rails/rails — pull request #7173 by yahonda (2012-07-27 01:39:42+00:00)
Title: Modify the preference attribute from `:null => false` to `:null => true`

This commit addresses ORA-01400 errors with Oracle enhanced adapter.

Issue #4856 had been fixed and tested with the attribute `:null => false, :default => ""`.
Now `:null => false` attribute is not necessary to test this issue.

You can see investigations [here](https://github.com/rails/rails/issues/7138#issuecomment-7295387).