mongoose - 一侧没有参考的猫鼬反向查询

Question

我以这个数据为例。我有两个不同的收藏books和publishers

"books": [
    {
      "isbn": "9781593275846",
      "title": "Eloquent JavaScript, Second Edition",
      "subtitle": "A Modern Introduction to Programming",
      "author": "Marijn Haverbeke",
      "published": "2014-12-14T00:00:00.000Z",
      "_publisher": "5f35578bf55f6cef9fd6193f",,
      "pages": 472,
      "description": "JavaScript lies at the heart of almost every modern web application, from social apps to the newest browser-based games. Though simple for beginners to pick up and play with, JavaScript is a flexible, complex language that you can use to build full-scale applications.",
      "website": "http://eloquentjavascript.net/"
    },
    {
      "isbn": "9781449331818",
      "title": "Learning JavaScript Design Patterns",
      "subtitle": "A JavaScript and jQuery Developer's Guide",
      "author": "Addy Osmani",
      "published": "2012-07-01T00:00:00.000Z",
      "publisher": "5f3557bd51bf64f398cb8853",,
      "pages": 254,
      "description": "With Learning JavaScript Design Patterns, you'll learn how to write beautiful, structured, and maintainable JavaScript by applying classical and modern design patterns to the language. If you want to keep your code efficient, more manageable, and up-to-date with the latest best practices, this book is for you.",
      "website": "http://www.addyosmani.com/resources/essentialjsdesignpatterns/book/"
    },
    {
      "isbn": "9781449365035",
      "title": "Speaking JavaScript",
      "subtitle": "An In-Depth Guide for Programmers",
      "author": "Axel Rauschmayer",
      "published": "2014-02-01T00:00:00.000Z",
      "publisher": "5f3557bd51bf64f398cb8853",
      "pages": 460,
      "description": "Like it or not, JavaScript is everywhere these days-from browser to server to mobile-and now you, too, need to learn the language or dive deeper than you have. This concise book guides you into and through JavaScript, written by a veteran programmer who once found himself in the same position.",
      "website": "http://speakingjs.com/"
    },
    {
      "isbn": "9781491950296",
      "title": "Programming JavaScript Applications",
      "subtitle": "Robust Web Architecture with Node, HTML5, and Modern JS Libraries",
      "author": "Eric Elliott",
      "published": "2014-07-01T00:00:00.000Z",
      "publisher": "5f3557bd51bf64f398cb8853",
      "pages": 254,
      "description": "Take advantage of JavaScript's power to build robust web-scale or enterprise applications that are easy to extend and maintain. By applying the design patterns outlined in this practical book, experienced JavaScript developers will learn how to write flexible and resilient code that's easier-yes, easier-to work with as your code base grows.",
      "website": "http://chimera.labs.oreilly.com/books/1234000000262/index.html"
    },
    {
      "isbn": "9781593277574",
      "title": "Understanding ECMAScript 6",
      "subtitle": "The Definitive Guide for JavaScript Developers",
      "author": "Nicholas C. Zakas",
      "published": "2016-09-03T00:00:00.000Z",
      "publisher": "No Starch Press",
      "pages": 352,
      "description": "ECMAScript 6 represents the biggest update to the core of JavaScript in the history of the language. In Understanding ECMAScript 6, expert developer Nicholas C. Zakas provides a complete guide to the object types, syntax, and other exciting changes that ECMAScript 6 brings to JavaScript.",
      "website": "https://leanpub.com/understandinges6/read"
    },
    {
      "isbn": "9781491904244",
      "title": "You Don't Know JS",
      "subtitle": "ES6 & Beyond",
      "author": "Kyle Simpson",
      "published": "2015-12-27T00:00:00.000Z",
      "publisher": "5f3557bd51bf64f398cb8853",
      "pages": 278,
      "description": "No matter how much experience you have with JavaScript, odds are you don’t fully understand the language. As part of the "You Don’t Know JS" series, this compact guide focuses on new features available in ECMAScript 6 (ES6), the latest version of the standard upon which JavaScript is built.",
      "website": "https://github.com/getify/You-Dont-Know-JS/tree/master/es6%20&%20beyond"
    },
    {
      "isbn": "9781449325862",
      "title": "Git Pocket Guide",
      "subtitle": "A Working Introduction",
      "author": "Richard E. Silverman",
      "published": "2013-08-02T00:00:00.000Z",
      "publisher": "5f3557bd51bf64f398cb8853",
      "pages": 234,
      "description": "This pocket guide is the perfect on-the-job companion to Git, the distributed version control system. It provides a compact, readable introduction to Git for new users, as well as a reference to common commands and procedures for those of you with Git experience.",
      "website": "http://chimera.labs.oreilly.com/books/1230000000561/index.html"
    },
    {
      "isbn": "9781449337711",
      "title": "Designing Evolvable Web APIs with ASP.NET",
      "subtitle": "Harnessing the Power of the Web",
      "author": "Glenn Block, et al.",
      "published": "2014-04-07T00:00:00.000Z",
      "publisher": "5f3557bd51bf64f398cb8853",
      "pages": 538,
      "description": "Design and build Web APIs for a broad range of clients—including browsers and mobile devices—that can adapt to change over time. This practical, hands-on guide takes you through the theory and tools you need to build evolvable HTTP services with Microsoft’s ASP.NET Web API framework. In the process, you’ll learn how design and implement a real-world Web API.",
      "website": "http://chimera.labs.oreilly.com/books/1234000001708/index.html"
    }
  ]

publishers: [
    {
        _id: "5f35578bf55f6cef9fd6193f",
        name: "No Starch Press",
        country: "USA",
        foundeed: "1994"


    },
    {
        _id: "5f3557bd51bf64f398cb8853",
        name: "O'Reilly Media",
        country: "USA",
        foundeed: "1978"

    }

]

我想使用 mongoose 和两个相关查询来查询它们

第一个是，如果我通过了，publisherId我想拥有出版商及其数据以及属于该出版商的所有书籍。请注意，书籍有_publisher _id，但出版商没有书籍参考。

如果我这样做，books.find({ _publisher: publisherId})我会得到出版商过滤的书籍，但如果我想添加出版商的数据并填充，出版商的数据将显示在每本书中

我想要的输出是

{
    publisher: {
        // publisherData
        books : [
            // filtered books
        ]
    }
}

第二个查询是获取所有书籍，但按出版商分组。该查询与第一个查询类似，但我不知道如何根据自己的喜好查询和投影输出，因为我没有关于图书出版商的数组。

如果我没有在两个方向上建立关系的数组字段，我不确定是否可以反转查询。

标签： mongoose

Answer 1

我认为您正在使用这样的管道寻找 $lookup：

https://mongoplayground.net/p/H_OsKvN_npf

db.publishers.aggregate([
    {$lookup: {
        from: 'books',
        as: 'books',
        let: {publisherId: '$_id'},
        pipeline: [
            {$match: {$expr: {
                $eq: ['$publisher', '$$publisherId']
            }}}
        ]
    }}    
])

然后让一个发布者添加一个匹配阶段：

db.publishers.aggregate([
    {$match: {_id: mongoose.Types.ObjectId('YOUROBJECTID')}},
    {$lookup: {
        from: 'books',
        as: 'books',
        let: {publisherId: '$_id'},
        pipeline: [
            {$match: {$expr: {
                $eq: ['$publisher', '$$publisherId']
            }}}
        ]
    }}    
])