Mongodb $ lookup不适用于_id [英] Mongodb $lookup Not working with _id

问题描述

尝试使用此查询，返回查找为空

wend try with this query, return the lookup is empty

db.getCollection('tests').aggregate([
    {$match: {typet:'Req'}},
    {$project: {incharge:1}},
    {$lookup:{
            from: "users",
            localField: "incharge", //this is the _id user from tests
            foreignField: "_id", //this is the _id from users
            as: "user"
    }}
])

返回json

  [
    {
        "_id": "57565d2e45bd27b012fc4db9",
        "incharge": "549e0bb67371ecc804ad23ef",
        "user": []
    },
    {
        "_id": "57565d2045bd27b012fc4cbb",
        "incharge": "549e0bb67371ecc804ad21ef",
        "user": []
    },
    {
        "_id": "57565d2245bd27b012fc4cc7",
        "incharge": "549e0bb67371ecc804ad24ef",
        "user": []
    }
]

我尝试了这篇文章，但没有任何反应 将MongoDB聚合项目字符串转换为ObjectId 并与此 以_id作为PHP中的ForeignField的MongoDB $ lookup

i try with this post but nothing happend MongoDB aggregation project string to ObjectId and with this MongoDB $lookup with _id as a foreignField in PHP

更新

这是文档的用户"

    {
        "_id" : ObjectId("549e0bb67371ecc804ad24ef"),
        "displayname" : "Jhon S."
    },
    {
        "_id" : ObjectId("549e0bb67371ecc804ad21ef"),
        "displayname" : "George F."
    },
    {
        "_id" : ObjectId("549e0bb67371ecc804ad23ef"),
        "displayname" : "Franc D."
    }

推荐答案

我最终找到了解决方案，这是我的模式在带有ObjectId的猫鼬模式中的问题

I finaly found the solution, is a problem with my Schema in mongoose with the ObjectId

我更改了

var Schema = new Schema({
    name: { type: String, required: true},
    incharge: { type: String, required: true},
});

与此

var Schema = new Schema({
    name: { type: String, required: true},
    incharge: { type: mongoose.Schema.ObjectId, required: true},
});

正在工作

这篇关于Mongodb $ lookup不适用于_id的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！