rails/rails — pull request #7987 by alexisbernard (2012-10-18 09:17:19+00:00)
Title: Fix find_in_batches with customized primary_key on 3-2-stable

Back port @spastorino fix (https://github.com/rails/rails/pull/7652) from rails4 into 3.2.

I also noticed that find_in_batches is broken with string IDs when start option is not provided, but it works perfectly when start has been given. I fixed it with a test case in commit 827942195cdf4c6f09f540b60ee7c1b7a0d051b6. Maybe I went too far with that last commit?