Upgrading to Rails 4.2

If you're upgrading an existing application, it's a great idea to have good test coverage before going in. You should also first upgrade to Rails 4.1 in case you haven't and make sure your application still runs as expected before attempting to upgrade to Rails 4.2.

Major features which are upgraded in Rails 4.2.

Active Job

Active Job is a new framework in Rails 4.2. It is a common interface on top of queuing systems like Resque, Delayed Job, Sidekiq, and more.

Adequate Record

Adequate Record is a set of performance improvements in Active Record that makes common find and find_by calls and some association queries up to 2x faster.

Active Record will automatically take advantage of this feature on supported operations without any user involvement or code changes. Here are some examples of supported operations:

Post.find(1)  # First call generates and cache the prepared statement

Post.find(2)  # Subsequent calls reuse the cached prepared statement

Post.find_by_title('first post')

Post.find_by_title('second post')

Post.find_by(title: 'first post')

Post.find_by(title: 'second post')

post.comments

post.comments(true)