
"_id": 2,
"unit_count": "Menit",
"counter": 3000
},
"module": {
"_id": "1",
"module_name": "Call",
"status": "Active"
},
"created_at": "2019-06-17T08:01:29.667Z",
},
{
"_id": 4,
"subscription_id": 2,
"billing_model": {
"_id": 4,
"unit_count": "SMS",
"counter": 5000
},
"module": {
"_id": 2,
"module_name": "SMS",
"status": "Active"
},
"created_at": "2019-06-17T08:01:50.285Z",
}
]
}
]
但是我的代码的输出是:
[
{
"_id": "1",
"package_name": "Small",
"package_desc": "AAA",
"package_price": 10,
"package_modules": {
"_id": 1,
"subscription_id": 1,
"billing_model_id": 1
"module_id": 1
"created_at": "2019-06-17T07:59:43.199Z",
},
},
"billing_model": [
{
"_id": 1,
"unit_count": "Menit",
"counter": 2000
},
],
"module": [
{
"_id": 1,
"module_name": "Call",
"status": "Active"
}
]
},
{
"_id": "1",
"package_name": "Small",
"package_desc": "AAA",
"package_price": 10,
"package_modules": {
"_id": 2,
"subscription_id": 2,
"billing_model_id": 3
"module_id": 2
"created_at": "2019-06-17T07:59:43.199Z",
},
},
"billing_model": [
{
"_id": 3,
"unit_count": "SMS",
"counter": 3000
},
],
"module": [
{
"_id": 2,
"module_name": "SMS",
"status": "Active"
}
]
}
..........
// And medium where is loop again
]
最佳答案
我认为您的代码中存在多个问题。
在
$lookup阶段，您需要将as字段设置为package_modules.billing_module和package_modules.module，而不是billing_module和module等，以便它成为package_module对象的字段，而不是单独的对象本身。您需要在每个
$lookup阶段之后展开，因为$lookup返回一个数组而不是对象。您需要在
聚合管道末尾处$group将一个订阅的所有package_modules推送到一个数组中。
解决以上所有问题后， 您的聚合管道应如下所示:
Package_subscription
.aggregate([
{
$lookup: {
from: "o_package_modules",
localField: "_id",
foreignField: "subscription_id",
as: "package_modules"
}
},
{
$unwind: {
path: "$package_modules",
preserveNullAndEmptyArrays: true
}
},
{
$lookup: {
from: "o_modules",
localField: "package_modules.module_id",
foreignField: "_id",
as: 'package_modules.module'
}
},
{
$unwind: {
path: "$package_modules.module",
preserveNullAndEmptyArrays: true
}
},
{
$lookup: {
from: "o_billing_models",
localField: "package_modules.billing_model_id",
foreignField: "_id",
as: 'package_modules.billing_module'
}
},
{
$unwind: {
path: "$package_modules.billing_module",
preserveNullAndEmptyArrays: true
}
},
{
$group: {
_id: "$_id",
package_modules : {$push : "$package_modules"},
package_name: {$first . : "$package_name"},
package_desc: {$first . : "$package_desc"},
package_price: {$first . : "$package_price"}
}
}
])
.exec()
.then((pricing) => {
res.json(pricing)
})
.catch((err) => {
res.send(err)
})
最后一个$group阶段中的$push会将所有package_modules合并到一个数组中。我认为这就是您最终想要的。
我希望这对你有用。
关于node.js - 如何在 mongoose 中组合嵌套 $lookup 3 层？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56678088/