List unindexed foreign keys

indexes.rake

namespace :indexes do
  desc "List unindexed foreign keys"
  task :unindexed_foreign_keys => :environment do 
    ActiveRecord::Base.logger = Logger.new('/dev/null')

    missing_indexes = {}

    connection = ActiveRecord::Base.connection

    connection.tables.collect do |table|
      columns                = connection.columns(table).collect(&:name).select{ |column| column =~ /.*(_id|_type)$/ }
      indexed_columns        = connection.indexes(table).collect(&:columns).flatten.uniq
      unindexed              = columns - indexed_columns
      missing_indexes[table] = unindexed unless unindexed.empty?
    end

    unless missing_indexes.empty?
      puts "def self.up"
      missing_indexes.each do |table, columns|
        columns.each { |column| puts "    add_index :#{table}, :#{column}" }
      end
      puts "end"

      puts "def self.down"
      missing_indexes.each do |table, columns|
        columns.each { |column| puts "    remove_index :#{table}, :#{column}" }
      end
      puts "end"
    end

  end
end