我有以下情况:
集合
部门
:{ "_id" : 0, "name" : "Dep_A_1", "description" : "Department A1" } { "_id" : 1, "name" : "Dep_B_1", "description" : "Department B1" } { "_id" : 2, "name" : "Dep_C_1", "description" : "Department C1" }
收集
技能
:{ "_id" : 0, "name" : "Creativity", "description" : "description", "type" : "soft", "categories" : [ 0, 2 ] }
集合
Angular 色
:{ "_id" : 0, "name" : "Software Developer Automation and Control", "description" : "Automation and Control expert", "departments" : [ 0, 2 ], "skills" : [ { "_id" : 18, "weight" : 30 } ] }
我需要这样的结果:
{
"_id" : 0,
"name" : "Software Developer Automation and Control",
"description" : "Automation and Control expert",
"departments" : [
{
"_id" : 0,
"name" : "Dep_A_1",
"description" : "Department A1"
},
{
"_id" : 2,
"name" : "Dep_C_1",
"description" : "Department C1"
}
],
"skills" : [
{
"_id" : 0,
"name" : "Creativity",
"description" : "description",
"type" : "soft",
"weight" : 30
}
]
}
我需要用 departments
和 roles< 中的相应对象替换
集合。有没有办法查询 Mongo 并得到这样的结果?role.departments
和 role.skills
数组
无论如何,我正在使用 Mongo 3.6 和 Pymongo。 谢谢。
最佳答案
为了避免昂贵的 $unwind
和 $group
阶段,您可以这样做:
db.roles.aggregate([{
$lookup: {
from: 'departments',
localField: 'departments',
foreignField: '_id',
as: 'departments'
}
}, {
$lookup: {
from: 'skills',
let: {
"skills": "$skills" // keep a reference to the "skills" field of the current document and make it accessible via "$$skills"
},
pipeline: [{
$match: {
$expr: {
$in: [ "$_id", "$$skills._id" ] // this just does the "joining"
}
}
}, {
$addFields: { // add a new field
"weight": { // called "weight"
$arrayElemAt: [ // which shall be set to the correct "weight"
"$$skills.weight", // that can be found in the "weight" field of the "skills" array
{ $indexOfArray: [ "$$skills._id", "$_id" ] } // at the position that has the matching "_id" value
]
}
}
}],
as: 'skills'
}
}])
关于javascript - 多聚合查询 MongoDB,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/51712760/