导轨：什么呢schema.rb办？ [英] Rails: what does schema.rb do?

问题描述

我曾经以为 DB / schema.rb 中存储的数据库架构，使的Rails 项目的ActiveRecord 可以知道什么表/列它。

I used to think the db/schema.rb in a Rails project stored the database schema, so that ActiveRecord can know what table/column it has.

不过，早前我令人惊讶的发现我的项目运行正常后，我删除 DB / schema.rb ！

But earlier I surprisingly noticed that my project runs normally after I delete db/schema.rb!

所以，因为的Rails 可以不用它的工作，是什么 schema.rb 真的？

So, since the Rails can work without it, what does schema.rb really do?

推荐答案

在 schema.rb 供应主要有两个目的：

The schema.rb serves mainly two purposes:

1. 它记录了数据库架构的最终当前状态。通常情况下，尤其是当你有不止一对夫妇迁移的，很难仅仅从单纯的迁移扣除架构。随着present schema.rb ，你可以去看看那里。 ActiveRecord的本身确实不使用它。运行时它会内省的数据库，因为这是更安全，而不是期望用户保持 schema.rb 最多最新的。然而，为了避免你的开发人员的困惑，你应该始终保持一个文件，该文件是最新的最新与您的迁移。

1. It documents the final current state of the database schema. Often, especially when you have more than a couple of migrations, it's hard to deduct the schema just from the migrations alone. With a present schema.rb, you can just have a look there. ActiveRecord itself will indeed not use it. It will introspect the database during runtime as this is much safer than to expect users to keep the schema.rb up-to-date. However to avoid confusion of your developers, you should always maintain a file that is up-to-date with your migrations.

据所使用的测试来填充数据库模式。作为这样的耙分贝：模式：转储常被作为耙的一部分运行测试：prepare 运行。其目的是测试数据库的模式发展现状数据库完全一致。

It is used by the tests to populate the database schema. As such a rake db:schema:dump is often run as part of the rake test:prepare run. The purpose is that the schema of the test database exactly matches the current development database.

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