Analysis of RocsksDB code

DEFINE_string(benchmarks,
              "fillseq,"
              "fillsync,"
              "fillrandom,"
              "overwrite,"
              "readrandom,"
              "newiterator,"
              "newiteratorwhilewriting,"
              "seekrandom,"
              "seekrandomwhilewriting,"
              "seekrandomwhilemerging,"
              "readseq,"
              "readreverse,"
              "compact,"
              "readrandom,"
              "multireadrandom,"
              "readseq,"
              "readtocache,"
              "readreverse,"
              "readwhilewriting,"
              "readwhilemerging,"
              "readrandomwriterandom,"
              "updaterandom,"
              "randomwithverify,"
              "fill100K,"
              "crc32c,"
              "xxhash,"
              "compress,"
              "uncompress,"
              "acquireload,"
              "fillseekseq,"
              "randomtransaction,"
              "randomreplacekeys",

              "Comma-separated list of operations to run in the specified"
              " order. Available benchmarks:\n"
              "\tfillseq       -- write N values in sequential key"
              " order in async mode\n"
              "\tfillrandom    -- write N values in random key order in async"
              " mode\n"
              "\toverwrite     -- overwrite N values in random key order in"
              " async mode\n"
              "\tfillsync      -- write N/100 values in random key order in "
              "sync mode\n"
              "\tfill100K      -- write N/1000 100K values in random order in"
              " async mode\n"
              "\tdeleteseq     -- delete N keys in sequential order\n"
              "\tdeleterandom  -- delete N keys in random order\n"
              "\treadseq       -- read N times sequentially\n"
              "\treadtocache   -- 1 thread reading database sequentially\n"
              "\treadreverse   -- read N times in reverse order\n"
              "\treadrandom    -- read N times in random order\n"
              "\treadmissing   -- read N missing keys in random order\n"
              "\treadwhilewriting      -- 1 writer, N threads doing random "
              "reads\n"
              "\treadwhilemerging      -- 1 merger, N threads doing random "
              "reads\n"
              "\treadrandomwriterandom -- N threads doing random-read, "
              "random-write\n"
              "\tprefixscanrandom      -- prefix scan N times in random order\n"
              "\tupdaterandom  -- N threads doing read-modify-write for random "
              "keys\n"
              "\tappendrandom  -- N threads doing read-modify-write with "
              "growing values\n"
              "\tmergerandom   -- same as updaterandom/appendrandom using merge"
              " operator. "
              "Must be used with merge_operator\n"
              "\treadrandommergerandom -- perform N random read-or-merge "
              "operations. Must be used with merge_operator\n"
              "\tnewiterator   -- repeated iterator creation\n"
              "\tseekrandom    -- N random seeks, call Next seek_nexts times "
              "per seek\n"
              "\tseekrandomwhilewriting -- seekrandom and 1 thread doing "
              "overwrite\n"
              "\tseekrandomwhilemerging -- seekrandom and 1 thread doing "
              "merge\n"
              "\tcrc32c        -- repeated crc32c of 4K of data\n"
              "\txxhash        -- repeated xxHash of 4K of data\n"
              "\tacquireload   -- load N*1000 times\n"
              "\tfillseekseq   -- write N values in sequential key, then read "
              "them by seeking to each key\n"
              "\trandomtransaction     -- execute N random transactions and "
              "verify correctness\n"
              "\trandomreplacekeys     -- randomly replaces N keys by deleting "
              "the old version and putting the new version\n\n"
              "Meta operations:\n"
              "\tcompact     -- Compact the entire DB\n"
              "\tstats       -- Print DB stats\n"
              "\tlevelstats  -- Print the number of files and bytes per level\n"
              "\tsstables    -- Print sstable info\n"
              "\theapprofile -- Dump a heap profile (if supported by this"
              " port)\n");

the texts above is way to benchmark rocksDB.

the following is the way to configure variable for benchmark. 

DEFINE_int64(num, 1000000, "Number of key/values to place in database");

DEFINE_int64(numdistinct, 1000,
             "Number of distinct keys to use. Used in RandomWithVerify to "
             "read/write on fewer keys so that gets are more likely to find the"
             " key and puts are more likely to update the same key");

#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS
#endif

#ifndef GFLAGS
#include <cstdio>
int main() {
  fprintf(stderr, "Please install gflags to run rocksdb tools\n");
  return 1;
}
#else
#include <rocksdb/db_bench_tool.h>
int main(int argc, char** argv) { rocksdb::db_bench_tool(argc, argv); }
#endif  // GFLAGS

int db_bench_tool(int argc, char** argv) {
  rocksdb::port::InstallStackTraceHandler();
  SetUsageMessage(std::string("\nUSAGE:\n") + std::string(argv[0]) +
                  " [OPTIONS]...");
  ParseCommandLineFlags(&argc, &argv, true);

  FLAGS_compaction_style_e = (rocksdb::CompactionStyle) FLAGS_compaction_style;
  if (FLAGS_statistics) {
    dbstats = rocksdb::CreateDBStatistics();
  }
  FLAGS_compaction_pri_e = (rocksdb::CompactionPri)FLAGS_compaction_pri;

  std::vector<std::string> fanout = rocksdb::StringSplit(
      FLAGS_max_bytes_for_level_multiplier_additional, ',');
  for (size_t j = 0; j < fanout.size(); j++) {
    FLAGS_max_bytes_for_level_multiplier_additional_v.push_back(
#ifndef CYGWIN
        std::stoi(fanout[j]));
#else
        stoi(fanout[j]));
#endif
  }

  FLAGS_compression_type_e =
    StringToCompressionType(FLAGS_compression_type.c_str());

  if (!FLAGS_hdfs.empty()) {
    FLAGS_env  = new rocksdb::HdfsEnv(FLAGS_hdfs);
  }

  if (!strcasecmp(FLAGS_compaction_fadvice.c_str(), "NONE"))
    FLAGS_compaction_fadvice_e = rocksdb::Options::NONE;
  else if (!strcasecmp(FLAGS_compaction_fadvice.c_str(), "NORMAL"))
    FLAGS_compaction_fadvice_e = rocksdb::Options::NORMAL;
  else if (!strcasecmp(FLAGS_compaction_fadvice.c_str(), "SEQUENTIAL"))
    FLAGS_compaction_fadvice_e = rocksdb::Options::SEQUENTIAL;
  else if (!strcasecmp(FLAGS_compaction_fadvice.c_str(), "WILLNEED"))
    FLAGS_compaction_fadvice_e = rocksdb::Options::WILLNEED;
  else {
    fprintf(stdout, "Unknown compaction fadvice:%s\n",
            FLAGS_compaction_fadvice.c_str());
  }

  FLAGS_rep_factory = StringToRepFactory(FLAGS_memtablerep.c_str());

  // The number of background threads should be at least as much the
  // max number of concurrent compactions.
  FLAGS_env->SetBackgroundThreads(FLAGS_max_background_compactions);
  FLAGS_env->SetBackgroundThreads(FLAGS_max_background_flushes,
                                  rocksdb::Env::Priority::HIGH);

  // Choose a location for the test database if none given with --db=<path>
  if (FLAGS_db.empty()) {
    std::string default_db_path;
    rocksdb::Env::Default()->GetTestDirectory(&default_db_path);
    default_db_path += "/dbbench";
    FLAGS_db = default_db_path;
  }

  if (FLAGS_stats_interval_seconds > 0) {
    // When both are set then FLAGS_stats_interval determines the frequency
    // at which the timer is checked for FLAGS_stats_interval_seconds
    FLAGS_stats_interval = 1000;
  }

  //so far, rocksdb option setting 

  rocksdb::Benchmark benchmark;   // from now on, benchmark go newly 
  benchmark.Run();                // Run() function is next target for source analyzation.
  return 0;
}

void Run() {
    if (!SanityCheck()) {
      exit(1);
    }
    PrintHeader();
    Open(&open_options_);
    std::stringstream benchmark_stream(FLAGS_benchmarks);
    std::string name;
    while (std::getline(benchmark_stream, name, ',')) {
      // Sanitize parameters
      num_ = FLAGS_num;
      reads_ = (FLAGS_reads < 0 ? FLAGS_num : FLAGS_reads);
      writes_ = (FLAGS_writes < 0 ? FLAGS_num : FLAGS_writes);
      value_size_ = FLAGS_value_size;
      key_size_ = FLAGS_key_size;
      entries_per_batch_ = FLAGS_batch_size;
      write_options_ = WriteOptions();
      read_random_exp_range_ = FLAGS_read_random_exp_range;
      if (FLAGS_sync) {
        write_options_.sync = true;
      }
      write_options_.disableWAL = FLAGS_disable_wal;

      void (Benchmark::*method)(ThreadState*) = nullptr;
      void (Benchmark::*post_process_method)() = nullptr;

      bool fresh_db = false;
      int num_threads = FLAGS_threads;

      if (name == "fillseq") {
        fresh_db = true;
        method = &Benchmark::WriteSeq;
      } else if (name == "fillbatch") {
        fresh_db = true;
        entries_per_batch_ = 1000;
        method = &Benchmark::WriteSeq;
      } else if (name == "fillrandom") {
        fresh_db = true;
        method = &Benchmark::WriteRandom;
      } else if (name == "filluniquerandom") {
        fresh_db = true;
        if (num_threads > 1) {
          fprintf(stderr,
                  "filluniquerandom multithreaded not supported"
                  ", use 1 thread");
          num_threads = 1;
        }
        method = &Benchmark::WriteUniqueRandom;
      } else if (name == "overwrite") {
        method = &Benchmark::WriteRandom;
      } else if (name == "fillsync") {
        fresh_db = true;
        num_ /= 1000;
        write_options_.sync = true;
        method = &Benchmark::WriteRandom;
      } else if (name == "fill100K") {
        fresh_db = true;
        num_ /= 1000;
        value_size_ = 100 * 1000;
        method = &Benchmark::WriteRandom;
      } else if (name == "readseq") {
        method = &Benchmark::ReadSequential;
      } else if (name == "readtocache") {
        method = &Benchmark::ReadSequential;
        num_threads = 1;
        reads_ = num_;
      } else if (name == "readreverse") {
        method = &Benchmark::ReadReverse;
      } else if (name == "readrandom") {
        method = &Benchmark::ReadRandom;
      } else if (name == "readrandomfast") {
        method = &Benchmark::ReadRandomFast;
      } else if (name == "multireadrandom") {
        fprintf(stderr, "entries_per_batch = %" PRIi64 "\n",
                entries_per_batch_);
        method = &Benchmark::MultiReadRandom;
      } else if (name == "readmissing") {
        ++key_size_;
        method = &Benchmark::ReadRandom;
      } else if (name == "newiterator") {
        method = &Benchmark::IteratorCreation;
      } else if (name == "newiteratorwhilewriting") {
        num_threads++;  // Add extra thread for writing
        method = &Benchmark::IteratorCreationWhileWriting;
      } else if (name == "seekrandom") {
        method = &Benchmark::SeekRandom;
      } else if (name == "seekrandomwhilewriting") {
        num_threads++;  // Add extra thread for writing
        method = &Benchmark::SeekRandomWhileWriting;
      } else if (name == "seekrandomwhilemerging") {
        num_threads++;  // Add extra thread for merging
        method = &Benchmark::SeekRandomWhileMerging;
      } else if (name == "readrandomsmall") {
        reads_ /= 1000;
        method = &Benchmark::ReadRandom;
      } else if (name == "deleteseq") {
        method = &Benchmark::DeleteSeq;
      } else if (name == "deleterandom") {
        method = &Benchmark::DeleteRandom;
      } else if (name == "readwhilewriting") {
        num_threads++;  // Add extra thread for writing
        method = &Benchmark::ReadWhileWriting;
      } else if (name == "readwhilemerging") {
        num_threads++;  // Add extra thread for writing
        method = &Benchmark::ReadWhileMerging;
      } else if (name == "readrandomwriterandom") {
        method = &Benchmark::ReadRandomWriteRandom;
      } else if (name == "readrandommergerandom") {
        if (FLAGS_merge_operator.empty()) {
          fprintf(stdout, "%-12s : skipped (--merge_operator is unknown)\n",
                  name.c_str());
          exit(1);
        }
        method = &Benchmark::ReadRandomMergeRandom;
      } else if (name == "updaterandom") {
        method = &Benchmark::UpdateRandom;
      } else if (name == "appendrandom") {
        method = &Benchmark::AppendRandom;
      } else if (name == "mergerandom") {
        if (FLAGS_merge_operator.empty()) {
          fprintf(stdout, "%-12s : skipped (--merge_operator is unknown)\n",
                  name.c_str());
          exit(1);
        }
        method = &Benchmark::MergeRandom;
      } else if (name == "randomwithverify") {
        method = &Benchmark::RandomWithVerify;
      } else if (name == "fillseekseq") {
        method = &Benchmark::WriteSeqSeekSeq;
      } else if (name == "compact") {
        method = &Benchmark::Compact;
      } else if (name == "crc32c") {
        method = &Benchmark::Crc32c;
      } else if (name == "xxhash") {
        method = &Benchmark::xxHash;
      } else if (name == "acquireload") {
        method = &Benchmark::AcquireLoad;
      } else if (name == "compress") {
        method = &Benchmark::Compress;
      } else if (name == "uncompress") {
        method = &Benchmark::Uncompress;
#ifndef ROCKSDB_LITE
      } else if (name == "randomtransaction") {
        method = &Benchmark::RandomTransaction;
        post_process_method = &Benchmark::RandomTransactionVerify;
#endif  // ROCKSDB_LITE
      } else if (name == "randomreplacekeys") {
        fresh_db = true;
        method = &Benchmark::RandomReplaceKeys;
      } else if (name == "stats") {
        PrintStats("rocksdb.stats");
      } else if (name == "levelstats") {
        PrintStats("rocksdb.levelstats");
      } else if (name == "sstables") {
        PrintStats("rocksdb.sstables");
      } else if (!name.empty()) {  // No error message for empty name
        fprintf(stderr, "unknown benchmark '%s'\n", name.c_str());
        exit(1);
      }

      if (fresh_db) {
        if (FLAGS_use_existing_db) {
          fprintf(stdout, "%-12s : skipped (--use_existing_db is true)\n",
                  name.c_str());
          method = nullptr;
        } else {
          if (db_.db != nullptr) {
            db_.DeleteDBs();
            DestroyDB(FLAGS_db, open_options_);
          }
          for (size_t i = 0; i < multi_dbs_.size(); i++) {
            delete multi_dbs_[i].db;
            DestroyDB(GetDbNameForMultiple(FLAGS_db, i), open_options_);
          }
          multi_dbs_.clear();
        }
        Open(&open_options_);  // use open_options for the last accessed
      }

      if (method != nullptr) {
        fprintf(stdout, "DB path: [%s]\n", FLAGS_db.c_str());
        RunBenchmark(num_threads, name, method);
      }
      if (post_process_method != nullptr) {
        (this->*post_process_method)();
      }
    }
    if (FLAGS_statistics) {
     fprintf(stdout, "STATISTICS:\n%s\n", dbstats->ToString().c_str());
    }
  }

void PrintHeader() {
    PrintEnvironment();
    fprintf(stdout, "Keys:       %d bytes each\n", FLAGS_key_size);
    fprintf(stdout, "Values:     %d bytes each (%d bytes after compression)\n",
            FLAGS_value_size,
            static_cast<int>(FLAGS_value_size * FLAGS_compression_ratio + 0.5));
    fprintf(stdout, "Entries:    %" PRIu64 "\n", num_);
    fprintf(stdout, "Prefix:    %d bytes\n", FLAGS_prefix_size);
    fprintf(stdout, "Keys per prefix:    %" PRIu64 "\n", keys_per_prefix_);
    fprintf(stdout, "RawSize:    %.1f MB (estimated)\n",
            ((static_cast<int64_t>(FLAGS_key_size + FLAGS_value_size) * num_)
             / 1048576.0));
    fprintf(stdout, "FileSize:   %.1f MB (estimated)\n",
            (((FLAGS_key_size + FLAGS_value_size * FLAGS_compression_ratio)
              * num_)
             / 1048576.0));
    fprintf(stdout, "Write rate: %" PRIu64 " bytes/second\n",
            FLAGS_benchmark_write_rate_limit);
    if (FLAGS_enable_numa) {
      fprintf(stderr, "Running in NUMA enabled mode.\n");
#ifndef NUMA
      fprintf(stderr, "NUMA is not defined in the system.\n");
      exit(1);
#else
      if (numa_available() == -1) {
        fprintf(stderr, "NUMA is not supported by the system.\n");
        exit(1);
      }
#endif
    }

    auto compression = CompressionTypeToString(FLAGS_compression_type_e);
    fprintf(stdout, "Compression: %s\n", compression.c_str());

    switch (FLAGS_rep_factory) {
      case kPrefixHash:
        fprintf(stdout, "Memtablerep: prefix_hash\n");
        break;
      case kSkipList:
        fprintf(stdout, "Memtablerep: skip_list\n");
        break;
      case kVectorRep:
        fprintf(stdout, "Memtablerep: vector\n");
        break;
      case kHashLinkedList:
        fprintf(stdout, "Memtablerep: hash_linkedlist\n");
        break;
      case kCuckoo:
        fprintf(stdout, "Memtablerep: cuckoo\n");
        break;
    }
    fprintf(stdout, "Perf Level: %d\n", FLAGS_perf_level);

    PrintWarnings(compression.c_str());
    fprintf(stdout, "------------------------------------------------\n");
  }

void Open(Options* opts) {
    Options& options = *opts;

    assert(db_.db == nullptr);

    options.create_if_missing = !FLAGS_use_existing_db;
    options.create_missing_column_families = FLAGS_num_column_families > 1;
    options.db_write_buffer_size = FLAGS_db_write_buffer_size;
    options.write_buffer_size = FLAGS_write_buffer_size;
    options.max_write_buffer_number = FLAGS_max_write_buffer_number;
    options.min_write_buffer_number_to_merge =
      FLAGS_min_write_buffer_number_to_merge;
    options.max_write_buffer_number_to_maintain =
        FLAGS_max_write_buffer_number_to_maintain;
    options.max_background_compactions = FLAGS_max_background_compactions;
    options.max_subcompactions = static_cast<uint32_t>(FLAGS_subcompactions);
    options.max_background_flushes = FLAGS_max_background_flushes;
    options.compaction_style = FLAGS_compaction_style_e;
    options.compaction_pri = FLAGS_compaction_pri_e;
    if (FLAGS_prefix_size != 0) {
      options.prefix_extractor.reset(
          NewFixedPrefixTransform(FLAGS_prefix_size));
    }
    if (FLAGS_use_uint64_comparator) {
      options.comparator = test::Uint64Comparator();
      if (FLAGS_key_size != 8) {
        fprintf(stderr, "Using Uint64 comparator but key size is not 8.\n");
        exit(1);
      }
    }
    options.memtable_prefix_bloom_bits = FLAGS_memtable_bloom_bits;
    options.bloom_locality = FLAGS_bloom_locality;
    options.max_open_files = FLAGS_open_files;
    options.max_file_opening_threads = FLAGS_file_opening_threads;
    options.new_table_reader_for_compaction_inputs =
        FLAGS_new_table_reader_for_compaction_inputs;
    options.compaction_readahead_size = FLAGS_compaction_readahead_size;
    options.random_access_max_buffer_size = FLAGS_random_access_max_buffer_size;
    options.writable_file_max_buffer_size = FLAGS_writable_file_max_buffer_size;
    options.statistics = dbstats;
    if (FLAGS_enable_io_prio) {
      FLAGS_env->LowerThreadPoolIOPriority(Env::LOW);
      FLAGS_env->LowerThreadPoolIOPriority(Env::HIGH);
    }
    if (FLAGS_disable_flashcache_for_background_threads &&
        cachedev_fd_ == -1) {
      // Avoid creating the env twice when an use_existing_db is true
      cachedev_fd_ = open(FLAGS_flashcache_dev.c_str(), O_RDONLY);
      if (cachedev_fd_ < 0) {
        fprintf(stderr, "Open flash device failed\n");
        exit(1);
      }
      flashcache_aware_env_ = NewFlashcacheAwareEnv(FLAGS_env, cachedev_fd_);
      if (flashcache_aware_env_.get() == nullptr) {
        fprintf(stderr, "Failed to open flashcache device at %s\n",
                FLAGS_flashcache_dev.c_str());
        std::abort();
      }
      options.env = flashcache_aware_env_.get();
    } else {
      options.env = FLAGS_env;
    }
    options.disableDataSync = FLAGS_disable_data_sync;
    options.use_fsync = FLAGS_use_fsync;
    options.wal_dir = FLAGS_wal_dir;
    options.num_levels = FLAGS_num_levels;
    options.target_file_size_base = FLAGS_target_file_size_base;
    options.target_file_size_multiplier = FLAGS_target_file_size_multiplier;
    options.max_bytes_for_level_base = FLAGS_max_bytes_for_level_base;
    options.level_compaction_dynamic_level_bytes =
        FLAGS_level_compaction_dynamic_level_bytes;
    options.max_bytes_for_level_multiplier =
        FLAGS_max_bytes_for_level_multiplier;
    options.filter_deletes = FLAGS_filter_deletes;
    if (FLAGS_row_cache_size) {
      if (FLAGS_cache_numshardbits >= 1) {
        options.row_cache =
            NewLRUCache(FLAGS_row_cache_size, FLAGS_cache_numshardbits);
      } else {
        options.row_cache = NewLRUCache(FLAGS_row_cache_size);
      }
    }
    if ((FLAGS_prefix_size == 0) && (FLAGS_rep_factory == kPrefixHash ||
                                     FLAGS_rep_factory == kHashLinkedList)) {
      fprintf(stderr, "prefix_size should be non-zero if PrefixHash or "
                      "HashLinkedList memtablerep is used\n");
      exit(1);
    }
    switch (FLAGS_rep_factory) {
      case kSkipList:
        options.memtable_factory.reset(new SkipListFactory(
            FLAGS_skip_list_lookahead));
        break;
#ifndef ROCKSDB_LITE
      case kPrefixHash:
        options.memtable_factory.reset(
            NewHashSkipListRepFactory(FLAGS_hash_bucket_count));
        break;
      case kHashLinkedList:
        options.memtable_factory.reset(NewHashLinkListRepFactory(
            FLAGS_hash_bucket_count));
        break;
      case kVectorRep:
        options.memtable_factory.reset(
          new VectorRepFactory
        );
        break;
      case kCuckoo:
        options.memtable_factory.reset(NewHashCuckooRepFactory(
            options.write_buffer_size, FLAGS_key_size + FLAGS_value_size));
        break;
#else
      default:
        fprintf(stderr, "Only skip list is supported in lite mode\n");
        exit(1);
#endif  // ROCKSDB_LITE
    }
    if (FLAGS_use_plain_table) {
#ifndef ROCKSDB_LITE
      if (FLAGS_rep_factory != kPrefixHash &&
          FLAGS_rep_factory != kHashLinkedList) {
        fprintf(stderr, "Waring: plain table is used with skipList\n");
      }
      if (!FLAGS_mmap_read && !FLAGS_mmap_write) {
        fprintf(stderr, "plain table format requires mmap to operate\n");
        exit(1);
      }

      int bloom_bits_per_key = FLAGS_bloom_bits;
      if (bloom_bits_per_key < 0) {
        bloom_bits_per_key = 0;
      }

      PlainTableOptions plain_table_options;
      plain_table_options.user_key_len = FLAGS_key_size;
      plain_table_options.bloom_bits_per_key = bloom_bits_per_key;
      plain_table_options.hash_table_ratio = 0.75;
      options.table_factory = std::shared_ptr<TableFactory>(
          NewPlainTableFactory(plain_table_options));
#else
      fprintf(stderr, "Plain table is not supported in lite mode\n");
      exit(1);
#endif  // ROCKSDB_LITE
    } else if (FLAGS_use_cuckoo_table) {
#ifndef ROCKSDB_LITE
      if (FLAGS_cuckoo_hash_ratio > 1 || FLAGS_cuckoo_hash_ratio < 0) {
        fprintf(stderr, "Invalid cuckoo_hash_ratio\n");
        exit(1);
      }
      rocksdb::CuckooTableOptions table_options;
      table_options.hash_table_ratio = FLAGS_cuckoo_hash_ratio;
      table_options.identity_as_first_hash = FLAGS_identity_as_first_hash;
      options.table_factory = std::shared_ptr<TableFactory>(
          NewCuckooTableFactory(table_options));
#else
      fprintf(stderr, "Cuckoo table is not supported in lite mode\n");
      exit(1);
#endif  // ROCKSDB_LITE
    } else {
      BlockBasedTableOptions block_based_options;
      if (FLAGS_use_hash_search) {
        if (FLAGS_prefix_size == 0) {
          fprintf(stderr,
              "prefix_size not assigned when enable use_hash_search \n");
          exit(1);
        }
        block_based_options.index_type = BlockBasedTableOptions::kHashSearch;
      } else {
        block_based_options.index_type = BlockBasedTableOptions::kBinarySearch;
      }
      if (cache_ == nullptr) {
        block_based_options.no_block_cache = true;
      }
      block_based_options.cache_index_and_filter_blocks =
          FLAGS_cache_index_and_filter_blocks;
      block_based_options.pin_l0_filter_and_index_blocks_in_cache =
          FLAGS_pin_l0_filter_and_index_blocks_in_cache;
      block_based_options.block_cache = cache_;
      block_based_options.block_cache_compressed = compressed_cache_;
      block_based_options.block_size = FLAGS_block_size;
      block_based_options.block_restart_interval = FLAGS_block_restart_interval;
      block_based_options.filter_policy = filter_policy_;
      block_based_options.skip_table_builder_flush =
          FLAGS_skip_table_builder_flush;
      block_based_options.format_version = 2;
      options.table_factory.reset(
          NewBlockBasedTableFactory(block_based_options));
    }
    if (FLAGS_max_bytes_for_level_multiplier_additional_v.size() > 0) {
      if (FLAGS_max_bytes_for_level_multiplier_additional_v.size() !=
          (unsigned int)FLAGS_num_levels) {
        fprintf(stderr, "Insufficient number of fanouts specified %d\n",
                (int)FLAGS_max_bytes_for_level_multiplier_additional_v.size());
        exit(1);
      }
      options.max_bytes_for_level_multiplier_additional =
        FLAGS_max_bytes_for_level_multiplier_additional_v;
    }
    options.level0_stop_writes_trigger = FLAGS_level0_stop_writes_trigger;
    options.level0_file_num_compaction_trigger =
        FLAGS_level0_file_num_compaction_trigger;
    options.level0_slowdown_writes_trigger =
      FLAGS_level0_slowdown_writes_trigger;
    options.compression = FLAGS_compression_type_e;
    options.compression_opts.level = FLAGS_compression_level;
    options.WAL_ttl_seconds = FLAGS_wal_ttl_seconds;
    options.WAL_size_limit_MB = FLAGS_wal_size_limit_MB;
    options.max_total_wal_size = FLAGS_max_total_wal_size;

    if (FLAGS_min_level_to_compress >= 0) {
      assert(FLAGS_min_level_to_compress <= FLAGS_num_levels);
      options.compression_per_level.resize(FLAGS_num_levels);
      for (int i = 0; i < FLAGS_min_level_to_compress; i++) {
        options.compression_per_level[i] = kNoCompression;
      }
      for (int i = FLAGS_min_level_to_compress;
           i < FLAGS_num_levels; i++) {
        options.compression_per_level[i] = FLAGS_compression_type_e;
      }
    }
    options.soft_rate_limit = FLAGS_soft_rate_limit;
    options.hard_rate_limit = FLAGS_hard_rate_limit;
    options.soft_pending_compaction_bytes_limit =
        FLAGS_soft_pending_compaction_bytes_limit;
    options.hard_pending_compaction_bytes_limit =
        FLAGS_hard_pending_compaction_bytes_limit;
    options.delayed_write_rate = FLAGS_delayed_write_rate;
    options.allow_concurrent_memtable_write =
        FLAGS_allow_concurrent_memtable_write;
    options.enable_write_thread_adaptive_yield =
        FLAGS_enable_write_thread_adaptive_yield;
    options.write_thread_max_yield_usec = FLAGS_write_thread_max_yield_usec;
    options.write_thread_slow_yield_usec = FLAGS_write_thread_slow_yield_usec;
    options.rate_limit_delay_max_milliseconds =
      FLAGS_rate_limit_delay_max_milliseconds;
    options.table_cache_numshardbits = FLAGS_table_cache_numshardbits;
    options.max_grandparent_overlap_factor =
      FLAGS_max_grandparent_overlap_factor;
    options.disable_auto_compactions = FLAGS_disable_auto_compactions;
    options.source_compaction_factor = FLAGS_source_compaction_factor;

    // fill storage options
    options.allow_os_buffer = FLAGS_bufferedio;
    options.allow_mmap_reads = FLAGS_mmap_read;
    options.allow_mmap_writes = FLAGS_mmap_write;
    options.advise_random_on_open = FLAGS_advise_random_on_open;
    options.access_hint_on_compaction_start = FLAGS_compaction_fadvice_e;
    options.use_adaptive_mutex = FLAGS_use_adaptive_mutex;
    options.bytes_per_sync = FLAGS_bytes_per_sync;
    options.wal_bytes_per_sync = FLAGS_wal_bytes_per_sync;

    // merge operator options
    options.merge_operator = MergeOperators::CreateFromStringId(
        FLAGS_merge_operator);
    if (options.merge_operator == nullptr && !FLAGS_merge_operator.empty()) {
      fprintf(stderr, "invalid merge operator: %s\n",
              FLAGS_merge_operator.c_str());
      exit(1);
    }
    options.max_successive_merges = FLAGS_max_successive_merges;
    options.compaction_measure_io_stats = FLAGS_compaction_measure_io_stats;

    // set universal style compaction configurations, if applicable
    if (FLAGS_universal_size_ratio != 0) {
      options.compaction_options_universal.size_ratio =
        FLAGS_universal_size_ratio;
    }
    if (FLAGS_universal_min_merge_width != 0) {
      options.compaction_options_universal.min_merge_width =
        FLAGS_universal_min_merge_width;
    }
    if (FLAGS_universal_max_merge_width != 0) {
      options.compaction_options_universal.max_merge_width =
        FLAGS_universal_max_merge_width;
    }
    if (FLAGS_universal_max_size_amplification_percent != 0) {
      options.compaction_options_universal.max_size_amplification_percent =
        FLAGS_universal_max_size_amplification_percent;
    }
    if (FLAGS_universal_compression_size_percent != -1) {
      options.compaction_options_universal.compression_size_percent =
        FLAGS_universal_compression_size_percent;
    }
    options.compaction_options_universal.allow_trivial_move =
        FLAGS_universal_allow_trivial_move;
    if (FLAGS_thread_status_per_interval > 0) {
      options.enable_thread_tracking = true;
    }
    if (FLAGS_rate_limiter_bytes_per_sec > 0) {
      options.rate_limiter.reset(
          NewGenericRateLimiter(FLAGS_rate_limiter_bytes_per_sec));
    }

#ifndef ROCKSDB_LITE
    if (FLAGS_readonly && FLAGS_transaction_db) {
      fprintf(stderr, "Cannot use readonly flag with transaction_db\n");
      exit(1);
    }
#endif  // ROCKSDB_LITE

    if (FLAGS_num_multi_db <= 1) {
      OpenDb(options, FLAGS_db, &db_);
    } else {
      multi_dbs_.clear();
      multi_dbs_.resize(FLAGS_num_multi_db);
      for (int i = 0; i < FLAGS_num_multi_db; i++) {
        OpenDb(options, GetDbNameForMultiple(FLAGS_db, i), &multi_dbs_[i]);
      }
    }
    if (FLAGS_min_level_to_compress >= 0) {
      options.compression_per_level.clear();
    }
  }