text: //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
  //  This source code is licensed under both the GPLv2 (found in the
  //  COPYING file in the root directory) and Apache 2.0 License
  //  (found in the LICENSE.Apache file in the root directory).
  //
  // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file. See the AUTHORS file for names of contributors.
  #pragma once
  
  #include <atomic>
  #include <deque>
  #include <functional>
  #include <limits>
  #include <set>
  #include <string>
  #include <utility>
  #include <vector>
  
  #include "db/column_family.h"
  #include "db/compaction_iterator.h"
  #include "db/dbformat.h"
  #include "db/flush_scheduler.h"
  #include "db/internal_stats.h"
  #include "db/job_context.h"
  #include "db/log_writer.h"
  #include "db/memtable_list.h"
  #include "db/range_del_aggregator.h"
  #include "db/version_edit.h"
  #include "db/write_controller.h"
  #include "db/write_thread.h"
  #include "options/db_options.h"
  #include "port/port.h"
  #include "rocksdb/compaction_filter.h"
  #include "rocksdb/compaction_job_stats.h"
  #include "rocksdb/db.h"
  #include "rocksdb/env.h"
  #include "rocksdb/memtablerep.h"
  #include "rocksdb/transaction_log.h"
  #include "table/scoped_arena_iterator.h"
  #include "util/autovector.h"
  #include "util/event_logger.h"
  #include "util/stop_watch.h"
  #include "util/thread_local.h"
  
  namespace rocksdb {
  
  class Arena;
  class MemTable;
  class SnapshotChecker;
  class TableCache;
  class Version;
  class VersionEdit;
  class VersionSet;
  
  class CompactionJob {
   public:
    CompactionJob(int job_id, Compaction* compaction,
                  const ImmutableDBOptions& db_options,
                  const EnvOptions env_options, VersionSet* versions,
                  const std::atomic<bool>* shutting_down,
                  const SequenceNumber preserve_deletes_seqnum,
                  LogBuffer* log_buffer,
                  Directory* db_directory, Directory* output_directory,
                  Statistics* stats, InstrumentedMutex* db_mutex,
                  Status* db_bg_error,
                  std::vector<SequenceNumber> existing_snapshots,
                  SequenceNumber earliest_write_conflict_snapshot,
                  const SnapshotChecker* snapshot_checker,
                  std::shared_ptr<Cache> table_cache, EventLogger* event_logger,
                  bool paranoid_file_checks, bool measure_io_stats,
                  const std::string& dbname,
                  CompactionJobStats* compaction_job_stats);
  
    ~CompactionJob();
  
    // no copy/move
    CompactionJob(CompactionJob&& job) = delete;
    CompactionJob(const CompactionJob& job) = delete;
    CompactionJob& operator=(const CompactionJob& job) = delete;
  
    // REQUIRED: mutex held
    void Prepare();
    // REQUIRED mutex not held
    Status Run();
  
    // REQUIRED: mutex held
    Status Install(const MutableCFOptions& mutable_cf_options);
  
   private:
    struct SubcompactionState;
  
    void AggregateStatistics();
    void GenSubcompactionBoundaries();
  
    // update the thread status for starting a compaction.
    void ReportStartedCompaction(Compaction* compaction);
    void AllocateCompactionOutputFileNumbers();
    // Call compaction filter. Then iterate through input and compact the
    // kv-pairs
    void ProcessKeyValueCompaction(SubcompactionState* sub_compact);
  
    Status FinishCompactionOutputFile(
        const Status& input_status, SubcompactionState* sub_compact,
        RangeDelAggregator* range_del_agg,
        CompactionIterationStats* range_del_out_stats,
        const Slice* next_table_min_key = nullptr);
    Status InstallCompactionResults(const MutableCFOptions& mutable_cf_options);
    void RecordCompactionIOStats();
    Status OpenCompactionOutputFile(SubcompactionState* sub_compact);
    void CleanupCompaction();
    void UpdateCompactionJobStats(
      const InternalStats::CompactionStats& stats) const;
    void RecordDroppedKeys(const CompactionIterationStats& c_iter_stats,
                           CompactionJobStats* compaction_job_stats = nullptr);
  
    void UpdateCompactionStats();
    void UpdateCompactionInputStatsHelper(
        int* num_files, uint64_t* bytes_read, int input_level);
  
    void LogCompaction();
  
    int job_id_;
  
    // CompactionJob state
    struct CompactionState;
    CompactionState* compact_;
    CompactionJobStats* compaction_job_stats_;
    InternalStats::CompactionStats compaction_stats_;
  
    // DBImpl state
    const std::string& dbname_;
    const ImmutableDBOptions& db_options_;
    const EnvOptions env_options_;
  
    Env* env_;
    // env_option optimized for compaction table reads
    EnvOptions env_optiosn_for_read_;
    VersionSet* versions_;
    const std::atomic<bool>* shutting_down_;
    const SequenceNumber preserve_deletes_seqnum_;
    LogBuffer* log_buffer_;
    Directory* db_directory_;
    Directory* output_directory_;
    Statistics* stats_;
    InstrumentedMutex* db_mutex_;
    Status* db_bg_error_;
    // If there were two snapshots with seq numbers s1 and
    // s2 and s1 < s2, and if we find two instances of a key k1 then lies
    // entirely within s1 and s2, then the earlier version of k1 can be safely
    // deleted because that version is not visible in any snapshot.
    std::vector<SequenceNumber> existing_snapshots_;
  
    // This is the earliest snapshot that could be used for write-conflict
    // checking by a transaction.  For any user-key newer than this snapshot, we
    // should make sure not to remove evidence that a write occurred.
    SequenceNumber earliest_write_conflict_snapshot_;
  
    const SnapshotChecker* const snapshot_checker_;
  
    std::shared_ptr<Cache> table_cache_;
  
    EventLogger* event_logger_;
  
    bool bottommost_level_;
    bool paranoid_file_checks_;
    bool measure_io_stats_;
    // Stores the Slices that designate the boundaries for each subcompaction
    std::vector<Slice> boundaries_;
    // Stores the approx size of keys covered in the range of each subcompaction
    std::vector<uint64_t> sizes_;
    Env::WriteLifeTimeHint write_hint_;
  };
  
  }  // namespace rocksdb
  