Refactoring, testing and documenting pg_connection.distinct

1 files changed, 29 insertions, 0 deletions

diff --git a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
index f1362dd15f..872204c644 100644
--- a/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb
@@ -216,6 +216,35 @@ module ActiveRecord
         assert_equal "(number > 100)", index.where
       end
 
+      def test_distinct_zero_orders
+        assert_equal "DISTINCT posts.id",
+          @connection.distinct("posts.id", [])
+      end
+
+      def test_distinct_one_order
+        assert_equal "DISTINCT posts.id, posts.created_at AS alias_0",
+          @connection.distinct("posts.id", ["posts.created_at desc"])
+      end
+
+      def test_distinct_few_orders
+        assert_equal "DISTINCT posts.id, posts.created_at AS alias_0, posts.position AS alias_1",
+          @connection.distinct("posts.id", ["posts.created_at desc", "posts.position asc"])
+      end
+
+      def test_distinct_blank_not_nil_orders
+        assert_equal "DISTINCT posts.id, posts.created_at AS alias_0",
+          @connection.distinct("posts.id", ["posts.created_at desc", "", "   "])
+      end
+
+      def test_distinct_with_arel_order
+        order = Object.new
+        def order.to_sql
+          "posts.created_at desc"
+        end
+        assert_equal "DISTINCT posts.id, posts.created_at AS alias_0",
+          @connection.distinct("posts.id", [order])
+      end
+
       def test_distinct_with_nulls
         assert_equal "DISTINCT posts.title, posts.updater_id AS alias_0", @connection.distinct("posts.title", ["posts.updater_id desc nulls first"])
         assert_equal "DISTINCT posts.title, posts.updater_id AS alias_0", @connection.distinct("posts.title", ["posts.updater_id desc nulls last"])