Skip to content
This repository
tree: bf00de03de
Fetching contributors…

Cannot retrieve contributors at this time

file 566 lines (499 sloc) 20.597 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566
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. 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
  # <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 connection
        ActiveRecord::Base.connection
      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
          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
Something went wrong with that request. Please try again.