Mongoid internal indexing for relational associations should happen i…

…n background

lib/mongoid/associations.rb

@@ -177,7 +177,7 @@ def referenced_in(name, options = {}, &block)
         opts = optionize(name, options, constraint(name, options, :in), &block)
         associate(Associations::ReferencedIn, opts)
         field(opts.foreign_key, :type => using_object_ids? ? BSON::ObjectID : String)
-        index(opts.foreign_key) if !embedded? && opts.index
+        index(opts.foreign_key, :background => true) if !embedded? && opts.index
         set_callback(:save, :before) { |document| document.update_foreign_keys }
       end
 
@@ -301,7 +301,7 @@ def reference_many(name, options, &block)
           foreign_key = "#{name.to_s.singularize}_ids"
           opts = optionize(name, options, constraint(name, options, :many_as_array), &block)
           field(foreign_key, :type => Array, :default => [])
-          index(foreign_key) if opts.index
+          index(foreign_key, :background => true) if opts.index
           associate(Associations::ReferencesManyAsArray, opts)
         else
           opts = optionize(name, options, constraint(name, options, :many), &block)

spec/unit/mongoid/associations_spec.rb

@@ -513,7 +513,7 @@
       context "when index is set" do
 
         it "puts an index on the foreign key" do
-          Game.expects(:index).with("person_id")
+          Game.expects(:index).with("person_id", :background => true)
           Game.referenced_in :person, :index => true
         end
       end
@@ -534,7 +534,6 @@
         Game.referenced_in :person
       end
     end
-
   end
 
   describe ".references_one" do
@@ -558,9 +557,7 @@
       it "defines the method on the association" do
         @person.game.extension.should == "Testing"
       end
-
     end
-
   end
 
   describe ".references_many" do
@@ -582,7 +579,6 @@
       it "defines the method on the association" do
         @person.posts.extension.should == "Testing"
       end
-
     end
 
     context "with a stored_as option provided" do