use LIMIT SQL word in first - Closes #2783

activerecord/lib/active_record/relation/finder_methods.rb

@@ -114,7 +114,7 @@ module ActiveRecord
     def first(*args)
       if args.any?
         if args.first.kind_of?(Integer) || (loaded? && !args.first.kind_of?(Hash))
-          to_a.first(*args)
+          limit(*args).to_a
         else
           apply_finder_options(args.first).first
         end

activerecord/test/cases/finder_test.rb

@@ -243,6 +243,15 @@ class FinderTest < ActiveRecord::TestCase
     end
   end
 
+  def test_first_with_integer_should_use_sql_limit
+    assert_sql(/LIMIT 2/) { Topic.first(2).entries }
+  end
+
+  def test_first_and_last_with_integer_should_return_an_array
+    assert_kind_of Array, Topic.first(5)
+    assert_kind_of Array, Topic.last(5)
+  end
+
   def test_unexisting_record_exception_handling
     assert_raise(ActiveRecord::RecordNotFound) {
       Topic.find(1).parent