```ruby
class NormalizeTitles < ActiveRecord::Migration
  def up
    execute "update articles set title = replace(title, ' ', '_')"
    execute "update assignments set article_title = replace(article_title, ' ', '_')"
  end
end
```

Destroy duplicate assignments that differ by underscores
user
```ruby
class NormalizeTitles < ActiveRecord::Migration
  def up
    execute "update articles set title = replace(title, ' ', '_')"
    Assignment.all.each do |assignment|
      update_assignment(assignment)
    end
  end

  private

  def update_assignment(assignment)
    assignment.article_title = Utils.format_article_title(assignment.article_title)
    assignment.save
  rescue ActiveRecord::RecordNotUnique
    assignment.destroy
  end
end
```
assistant