Class: ActiveRecord::Migration

Inherits:
Object
  • Object
show all
Defined in:
lib/migration_revert/ext/migration.rb,
lib/migration_revert/ext/command_recorder.rb

Defined Under Namespace

Classes: CommandRecorder, ReversibleBlockHelper

Instance Method Summary collapse

Instance Method Details

#exec_migration(conn, direction) ⇒ Object 



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# File 'lib/migration_revert/ext/migration.rb', line 143

def exec_migration(conn, direction)
  @connection = conn
  if respond_to?(:change)
    if direction == :down
      revert { change }
    else
      change
    end
  else
    send(direction)
  end
ensure
  @connection = nil
end

#migrate(direction) ⇒ Object

Execute this migration in the named direction



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# File 'lib/migration_revert/ext/migration.rb', line 122

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|
    time = Benchmark.measure do
      exec_migration(conn, direction)
    end
  end

  case direction
  when :up   then announce "migrated (%.4fs)" % time.real; write
  when :down then announce "reverted (%.4fs)" % time.real; write
  end
end

#reversible ⇒ Object

Used to specify an operation that can be run in one direction or another. Call the methods up and down of the yielded object to run a block only in one given direction. The whole block will be called in the right order within the migration. In the following example, the looping on users will always be done when the three columns ‘first_name’, ‘last_name’ and ‘full_name’ exist, even when migrating down:

class SplitName < ActiveRecord::Migration
  def change
    add_column :users, :first_name, :string
    add_column :users, :last_name, :string

    reversible do |dir|
      User.reset_column_information
      User.all.each do |u|
        dir.up   { u.first_name, u.last_name = u.full_name.split(' ') }
        dir.down { u.full_name = "#{u.first_name} #{u.last_name}" }
        u.save
      end
    end

    revert { add_column :users, :full_name, :string }
  end
end



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# File 'lib/migration_revert/ext/migration.rb', line 97

def reversible
  helper = ReversibleBlockHelper.new(reverting?)
  transaction{ yield helper }
end

#revert(*migration_classes) ⇒ Object

Reverses the migration commands for the given block and the given migrations.

The following migration will remove the table ‘horses’ and create the table ‘apples’ on the way up, and the reverse on the way down.

class FixTLMigration < ActiveRecord::Migration
  def change
    revert do
      create_table(:horses) do |t|
        t.text :content
        t.datetime :remind_at
      end
    end
    create_table(:apples) do |t|
      t.string :variety
    end
  end
end

Or equivalently, if TenderloveMigration is defined as in the documentation for Migration:

class FixupTLMigration < ActiveRecord::Migration
  def change
    revert TenderloveMigration

    create_table(:apples) do |t|
      t.string :variety
    end
  end
end

This command can be nested.



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# File 'lib/migration_revert/ext/migration.rb', line 39

def revert(*migration_classes)
  run(*migration_classes.reverse, :revert => true) unless migration_classes.empty?
  if block_given?
    if @connection.respond_to? :revert
      @connection.revert { yield }
    else
      recorder = CommandRecorder.new(@connection)
      @connection = recorder
      suppress_messages do
        @connection.revert { yield }
      end
      @connection = recorder.delegate
      recorder.commands.each do |cmd, args, block|
        send(cmd, *args, &block)
      end
    end
  end
end

#reverting? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/migration_revert/ext/migration.rb', line 58

def reverting?
  @connection.respond_to?(:reverting) && @connection.reverting
end

#run(*migration_classes) ⇒ Object

Runs the given migration classes. Last argument can specify options:

  • :direction (default is :up)

  • :revert (default is false)



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# File 'lib/migration_revert/ext/migration.rb', line 107

def run(*migration_classes)
  opts = migration_classes.extract_options!
  dir = opts[:direction] || :up
  dir = (dir == :down ? :up : :down) if opts[:revert]
  if reverting?
    # If in revert and going :up, say, we want to execute :down without reverting, so
    revert { run(*migration_classes, direction: dir, revert: true) }
  else
    migration_classes.each do |migration_class|
      migration_class.new.exec_migration(@connection, dir)
    end
  end
end