/**
 * 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_STORAGE_PRELOADER_THREAD_HPP_
#define QUICKSTEP_STORAGE_PRELOADER_THREAD_HPP_

#include <cstddef>

#include "storage/StorageConfig.h"
#include "threading/Thread.hpp"
#include "utility/Macros.hpp"

namespace quickstep {

class CatalogDatabase;
class CatalogDatabaseLite;
class CatalogRelation;
class StorageManager;

/** \addtogroup Storage
 *  @{
 */

/**
 * @brief A thread that preloads all known blocks in a database into a
 *        StorageManager's buffer pool. A separate thread is used so that we
 *        can affinitize it like a worker and get allocations for buffer memory
 *        that are NUMA-local for at least some workers where possible.
 **/
class PreloaderThread : public Thread {
 public:
  /**
   * @brief Constructor.
   *
   * @param database All blocks in all non-temporary relations in this database
   *        will be loaded into the buffer pool.
   * @param storage_manager Blocks will be loaded into this StorageManager's
   *        buffer pool. Note that if the total blocks in the database exceed
   *        the size of the StorageManager's buffer pool, some blocks will be
   *        evicted and the database will not be fully preloaded.
   * @param cpu_id The ID of the CPU to affinitize this thread to, or -1 to
   *        indicate no affinity.
   * @param database_for_schemas All non-temporary relations in this database
   *        will be used for referencing the schema in a block for the
   *        distributed version.
   **/
  PreloaderThread(const CatalogDatabase &database,
                  StorageManager *storage_manager,
                  const int cpu_id = -1,
                  const CatalogDatabaseLite *database_for_schemas = nullptr)
      : database_(database),
        storage_manager_(storage_manager),
        cpu_id_(cpu_id),
        database_for_schemas_(database_for_schemas) {
  }

  ~PreloaderThread() override {
  }

 protected:
  void run() override;

 private:
#ifdef QUICKSTEP_HAVE_LIBNUMA
  /**
   * @brief Preload a relation which has a partition and a NUMA placement scheme.
   *
   * @param relation The relation to be preloaded.
   * @param num_previously_loaded_blocks The number of blocks already preloaded.
   * @param num_slots The maximum number of slots in the StorageManager.
   *
   * @warning This function may not detect skew on NUMA sockets, i.e. if a given
   *          NUMA socket has large number of blocks, preloading may cause the
   *          memory on that NUMA socket to be full. It is recommended to use
   *          this preloading when we are sure that each NUMA socket has been
   *          allocated sufficient amount of memory so as not to exceed that
   *          socket's memory limit.
   *
   * TODO(harshad) - Allow multiple preloader threads, each pinned to a NUMA
   *          socket in the system. Each thread should preload only its share of
   *          storage blocks.
   *
   * @return The number of blocks loaded during this function call.
   **/
  std::size_t preloadNUMAAware(const CatalogRelation &relation,
                               const std::size_t num_previously_loaded_blocks,
                               const std::size_t num_slots);
#endif

  const CatalogDatabase &database_;
  StorageManager *storage_manager_;

  const int cpu_id_;

  const CatalogDatabaseLite *database_for_schemas_;

  DISALLOW_COPY_AND_ASSIGN(PreloaderThread);
};

/** @} */

}  // namespace quickstep

#endif  // QUICKSTEP_STORAGE_PRELOADER_THREAD_HPP_