Little active record extension to make zero downtime column removal a lil more convenient in Rails

active_record_extensions.rb

# Put this in config/initializers
module ActiveRecord
  class Base
    def self.removed_columns(*names)
      @@removed_columns = Set.new(names.map(&:to_s))

      instance_eval do
        def columns
          cols = super
          cols.reject { |col| @@removed_columns.include?(col.name) }
        end
      end
    end
  end
end

example_model.rb

class Example < ActiveRecord::Base
  removed_columns :name, :removed
end