Example Rails migration to identify problematic database column names

remove_column.rb

class RemoveColumns < ActiveRecord::Migration[5.1]
  def change
    working = false
    columns = Answer.columns.map &:name
    rm_cols = columns - %w[cols to keep]
    rm_target = ''
    until working || rm_cols.empty?
      working = true
      begin
        puts "attempting to run query with #{rm_cols.first} column present"
        Question.last.reload.replies.reload.count
      rescue => e
        rm_target = rm_cols.shift.to_s.downcase.to_sym
        puts "had to rescue #{rm_target} column #{e}"
        remove_column :answer, rm_target
        working = false
      end
    end
    puts "works after removing #{rm_target}" if working
    # Stop the migration from passing, as we 
    # need to rerun this script multiple times
    exit 1
  end
end