Github user jianqiao commented on a diff in the pull request:
https://github.com/apache/incubator-quickstep/pull/171#discussion_r98543320
--- Diff: query_optimizer/rules/ReorderColumns.hpp ---
@@ -0,0 +1,75 @@
+/**
+ * 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_REORDER_COLUMNS_HPP_
+#define QUICKSTEP_QUERY_OPTIMIZER_RULES_REORDER_COLUMNS_HPP_
+
+#include <string>
+
+#include "query_optimizer/physical/Physical.hpp"
+#include "query_optimizer/rules/Rule.hpp"
+#include "utility/Macros.hpp"
+
+namespace quickstep {
+namespace optimizer {
+
+/** \addtogroup OptimizerRules
+ * @{
+ */
+
+/**
+ * @brief Rule that applies to a physical plan to adjust the orderings of
some
+ * intermediate nodes' output attributes to improve copy
performance.
+ *
+ * @note This optimization is based on the fact that the intermediate
relations
+ * all have SPLIT_ROW_STORE layouts. If this fact gets changed, the
rule's
+ * algorithm may need to be updated and the performance impact
should be
+ * re-evaluated.
+ */
+class ReorderColumns : public Rule<physical::Physical> {
+ public:
+ /**
+ * @brief Constructor.
+ */
+ ReorderColumns() {}
+
+ ~ReorderColumns() override {}
+
+ std::string getName() const override {
+ return "ReorderColumns";
+ }
+
+ physical::PhysicalPtr apply(const physical::PhysicalPtr &input) override;
+
+ private:
+ physical::PhysicalPtr applyInternal(const physical::PhysicalPtr &input,
+ bool lock_ordering);
+
+ // Whether the physical node can
+ inline static bool IsTransformable(const physical::PhysicalPtr &input);
+
+ DISALLOW_COPY_AND_ASSIGN(ReorderColumns);
+};
+
+/** @} */
+
+} // namespace optimizer
+} // namespace quickstep
+
+#endif /* QUICKSTEP_QUERY_OPTIMIZER_RULES_REORDER_COLUMNS_HPP_ */
--- End diff --
Updated.
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