require "active_support/core_ext/module/delegation" require "active_support/core_ext/class/attribute_accessors" require "active_support/core_ext/array/wrap" module ActiveRecord # Exception that can be raised to stop migrations from going backwards. class IrreversibleMigration < ActiveRecordError end class DuplicateMigrationVersionError < ActiveRecordError#:nodoc: def initialize(version) super("Multiple migrations have the version number #{version}") end end class DuplicateMigrationNameError < ActiveRecordError#:nodoc: def initialize(name) super("Multiple migrations have the name #{name}") end end class UnknownMigrationVersionError < ActiveRecordError #:nodoc: def initialize(version) super("No migration with version number #{version}") end end class IllegalMigrationNameError < ActiveRecordError#:nodoc: def initialize(name) super("Illegal name for migration file: #{name}\n\t(only lower case letters, numbers, and '_' allowed)") end end # = Active Record Migrations # # Migrations can manage the evolution of a schema used by several physical # databases. It's a solution to the common problem of adding a field to make # a new feature work in your local database, but being unsure of how to # push that change to other developers and to the production server. With # migrations, you can describe the transformations in self-contained classes # that can be checked into version control systems and executed against # another database that might be one, two, or five versions behind. # # Example of a simple migration: # # class AddSsl < ActiveRecord::Migration # def up # add_column :accounts, :ssl_enabled, :boolean, :default => 1 # end # # def down # remove_column :accounts, :ssl_enabled # end # end # # This migration will add a boolean flag to the accounts table and remove it # if you're backing out of the migration. It shows how all migrations have # two methods +up+ and +down+ that describes the transformations # required to implement or remove the migration. These methods can consist # of both the migration specific methods like add_column and remove_column, # but may also contain regular Ruby code for generating data needed for the # transformations. # # Example of a more complex migration that also needs to initialize data: # # class AddSystemSettings < ActiveRecord::Migration # def up # create_table :system_settings do |t| # t.string :name # t.string :label # t.text :value # t.string :type # t.integer :position # end # # SystemSetting.create :name => "notice", # :label => "Use notice?", # :value => 1 # end # # def down # drop_table :system_settings # end # end # # This migration first adds the system_settings table, then creates the very # first row in it using the Active Record model that relies on the table. It # also uses the more advanced create_table syntax where you can specify a # complete table schema in one block call. # # == Available transformations # # * create_table(name, options) Creates a table called +name+ and # makes the table object available to a block that can then add columns to it, # following the same format as add_column. See example above. The options hash # is for fragments like "DEFAULT CHARSET=UTF-8" that are appended to the create # table definition. # * drop_table(name): Drops the table called +name+. # * rename_table(old_name, new_name): Renames the table called +old_name+ # to +new_name+. # * add_column(table_name, column_name, type, options): Adds a new column # to the table called +table_name+ # named +column_name+ specified to be one of the following types: # :string, :text, :integer, :float, # :decimal, :datetime, :timestamp, :time, # :date, :binary, :boolean. A default value can be # specified by passing an +options+ hash like { :default => 11 }. # Other options include :limit and :null (e.g. # { :limit => 50, :null => false }) -- see # ActiveRecord::ConnectionAdapters::TableDefinition#column for details. # * rename_column(table_name, column_name, new_column_name): Renames # a column but keeps the type and content. # * change_column(table_name, column_name, type, options): Changes # the column to a different type using the same parameters as add_column. # * remove_column(table_name, column_name): Removes the column named # +column_name+ from the table called +table_name+. # * add_index(table_name, column_names, options): Adds a new index # with the name of the column. Other options include # :name and :unique (e.g. # { :name => "users_name_index", :unique => true }). # * remove_index(table_name, :column => column_name): Removes the index # specified by +column_name+. # * remove_index(table_name, :name => index_name): Removes the index # specified by +index_name+. # # == Irreversible transformations # # Some transformations are destructive in a manner that cannot be reversed. # Migrations of that kind should raise an ActiveRecord::IrreversibleMigration # exception in their +down+ method. # # == Running migrations from within Rails # # The Rails package has several tools to help create and apply migrations. # # To generate a new migration, you can use # rails generate migration MyNewMigration # # where MyNewMigration is the name of your migration. The generator will # create an empty migration file timestamp_my_new_migration.rb # in the db/migrate/ directory where timestamp is the # UTC formatted date and time that the migration was generated. # # You may then edit the up and down methods of # MyNewMigration. # # There is a special syntactic shortcut to generate migrations that add fields to a table. # # rails generate migration add_fieldname_to_tablename fieldname:string # # This will generate the file timestamp_add_fieldname_to_tablename, which will look like this: # class AddFieldnameToTablename < ActiveRecord::Migration # def up # add_column :tablenames, :fieldname, :string # end # # def down # remove_column :tablenames, :fieldname # end # end # # To run migrations against the currently configured database, use # rake db:migrate. This will update the database by running all of the # pending migrations, creating the schema_migrations table # (see "About the schema_migrations table" section below) if missing. It will also # invoke the db:schema:dump task, which will update your db/schema.rb file # to match the structure of your database. # # To roll the database back to a previous migration version, use # rake db:migrate VERSION=X where X is the version to which # you wish to downgrade. If any of the migrations throw an # ActiveRecord::IrreversibleMigration exception, that step will fail and you'll # have some manual work to do. # # == Database support # # Migrations are currently supported in MySQL, PostgreSQL, SQLite, # SQL Server, Sybase, and Oracle (all supported databases except DB2). # # == More examples # # Not all migrations change the schema. Some just fix the data: # # class RemoveEmptyTags < ActiveRecord::Migration # def up # Tag.all.each { |tag| tag.destroy if tag.pages.empty? } # end # # def down # # not much we can do to restore deleted data # raise ActiveRecord::IrreversibleMigration, "Can't recover the deleted tags" # end # end # # Others remove columns when they migrate up instead of down: # # class RemoveUnnecessaryItemAttributes < ActiveRecord::Migration # def up # remove_column :items, :incomplete_items_count # remove_column :items, :completed_items_count # end # # def down # add_column :items, :incomplete_items_count # add_column :items, :completed_items_count # end # end # # And sometimes you need to do something in SQL not abstracted directly by migrations: # # class MakeJoinUnique < ActiveRecord::Migration # def up # execute "ALTER TABLE `pages_linked_pages` ADD UNIQUE `page_id_linked_page_id` (`page_id`,`linked_page_id`)" # end # # def down # execute "ALTER TABLE `pages_linked_pages` DROP INDEX `page_id_linked_page_id`" # end # end # # == Using a model after changing its table # # Sometimes you'll want to add a column in a migration and populate it # immediately after. In that case, you'll need to make a call to # Base#reset_column_information in order to ensure that the model has the # latest column data from after the new column was added. Example: # # class AddPeopleSalary < ActiveRecord::Migration # def up # add_column :people, :salary, :integer # Person.reset_column_information # Person.all.each do |p| # p.update_attribute :salary, SalaryCalculator.compute(p) # end # end # end # # == Controlling verbosity # # By default, migrations will describe the actions they are taking, writing # them to the console as they happen, along with benchmarks describing how # long each step took. # # You can quiet them down by setting ActiveRecord::Migration.verbose = false. # # You can also insert your own messages and benchmarks by using the +say_with_time+ # method: # # def up # ... # say_with_time "Updating salaries..." do # Person.all.each do |p| # p.update_attribute :salary, SalaryCalculator.compute(p) # end # end # ... # end # # The phrase "Updating salaries..." would then be printed, along with the # benchmark for the block when the block completes. # # == About the schema_migrations table # # Rails versions 2.0 and prior used to create a table called # schema_info when using migrations. This table contained the # version of the schema as of the last applied migration. # # Starting with Rails 2.1, the schema_info table is # (automatically) replaced by the schema_migrations table, which # contains the version numbers of all the migrations applied. # # As a result, it is now possible to add migration files that are numbered # lower than the current schema version: when migrating up, those # never-applied "interleaved" migrations will be automatically applied, and # when migrating down, never-applied "interleaved" migrations will be skipped. # # == Timestamped Migrations # # By default, Rails generates migrations that look like: # # 20080717013526_your_migration_name.rb # # The prefix is a generation timestamp (in UTC). # # If you'd prefer to use numeric prefixes, you can turn timestamped migrations # off by setting: # # config.active_record.timestamped_migrations = false # # In application.rb. # # == Reversible Migrations # # Starting with Rails 3.1, you will be able to define reversible migrations. # Reversible migrations are migrations that know how to go +down+ for you. # You simply supply the +up+ logic, and the Migration system will figure out # how to execute the down commands for you. # # To define a reversible migration, define the +change+ method in your # migration like this: # # class TenderloveMigration < ActiveRecord::Migration # def change # create_table(:horses) do # t.column :content, :text # t.column :remind_at, :datetime # end # end # end # # This migration will create the horses table for you on the way up, and # automatically figure out how to drop the table on the way down. # # Some commands like +remove_column+ cannot be reversed. If you care to # define how to move up and down in these cases, you should define the +up+ # and +down+ methods as before. # # If a command cannot be reversed, an # ActiveRecord::IrreversibleMigration exception will be raised when # the migration is moving down. # # For a list of commands that are reversible, please see # ActiveRecord::Migration::CommandRecorder. class Migration autoload :CommandRecorder, 'active_record/migration/command_recorder' class << self attr_accessor :delegate # :nodoc: end def self.method_missing(name, *args, &block) # :nodoc: (delegate || superclass.delegate).send(name, *args, &block) end cattr_accessor :verbose attr_accessor :name, :version def initialize @name = self.class.name @version = nil @connection = nil end # instantiate the delegate object after initialize is defined self.verbose = true self.delegate = new def up self.class.delegate = self return unless self.class.respond_to?(:up) self.class.up end def down self.class.delegate = self return unless self.class.respond_to?(:down) self.class.down end # Execute this migration in the named direction def migrate(direction) return unless respond_to?(direction) case direction when :up then announce "migrating" when :down then announce "reverting" end time = nil ActiveRecord::Base.connection_pool.with_connection do |conn| @connection = conn if respond_to?(:change) if direction == :down recorder = CommandRecorder.new(@connection) suppress_messages do @connection = recorder change end @connection = conn time = Benchmark.measure { recorder.inverse.each do |cmd, args| send(cmd, *args) end } else time = Benchmark.measure { change } end else time = Benchmark.measure { send(direction) } end @connection = nil end case direction when :up then announce "migrated (%.4fs)" % time.real; write when :down then announce "reverted (%.4fs)" % time.real; write end end def write(text="") puts(text) if verbose end def announce(message) text = "#{version} #{name}: #{message}" length = [0, 75 - text.length].max write "== %s %s" % [text, "=" * length] end def say(message, subitem=false) write "#{subitem ? " ->" : "--"} #{message}" end def say_with_time(message) say(message) result = nil time = Benchmark.measure { result = yield } say "%.4fs" % time.real, :subitem say("#{result} rows", :subitem) if result.is_a?(Integer) result end def suppress_messages save, self.verbose = verbose, false yield ensure self.verbose = save end def connection @connection || ActiveRecord::Base.connection end def method_missing(method, *arguments, &block) arg_list = arguments.map{ |a| a.inspect } * ', ' say_with_time "#{method}(#{arg_list})" do unless arguments.empty? || method == :execute arguments[0] = Migrator.proper_table_name(arguments.first) end return super unless connection.respond_to?(method) connection.send(method, *arguments, &block) end end def copy(destination, sources, options = {}) copied = [] FileUtils.mkdir_p(destination) unless File.exists?(destination) destination_migrations = ActiveRecord::Migrator.migrations(destination) last = destination_migrations.last sources.each do |name, path| source_migrations = ActiveRecord::Migrator.migrations(path) source_migrations.each do |migration| source = File.read(migration.filename) source = "# This migration comes from #{name} (originally #{migration.version})\n#{source}" if duplicate = destination_migrations.detect { |m| m.name == migration.name } options[:on_skip].call(name, migration) if File.read(duplicate.filename) != source && options[:on_skip] next end migration.version = next_migration_number(last ? last.version + 1 : 0).to_i new_path = File.join(destination, "#{migration.version}_#{migration.name.underscore}.rb") old_path, migration.filename = migration.filename, new_path last = migration FileUtils.cp(old_path, migration.filename) copied << migration options[:on_copy].call(name, migration, old_path) if options[:on_copy] destination_migrations << migration end end copied end def next_migration_number(number) if ActiveRecord::Base.timestamped_migrations [Time.now.utc.strftime("%Y%m%d%H%M%S"), "%.14d" % number].max else "%.3d" % number end end end # MigrationProxy is used to defer loading of the actual migration classes # until they are needed class MigrationProxy < Struct.new(:name, :version, :filename) def initialize(name, version, filename) super @migration = nil end def basename File.basename(filename) end delegate :migrate, :announce, :write, :to=>:migration private def migration @migration ||= load_migration end def load_migration require(File.expand_path(filename)) name.constantize.new end end class Migrator#:nodoc: class << self attr_writer :migrations_paths alias :migrations_path= :migrations_paths= def migrate(migrations_paths, target_version = nil) case when target_version.nil? up(migrations_paths, target_version) when current_version == 0 && target_version == 0 [] when current_version > target_version down(migrations_paths, target_version) else up(migrations_paths, target_version) end end def rollback(migrations_paths, steps=1) move(:down, migrations_paths, steps) end def forward(migrations_paths, steps=1) move(:up, migrations_paths, steps) end def up(migrations_paths, target_version = nil) self.new(:up, migrations_paths, target_version).migrate end def down(migrations_paths, target_version = nil) self.new(:down, migrations_paths, target_version).migrate end def run(direction, migrations_paths, target_version) self.new(direction, migrations_paths, target_version).run end def schema_migrations_table_name Base.table_name_prefix + 'schema_migrations' + Base.table_name_suffix end def get_all_versions table = Arel::Table.new(schema_migrations_table_name) Base.connection.select_values(table.project(table['version']).to_sql).map{ |v| v.to_i }.sort end def current_version sm_table = schema_migrations_table_name if Base.connection.table_exists?(sm_table) get_all_versions.max || 0 else 0 end end def proper_table_name(name) # Use the Active Record objects own table_name, or pre/suffix from ActiveRecord::Base if name is a symbol/string name.table_name rescue "#{ActiveRecord::Base.table_name_prefix}#{name}#{ActiveRecord::Base.table_name_suffix}" end def migrations_paths @migrations_paths ||= ['db/migrate'] # just to not break things if someone uses: migration_path = some_string Array.wrap(@migrations_paths) end def migrations_path migrations_paths.first end def migrations(paths) paths = Array.wrap(paths) files = Dir[*paths.map { |p| "#{p}/[0-9]*_*.rb" }] seen = Hash.new false migrations = files.map do |file| version, name = file.scan(/([0-9]+)_([_a-z0-9]*).rb/).first raise IllegalMigrationNameError.new(file) unless version version = version.to_i name = name.camelize raise DuplicateMigrationVersionError.new(version) if seen[version] raise DuplicateMigrationNameError.new(name) if seen[name] seen[version] = seen[name] = true MigrationProxy.new(name, version, file) end migrations.sort_by(&:version) end private def move(direction, migrations_paths, steps) migrator = self.new(direction, migrations_paths) start_index = migrator.migrations.index(migrator.current_migration) if start_index finish = migrator.migrations[start_index + steps] version = finish ? finish.version : 0 send(direction, migrations_paths, version) end end end def initialize(direction, migrations_paths, target_version = nil) raise StandardError.new("This database does not yet support migrations") unless Base.connection.supports_migrations? Base.connection.initialize_schema_migrations_table @direction, @migrations_paths, @target_version = direction, migrations_paths, target_version end def current_version migrated.last || 0 end def current_migration migrations.detect { |m| m.version == current_version } end def run target = migrations.detect { |m| m.version == @target_version } raise UnknownMigrationVersionError.new(@target_version) if target.nil? unless (up? && migrated.include?(target.version.to_i)) || (down? && !migrated.include?(target.version.to_i)) target.migrate(@direction) record_version_state_after_migrating(target.version) end end def migrate current = migrations.detect { |m| m.version == current_version } target = migrations.detect { |m| m.version == @target_version } if target.nil? && @target_version && @target_version > 0 raise UnknownMigrationVersionError.new(@target_version) end start = up? ? 0 : (migrations.index(current) || 0) finish = migrations.index(target) || migrations.size - 1 runnable = migrations[start..finish] # skip the last migration if we're headed down, but not ALL the way down runnable.pop if down? && target ran = [] runnable.each do |migration| Base.logger.info "Migrating to #{migration.name} (#{migration.version})" if Base.logger seen = migrated.include?(migration.version.to_i) # On our way up, we skip migrating the ones we've already migrated next if up? && seen # On our way down, we skip reverting the ones we've never migrated if down? && !seen migration.announce 'never migrated, skipping'; migration.write next end begin ddl_transaction do migration.migrate(@direction) record_version_state_after_migrating(migration.version) end ran << migration rescue => e canceled_msg = Base.connection.supports_ddl_transactions? ? "this and " : "" raise StandardError, "An error has occurred, #{canceled_msg}all later migrations canceled:\n\n#{e}", e.backtrace end end ran end def migrations @migrations ||= begin migrations = self.class.migrations(@migrations_paths) down? ? migrations.reverse : migrations end end def pending_migrations already_migrated = migrated migrations.reject { |m| already_migrated.include?(m.version.to_i) } end def migrated @migrated_versions ||= self.class.get_all_versions end private def record_version_state_after_migrating(version) table = Arel::Table.new(self.class.schema_migrations_table_name) @migrated_versions ||= [] if down? @migrated_versions.delete(version) stmt = table.where(table["version"].eq(version.to_s)).compile_delete Base.connection.delete stmt.to_sql else @migrated_versions.push(version).sort! stmt = table.compile_insert table["version"] => version.to_s Base.connection.insert stmt.to_sql end end def up? @direction == :up end def down? @direction == :down end # Wrap the migration in a transaction only if supported by the adapter. def ddl_transaction(&block) if Base.connection.supports_ddl_transactions? Base.transaction { block.call } else block.call end end end end