1 files changed, 27 insertions, 0 deletions
diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 11eb47917d..a3e3051b96 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,32 @@
 *Rails 3.1.0 (unreleased)*
 
+* Migrations can be defined as reversible, meaning that the migration system
+will figure out how to reverse your migration.  To use reversible migrations,
+just define the "change" method.  For example:
+
+    class MyMigration < ActiveRecord::Migration
+      def change
+        create_table(:horses) do
+          t.column :content, :text
+          t.column :remind_at, :datetime
+        end
+      end
+    end
+
+Some things cannot be automatically reversed for you.  If you know how to
+reverse those things, you should define 'up' and 'down' in your migration.  If
+you define something in `change` that cannot be reversed, an
+IrreversibleMigration exception will be raised when going down.
+
+* Migrations should use instance methods rather than class methods:
+    class FooMigration < ActiveRecord::Migration
+      def up
+        ...
+      end
+    end
+
+  [Aaron Patterson]
+
 * has_one maintains the association with separate after_create/after_update instead
   of a single after_save. [fxn]