Added query option for Collection#distinct

lib/mongo/collection.rb

@@ -441,11 +441,17 @@ EOS
     #     [10010, 94108, 99701]
     #   @collection.distinct("name.age")
     #     [27, 24]
-    def distinct(key)
+    #
+    # You may also pass a document selector as the second parameter
+    # to limit the documents over which distinct is run:
+    #   @collection.distinct("name.age", {"name.age" => {"$gt" => 24}})
+    #     [27]
+    def distinct(key, query=nil)
       raise MongoArgumentError unless [String, Symbol].include?(key.class)
       command = OrderedHash.new
       command[:distinct] = @name
       command[:key]      = key.to_s
+      command[:query]    = query
 
       @db.command(command)["values"]
     end

test/test_collection.rb

@@ -75,7 +75,8 @@ class TestCollection < Test::Unit::TestCase
   end
 
   if @@version > "1.1"
-    def test_distinct
+    context "distinct queries" do
+      setup do
         @@test.remove
         @@test.insert([{:a => 0, :b => {:c => "a"}},
                        {:a => 1, :b => {:c => "b"}},
@@ -83,10 +84,21 @@ class TestCollection < Test::Unit::TestCase
                        {:a => 2, :b => {:c => "a"}},
                        {:a => 3},
                        {:a => 3}])
+      end
 
+      should "return distinct values" do
         assert_equal [0, 1, 2, 3], @@test.distinct(:a).sort
         assert_equal ["a", "b", "c"], @@test.distinct("b.c").sort
       end
+
+      should "filter collection with query" do 
+        assert_equal [2, 3], @@test.distinct(:a, {:a => {"$gt" => 1}}).sort
+      end
+
+      should "filter nested objects" do 
+        assert_equal ["a", "b"], @@test.distinct("b.c", {"b.c" => {"$ne" => "c"}}).sort
+      end
+    end
   end
 
   def test_safe_insert