Rake Task to show installed and pending migrations

While developing with Rails I often want to know which migrations are already installed and which are pending. Migrations have names and version numbers. In some rake migration tasks you must specify a migration - but this must be the number :-|

To rest my brain I wrote two rake tasks to show the installed and pending migrations. Feel free to use it for your own - just copy it to a .rake file in your /lib/task directory.

namespace :db do
  namespace :migrate do
    desc 'Shows installed migrations'
    task :installed => :environment do
      mt = ActiveRecord::Migrator.new(:up, "db/migrate/")
      list = mt.migrations.select{ |mi| mt.migrated.include?(mi.version.to_i) }
      print_migration_list(list)
    end

    desc 'Shows pending migrations'
    task :pending => :environment do
      mt = ActiveRecord::Migrator.new(:up, "db/migrate/")
      print_migration_list(mt.pending_migrations)
    end
  end
end

def print_migration_list(migrations)
  return if migrations.empty?
  
  max_length = migrations.inject(0) {|max, m| [max, m.name.length].max }
  puts "Version        Name"
  puts "---------------" + "-" * max_length
  migrations.each do |m|
    puts "#{m.version} #{m.name}"
  end
end

See also pastie.org