Ruby-on-rails 如何删除 Rails 3 中的迁移文件

How to delete migration files in Rails 3

提问by alvincrespo

I would like to remove/delete a migration file. How would I go about doing that? I know there are similar questions on here but as an update, is there a better way than doing script/destroy?

我想移除/删除迁移文件。我该怎么做？我知道这里有类似的问题，但作为更新，有没有比执行脚本/销毁更好的方法？

Also, should I do a db:resetor db:dropif I remove/delete a migration?

另外，我应该执行db:reset还是db:drop删除/删除迁移？

回答by Fábio Batista

I usually:

我通常：

1. Perform a rake db:migrate VERSION=XXXon all environments, to the version before the one I want to delete.
2. Delete the migration file manually.
3. If there are pending migrations (i.e., the migration I removed was not the last one), I just perform a new rake db:migrateagain.

1. rake db:migrate VERSION=XXX对所有环境执行 a到我要删除的版本之前的版本。
2. 手动删除迁移文件。
3. 如果有待处理的迁移（即，我删除的迁移不是最后一个），我只需rake db:migrate再次执行新的迁移。

If your application is already on production or staging, it's safer to just write another migration that destroys your table or columns.

如果您的应用程序已经在生产或暂存中，那么编写另一个会破坏您的表或列的迁移会更安全。

Another great reference for migrations is: http://guides.rubyonrails.org/migrations.html

迁移的另一个重要参考是：http: //guides.rubyonrails.org/migrations.html

回答by Gediminas

Another way to delete the migration:

删除迁移的另一种方法：

$ rails d migration SameMigrationNameAsUsedToGenerate

Use it before rake db:migrateis executed because changes in database will stay forever :) - or remove changes manually

在rake db:migrate执行之前使用它，因为数据库中的更改将永远保留:) - 或手动删除更改

回答by fOx

Run below commands from app's home directory:

从应用程序的主目录运行以下命令：

1. rake db:migrate:down VERSION="20140311142212"(here version is the timestamp prepended by rails when migration was created. This action will revert DB changes due to this migration)

2. Run "rails destroy migration migration_name"(migration_name is the one use chose while creating migration. Remove "timestamp_" from your migration file name to get it)

1. rake db:migrate:down VERSION="20140311142212"（这里的 version 是创建迁移时由 rails 加上的时间戳。此操作将还原由于此迁移而导致的数据库更改）

2. Run "rails destroy migration migration_name"（migration_name 是创建迁移时选择的一种用途。从迁移文件名中删除“ timestamp_”以获得它）

回答by Vicky

You can also run a down migration like so:

您还可以像这样运行向下迁移：

rake db:migrate:down VERSION=versionnumber

Refer to the Ruby on Rails guideon migrations for more info.

有关更多信息，请参阅有关迁移的Ruby on Rails 指南。

回答by Agnes

We can use,

我们可以用，

$ rails d migration table_name  

Which will delete the migration.

这将删除迁移。

回答by frenesim

Sometimes I found myself deleting the migration file and then deleting the corresponding entry on the table schema_migrations from the database. Not pretty but it works.

有时我发现自己删除了迁移文件，然后从数据库中删除了表 schema_migrations 上的相应条目。不漂亮，但它有效。

回答by random_user_0891

This also works in Rails 5.

这也适用于 Rails 5。

If the migration was the most recent one you can remove the database column(s) that the migration added by doing:

如果迁移是最新的，您可以通过执行以下操作删除迁移添加的数据库列：

rake db:rollback

then remove the migration file itself by running:

然后通过运行删除迁移文件本身：

rails d migration WhateverYourMigrationWasNamed.rb 

回答by stackPusher

None of these answers quite fit the problem i had as the migration i wanted to delete was missing: I had created and run a migration in some other branch, which was then discarded. The problem is when a migration is run, rails adds the version into a schema_migrationstable in the database. So even if it isn't listed in your db structure or schema, rails looks for it. You can reveal these orphaned migrations by running:

这些答案都不太适合我遇到的问题，因为我想删除的迁移丢失了：我已经在其他分支中创建并运行了迁移，然后将其丢弃。问题是在运行迁移时，rails 会将版本添加到schema_migrations数据库中的表中。因此，即使它未在您的数据库结构或模式中列出，rails 也会查找它。您可以通过运行来显示这些孤立的迁移：

rails db:migrate:status

rails db:migrate:status

Note the versions of the missing migrations and head into the db console:

注意缺少迁移的版本并进入数据库控制台：

rails dbconsole

rails dbconsole

Now remove the versions from the migration table manually:

现在手动从迁移表中删除版本：

delete from schema_migrations where version='<version>';

delete from schema_migrations where version='<version>';

You should now be good.

你现在应该很好。

回答by stackPusher

Look at 4.1 Rolling Back

看4.1回滚

http://guides.rubyonrails.org/migrations.html

http://guides.rubyonrails.org/migrations.html

$ rake db:rollback

$耙分贝：回滚

回答by Miguel Alatorre

I just had this same problem:

我刚刚遇到了同样的问题：

1. rails d migration fuu-this deleted the migration with the last timestamp
2. rails d migration fuu-this deleted the other migration
3. use git status to check that is not on the untracked files anymore
4. rails g migration fuu

1. rails d migration fuu- 这删除了具有最后时间戳的迁移
2. rails d migration fuu- 这删除了另一个迁移
3. 使用 git status 检查它不再位于未跟踪的文件中
4. rails g 迁移 fuu

That fixed it for me

那为我修好了