How to eager load association for an array of model records

Well, you could refind those objects. Map ':id' over your array, to get the records' ids, and then refind, this time eager-loading.

If your array of, say, Post model records is posts, then it'd be:

Post.find(posts.map &:id).includes(:blah)

In Rails 3, one can use preloader to eager-load associations on existing records.

ActiveRecord::Associations::Preloader.new(posts,:comments).run()

In Rails 4.1+ the call signature changed slightly:

ActiveRecord::Associations::Preloader.new.preload(posts,:comments)

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