$regex在MongoDB中不起作用

Question

我知道有很多与$regex相关的答案，但我已经尝试了几个小时了，我无法让它起作用。

我想要的是找到那些courses，在courseName中包含一个字母"D“。我做错了什么？请帮帮我!

我有以下文件：

{
            "firstName": "Sarah",
            "lastName": "Jepsen",
            "age": 27,
            "courses": [
                {
                    "courseName": "Web-Development",
                    "teachers": [
                        {
                            "firstName": "Santiago",
                            "lastName": "Donoso"
                        }
                    ]
                },

                {
                    "courseName": "Databases",
                    "teachers": [
                        {
                            "firstName": "Dany",
                            "lastName": "Kallas"
                        },
                        {
                            "firstName": "Rune",
                            "lastName": "Lyng"
                        }
                    ]
                },
                {
                    "courseName": "Interface-Design",
                    "teachers": [
                        {
                            "firstName": "Roxana",
                            "lastName": "Stolniceanu"
                        }
                    ]
                }
            ]
        }

这是我的查找查询：

student.findCourses = (fcallback) => {
    global.db.collection('students').find({ "courses.courseName": { $regex: "/D/" }, _id: false }).toArray((err, result) => {

        if (err) {
            var jError = { "status": "error", "message": "ERROR -> student.js -> 001" }
            console.log(jError)
            return fcallback(true, jError)
        }
        var jOk = { "status": "ok", "message": "student.js -> found -> 000" }
        console.log(jOk)
        console.log(JSON.stringify(result))
        return fcallback(false, jOk)
    })
}

Answer 1

要获得与正则表达式匹配的所有课程，您必须手动筛选它们。考虑您的情况，使用另一个courses数组项：

{
    "courseName": "Unmatching", // no letter "D"
    "teachers": [
        {
            "firstName": "Dany",
            "lastName": "Kallas"
        }
    ]
}

您的查询无论如何都会返回它，因为学生文档中的其他课程与您的regex匹配。

你能做的是：

1. 对具有匹配课程名称的文档的查询(.find())
2. 手动过滤它们-循环遍历每一项以检查其名称是否与regex匹配。

示例数据：

// 1
{
    "_id" : ObjectId("5a019896f89c24926108e2bf"),
    "firstName" : "Sarah",
    "lastName" : "Jepsen",
    "age" : 27,
    "courses" : [ 
        {
            "courseName" : "Lorem",
            "teachers" : []
        },
        {
            "courseName" : "Ipsum",
            "teachers" : []
        },
        {
            "courseName" : "Dolor",
            "teachers" : []
        },
        {
            "courseName" : "Sit",
            "teachers" : []
        },
        {
            "courseName" : "Dolor 2",
            "teachers" : []
        }
    ]
},
// 2
{
    "_id" : ObjectId("5a019896f89c24926108e2be"),
    "firstName" : "John",
    "lastName" : "Smith",
    "age" : 22,
    "courses" : [ 
        {
            "courseName" : "Dioptry",
            "teachers" : []
        },
        {
            "courseName" : "Dino",
            "teachers" : []
        },
        {
            "courseName" : "A",
            "teachers" : []
        },
        {
            "courseName" : "B",
            "teachers" : []
        },
        {
            "courseName" : "C",
            "teachers" : []
        }
    ]
}

查询和筛选代码：

student.findCourses = (fcallback) => {

    var regexp = new RegExp('D');

    global.db.collection('students').find({ "courses.courseName": { $regex: regexp } }, { _id: 0, courses: 1 } }).toArray((err, result) => {

        // here, you'll receive:
        // [{ courses: [] }, { courses: [] }]
        // with all the courses inside
        // no matter if their names match the given regex
        // as it's enough that one of them does
        // to return the whole document

        // filtering:
        var filtered = result.map(student => {
            student.courses = student.courses.filter(course => regexp.test(course.courseName));
            return student;
        });

        // now, your filtered has exactly the same format
        // [{ courses: [] }, { courses: [] }]
        // but only with courses matching the regexp inside it

        console.log(JSON.stringify(filtered);

        // what you can do to get flat courses array is:
        var flat = filtered.reduce((p, c) => p.concat(c.courses), [])

        console.log(JSON.stringify(flat));


        if (err) {
            var jError = { "status": "error", "message": "ERROR -> student.js -> 001" }
            console.log(jError)
            return fcallback(true, jError)
        }
        var jOk = { "status": "ok", "message": "student.js -> found -> 000" }
        console.log(jOk)
        console.log(JSON.stringify(result))
        return fcallback(false, jOk)
    })
}

Answer 2

你试过这个吗？

global.db.collection('students')
    .find({ "courses.courseName": { $regex: new RegExp('D') }, _id: false })

我认为MongoDB客户端可以理解RegExp或字符串文本模式，但我认为您可能在这里混合了两个不同的模式。如果你把"/D/"放在你的名字里，你要找的是一门包含字面/D/的课程，而不仅仅是D。

相关：MongoDB Regular Expression Search - Starts with using javascript driver and NodeJS

编辑：

_id: false是干什么用的？如果试图执行投影(并删除_id字段)，则语法不正确。{ _id: false }应该作为第二个参数传递给.find()。当前查询与regex匹配，并检查_id是否等于false。

global.db.collection('students')
    .find({ "courses.courseName": { $regex: /D/ } }, { _id: false })