问题描述
我有这三个模型:
-
Institution
模型:
const InstitutionSchema = new Schema({
current_students: [
{
type: Schema.Types.ObjectId,ref: "users",},],});
module.exports = Institution = mongoose.model("institutions",InstitutionSchema);
在 User
字段中包含对 current_students
模型的引用数组。
-
User
模型:
const UserSchema = new Schema({
profile: {
type: Schema.Types.ObjectId,ref: "profiles",});
module.exports = User = mongoose.model("users",UserSchema);
在 Profile
字段中引用了 profile
模型。
-
Profile
模型:
const ProfileSchema = new Schema({
videoURL: {
type: String,});
module.exports = Profile = mongoose.model("profiles",ProfileSchema);
我正在尝试获取 Profile.videoURL
不是 null
或 undefined
的机构用户的个人资料列表。这是我尝试过的:
Institution.aggregate([
{
$lookup: {
from: "users",localField: "current_students",foreignField: "_id",as: "current_student",{
$unwind: {
path: "$current_student",preserveNullAndEmptyArrays: true,{
$lookup: {
from: "profiles",localField: "current_student.profile",as: "current_student_profile",pipeline: [
{
$match: {
videoURL: { $nin: [undefined,null] },]);
但是,由于执行 $match
操作的最后一个管道,我不断收到此错误。
Error: Arguments must be aggregate pipeline operators
知道如何解决这个问题吗?
解决方法
您的查询有误。你不能像那样通过 pipeline
。看看 $lookup
语法。此外,如果您想了解有关聚合的更多信息,我建议您使用 MongoDB 自己提供的 Aggregation course。对所有人免费。
试试这个查询:
db.institutions.aggregate([
{
$lookup: {
from: "users",localField: "current_students",foreignField: "_id",as: "current_student",}
},{
$unwind: {
path: "$current_student",preserveNullAndEmptyArrays: true,{
$lookup: {
from: "profiles",localField: "current_student.profile",as: "current_student_profile",{ $unwind: "$current_student_profile" },{
$match: {
"current_student_profile.videoURL": { $nin: [undefined,null] },}
}
]);
输出:
/* 1 createdAt:3/13/2021,6:18:26 PM*/
{
"_id" : ObjectId("604cb49a6b2dcb17e8b152b2"),"name" : "Institute 1","current_students" : [
ObjectId("604cb4c36b2dcb17e8b152b8"),ObjectId("604cb4c36b2dcb17e8b152b9")
],"current_student" : {
"_id" : ObjectId("604cb4c36b2dcb17e8b152b8"),"name" : "Dheemanth Bhat","profile" : ObjectId("604cb4b16b2dcb17e8b152b5")
},"current_student_profile" : {
"_id" : ObjectId("604cb4b16b2dcb17e8b152b5"),"videoURL" : "http://abc1@xyz.com"
}
},/* 2 createdAt:3/13/2021,6:18:26 PM*/
{
"_id" : ObjectId("604cb49a6b2dcb17e8b152b3"),"name" : "Institute 2","current_students" : [
ObjectId("604cb4c36b2dcb17e8b152ba")
],"current_student" : {
"_id" : ObjectId("604cb4c36b2dcb17e8b152ba"),"name" : "Alex Rider","profile" : ObjectId("604cb4b16b2dcb17e8b152b7")
},"current_student_profile" : {
"_id" : ObjectId("604cb4b16b2dcb17e8b152b7"),"videoURL" : "http://abc3@xyz.com"
}
}
测试数据:
users
集合:
/* 1 createdAt:3/13/2021,6:19:07 PM*/
{
"_id" : ObjectId("604cb4c36b2dcb17e8b152b8"),"profile" : ObjectId("604cb4b16b2dcb17e8b152b5")
},6:19:07 PM*/
{
"_id" : ObjectId("604cb4c36b2dcb17e8b152b9"),"name" : "Ahmed Ghrib","profile" : ObjectId("604cb4b16b2dcb17e8b152b6")
},/* 3 createdAt:3/13/2021,6:19:07 PM*/
{
"_id" : ObjectId("604cb4c36b2dcb17e8b152ba"),"profile" : ObjectId("604cb4b16b2dcb17e8b152b7")
}
profiles
集合:
/* 1 createdAt:3/13/2021,6:18:49 PM*/
{
"_id" : ObjectId("604cb4b16b2dcb17e8b152b5"),"videoURL" : "http://abc1@xyz.com"
},6:18:49 PM*/
{
"_id" : ObjectId("604cb4b16b2dcb17e8b152b6")
},6:18:49 PM*/
{
"_id" : ObjectId("604cb4b16b2dcb17e8b152b7"),"videoURL" : "http://abc3@xyz.com"
}
institutions
集合
/* 1 createdAt:3/13/2021,ObjectId("604cb4c36b2dcb17e8b152b9")
]
},"current_students" : [
ObjectId("604cb4c36b2dcb17e8b152ba")
]
}
,
一定是这样的:
Institution.aggregate([
{
$lookup: {
from: "users",},{
$unwind: {
path: "$current_student",{
$lookup: {
from: "profiles",}
},{
$match: {
videoURL: { $nin: [undefined,}
]);
注意,这看起来像是关系 RDBMS 设计的“一对一”转换。通常将每个表格转换为集合并不是最好的方法,通常集合应该有不同的设计。