2 files changed, 20 insertions, 1 deletions
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
index 38960ab873..7ec6abbc45 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb
@@ -324,6 +324,7 @@ module ActiveRecord
     #   change_table :table do |t|
     #     t.column
     #     t.index
+    #     t.rename_index
     #     t.timestamps
     #     t.change
     #     t.change_default
@@ -386,6 +387,13 @@ module ActiveRecord
         @base.index_exists?(@table_name, column_name, options)
       end
 
+      # Renames the given index on the table.
+      #
+      #  t.rename_index(:user_id, :account_id)
+      def rename_index(index_name, new_index_name)
+        @base.rename_index(@table_name, index_name, new_index_name)
+      end
+
       # Adds timestamps (+created_at+ and +updated_at+) columns to the table. See SchemaStatements#add_timestamps
       #
       #  t.timestamps
diff --git a/activerecord/lib/active_record/persistence.rb b/activerecord/lib/active_record/persistence.rb
index 8e749772a1..45f5406cc3 100644
--- a/activerecord/lib/active_record/persistence.rb
+++ b/activerecord/lib/active_record/persistence.rb
@@ -155,7 +155,18 @@ module ActiveRecord
       became.instance_variable_set("@new_record", new_record?)
       became.instance_variable_set("@destroyed", destroyed?)
       became.instance_variable_set("@errors", errors)
-      became.public_send("#{klass.inheritance_column}=", klass.name) unless self.class.descends_from_active_record?
+      became
+    end
+
+    # Wrapper around +becomes+ that also changes the instance's sti column value.
+    # This is especially useful if you want to persist the changed class in your
+    # database.
+    #
+    # Note: The old instance's sti column value will be changed too, as both objects
+    # share the same set of attributes.
+    def becomes!(klass)
+      became = becomes(klass)
+      became.public_send("#{klass.inheritance_column}=", klass.sti_name) unless self.class.descends_from_active_record?
       became
     end