Github user zuyu commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/300#discussion_r140575177
--- Diff: query_optimizer/rules/FuseHashSelect.hpp ---
@@ -0,0 +1,67 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied. See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ **/
+
+#ifndef QUICKSTEP_QUERY_OPTIMIZER_RULES_FUSE_HASH_SELECT_HPP_
+#define QUICKSTEP_QUERY_OPTIMIZER_RULES_FUSE_HASH_SELECT_HPP_
+
+#include <cstdint>
+#include <memory>
+#include <string>
+
+
--- End diff --
Remove this duplicated empty line, and unused headers, if any.
---
