How to check if Rails code is running within a migration

Is there some easy way to detect it?

I want to skip some code in the envirmonment.rb file wh开发者_如何学运维en the rake/rails migrations are running.

I had this problem in a legacy application I was maintaining. There were some observers that were interfering with migrations past a certain point, so I disabled them during migration by checking the application name and arguments

  # Activate observers that should always be running
  # config.active_record.observers = :cacher, :garbage_collector, :forum_observer# observers break a migrate from VERSION xxx - disable them for rake db:migrate
unless ( File.basename($0) == "rake" && ARGV.include?("db:migrate") )
  config.active_record.observers = :user_observer
end

Incorporating the comment below by @strw667, in Rails 6.1:

  # Activate observers that should always be running
  # config.active_record.observers = :cacher, :garbage_collector, :forum_observer# observers break a migrate from VERSION xxx - disable them for rake db:migrate
unless (File.basename($0) == "rake" &&  Rake.application.top_level_tasks == ["db:migrate")
  config.active_record.observers = :user_observer
end

Use the following code to disable/enable specific code during migrations:

if !ARGV.include?("db:migrate") )
  config.active_record.observers = :user_observer
end

If you are running code that need the DB up to date I would suggest:

ActiveRecord::Base.connected? # This returns false if the db couldn't be connected to.
&& !ActiveRecord::Migrator.needs_migration? # This checks if a migration needs to run.

This will handle if you are running other db: tasks like db:setup.

i think if u want to skip, just comment (#) on code.

or many choose on migration rake.

for example : rake db:migrate:up VERSION=2000123232 its mean , only 2000123232_create_article do migration.

or rake db:migrate VERSION=2000123232 mean start from after 2000123232

or rake db:migrate:down VERSION=2000123232

just rake help u can see what u need to rake.

Do you mean that?