Checks for database tables that have unindexed columns, and suggests how it can be remedied.

index.rake

namespace :db do
  desc "Output information about the indexes of a database"
  task indexes: :environment do
    connection = ActiveRecord::Base.connection
    tables = {}
    columns = []
    indexed_columns = []
    unindexed_columns = []
    
    connection.tables.collect do |table|
      table_columns = connection.columns(table).collect(&:name).select { |column| column.ends_with?("_id" || column.ends_with("_type")) }
      table_indexed_columns = connection.indexes(table).collect(&:columns).flatten.uniq
      table_unindexed_columns = table_columns - table_indexed_columns
      unindexed_columns << table_unindexed_columns
      tables[table.to_sym] = table_unindexed_columns if table_unindexed_columns.any?
    end

    unless tables.empty?
      tables.each_pair do |k, v|
        puts "#{k} has the following unindexed columns: #{v.join(", ")}"
      end
      
      puts "To add these index, paste the following into a migration file:\n\n"
      
      puts "def up"
      tables.each_pair do |k, v|
        v.each do |value|
          puts "  add_index :#{k}, :#{value}"
        end
      end
      puts "end\n\n"
        
      puts "def down"
      tables.each_pair do |k, v|
        v.each do |value|
          puts "  remove_index :#{k}, :#{value}"
        end
      end
      puts "end"
    end
  end
end