Rails 迁移更改顺序或顺序 [英] Rails migration change sequence or order

问题描述

我为我的 Rails 3 应用程序编写了一些迁移，但我想更改迁移的顺序.如何更改迁移顺序或顺序?是否像使用时间戳重命名迁移文件一样简单?

I wrote a few migrations for my Rails 3 app, but I would like to change the order of the migrations. How can I change the migration order or sequence? Is it as simple as renaming the migration file with what appears to be the timestamp?

我知道这是一个奇怪的问题，但基本上，我弄乱了我的迁移并删除了一些旧的迁移，现在我需要在创建新表之前删除一个表.我也知道我可以在 create-the-new-table 迁移中包含 drop 语句，但我很想知道如何重新排序迁移.

I know this is an odd question, but basically, I made a mess of my migrations and removed some old migrations and now I need to drop a table before creating a new one. I also know I can include the drop statement in the create-the-new-table migration, but I'm curious to know how to reorder migrations.

推荐答案

是的，它会按照前缀的顺序运行没有运行过的迁移.在早期版本的 Rails 中，可能是 2.1 或 2.2，它们曾经以 01 开始编号，但它们切换到时间戳.

Yes, it runs the migrations which have not been run in the order of the prefix. In earlier versions of rails, maybe 2.1 or 2.2, they used to be numbered starting with 01, but they switched to timestamps.

有一个表格可以跟踪已运行的迁移.目的是，多个开发人员添加了迁移，并稍后在版本控制中检查它们.因此，可能存在尚未运行但编号在已运行的最高编号迁移之前的迁移.

There is a table which keeps track of which migrations have run. The intentions is, multiple developers my have added migrations, and checked them in version control later. So, there may be a migration which has not run, but is numbered before the highest numbered migration which has run.

如果您更改了迁移顺序，(我也有)最好在重新排序的所有迁移之前先降低版本.将 VERSION 选项与 db:migrate 一起使用.如果您要保留(而不是向下运行)编号最高的迁移是 20120318143249，请这样调用.

If you change the migration sequence, (and I have) it's better to first down version before all the migrations you are re-sequencing. Use the VERSION option with db:migrate. If the highest numbered migration that you want to keep (not run the down) is 20120318143249, call it this way.

rake db:migrate VERSION=20120318143249

我经常运行一个迁移，然后重新运行它，直到我得到满意的迁移细节.有时我会重新订购它们，当我想为其中一个工作时，我希望它是最后一个.

I often run the down on a migration, and re-run it until I get the details of the migration to my satisfaction. Sometimes I re-order them, when I want to work on one of them, and I want it to be the last.

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