Standalone migrations for postgres with foreign key support.

databases.rake

require 'yaml'
require 'logger'
require 'active_record'
require 'foreigner'

namespace :db do
  def create_database config
    options = {:charset => 'utf8'}

    create_db = lambda do |config|
      ActiveRecord::Base.establish_connection config.merge('database' => 'postgres')
      ActiveRecord::Base.connection.create_database config['database'], options
      ActiveRecord::Base.establish_connection config
    end

    begin
      create_db.call config
    rescue Exception => sqlerr
      $stderr.puts sqlerr
      $stderr.puts "Couldn't create database for #{config.inspect}, charset: utf8, collation: utf8_unicode_ci"
      $stderr.puts "(if you set the charset manually, make sure you have a matching collation)" if config['charset']
    end

  end

  def configure_connection(config = @config)
    ActiveRecord::Base.establish_connection config
    ActiveRecord::Base.logger = Logger.new STDOUT if config['logger']
    Foreigner.load
  end

  task :environment do
    DATABASE_ENV = ENV['DATABASE_ENV'] || 'development'
    MIGRATIONS_DIR = ENV['MIGRATIONS_DIR'] || 'db/migrate'
  end

  task :configuration => :environment do
    @config = YAML.load_file('db/config.yml')[DATABASE_ENV]
  end

  task :configure_connection => :configuration do
    configure_connection
  end

  desc 'Create the database from config/database.yml for the current DATABASE_ENV'
  task :create => :configure_connection do
    create_database @config
  end

  desc 'Drops the database for the current DATABASE_ENV'
  task :drop => :environment do
    config = YAML.load_file('db/config.yml')[DATABASE_ENV]
    db_to_drop = config['database']
    config['database'] = 'postgres'
    configure_connection config
    ActiveRecord::Base.connection.drop_database db_to_drop
  end

  desc 'Migrate the database (options: VERSION=x, VERBOSE=false).'
  task :migrate => :configure_connection do
    ActiveRecord::Migration.verbose = true
    ActiveRecord::Migrator.migrate MIGRATIONS_DIR, ENV['VERSION'] ? ENV['VERSION'].to_i : nil
  end

  desc 'Rolls the schema back to the previous version (specify steps w/ STEP=n).'
  task :rollback => :configure_connection do
    step = ENV['STEP'] ? ENV['STEP'].to_i : 1
    ActiveRecord::Migrator.rollback MIGRATIONS_DIR, step
  end

  desc "Retrieves the current schema version number"
  task :version => :configure_connection do
    puts "Current version: #{ActiveRecord::Migrator.current_version}"
  end

  namespace :schema do
    desc "Retrieves the current schema version number"
    task :dump => :configure_connection do
      ActiveRecord::SchemaDumper.dump
    end

    desc "Retrieves the current schema version number"
    task :load => :configure_connection do
      load("db/schema.rb")
    end
  end
end