C++ PtrVector::back方法代码示例

int main(int argc, char* argv[]) {
  google::InitGoogleLogging(argv[0]);
  gflags::ParseCommandLineFlags(&argc, &argv, true);

  // Detect the hardware concurrency level.
  const std::size_t num_hw_threads =
      DefaultsConfigurator::GetNumHardwareThreads();

  // Use the command-line value if that was supplied, else use the value
  // that we computed above, provided it did return a valid value.
  // TODO(jmp): May need to change this at some point to keep one thread
  //            available for the OS if the hardware concurrency level is high.
  const unsigned int real_num_workers = quickstep::FLAGS_num_workers != 0
                                      ? quickstep::FLAGS_num_workers
                                      : (num_hw_threads != 0 ?
                                         num_hw_threads
                                         : 1);

  if (real_num_workers > 0) {
    printf("Starting Quickstep with %d worker thread(s) and a %.2f GB buffer pool\n",
           real_num_workers,
           (static_cast<double>(quickstep::FLAGS_buffer_pool_slots) * quickstep::kSlotSizeBytes)/quickstep::kAGigaByte);
  } else {
    LOG(FATAL) << "Quickstep needs at least one worker thread to run";
  }

#ifdef QUICKSTEP_HAVE_FILE_MANAGER_HDFS
  if (quickstep::FLAGS_use_hdfs) {
    LOG(INFO) << "Using HDFS as the default persistent storage, with namenode at "
              << quickstep::FLAGS_hdfs_namenode_host << ":"
              << quickstep::FLAGS_hdfs_namenode_port << " and block replication factor "
              << quickstep::FLAGS_hdfs_num_replications << "\n";
  }
#endif

  // Initialize the thread ID based map here before the Foreman and workers are
  // constructed because the initialization isn't thread safe.
  quickstep::ClientIDMap::Instance();

  MessageBusImpl bus;
  bus.Initialize();

  // The TMB client id for the main thread, used to kill workers at the end.
  const client_id main_thread_client_id = bus.Connect();
  bus.RegisterClientAsSender(main_thread_client_id, kPoisonMessage);

  // Setup the paths used by StorageManager.
  string fixed_storage_path(quickstep::FLAGS_storage_path);
  if (!fixed_storage_path.empty()
      && (fixed_storage_path.back() != quickstep::kPathSeparator)) {
    fixed_storage_path.push_back(quickstep::kPathSeparator);
  }

  string catalog_path(fixed_storage_path);
  catalog_path.append("catalog.pb.bin");
  if (quickstep::FLAGS_initialize_db) {  // Initialize the database
    // TODO(jmp): Refactor the code in this file!
    LOG(INFO) << "Initializing the database, creating a new catalog file and storage directory\n";

    // Create the directory
    // TODO(jmp): At some point, likely in C++-17, we will just have the
    //            filesystem path, and we can clean this up
#ifdef QUICKSTEP_OS_WINDOWS
    std::filesystem::create_directories(fixed_storage_path);
    LOG(FATAL) << "Failed when attempting to create the directory: " << fixed_storage_path << "\n";
    LOG(FATAL) << "Check if the directory already exists. If so, delete it or move it before initializing \n";
#else
    {
      string path_name = "mkdir " + fixed_storage_path;
      if (std::system(path_name.c_str())) {
        LOG(FATAL) << "Failed when attempting to create the directory: " << fixed_storage_path << "\n";
      }
    }
#endif

    // Create the default catalog file.
    std::ofstream catalog_file(catalog_path);
    if (!catalog_file.good()) {
      LOG(FATAL) << "ERROR: Unable to open catalog.pb.bin for writing.\n";
    }

    quickstep::Catalog catalog;
    catalog.addDatabase(new quickstep::CatalogDatabase(nullptr, "default"));

    if (!catalog.getProto().SerializeToOstream(&catalog_file)) {
      LOG(FATAL) << "ERROR: Unable to serialize catalog proto to file catalog.pb.bin\n";
      return 1;
    }

    // Close the catalog file - it will be reopened below by the QueryProcessor.
    catalog_file.close();
  }

  // Setup QueryProcessor, including CatalogDatabase and StorageManager.
  std::unique_ptr<QueryProcessor> query_processor;
  try {
    query_processor.reset(new QueryProcessor(catalog_path, fixed_storage_path));
  } catch (const std::exception &e) {
    LOG(FATAL) << "FATAL ERROR DURING STARTUP: "
               << e.what()
//.........这里部分代码省略.........