使用文档引用建立一对多关系模型

Overview

本页描述的数据模型使用文档之间的引用来建立一对多关系。

模式

以下示例映射了出版商和图书的关系。它说明了引用相对于嵌入在避免重复发布者信息方面的优势。

将出版商文档嵌入图书文档会重复出版商数据，如以下示例所示：

{   title: "MongoDB: The Definitive Guide",   author: [ "Kristina Chodorow", "Mike Dirolf" ],   published_date: ISODate("2010-09-24"),   pages: 216,   language: "English",   publisher: {              name: "O'Reilly Media",              founded: 1980,              location: "CA"            }}
{   title: "50 Tips and Tricks for MongoDB Developer",   author: "Kristina Chodorow",   published_date: ISODate("2011-05-06"),   pages: 68,   language: "English",   publisher: {              name: "O'Reilly Media",              founded: 1980,              location: "CA"            }}

为避免重复的出版商数据，请使用引用并将出版商信息保存在与图书集合不同的单独集合中。

关系的发展决定了引用的存储位置。如果每个出版商的图书数量较少且增长有限，请将图书引用存储在出版商文档中。如果每个出版商的图书数量无限制，则此数据模型将创建可变的增长数组，如以下示例所示：

{   name: "O'Reilly Media",   founded: 1980,   location: "CA",   books: [123456789, 234567890, ...]}
{    _id: 123456789,    title: "MongoDB: The Definitive Guide",    author: [ "Kristina Chodorow", "Mike Dirolf" ],    published_date: ISODate("2010-09-24"),    pages: 216,    language: "English"}
{   _id: 234567890,   title: "50 Tips and Tricks for MongoDB Developer",   author: "Kristina Chodorow",   published_date: ISODate("2011-05-06"),   pages: 68,   language: "English"}

为避免出现可变且不断增长的数组，请将出版商的引用存储在图书文档中：

{   _id: "oreilly",   name: "O'Reilly Media",   founded: 1980,   location: "CA"}
{   _id: 123456789,   title: "MongoDB: The Definitive Guide",   author: [ "Kristina Chodorow", "Mike Dirolf" ],   published_date: ISODate("2010-09-24"),   pages: 216,   language: "English",   publisher_id: "oreilly"}
{   _id: 234567890,   title: "50 Tips and Tricks for MongoDB Developer",   author: "Kristina Chodorow",   published_date: ISODate("2011-05-06"),   pages: 68,   language: "English",   publisher_id: "oreilly"}