Is there a way to know that a migration is running?

I have a model and I want to "register" meta-data about the columns, e.g. a label, description, in an initializer.

As part of this I want to check the column actually exists and raise if not.

However the column will not exist until the migration to add the column has been run.

Therefore I wish to skip this check if the environment is being initalized for the purposes of a migration.

Is there a way to know that a migration is running? Or that the db:migrate rake task triggered the loading of the environment...

db:migrate

class Preferences < ActiveRecord::Base
def self.register(attrs)
raise if migration_not_running? && !column_names.include?(attrs.fetch(:column_name))
@schema << atrs
end

def self.schema
@schema ||=
end

private

def self.migration_not_running?
# ...?
end
end


1 Answer
1

What about checking if there are pending migrations, like the server does, when you try to load the views.

There's ActiveRecord::Migration.check_pending!, which raises ActiveRecord::PendingMigrationError if there are ones. But it uses connection.migration_context.needs_migration? logic under the hood, so it can be checked just like:

ActiveRecord::PendingMigrationError

connection.migration_context.needs_migration?

ActiveRecord::Base.connection.migration_context.needs_migration?


I understand, that it doesn't directly answers your question, but it's suggesting a possible alternative.

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