/**
 *   Copyright 2016, Quickstep Research Group, Computer Sciences Department,
 *     University of Wisconsin—Madison.
 *
 *   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_EXECUTION_HEURISTICS_HPP_
#define QUICKSTEP_QUERY_OPTIMIZER_EXECUTION_HEURISTICS_HPP_

#include <vector>

#include "catalog/CatalogRelation.hpp"
#include "catalog/CatalogTypedefs.hpp"
#include "query_execution/QueryContext.hpp"
#include "query_execution/QueryContext.pb.h"
#include "query_optimizer/QueryPlan.hpp"
#include "utility/Macros.hpp"

#include "glog/logging.h"

namespace quickstep {
namespace optimizer {

/** \addtogroup QueryOptimizer
 *  @{
 */

/**
 * @brief The ExecutionHeuristics compiles certain heuristics for an execution plan
 *        as it is being converted to a physical plan. These heuristics can then be
 *        used to optimize the execution plan after it has been generated.
 **/
class ExecutionHeuristics {
 public:
  static const std::size_t kOneHundred = 100;
  static const std::size_t kOneThousand = 1000;
  static const std::size_t kTenThousand = 10000;
  static const std::size_t kHundredThousand = 100000;
  static const std::size_t kMillion = 1000000;

  static const std::size_t kCompressionFactor = 10;

  static const std::size_t kVeryLowSparsityHash = 1;
  static const std::size_t kLowSparsityHash = 2;
  static const std::size_t kMediumSparsityHash = 5;
  static const std::size_t kHighSparsityHash = 10;

  /**
   * @brief A simple internal class that holds information about various
   *        hash joins within the execution plan for a query.
   **/
  struct HashJoinInfo {
    HashJoinInfo(const QueryPlan::DAGNodeIndex build_operator_index,
                 const QueryPlan::DAGNodeIndex join_operator_index,
                 const CatalogRelation *referenced_stored_build_relation,
                 const CatalogRelation *referenced_stored_probe_relation,
                 std::vector<attribute_id> &&build_attributes,
                 std::vector<attribute_id> &&probe_attributes,
                 const QueryContext::join_hash_table_id join_hash_table_id)
        : build_operator_index_(build_operator_index),
          join_operator_index_(join_operator_index),
          referenced_stored_build_relation_(referenced_stored_build_relation),
          referenced_stored_probe_relation_(referenced_stored_probe_relation),
          build_attributes_(std::move(build_attributes)),
          probe_attributes_(std::move(probe_attributes)),
          join_hash_table_id_(join_hash_table_id) {
    }

    const QueryPlan::DAGNodeIndex build_operator_index_;
    const QueryPlan::DAGNodeIndex join_operator_index_;
    const CatalogRelation *referenced_stored_build_relation_;
    const CatalogRelation *referenced_stored_probe_relation_;
    const std::vector<attribute_id> build_attributes_;
    const std::vector<attribute_id> probe_attributes_;
    const QueryContext::join_hash_table_id join_hash_table_id_;
  };


  /**
   * @brief Constructor.
   **/
  ExecutionHeuristics() {}

  /**
   * @brief Saves information about a hash join used within the execution plan
   *        for a query.
   *
   * @param build_operator_index Index of the build operator of the hash join.
   * @param join_operator_index Index of the join operator of the hash join.
   * @param build_relation_id Id of the relation on which hash table is being built.
   * @param probe_relation_id Id of the relation on which hash table is being probed.
   * @param build_attributes List of attributes on which hash table is being built.
   * @param probe_attributes List of attributes on which hash table is being probed.
   * @param join_hash_table_id Id of the hash table which refers to the actual hash
   *        table within the query context.
   **/
  inline void addHashJoinInfo(const QueryPlan::DAGNodeIndex build_operator_index,
                              const QueryPlan::DAGNodeIndex join_operator_index,
                              const CatalogRelation *referenced_stored_build_relation,
                              const CatalogRelation *referenced_stored_probe_relation,
                              std::vector<attribute_id> &&build_attributes,
                              std::vector<attribute_id> &&probe_attributes,
                              const QueryContext::join_hash_table_id join_hash_table_id) {
    hash_joins_.push_back(HashJoinInfo(build_operator_index,
                                       join_operator_index,
                                       referenced_stored_build_relation,
                                       referenced_stored_probe_relation,
                                       std::move(build_attributes),
                                       std::move(probe_attributes),
                                       join_hash_table_id));
  }

  /**
   * @brief Optimize the execution plan based on heuristics generated
   *        during physical plan to execution plan conversion.
   *
   * @param query_plan A mutable reference to the query execution plan.
   * @param query_context_proto A mutable reference to the protobuf representation
   *        of the query context.
   **/
  void optimizeExecutionPlan(QueryPlan *query_plan, serialization::QueryContext *query_context_proto);

  /**
   * @brief Set the properties of the bloom filter proto based on the statistics
   *        of the given relation.
   *
   * @param bloom_filter_proto A mutable reference to the bloom filter protobuf representation.
   * @param relation The catalog relation on which bloom filter is being built.
   **/
  void setBloomFilterProperties(serialization::BloomFilter *bloom_filter_proto,
                                const CatalogRelation *relation);

 private:
  std::vector<HashJoinInfo> hash_joins_;

  DISALLOW_COPY_AND_ASSIGN(ExecutionHeuristics);
};

/** @} */

}  // namespace optimizer
}  // namespace quickstep

#endif /* QUICKSTEP_QUERY_OPTIMIZER_EXECUTION_HEURISTICS_HPP_ */