2 files changed, 27 insertions, 2 deletions
diff --git a/activerecord/lib/active_record/migration/command_recorder.rb b/activerecord/lib/active_record/migration/command_recorder.rb
index 4e27293cb4..96b62fdd61 100644
--- a/activerecord/lib/active_record/migration/command_recorder.rb
+++ b/activerecord/lib/active_record/migration/command_recorder.rb
@@ -8,11 +8,14 @@ module ActiveRecord
     # * add_index
     # * add_timestamps
     # * create_table
+    # * create_join_table
     # * remove_timestamps
     # * rename_column
     # * rename_index
     # * rename_table
     class CommandRecorder
+      include JoinTable
+
       attr_accessor :commands, :delegate
 
       def initialize(delegate = nil)
@@ -48,7 +51,7 @@ module ActiveRecord
         super || delegate.respond_to?(*args)
       end
 
-      [:create_table, :change_table, :rename_table, :add_column, :remove_column, :rename_index, :rename_column, :add_index, :remove_index, :add_timestamps, :remove_timestamps, :change_column, :change_column_default].each do |method|
+      [:create_table, :create_join_table, :change_table, :rename_table, :add_column, :remove_column, :rename_index, :rename_column, :add_index, :remove_index, :add_timestamps, :remove_timestamps, :change_column, :change_column_default].each do |method|
         class_eval <<-EOV, __FILE__, __LINE__ + 1
           def #{method}(*args)          # def create_table(*args)
             record(:"#{method}", args)  #   record(:create_table, args)
@@ -62,6 +65,12 @@ module ActiveRecord
         [:drop_table, [args.first]]
       end
 
+      def invert_create_join_table(args)
+        table_name = find_join_table_name(*args)
+
+        [:drop_table, [table_name]]
+      end
+
       def invert_rename_table(args)
         [:rename_table, args.reverse]
       end
@@ -99,7 +108,6 @@ module ActiveRecord
       rescue NoMethodError => e
         raise e, e.message.sub(/ for #<.*$/, " via proxy for #{@delegate}")
       end
-
     end
   end
 end
diff --git a/activerecord/lib/active_record/migration/join_table.rb b/activerecord/lib/active_record/migration/join_table.rb
new file mode 100644
index 0000000000..01a580781b
--- /dev/null
+++ b/activerecord/lib/active_record/migration/join_table.rb
@@ -0,0 +1,17 @@
+module ActiveRecord
+  class Migration
+    module JoinTable #:nodoc:
+      private
+
+      def find_join_table_name(table_1, table_2, options = {})
+        options.delete(:table_name) { join_table_name(table_1, table_2) }
+      end
+
+      def join_table_name(table_1, table_2)
+        tables_names = [table_1, table_2].map(&:to_s).sort
+
+        tables_names.join("_").to_sym
+      end
+    end
+  end
+end