Merge pull request #23 from ff2248/fix/from-nil-in-mysql

Fix - `from(nil)` did not generate the expected SQL

lib/atomically/query_service.rb

@@ -88,7 +88,7 @@ def update_all_and_get_ids(*args)
     @klass.transaction do
       @relation.connection.execute('SET @ids := NULL')
       @relation.where("(SELECT @ids := CONCAT_WS(',', #{id_column}, @ids))").update_all(*args) # 撈出有真的被更新的 id，用逗號串在一起
-      ids = @klass.from(nil).pluck(Arel.sql('@ids')).first
+      ids = @klass.from(Arel.sql('DUAL')).pluck(Arel.sql('@ids')).first
     end
     return ids.try{|s| s.split(',').map(&:to_i).uniq.sort } || [] # 將 id 從字串取出來 @id 的格式範例: '1,4,12'
   end

test/test_helper.rb

@@ -51,3 +51,21 @@ def assert_queries(expected_count, event_key = 'sql.active_record')
 ensure
   ActiveSupport::Notifications.unsubscribe(subscriber)
 end
+
+def assert_sqls(expected_sqls, event_key = 'sql.active_record')
+  sqls = []
+  subscriber = ActiveSupport::Notifications.subscribe(event_key) do |_, _, _, _, payload|
+    next if payload[:sql].start_with?('PRAGMA table_info')
+    next if payload[:sql] =~ /\A(?:BEGIN TRANSACTION|COMMIT TRANSACTION|BEGIN|COMMIT)\z/i
+
+    sqls << payload[:sql]
+  end
+  yield
+
+  missing_sqls = expected_sqls - sqls
+  if missing_sqls.any?
+    assert_equal "expect #{expected_sqls} queried, but query following sqls:\n#{sqls.join("\n").tr('"', "'")}\n", "\nmissing sqls:\n#{missing_sqls.join("\n").tr('"', "'")}\n"
+  end
+ensure
+  ActiveSupport::Notifications.unsubscribe(subscriber)
+end

test/update_all_and_get_ids_test.rb

@@ -65,4 +65,15 @@ def test_on_relation_and_with_race_condition
       assert_equal ['bomb', '', 'flame thrower'], Item.order('id').pluck(:name)
     end
   end
+
+  def test_select_from_dual
+    skip if not Atomically::AdapterCheckService.new(UserItem).mysql?
+
+    in_sandbox do
+      assert_sqls(['SELECT @ids FROM DUAL']) do
+        assert_equal [1, 2], Item.joins(:users).atomically.update_all_and_get_ids('items.name = ""')
+        assert_equal ['', '', 'flame thrower'], Item.order('id').pluck(:name)
+      end
+    end
+  end
 end