query_optimizer/rules/UpdateExpression.hpp

/**
 * 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_UPDATE_EXPRESSION_HPP_
#define QUICKSTEP_QUERY_OPTIMIZER_RULES_UPDATE_EXPRESSION_HPP_

#include <string>
#include <unordered_map>

#include "query_optimizer/expressions/Expression.hpp"
#include "query_optimizer/expressions/ExprId.hpp"
#include "query_optimizer/rules/BottomUpRule.hpp"
#include "utility/Macros.hpp"

namespace quickstep {
namespace optimizer {

/** \addtogroup OptimizerRules
 *  @{
 */

/**
 * @brief Performs a bottom-up traverse on an expression tree and replaces named
 *        expressions with new expressions based on a substitution map.
 */
class UpdateExpression : public BottomUpRule<expressions::Expression> {
 public:
  /**
   * @brief Constructor.
   *
   * @param substitution_map Map from an ExprId of the named expression to
   *                         replace with an expression to be replaced with.
   */
  explicit UpdateExpression(
      const std::unordered_map<expressions::ExprId, expressions::ExpressionPtr> &substitution_map)
      : substitution_map_(substitution_map) {}

  std::string getName() const override { return "UpdateExpressions"; }

 protected:
  expressions::ExpressionPtr applyToNode(const expressions::ExpressionPtr &input) override;

 private:
  const std::unordered_map<expressions::ExprId, expressions::ExpressionPtr> &substitution_map_;

  DISALLOW_COPY_AND_ASSIGN(UpdateExpression);
};

/** @} */

}  // namespace optimizer
}  // namespace quickstep

#endif /* QUICKSTEP_QUERY_OPTIMIZER_RULES_UPDATE_EXPRESSION_HPP_ */