请注意，在 Cloud Firestore 中设计数据结构时，您可以使用几种不同的方案：
- 文档
- 多个集合
- 在文档中使用子集合
请根据您的使用场景考虑每种选项的优势。本指南概述了分层数据的一些示例结构。
文档中的嵌套数据
您可以在文档中嵌套复杂的对象，例如数组（映射）。
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子集合
如果您的数据可能会随着时间的推移而增加，您可以在文档中创建集合。
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根级集合
在数据库的根级别上创建集合，以整理不同的数据集。
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选择数据结构
如未另行说明，那么本页面中的内容已根据知识共享署名 4.0 许可获得了许可，并且代码示例已根据 Apache 2.0 许可获得了许可。有关详情，请参阅 Google 开发者网站政策。Java 是 Oracle 和/或其关联公司的注册商标。
最后更新时间 (UTC)：2025-08-16。
[null,null,["最后更新时间 (UTC)：2025-08-16。"],[],[],null,["\u003cbr /\u003e\n\nRemember, when you structure your data in Cloud Firestore, you\nhave a few different options:\n\n- Documents\n- Multiple collections\n- Subcollections within documents\n\nConsider the advantages of each option as they\nrelate to your use case. A few example structures for hierarchical data\nare outlined in this guide.\n\n\u003cbr /\u003e\n\nNested data in documents\n\nYou can nest complex objects like arrays or maps within documents.\n\n|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------|\n| - **Advantages:** If you have simple, fixed lists of data that you want to keep within your documents, this is easy to set up and streamlines your data structure. - **Limitations:** This isn't as scalable as other options, especially if your data expands over time. With larger or growing lists, the document also grows, which can lead to slower document retrieval times. - **What's a possible use case?** In a chat app, for example, you might store a user's 3 most recently visited chat rooms as a nested list in their profile. | - class alovelace - name : first : \"Ada\" last : \"Lovelace\" born : 1815 rooms : 0 : \"Software Chat\" 1 : \"Famous Figures\" 2 : \"Famous SWEs\" |\n\nSubcollections\n\nYou can create collections within documents when you have data that might expand\nover time.\n\n|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| - **Advantages:** As your lists grow, the size of the parent document doesn't change. You also get full query capabilities on subcollections, and you can issue [collection group queries](../query-data/queries) across subcollections. - **Limitations:** You can't easily delete subcollections. - **What's a possible use case?** In the same chat app, for example, you might create collections of users or messages within chat room documents. | - collections_bookmark science - class software name : \"software chat\" - collections_bookmark users - class alovelace first : \"Ada\" last : \"Lovelace\" - class sride first : \"Sally\" last : \"Ride\"\\` \u003cbr /\u003e \u003cbr /\u003e - class astrophysics - ... |\n\nRoot-level collections\n\nCreate collections at the root level of your database to organize disparate data\nsets.\n\n|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| - **Advantages:** Root-level collections are good for many-to-many relationships and provide powerful querying within each collection. - **Limitations:** Getting data that is naturally hierarchical might become increasingly complex as your database grows. - **What's a possible use case?** In the same chat app, for example, you might create one collection for users and another for rooms and messages. | - collections_bookmark users - class alovelace first : \"Ada\" last : \"Lovelace\" born : 1815 - class sride first : \"Sally\" last : \"Ride\" born : 1951 - collections_bookmark rooms - class software - collections_bookmark messages - class message1 from : \"alovelace\" content : \"...\" - class message2 from : \"sride\" content : \"...\" |"]]