query_optimizer/physical/TopLevelPlan.hpp

/**
 *   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_PHYSICAL_TOP_LEVEL_PLAN_HPP_
#define QUICKSTEP_QUERY_OPTIMIZER_PHYSICAL_TOP_LEVEL_PLAN_HPP_

#include <memory>
#include <string>
#include <vector>

#include "query_optimizer/OptimizerTree.hpp"
#include "query_optimizer/expressions/AttributeReference.hpp"
#include "query_optimizer/expressions/ExpressionUtil.hpp"
#include "query_optimizer/expressions/NamedExpression.hpp"
#include "query_optimizer/physical/Physical.hpp"
#include "query_optimizer/physical/PhysicalType.hpp"
#include "utility/Macros.hpp"

#include "glog/logging.h"

namespace quickstep {
namespace optimizer {
namespace physical {

/** \addtogroup OptimizerPhysical
 *  @{
 */

class TopLevelPlan;
typedef std::shared_ptr<const TopLevelPlan> TopLevelPlanPtr;

/**
 * @brief Root node of a physical plan tree. It contains the complete plan for
 *        a query and shared subplans referenced used in multiple places in
 *        the query plan.
 */
class TopLevelPlan : public Physical {
 public:
  PhysicalType getPhysicalType() const override {
    return PhysicalType::kTopLevelPlan;
  }

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

  /**
   * @return The complete query plan.
   */
  const PhysicalPtr& plan() const { return plan_; }

  /**
   * @return The vector of the shared subplans.
   */
  const std::vector<PhysicalPtr>& shared_subplans() const {
    return shared_subplans_;
  }

  /**
   * @brief Gets a shared subquery given by the position.
   *
   * @param index The position of the shared subplan to be returned.
   * @return The shared subplan at the index \p index in <shared_subplans_>.
   */
  const PhysicalPtr& shared_subplan_at(int index) const {
    return shared_subplans_[index];
  }

  PhysicalPtr copyWithNewChildren(
      const std::vector<PhysicalPtr> &new_children) const override {
    DCHECK_EQ(getNumChildren(), new_children.size());
    // The first child in the new_children is the main plan, and the remaining
    // children are shared subplans referenced in the main plan.
    std::vector<PhysicalPtr> new_shared_subplans;
    if (new_children.size() > 1u) {
      new_shared_subplans.insert(new_shared_subplans.end(),
                                 ++new_children.begin(),
                                 new_children.end());
    }
    return TopLevelPlan::Create(new_children[0], new_shared_subplans);
  }

  std::vector<expressions::AttributeReferencePtr> getOutputAttributes() const override {
    return plan()->getOutputAttributes();
  }

  std::vector<expressions::AttributeReferencePtr> getReferencedAttributes() const override {
    return {};
  }

  bool maybeCopyWithPrunedExpressions(
      const expressions::UnorderedNamedExpressionSet &referenced_expressions,
      PhysicalPtr *output) const override {
    // TopLevelPlan does not have any project expressions.
    return false;
  }

  /**
   * @brief Creates a TopLevelPlan.
   *
   * @param plan The query plan.
   * @param shared_subplans The subplans referenced in the main input plan.
   * @return An immutable TopLevelPlan.
   */
  static TopLevelPlanPtr Create(const PhysicalPtr &plan,
                                const std::vector<PhysicalPtr> &shared_subplans = std::vector<PhysicalPtr>()) {
    return TopLevelPlanPtr(new TopLevelPlan(plan, shared_subplans));
  }

 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:
  TopLevelPlan(const PhysicalPtr &plan,
               const std::vector<PhysicalPtr> &shared_subplans)
        : plan_(plan),
          shared_subplans_(shared_subplans) {
    addChild(plan);
    for (const PhysicalPtr &shared_subplan : shared_subplans) {
      addChild(shared_subplan);
    }
  }

  PhysicalPtr plan_;
  // Stored in the topological ordering based on dependencies.
  std::vector<PhysicalPtr> shared_subplans_;

  DISALLOW_COPY_AND_ASSIGN(TopLevelPlan);
};

/** @} */

}  // namespace physical
}  // namespace optimizer
}  // namespace quickstep

#endif /* QUERY_PLANNER_PHYSICAL_TOPLEVEL_PLAN_HPP_ */