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我试图在我的 Rails 应用程序中运行一系列迁移中的一个。我怎么能这么做？我不想在它之前或之后运行任何迁移。谢谢。

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rake db:migrate VERSION=20098252345

give that a try.

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There's got to be a way to run the migration class via the console. I can't seem to get the migrations code to be recognizable.

However, as the comments indicate, it's preferred to run the migrations in order. Use:

rake db:migrate VERSION=##########

Copy and paste your code in the migration to script/console?

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最佳答案

rake db:migrate:redo VERSION=xxxxxxx, but that will run the down and then the up step. You could do this in conjunction with commenting out the down step temporarily.

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rake db:migrate:up VERSION=1234567890

similarly rake db:migrate:down to take a specific migration down. You can get a list of available rake tasks with rake -T.

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I've had to run a single migration that changed and needed to be re-run independently of all other migrations. Fire up the console and do this:

>> require 'db/migrate/your_migrations.rb'
=> ["YourMigrations"]
>> YourMigrations.up
=> etc... as the migration runs
>> YourMigration.down

More usefully this could be put into a rake task etc.

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I have a utility method that makes this very easy in development. I find that it helps me avoid creating too many migrations--normally I modify migrations until they have been deployed.

http://fullware.net/index.php/2011/05/26/easily-load-rails-migrations-for-console-execution/

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rake db:migrate:up VERSION=version_no

Will migrate( add) specific migration script

rake db:migrate:down VERSION=version_no

Will delete specific migration script

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Expanding on the answer by korch above, require did not work for me, but load did. To be concrete, for the migration file:

    class ChangeMinQuantityToRaces < ActiveRecord::Migration
def change
change_column :races, :min_quantity, :integer, :default => 0
end
end

in the console typing

    > load 'db/migrate/30130925110821_change_min_quantity_to_races.rb'
> ChangeMinQuantityToRaces.new.change

worked for me. 

    > Race.new.min_quantity # => 0

This was for ruby 1.9.3p484 (2013-11-22 revision 43786) [x86_64-linux] and Rails 3.2.13.

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rake db:migrate:redo version='xxxx'

Remember to put the quotation mark around xxxx, xxxx is the timestamp (or Migration ID) for your migration.

You may check the timestamps (Migration ID) for the previous migrations you've done by using

rake db:migrate:status
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Adding my 2¢ to this because I ran into this same issue:

If you absolutely want to run a migration over again without creating a new one, you can do the following:

rails dbconsole -p devdb=# delete from public.schema_migrations where version = '20150105181157';

And rails will "forget" that it ran the migration for 20150105181157. Now when you run db:migrate it will run it again.

This is almost always a bad idea though. The one instance where it could make sense is if you have a development branch and you haven't fleshed out your migration yet and want to add some things to it in development. But even then it's better to make your migration 2-way so you can properly rollback and retry repeatedly.

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I use this technique in development when I change a migration a significant amount, and I don't want to migrate down a ton and lose any data in those along the way (especially when I'm importing legacy data that takes a long time that I don't want to have to re-import again).

This is 100% hackish and I would definitely not recommend doing this in production, but it will do the trick:

  1. Move migration that you want to re-run out of its directory to a temporary place
  2. Generate another migration with the same name
  3. Copy/paste the original migration code into the newly generated migration file
  4. Run the new migration
  5. Delete the newly generated migration file
  6. Edit your schema migrations to remove the most recent value
  7. Restore the old migration file

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