Optimize none? and one? relation query methods to use LIMIT and COUNT.

Use SQL COUNT and LIMIT 1 queries for none? and one? methods if no block or limit is given,
instead of loading the entire collection to memory. The any? and many? methods already
follow this behavior.

[Eugene Gilburg & Rafael Mendonça França]

1 files changed, 34 insertions, 0 deletions

diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 5c5ab499a0..dec3a37f42 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -342,7 +342,9 @@ class RelationTest < ActiveRecord::TestCase
       assert_equal 0,     Developer.none.size
       assert_equal 0,     Developer.none.count
       assert_equal true,  Developer.none.empty?
+      assert_equal true, Developer.none.none?
       assert_equal false, Developer.none.any?
+      assert_equal false, Developer.none.one?
       assert_equal false, Developer.none.many?
     end
   end
@@ -1102,6 +1104,38 @@ class RelationTest < ActiveRecord::TestCase
     assert ! posts.limit(1).many?
   end
 
+  def test_none?
+    posts = Post.all
+    assert_queries(1) do
+      assert ! posts.none? # Uses COUNT()
+    end
+
+    assert ! posts.loaded?
+
+    assert_queries(1) do
+      assert posts.none? {|p| p.id < 0 }
+      assert ! posts.none? {|p| p.id == 1 }
+    end
+
+    assert posts.loaded?
+  end
+
+  def test_one
+    posts = Post.all
+    assert_queries(1) do
+      assert ! posts.one? # Uses COUNT()
+    end
+
+    assert ! posts.loaded?
+
+    assert_queries(1) do
+      assert ! posts.one? {|p| p.id < 3 }
+      assert posts.one? {|p| p.id == 1 }
+    end
+
+    assert posts.loaded?
+  end
+
   def test_build
     posts = Post.all