Configurable generation of add_index for references columns

Signed-off-by: Santiago Pastorino <santiago@wyeworks.com>

activerecord/lib/rails/generators/active_record/model/model_generator.rb

@@ -10,6 +10,7 @@ module ActiveRecord
       class_option :migration,  :type => :boolean
       class_option :timestamps, :type => :boolean
       class_option :parent,     :type => :string, :desc => "The parent class for the generated model"
+      class_option :indexes,    :type => :boolean, :default => true, :desc => "Add indexes for references and belongs_to columns"
 
       def create_migration_file
         return unless options[:migration] && options[:parent].nil?

activerecord/lib/rails/generators/active_record/model/templates/migration.rb

@@ -9,8 +9,10 @@ class <%= migration_class_name %> < ActiveRecord::Migration
 <% end  -%>
     end
 
+<% if  options[:indexes] %>
 <% attributes.select  {|attr| attr.reference? }.each do |attribute| -%>
     add_index :<%= table_name %>, :<%= attribute.name %>_id
 <% end  -%>
+<% end  %>
   end
 end

railties/test/generators/model_generator_test.rb

@@ -203,4 +203,45 @@ class ModelGeneratorTest < Rails::Generators::TestCase
     content = capture(:stderr){ run_generator ["object"] }
     assert_match /The name 'Object' is either already used in your application or reserved/, content
   end
+
+  def test_index_is_added_for_belongs_to_association
+    run_generator ["account", "supplier:belongs_to"]
+
+    assert_migration "db/migrate/create_accounts.rb" do |m|
+      assert_method :change, m do |up|
+        assert_match /add_index/, up
+      end
+    end
+  end
+
+  def test_index_is_added_for_references_association
+    run_generator ["account", "supplier:references"]
+
+    assert_migration "db/migrate/create_accounts.rb" do |m|
+      assert_method :change, m do |up|
+        assert_match /add_index/, up
+      end
+    end
+  end
+
+  def test_index_is_skipped_for_belongs_to_association
+    run_generator ["account", "supplier:belongs_to", "--no-indexes"]
+
+    assert_migration "db/migrate/create_accounts.rb" do |m|
+      assert_method :change, m do |up|
+        assert_no_match /add_index/, up
+      end
+    end
+  end
+
+  def test_index_is_skipped_for_references_association
+    run_generator ["account", "supplier:references", "--no-indexes"]
+
+    assert_migration "db/migrate/create_accounts.rb" do |m|
+      assert_method :change, m do |up|
+        assert_no_match /add_index/, up
+      end
+    end
+  end
+
 end