--- /dev/null
+module ActiveRecord
+ class IrreversibleMigration < ActiveRecordError#:nodoc:
+ 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
+
+ # 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 self.up
+ # add_column :accounts, :ssl_enabled, :boolean, :default => 1
+ # end
+ #
+ # def self.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 class 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 self.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 self.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
+ #
+ # * <tt>create_table(name, options)</tt> 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.
+ # * <tt>drop_table(name)</tt>: Drops the table called +name+.
+ # * <tt>rename_table(old_name, new_name)</tt>: Renames the table called +old_name+ to +new_name+.
+ # * <tt>add_column(table_name, column_name, type, options)</tt>: Adds a new column to the table called +table_name+
+ # named +column_name+ specified to be one of the following types:
+ # <tt>:string</tt>, <tt>:text</tt>, <tt>:integer</tt>, <tt>:float</tt>, <tt>:decimal</tt>, <tt>:datetime</tt>, <tt>:timestamp</tt>, <tt>:time</tt>,
+ # <tt>:date</tt>, <tt>:binary</tt>, <tt>:boolean</tt>. A default value can be specified by passing an
+ # +options+ hash like <tt>{ :default => 11 }</tt>. Other options include <tt>:limit</tt> and <tt>:null</tt> (e.g. <tt>{ :limit => 50, :null => false }</tt>)
+ # -- see ActiveRecord::ConnectionAdapters::TableDefinition#column for details.
+ # * <tt>rename_column(table_name, column_name, new_column_name)</tt>: Renames a column but keeps the type and content.
+ # * <tt>change_column(table_name, column_name, type, options)</tt>: Changes the column to a different type using the same
+ # parameters as add_column.
+ # * <tt>remove_column(table_name, column_name)</tt>: Removes the column named +column_name+ from the table called +table_name+.
+ # * <tt>add_index(table_name, column_names, options)</tt>: Adds a new index with the name of the column. Other options include
+ # <tt>:name</tt> and <tt>:unique</tt> (e.g. <tt>{ :name => "users_name_index", :unique => true }</tt>).
+ # * <tt>remove_index(table_name, index_name)</tt>: 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 <tt>ActiveRecord::IrreversibleMigration</tt> 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
+ # script/generate migration MyNewMigration
+ #
+ # where MyNewMigration is the name of your migration. The generator will
+ # create an empty migration file <tt>nnn_my_new_migration.rb</tt> in the <tt>db/migrate/</tt>
+ # directory where <tt>nnn</tt> is the next largest migration number.
+ #
+ # You may then edit the <tt>self.up</tt> and <tt>self.down</tt> methods of
+ # MyNewMigration.
+ #
+ # There is a special syntactic shortcut to generate migrations that add fields to a table.
+ # script/generate migration add_fieldname_to_tablename fieldname:string
+ #
+ # This will generate the file <tt>nnn_add_fieldname_to_tablename</tt>, which will look like this:
+ # class AddFieldnameToTablename < ActiveRecord::Migration
+ # def self.up
+ # add_column :tablenames, :fieldname, :string
+ # end
+ #
+ # def self.down
+ # remove_column :tablenames, :fieldname
+ # end
+ # end
+ #
+ # To run migrations against the currently configured database, use
+ # <tt>rake db:migrate</tt>. This will update the database by running all of the
+ # pending migrations, creating the <tt>schema_migrations</tt> table
+ # (see "About the schema_migrations table" section below) if missing.
+ #
+ # To roll the database back to a previous migration version, use
+ # <tt>rake db:migrate VERSION=X</tt> where <tt>X</tt> is the version to which
+ # you wish to downgrade. If any of the migrations throw an
+ # <tt>ActiveRecord::IrreversibleMigration</tt> 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 self.up
+ # Tag.find(:all).each { |tag| tag.destroy if tag.pages.empty? }
+ # end
+ #
+ # def self.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 self.up
+ # remove_column :items, :incomplete_items_count
+ # remove_column :items, :completed_items_count
+ # end
+ #
+ # def self.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 self.up
+ # execute "ALTER TABLE `pages_linked_pages` ADD UNIQUE `page_id_linked_page_id` (`page_id`,`linked_page_id`)"
+ # end
+ #
+ # def self.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 self.up
+ # add_column :people, :salary, :integer
+ # Person.reset_column_information
+ # Person.find(: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 self.up
+ # ...
+ # say_with_time "Updating salaries..." do
+ # Person.find(: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
+ # <tt>schema_info</tt> when using migrations. This table contained the
+ # version of the schema as of the last applied migration.
+ #
+ # Starting with Rails 2.1, the <tt>schema_info</tt> table is
+ # (automatically) replaced by the <tt>schema_migrations</tt> 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 environment.rb.
+ #
+ class Migration
+ @@verbose = true
+ cattr_accessor :verbose
+
+ class << self
+ def up_with_benchmarks #:nodoc:
+ migrate(:up)
+ end
+
+ def down_with_benchmarks #:nodoc:
+ migrate(: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
+
+ result = nil
+ time = Benchmark.measure { result = send("#{direction}_without_benchmarks") }
+
+ case direction
+ when :up then announce "migrated (%.4fs)" % time.real; write
+ when :down then announce "reverted (%.4fs)" % time.real; write
+ end
+
+ result
+ end
+
+ # Because the method added may do an alias_method, it can be invoked
+ # recursively. We use @ignore_new_methods as a guard to indicate whether
+ # it is safe for the call to proceed.
+ def singleton_method_added(sym) #:nodoc:
+ return if defined?(@ignore_new_methods) && @ignore_new_methods
+
+ begin
+ @ignore_new_methods = true
+
+ case sym
+ when :up, :down
+ klass = (class << self; self; end)
+ klass.send(:alias_method_chain, sym, "benchmarks")
+ end
+ ensure
+ @ignore_new_methods = false
+ 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 method_missing(method, *arguments, &block)
+ arg_list = arguments.map(&:inspect) * ', '
+
+ say_with_time "#{method}(#{arg_list})" do
+ unless arguments.empty? || method == :execute
+ arguments[0] = Migrator.proper_table_name(arguments.first)
+ end
+ ActiveRecord::Base.connection.send(method, *arguments, &block)
+ end
+ end
+ end
+ end
+
+ # MigrationProxy is used to defer loading of the actual migration classes
+ # until they are needed
+ class MigrationProxy
+
+ attr_accessor :name, :version, :filename
+
+ delegate :migrate, :announce, :write, :to=>:migration
+
+ private
+
+ def migration
+ @migration ||= load_migration
+ end
+
+ def load_migration
+ load(filename)
+ name.constantize
+ end
+
+ end
+
+ class Migrator#:nodoc:
+ class << self
+ def migrate(migrations_path, target_version = nil)
+ case
+ when target_version.nil? then up(migrations_path, target_version)
+ when current_version > target_version then down(migrations_path, target_version)
+ else up(migrations_path, target_version)
+ end
+ end
+
+ def rollback(migrations_path, steps=1)
+ migrator = self.new(:down, migrations_path)
+ start_index = migrator.migrations.index(migrator.current_migration)
+
+ return unless start_index
+
+ finish = migrator.migrations[start_index + steps]
+ down(migrations_path, finish ? finish.version : 0)
+ end
+
+ def up(migrations_path, target_version = nil)
+ self.new(:up, migrations_path, target_version).migrate
+ end
+
+ def down(migrations_path, target_version = nil)
+ self.new(:down, migrations_path, target_version).migrate
+ end
+
+ def run(direction, migrations_path, target_version)
+ self.new(direction, migrations_path, target_version).run
+ end
+
+ def schema_migrations_table_name
+ Base.table_name_prefix + 'schema_migrations' + Base.table_name_suffix
+ end
+
+ def get_all_versions
+ Base.connection.select_values("SELECT version FROM #{schema_migrations_table_name}").map(&: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
+ end
+
+ def initialize(direction, migrations_path, 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_path, @target_version = direction, migrations_path, 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.nil? && @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.nil?
+
+ runnable.each do |migration|
+ Base.logger.info "Migrating to #{migration.name} (#{migration.version})"
+
+ # On our way up, we skip migrating the ones we've already migrated
+ next if up? && migrated.include?(migration.version.to_i)
+
+ # On our way down, we skip reverting the ones we've never migrated
+ if down? && !migrated.include?(migration.version.to_i)
+ migration.announce 'never migrated, skipping'; migration.write
+ next
+ end
+
+ begin
+ ddl_transaction do
+ migration.migrate(@direction)
+ record_version_state_after_migrating(migration.version)
+ end
+ 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
+ end
+
+ def migrations
+ @migrations ||= begin
+ files = Dir["#{@migrations_path}/[0-9]*_*.rb"]
+
+ migrations = files.inject([]) do |klasses, file|
+ version, name = file.scan(/([0-9]+)_([_a-z0-9]*).rb/).first
+
+ raise IllegalMigrationNameError.new(file) unless version
+ version = version.to_i
+
+ if klasses.detect { |m| m.version == version }
+ raise DuplicateMigrationVersionError.new(version)
+ end
+
+ if klasses.detect { |m| m.name == name.camelize }
+ raise DuplicateMigrationNameError.new(name.camelize)
+ end
+
+ klasses << returning(MigrationProxy.new) do |migration|
+ migration.name = name.camelize
+ migration.version = version
+ migration.filename = file
+ end
+ end
+
+ migrations = migrations.sort_by(&:version)
+ 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)
+ sm_table = self.class.schema_migrations_table_name
+
+ @migrated_versions ||= []
+ if down?
+ @migrated_versions.delete(version.to_i)
+ Base.connection.update("DELETE FROM #{sm_table} WHERE version = '#{version}'")
+ else
+ @migrated_versions.push(version.to_i).sort!
+ Base.connection.insert("INSERT INTO #{sm_table} (version) VALUES ('#{version}')")
+ 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
projects / depot.git / blobdiff