text: /**
   *   Copyright 2011-2015 Quickstep Technologies LLC.
   *   Copyright 2015 Pivotal Software, Inc.
   *
   *   Licensed 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_EXPRESSIONS_NAMED_EXPRESSION_HPP_
  #define QUICKSTEP_QUERY_OPTIMIZER_EXPRESSIONS_NAMED_EXPRESSION_HPP_
  
  #include <memory>
  #include <string>
  #include <vector>
  
  #include "query_optimizer/OptimizerTree.hpp"
  #include "query_optimizer/expressions/ExprId.hpp"
  #include "query_optimizer/expressions/Scalar.hpp"
  #include "utility/Macros.hpp"
  
  namespace quickstep {
  namespace optimizer {
  namespace expressions {
  
  /** \addtogroup OptimizerExpressions
   *  @{
   */
  
  class NamedExpression;
  typedef std::shared_ptr<const NamedExpression> NamedExpressionPtr;
  
  /**
   * @brief Expression with an expression ID and name, including Alias and
   *        AttributeReference. A NamedExpression can be referenced by other
   *        expressions.
   */
  class NamedExpression : public Scalar {
   public:
    ~NamedExpression() override {}
  
    /**
     * @return The expression ID.
     */
    inline ExprId id() const { return id_; }
  
    /**
     * @return The (internal) attribute name.
     */
    inline const std::string& attribute_name() const { return attribute_name_; }
  
    /**
     * @return The attribute alias.
     */
    inline const std::string& attribute_alias() const { return attribute_alias_; }
  
    /**
     * @return The relation name. May be empty.
     */
    inline const std::string& relation_name() const { return relation_name_; }
  
    /**
     * @brief Compares this named expression with \p other. Two named expressions
     *        are equal if they have the same ExprId and are both Alias or
     *        AttributeReference.
     *
     * @param other Another named expression to compare with.
     * @return True if the named expression is equal to \p other.
     */
    inline bool equals(const NamedExpressionPtr &other) const {
      return getExpressionType() == other->getExpressionType() &&
             id_ == other->id();
    }
  
   protected:
    /**
     * @brief Constructor.
     *
     * @param id ExprId assigned to this expression.
     * @param attribute_name The (internal) attribute name.
     * @param attribute_alias The attribute name for display.
     * @param relation_name A relation name indicating where it comes from. Can be
     *                      empty. This is only for the printing purpose only.
     *                      When this named expression is converted to a
     *                      CatalogAttribute, the relation name may not be
     *                      \p relation_name.
     */
    NamedExpression(const ExprId id,
                    const std::string &attribute_name,
                    const std::string &attribute_alias,
                    const std::string &relation_name)
        : id_(id),
          attribute_name_(attribute_name),
          attribute_alias_(attribute_alias),
          relation_name_(relation_name) {}
  
   protected:
    void getFieldStringItems(
        std::vector<std::string> *inline_field_names,
        std::vector<std::string> *inline_field_values,
        std::vector<std::string> *non_container_child_field_names,
        std::vector<OptimizerTreeBaseNodePtr> *non_container_child_fields,
        std::vector<std::string> *container_child_field_names,
        std::vector<std::vector<OptimizerTreeBaseNodePtr>> *container_child_fields) const override;
  
   private:
    ExprId id_;
    std::string attribute_name_;
    std::string attribute_alias_;
    std::string relation_name_;
  
    DISALLOW_COPY_AND_ASSIGN(NamedExpression);
  };
  
  /** @} */
  
  }  // namespace expressions
  }  // namespace optimizer
  }  // namespace quickstep
  
  #endif /* QUICKSTEP_QUERY_OPTIMIZER_EXPRESSIONS_NAMED_EXPRESSION_HPP_ */
  