Added a VERSION parameter to the migrate task that allows you to do "rake migrate VERSION=34" to migrate to the 34th version traveling up or down depending on the current version. Added ActiveRecord::Migrator.migrate that can figure out whether to go up or down based on the target version and the current

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@1780 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

3 files changed, 40 insertions, 0 deletions

diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 1c09b4e6dc..6eec1c03cf 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Added ActiveRecord::Migrator.migrate that can figure out whether to go up or down based on the target version and the current
+
 * Added better error message for "packets out of order" #1630 [courtenay]
 
 * Fixed first run of "rake migrate" on PostgreSQL by not expecting a return value on the id #1640
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index 365f57f366..a71e367ef2 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -108,6 +108,18 @@ module ActiveRecord
   #       add_column :items, :completed_items_count
   #     end
   #   end
+  #
+  # And some times 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
   class Migration
     class << self
       def up() end
@@ -122,6 +134,17 @@ module ActiveRecord
 
   class Migrator#:nodoc:
     class << self
+      def migrate(migrations_path, target_version = nil)
+        case
+          when target_version.nil?, current_version < target_version
+            up(migrations_path, target_version)
+          when current_version > target_version
+            down(migrations_path, target_version)
+          when current_version == target_version
+            return # You're on the right version
+        end
+      end
+      
       def up(migrations_path, target_version = nil)
         self.new(:up, migrations_path, target_version).migrate
       end
diff --git a/activerecord/test/migration_test.rb b/activerecord/test/migration_test.rb
index 9e84978395..d5081e5335 100644
--- a/activerecord/test/migration_test.rb
+++ b/activerecord/test/migration_test.rb
@@ -182,5 +182,20 @@ if ActiveRecord::Base.connection.supports_migrations?
       assert !Person.column_methods_hash.include?(:last_name)
       assert_raises(ActiveRecord::StatementInvalid) { Reminder.column_methods_hash }
     end
+    
+    def test_migrator_going_down_due_to_version_target
+      ActiveRecord::Migrator.up(File.dirname(__FILE__) + '/fixtures/migrations/', 1)
+      ActiveRecord::Migrator.migrate(File.dirname(__FILE__) + '/fixtures/migrations/', 0)
+
+      assert !Person.column_methods_hash.include?(:last_name)
+      assert_raises(ActiveRecord::StatementInvalid) { Reminder.column_methods_hash }
+
+      ActiveRecord::Migrator.migrate(File.dirname(__FILE__) + '/fixtures/migrations/')
+
+      Person.reset_column_information
+      assert Person.column_methods_hash.include?(:last_name)
+      assert Reminder.create("content" => "hello world", "remind_at" => Time.now)
+      assert_equal "hello world", Reminder.find(:first).content
+    end
   end
 end
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