Change ColumnFamilyData from struct to class

Summary: ColumnFamilyData grew a lot, there's much more data that it holds now. It makes more sense to encapsulate it better by making it a class. Test Plan: make check Reviewers: dhruba, haobo, kailiu, sdong CC: leveldb Differential Revision: https://reviews.facebook.net/D15579
11 years ago · fa99d53e55
parent 15999e728e
commit fa99d53e55
10 changed files with 203 additions and 183 deletions
--- a/db/column_family.cc
+++ b/db/column_family.cc
@ -62,45 +62,59 @@ void SuperVersion::Init(MemTable* new_mem, MemTableListVersion* new_imm,
 ColumnFamilyData::ColumnFamilyData(uint32_t id, const std::string& name,
                                   Version* dummy_versions,
                                   const ColumnFamilyOptions& options)
-    : id(id),
-      name(name),
-      dummy_versions(dummy_versions),
-      current(nullptr),
-      options(options),
-      mem(nullptr),
-      imm(options.min_write_buffer_number_to_merge),
-      super_version(nullptr),
-      log_number(0) {}
+    : id_(id),
+      name_(name),
+      dummy_versions_(dummy_versions),
+      current_(nullptr),
+      options_(options),
+      mem_(nullptr),
+      imm_(options.min_write_buffer_number_to_merge),
+      super_version_(nullptr),
+      super_version_number_(0),
+      log_number_(0) {}

 ColumnFamilyData::~ColumnFamilyData() {
-  if (super_version != nullptr) {
+  if (super_version_ != nullptr) {
    bool is_last_reference __attribute__((unused));
-    is_last_reference = super_version->Unref();
+    is_last_reference = super_version_->Unref();
    assert(is_last_reference);
-    super_version->Cleanup();
-    delete super_version;
+    super_version_->Cleanup();
+    delete super_version_;
  }
  // List must be empty
-  assert(dummy_versions->next_ == dummy_versions);
-  delete dummy_versions;
+  assert(dummy_versions_->next_ == dummy_versions_);
+  delete dummy_versions_;

-  if (mem != nullptr) {
-    delete mem->Unref();
+  if (mem_ != nullptr) {
+    delete mem_->Unref();
  }
  std::vector<MemTable*> to_delete;
-  imm.current()->Unref(&to_delete);
+  imm_.current()->Unref(&to_delete);
  for (MemTable* m : to_delete) {
    delete m;
  }
 }

 void ColumnFamilyData::CreateNewMemtable() {
-  assert(current != nullptr);
-  if (mem != nullptr) {
-    delete mem->Unref();
+  assert(current_ != nullptr);
+  if (mem_ != nullptr) {
+    delete mem_->Unref();
  }
-  mem = new MemTable(current->vset_->icmp_, options);
-  mem->Ref();
+  mem_ = new MemTable(current_->vset_->icmp_, options_);
+  mem_->Ref();
+}
+
+SuperVersion* ColumnFamilyData::InstallSuperVersion(
+    SuperVersion* new_superversion) {
+  new_superversion->Init(mem_, imm_.current(), current_);
+  SuperVersion* old_superversion = super_version_;
+  super_version_ = new_superversion;
+  ++super_version_number_;
+  if (old_superversion != nullptr && old_superversion->Unref()) {
+    old_superversion->Cleanup();
+    return old_superversion;  // will let caller delete outside of mutex
+  }
+  return nullptr;
 }

 ColumnFamilySet::ColumnFamilySet() : max_column_family_(0) {}
@ -162,8 +176,8 @@ ColumnFamilyData* ColumnFamilySet::CreateColumnFamily(
 void ColumnFamilySet::DropColumnFamily(uint32_t id) {
  auto cfd = column_family_data_.find(id);
  assert(cfd != column_family_data_.end());
-  column_families_.erase(cfd->second->name);
-  cfd->second->current->Unref();
+  column_families_.erase(cfd->second->GetName());
+  cfd->second->current()->Unref();
  droppped_column_families_.push_back(cfd->second);
  column_family_data_.erase(cfd);
 }
@ -175,8 +189,8 @@ MemTable* ColumnFamilyMemTablesImpl::GetMemTable(uint32_t column_family_id) {
  // API change in WriteBatch::Handler, which is a public API
  assert(cfd != nullptr);

-  if (log_number_ == 0 || log_number_ >= cfd->log_number) {
-    return cfd->mem;
+  if (log_number_ == 0 || log_number_ >= cfd->GetLogNumber()) {
+    return cfd->mem();
  } else {
    return nullptr;
  }
--- a/db/column_family.h
+++ b/db/column_family.h
@ -52,30 +52,63 @@ struct SuperVersion {
            Version* new_current);
 };

-// column family metadata
-struct ColumnFamilyData {
-  uint32_t id;
-  std::string name;
-  Version* dummy_versions; // Head of circular doubly-linked list of versions.
-  Version* current;        // == dummy_versions->prev_
-  ColumnFamilyOptions options;
-
-  MemTable* mem;
-  MemTableList imm;
-  SuperVersion* super_version;
-
-  // This is the earliest log file number that contains data from this
-  // Column Family. All earlier log files must be ignored and not
-  // recovered from
-  uint64_t log_number;
-
+// column family metadata. not thread-safe. should be protected by db_mutex
+class ColumnFamilyData {
+ public:
  ColumnFamilyData(uint32_t id, const std::string& name,
                   Version* dummy_versions, const ColumnFamilyOptions& options);
  ~ColumnFamilyData();

+  uint32_t GetID() const { return id_; }
+  const std::string& GetName() { return name_; }
+
+  void SetLogNumber(uint64_t log_number) { log_number_ = log_number; }
+  uint64_t GetLogNumber() const { return log_number_; }
+
+  ColumnFamilyOptions* options() { return &options_; }
+
+  MemTableList* imm() { return &imm_; }
+  MemTable* mem() { return mem_; }
+  Version* current() { return current_; }
+  Version* dummy_versions() { return dummy_versions_; }
+  void SetMemtable(MemTable* new_mem) { mem_ = new_mem; }
+  void SetCurrent(Version* current) { current_ = current; }
  void CreateNewMemtable();
+
+  SuperVersion* GetSuperVersion() const { return super_version_; }
+  uint64_t GetSuperVersionNumber() const {
+    return super_version_number_.load();
+  }
+  // will return a pointer to SuperVersion* if previous SuperVersion
+  // if its reference count is zero and needs deletion or nullptr if not
+  // As argument takes a pointer to allocated SuperVersion to enable
+  // the clients to allocate SuperVersion outside of mutex.
+  SuperVersion* InstallSuperVersion(SuperVersion* new_superversion);
+
+ private:
+  uint32_t id_;
+  const std::string name_;
+  Version* dummy_versions_;  // Head of circular doubly-linked list of versions.
+  Version* current_;         // == dummy_versions->prev_
+  ColumnFamilyOptions options_;
+
+  MemTable* mem_;
+  MemTableList imm_;
+  SuperVersion* super_version_;
+
+  // An ordinal representing the current SuperVersion. Updated by
+  // InstallSuperVersion(), i.e. incremented every time super_version_
+  // changes.
+  std::atomic<uint64_t> super_version_number_;
+
+  // This is the earliest log file number that contains data from this
+  // Column Family. All earlier log files must be ignored and not
+  // recovered from
+  uint64_t log_number_;
 };

+// Thread safe only for reading without a writer. All access should be
+// locked when adding or dropping column family
 class ColumnFamilySet {
 public:
  class iterator {
--- a/db/db_filesnapshot.cc
+++ b/db/db_filesnapshot.cc
@ -74,7 +74,7 @@ Status DBImpl::GetLiveFiles(std::vector<std::string>& ret,

  // Make a set of all of the live *.sst files
  std::set<uint64_t> live;
-  default_cfd_->current->AddLiveFiles(&live);
+  default_cfd_->current()->AddLiveFiles(&live);

  ret.clear();
  ret.reserve(live.size() + 2); //*.sst + CURRENT + MANIFEST
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@ -267,7 +267,6 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)
      shutting_down_(nullptr),
      bg_cv_(&mutex_),
      logfile_number_(0),
-      super_version_number_(0),
      tmp_batch_(),
      bg_compaction_scheduled_(0),
      bg_manual_only_(0),
@ -331,7 +330,7 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)

 DBImpl::~DBImpl() {
  // Wait for background work to finish
-  if (flush_on_destroy_ && default_cfd_->mem->GetFirstSequenceNumber() != 0) {
+  if (flush_on_destroy_ && default_cfd_->mem()->GetFirstSequenceNumber() != 0) {
    FlushMemTable(FlushOptions());
  }
  mutex_.Lock();
@ -930,8 +929,8 @@ Status DBImpl::RecoverLogFile(uint64_t log_number, SequenceNumber* max_sequence,
  std::unordered_map<int, VersionEdit> version_edits;
  for (auto cfd : *versions_->GetColumnFamilySet()) {
    VersionEdit edit;
-    edit.SetColumnFamily(cfd->id);
-    version_edits.insert({cfd->id, edit});
+    edit.SetColumnFamily(cfd->GetID());
+    version_edits.insert({cfd->GetID(), edit});
  }

  // Open the log file
@ -991,12 +990,12 @@ Status DBImpl::RecoverLogFile(uint64_t log_number, SequenceNumber* max_sequence,

    if (!read_only) {
      for (auto cfd : *versions_->GetColumnFamilySet()) {
-        if (cfd->mem->ApproximateMemoryUsage() >
-            cfd->options.write_buffer_size) {
-          auto iter = version_edits.find(cfd->id);
+        if (cfd->mem()->ApproximateMemoryUsage() >
+            cfd->options()->write_buffer_size) {
+          auto iter = version_edits.find(cfd->GetID());
          assert(iter != version_edits.end());
          VersionEdit* edit = &iter->second;
-          status = WriteLevel0TableForRecovery(cfd->mem, edit);
+          status = WriteLevel0TableForRecovery(cfd->mem(), edit);
          // we still want to clear the memtable, even if the recovery failed
          cfd->CreateNewMemtable();
          if (!status.ok()) {
@ -1011,12 +1010,12 @@ Status DBImpl::RecoverLogFile(uint64_t log_number, SequenceNumber* max_sequence,

  if (!read_only) {
    for (auto cfd : *versions_->GetColumnFamilySet()) {
-      auto iter = version_edits.find(cfd->id);
+      auto iter = version_edits.find(cfd->GetID());
      assert(iter != version_edits.end());
      VersionEdit* edit = &iter->second;

      // flush the final memtable
-      status = WriteLevel0TableForRecovery(cfd->mem, edit);
+      status = WriteLevel0TableForRecovery(cfd->mem(), edit);
      // we still want to clear the memtable, even if the recovery failed
      cfd->CreateNewMemtable();
      if (!status.ok()) {
@ -1104,7 +1103,7 @@ Status DBImpl::WriteLevel0Table(std::vector<MemTable*> &mems, VersionEdit* edit,
  const SequenceNumber newest_snapshot = snapshots_.GetNewest();
  const SequenceNumber earliest_seqno_in_memtable =
    mems[0]->GetFirstSequenceNumber();
-  Version* base = default_cfd_->current;
+  Version* base = default_cfd_->current();
  base->Ref();          // it is likely that we do not need this reference
  Status s;
  {
@ -1141,7 +1140,7 @@ Status DBImpl::WriteLevel0Table(std::vector<MemTable*> &mems, VersionEdit* edit,


  // re-acquire the most current version
-  base = default_cfd_->current;
+  base = default_cfd_->current();

  // There could be multiple threads writing to its own level-0 file.
  // The pending_outputs cannot be cleared here, otherwise this newly
@ -1182,9 +1181,9 @@ Status DBImpl::WriteLevel0Table(std::vector<MemTable*> &mems, VersionEdit* edit,
 Status DBImpl::FlushMemTableToOutputFile(bool* madeProgress,
                                         DeletionState& deletion_state) {
  mutex_.AssertHeld();
-  assert(default_cfd_->imm.size() != 0);
+  assert(default_cfd_->imm()->size() != 0);

-  if (!default_cfd_->imm.IsFlushPending()) {
+  if (!default_cfd_->imm()->IsFlushPending()) {
    Log(options_.info_log, "FlushMemTableToOutputFile already in progress");
    Status s = Status::IOError("FlushMemTableToOutputFile already in progress");
    return s;
@ -1193,7 +1192,7 @@ Status DBImpl::FlushMemTableToOutputFile(bool* madeProgress,
  // Save the contents of the earliest memtable as a new Table
  uint64_t file_number;
  std::vector<MemTable*> mems;
-  default_cfd_->imm.PickMemtablesToFlush(&mems);
+  default_cfd_->imm()->PickMemtablesToFlush(&mems);
  if (mems.empty()) {
    Log(options_.info_log, "Nothing in memstore to flush");
    Status s = Status::IOError("Nothing in memstore to flush");
@ -1228,7 +1227,7 @@ Status DBImpl::FlushMemTableToOutputFile(bool* madeProgress,
  }

  // Replace immutable memtable with the generated Table
-  s = default_cfd_->imm.InstallMemtableFlushResults(
+  s = default_cfd_->imm()->InstallMemtableFlushResults(
      default_cfd_, mems, versions_.get(), s, &mutex_, options_.info_log.get(),
      file_number, pending_outputs_, &deletion_state.memtables_to_free,
      db_directory_.get());
@ -1264,7 +1263,7 @@ Status DBImpl::CompactRange(const ColumnFamilyHandle& column_family,
  int max_level_with_files = 1;
  {
    MutexLock l(&mutex_);
-    Version* base = default_cfd_->current;
+    Version* base = default_cfd_->current();
    for (int level = 1; level < NumberLevels(); level++) {
      if (base->OverlapInLevel(level, begin, end)) {
        max_level_with_files = level;
@ -1297,7 +1296,7 @@ Status DBImpl::CompactRange(const ColumnFamilyHandle& column_family,
 // return the same level if it cannot be moved
 int DBImpl::FindMinimumEmptyLevelFitting(int level) {
  mutex_.AssertHeld();
-  Version* current = default_cfd_->current;
+  Version* current = default_cfd_->current();
  int minimum_level = level;
  for (int i = level - 1; i > 0; --i) {
    // stop if level i is not empty
@ -1348,10 +1347,10 @@ Status DBImpl::ReFitLevel(int level, int target_level) {
  Status status;
  if (to_level < level) {
    Log(options_.info_log, "Before refitting:\n%s",
-        default_cfd_->current->DebugString().data());
+        default_cfd_->current()->DebugString().data());

    VersionEdit edit;
-    for (const auto& f : default_cfd_->current->files_[level]) {
+    for (const auto& f : default_cfd_->current()->files_[level]) {
      edit.DeleteFile(level, f->number);
      edit.AddFile(to_level, f->number, f->file_size, f->smallest, f->largest,
                   f->smallest_seqno, f->largest_seqno);
@ -1361,14 +1360,14 @@ Status DBImpl::ReFitLevel(int level, int target_level) {

    status = versions_->LogAndApply(default_cfd_, &edit, &mutex_,
                                    db_directory_.get());
-    superversion_to_free = InstallSuperVersion(default_cfd_, new_superversion);
+    superversion_to_free = default_cfd_->InstallSuperVersion(new_superversion);
    new_superversion = nullptr;

    Log(options_.info_log, "LogAndApply: %s\n", status.ToString().data());

    if (status.ok()) {
      Log(options_.info_log, "After refitting:\n%s",
-          default_cfd_->current->DebugString().data());
+          default_cfd_->current()->DebugString().data());
    }
  }

@ -1394,7 +1393,7 @@ int DBImpl::Level0StopWriteTrigger(const ColumnFamilyHandle& column_family) {
 }

 uint64_t DBImpl::CurrentVersionNumber() const {
-  return super_version_number_.load();
+  return default_cfd_->GetSuperVersionNumber();
 }

 Status DBImpl::Flush(const FlushOptions& options,
@ -1688,10 +1687,10 @@ Status DBImpl::WaitForFlushMemTable() {
  Status s;
  // Wait until the compaction completes
  MutexLock l(&mutex_);
-  while (default_cfd_->imm.size() > 0 && bg_error_.ok()) {
+  while (default_cfd_->imm()->size() > 0 && bg_error_.ok()) {
    bg_cv_.Wait();
  }
-  if (default_cfd_->imm.size() != 0) {
+  if (default_cfd_->imm()->size() != 0) {
    s = bg_error_;
  }
  return s;
@ -1727,7 +1726,7 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
  } else if (shutting_down_.Acquire_Load()) {
    // DB is being deleted; no more background compactions
  } else {
-    bool is_flush_pending = default_cfd_->imm.IsFlushPending();
+    bool is_flush_pending = default_cfd_->imm()->IsFlushPending();
    if (is_flush_pending &&
        (bg_flush_scheduled_ < options_.max_background_flushes)) {
      // memtable flush needed
@ -1739,7 +1738,7 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
    // flush, but the HIGH pool is not enabled). Do it only if
    // max_background_compactions hasn't been reached and, in case
    // bg_manual_only_ > 0, if it's a manual compaction.
-    if ((manual_compaction_ || default_cfd_->current->NeedsCompaction() ||
+    if ((manual_compaction_ || default_cfd_->current()->NeedsCompaction() ||
         (is_flush_pending && (options_.max_background_flushes <= 0))) &&
        bg_compaction_scheduled_ < options_.max_background_compactions &&
        (!bg_manual_only_ || manual_compaction_)) {
@ -1761,7 +1760,7 @@ void DBImpl::BGWorkCompaction(void* db) {
 Status DBImpl::BackgroundFlush(bool* madeProgress,
                               DeletionState& deletion_state) {
  Status stat;
-  while (stat.ok() && default_cfd_->imm.IsFlushPending()) {
+  while (stat.ok() && default_cfd_->imm()->IsFlushPending()) {
    Log(options_.info_log,
        "BackgroundCallFlush doing FlushMemTableToOutputFile, flush slots available %d",
        options_.max_background_flushes - bg_flush_scheduled_);
@ -1818,7 +1817,7 @@ void DBImpl::TEST_PurgeObsoleteteWAL() {

 uint64_t DBImpl::TEST_GetLevel0TotalSize() {
  MutexLock l(&mutex_);
-  return default_cfd_->current->NumLevelBytes(0);
+  return default_cfd_->current()->NumLevelBytes(0);
 }

 void DBImpl::BackgroundCallCompaction() {
@ -1881,7 +1880,7 @@ Status DBImpl::BackgroundCompaction(bool* madeProgress,
  mutex_.AssertHeld();

  // TODO: remove memtable flush from formal compaction
-  while (default_cfd_->imm.IsFlushPending()) {
+  while (default_cfd_->imm()->IsFlushPending()) {
    Log(options_.info_log,
        "BackgroundCompaction doing FlushMemTableToOutputFile, compaction slots "
        "available %d",
@ -1940,7 +1939,7 @@ Status DBImpl::BackgroundCompaction(bool* madeProgress,
    Log(options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
        static_cast<unsigned long long>(f->number), c->level() + 1,
        static_cast<unsigned long long>(f->file_size),
-        status.ToString().c_str(), default_cfd_->current->LevelSummary(&tmp));
+        status.ToString().c_str(), default_cfd_->current()->LevelSummary(&tmp));
    versions_->ReleaseCompactionFiles(c.get(), status);
    *madeProgress = true;
  } else {
@ -2287,11 +2286,11 @@ Status DBImpl::DoCompactionWork(CompactionState* compact,
  for (; input->Valid() && !shutting_down_.Acquire_Load(); ) {
    // Prioritize immutable compaction work
    // TODO: remove memtable flush from normal compaction work
-    if (default_cfd_->imm.imm_flush_needed.NoBarrier_Load() != nullptr) {
+    if (default_cfd_->imm()->imm_flush_needed.NoBarrier_Load() != nullptr) {
      const uint64_t imm_start = env_->NowMicros();
      LogFlush(options_.info_log);
      mutex_.Lock();
-      if (default_cfd_->imm.IsFlushPending()) {
+      if (default_cfd_->imm()->IsFlushPending()) {
        FlushMemTableToOutputFile(nullptr, deletion_state);
        bg_cv_.SignalAll();  // Wakeup MakeRoomForWrite() if necessary
      }
@ -2669,11 +2668,11 @@ Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
  // Collect together all needed child iterators for mem
  mutex_.Lock();
  *latest_snapshot = versions_->LastSequence();
-  mutable_mem = default_cfd_->mem;
+  mutable_mem = default_cfd_->mem();
  mutable_mem->Ref();
-  immutable_mems = default_cfd_->imm.current();
+  immutable_mems = default_cfd_->imm()->current();
  immutable_mems->Ref();
-  version = default_cfd_->current;
+  version = default_cfd_->current();
  version->Ref();
  mutex_.Unlock();

@ -2710,11 +2709,11 @@ std::pair<Iterator*, Iterator*> DBImpl::GetTailingIteratorPair(

  // get all child iterators and bump their refcounts under lock
  mutex_.Lock();
-  mutable_mem = default_cfd_->mem;
+  mutable_mem = default_cfd_->mem();
  mutable_mem->Ref();
-  immutable_mems = default_cfd_->imm.current();
+  immutable_mems = default_cfd_->imm()->current();
  immutable_mems->Ref();
-  version = default_cfd_->current;
+  version = default_cfd_->current();
  version->Ref();
  if (superversion_number != nullptr) {
    *superversion_number = CurrentVersionNumber();
@ -2756,7 +2755,7 @@ std::pair<Iterator*, Iterator*> DBImpl::GetTailingIteratorPair(

 int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes() {
  MutexLock l(&mutex_);
-  return default_cfd_->current->MaxNextLevelOverlappingBytes();
+  return default_cfd_->current()->MaxNextLevelOverlappingBytes();
 }

 Status DBImpl::Get(const ReadOptions& options,
@ -2777,11 +2776,12 @@ Status DBImpl::Get(const ReadOptions& options,
 // for superversion_to_free
 void DBImpl::InstallSuperVersion(ColumnFamilyData* cfd,
                                 DeletionState& deletion_state) {
+  mutex_.AssertHeld();
  // if new_superversion == nullptr, it means somebody already used it
  SuperVersion* new_superversion =
    (deletion_state.new_superversion != nullptr) ?
    deletion_state.new_superversion : new SuperVersion();
-  SuperVersion* old_superversion = InstallSuperVersion(cfd, new_superversion);
+  SuperVersion* old_superversion = cfd->InstallSuperVersion(new_superversion);
  deletion_state.new_superversion = nullptr;
  if (deletion_state.superversion_to_free != nullptr) {
    // somebody already put it there
@ -2791,23 +2791,6 @@ void DBImpl::InstallSuperVersion(ColumnFamilyData* cfd,
  }
 }

-SuperVersion* DBImpl::InstallSuperVersion(ColumnFamilyData* cfd,
-                                          SuperVersion* new_superversion) {
-  mutex_.AssertHeld();
-  new_superversion->Init(cfd->mem, cfd->imm.current(), cfd->current);
-  SuperVersion* old_superversion = cfd->super_version;
-  cfd->super_version = new_superversion;
-  if (cfd->id == 0) {
-    // TODO this is only for default column family for now
-    ++super_version_number_;
-  }
-  if (old_superversion != nullptr && old_superversion->Unref()) {
-    old_superversion->Cleanup();
-    return old_superversion; // will let caller delete outside of mutex
-  }
-  return nullptr;
-}
-
 Status DBImpl::GetImpl(const ReadOptions& options,
                       const ColumnFamilyHandle& column_family,
                       const Slice& key, std::string* value,
@ -2819,7 +2802,7 @@ Status DBImpl::GetImpl(const ReadOptions& options,
  // this is asserting because client calling Get() with undefined
  // ColumnFamilyHandle is undefined behavior.
  assert(cfd != nullptr);
-  SuperVersion* get_version = cfd->super_version->Ref();
+  SuperVersion* get_version = cfd->GetSuperVersion()->Ref();
  mutex_.Unlock();

  SequenceNumber snapshot;
@ -2899,9 +2882,9 @@ std::vector<Status> DBImpl::MultiGet(
  }

  // TODO only works for default column family
-  MemTable* mem = default_cfd_->mem;
-  MemTableListVersion* imm = default_cfd_->imm.current();
-  Version* current = default_cfd_->current;
+  MemTable* mem = default_cfd_->mem();
+  MemTableListVersion* imm = default_cfd_->imm()->current();
+  Version* current = default_cfd_->current();
  mem->Ref();
  imm->Ref();
  current->Ref();
@ -3340,7 +3323,7 @@ Status DBImpl::MakeRoomForWrite(bool force,
      // this delay hands over some CPU to the compaction thread in
      // case it is sharing the same core as the writer.
      uint64_t slowdown =
-          SlowdownAmount(default_cfd_->current->NumLevelFiles(0),
+          SlowdownAmount(default_cfd_->current()->NumLevelFiles(0),
                         options_.level0_slowdown_writes_trigger,
                         options_.level0_stop_writes_trigger);
      mutex_.Unlock();
@ -3356,14 +3339,14 @@ Status DBImpl::MakeRoomForWrite(bool force,
      allow_delay = false;  // Do not delay a single write more than once
      mutex_.Lock();
      delayed_writes_++;
-    } else if (!force && (default_cfd_->mem->ApproximateMemoryUsage() <=
+    } else if (!force && (default_cfd_->mem()->ApproximateMemoryUsage() <=
                          options_.write_buffer_size)) {
      // There is room in current memtable
      if (allow_delay) {
        DelayLoggingAndReset();
      }
      break;
-    } else if (default_cfd_->imm.size() ==
+    } else if (default_cfd_->imm()->size() ==
               options_.max_write_buffer_number - 1) {
      // We have filled up the current memtable, but the previous
      // ones are still being compacted, so we wait.
@ -3380,7 +3363,7 @@ Status DBImpl::MakeRoomForWrite(bool force,
                 STALL_MEMTABLE_COMPACTION_MICROS, stall);
      stall_memtable_compaction_ += stall;
      stall_memtable_compaction_count_++;
-    } else if (default_cfd_->current->NumLevelFiles(0) >=
+    } else if (default_cfd_->current()->NumLevelFiles(0) >=
               options_.level0_stop_writes_trigger) {
      // There are too many level-0 files.
      DelayLoggingAndReset();
@ -3396,10 +3379,10 @@ Status DBImpl::MakeRoomForWrite(bool force,
      stall_level0_num_files_ += stall;
      stall_level0_num_files_count_++;
    } else if (allow_hard_rate_limit_delay && options_.hard_rate_limit > 1.0 &&
-               (score = default_cfd_->current->MaxCompactionScore()) >
+               (score = default_cfd_->current()->MaxCompactionScore()) >
                   options_.hard_rate_limit) {
      // Delay a write when the compaction score for any level is too large.
-      int max_level = default_cfd_->current->MaxCompactionScoreLevel();
+      int max_level = default_cfd_->current()->MaxCompactionScoreLevel();
      mutex_.Unlock();
      uint64_t delayed;
      {
@ -3422,7 +3405,7 @@ Status DBImpl::MakeRoomForWrite(bool force,
      }
      mutex_.Lock();
    } else if (allow_soft_rate_limit_delay && options_.soft_rate_limit > 0.0 &&
-               (score = default_cfd_->current->MaxCompactionScore()) >
+               (score = default_cfd_->current()->MaxCompactionScore()) >
                   options_.soft_rate_limit) {
      // Delay a write when the compaction score for any level is too large.
      // TODO: add statistics
@ -3473,21 +3456,20 @@ Status DBImpl::MakeRoomForWrite(bool force,
      }
      logfile_number_ = new_log_number;
      log_.reset(new log::Writer(std::move(lfile)));
-      default_cfd_->mem->SetNextLogNumber(logfile_number_);
-      default_cfd_->imm.Add(default_cfd_->mem);
+      default_cfd_->mem()->SetNextLogNumber(logfile_number_);
+      default_cfd_->imm()->Add(default_cfd_->mem());
      if (force) {
-        default_cfd_->imm.FlushRequested();
+        default_cfd_->imm()->FlushRequested();
      }
-      default_cfd_->mem = memtmp;
-      default_cfd_->mem->Ref();
-      Log(options_.info_log,
-          "New memtable created with log file: #%lu\n",
+      memtmp->Ref();
+      memtmp->SetLogNumber(logfile_number_);
+      default_cfd_->SetMemtable(memtmp);
+      Log(options_.info_log, "New memtable created with log file: #%lu\n",
          (unsigned long)logfile_number_);
-      default_cfd_->mem->SetLogNumber(logfile_number_);
      force = false;   // Do not force another compaction if have room
      MaybeScheduleFlushOrCompaction();
      *superversion_to_free =
-          InstallSuperVersion(default_cfd_, new_superversion);
+          default_cfd_->InstallSuperVersion(new_superversion);
    }
  }
  return s;
@ -3511,7 +3493,7 @@ bool DBImpl::GetProperty(const ColumnFamilyHandle& column_family,
  value->clear();

  MutexLock l(&mutex_);
-  Version* current = default_cfd_->current;
+  Version* current = default_cfd_->current();
  Slice in = property;
  Slice prefix("rocksdb.");
  if (!in.starts_with(prefix)) return false;
@ -3792,10 +3774,10 @@ bool DBImpl::GetProperty(const ColumnFamilyHandle& column_family,

    return true;
  } else if (in == "sstables") {
-    *value = default_cfd_->current->DebugString();
+    *value = default_cfd_->current()->DebugString();
    return true;
  } else if (in == "num-immutable-mem-table") {
-    *value = std::to_string(default_cfd_->imm.size());
+    *value = std::to_string(default_cfd_->imm()->size());
    return true;
  }

@ -3808,7 +3790,7 @@ void DBImpl::GetApproximateSizes(const ColumnFamilyHandle& column_family,
  Version* v;
  {
    MutexLock l(&mutex_);
-    v = default_cfd_->current;
+    v = default_cfd_->current();
    v->Ref();
  }

@ -3885,7 +3867,7 @@ Status DBImpl::DeleteFile(std::string name) {
    // This is to make sure that any deletion tombstones are not
    // lost. Check that the level passed is the last level.
    for (int i = level + 1; i < maxlevel; i++) {
-      if (cfd->current->NumLevelFiles(i) != 0) {
+      if (cfd->current()->NumLevelFiles(i) != 0) {
        Log(options_.info_log,
            "DeleteFile %s FAILED. File not in last level\n", name.c_str());
        return Status::InvalidArgument("File not in last level");
@ -4060,8 +4042,8 @@ Status DB::OpenWithColumnFamilies(
    }
    if (s.ok()) {
      for (auto cfd : *impl->versions_->GetColumnFamilySet()) {
-        delete impl->InstallSuperVersion(cfd, new SuperVersion());
-        cfd->mem->SetLogNumber(impl->logfile_number_);
+        delete cfd->InstallSuperVersion(new SuperVersion());
+        cfd->mem()->SetLogNumber(impl->logfile_number_);
      }
      impl->DeleteObsoleteFiles();
      impl->MaybeScheduleFlushOrCompaction();
@ -4071,7 +4053,7 @@ Status DB::OpenWithColumnFamilies(
  }

  if (s.ok() && impl->options_.compaction_style == kCompactionStyleUniversal) {
-    Version* current = impl->default_cfd_->current;
+    Version* current = impl->default_cfd_->current();
    for (int i = 1; i < impl->NumberLevels(); i++) {
      int num_files = current->NumLevelFiles(i);
      if (num_files > 0) {
--- a/db/db_impl.h
+++ b/db/db_impl.h
@ -401,11 +401,6 @@ class DBImpl : public DB {
  ColumnFamilyData* default_cfd_;
  unique_ptr<ColumnFamilyMemTablesImpl> column_family_memtables_;

-  // An ordinal representing the current SuperVersion. Updated by
-  // InstallSuperVersion(), i.e. incremented every time super_version_
-  // changes.
-  std::atomic<uint64_t> super_version_number_;
-
  std::string host_name_;

  std::unique_ptr<Directory> db_directory_;
@ -587,16 +582,8 @@ class DBImpl : public DB {
    std::vector<SequenceNumber>& snapshots,
    SequenceNumber* prev_snapshot);

-  // will return a pointer to SuperVersion* if previous SuperVersion
-  // if its reference count is zero and needs deletion or nullptr if not
-  // As argument takes a pointer to allocated SuperVersion
-  // Foreground threads call this function directly (they don't carry
-  // deletion state and have to handle their own creation and deletion
-  // of SuperVersion)
-  SuperVersion* InstallSuperVersion(ColumnFamilyData* cfd,
-                                    SuperVersion* new_superversion);
  // Background threads call this function, which is just a wrapper around
-  // the InstallSuperVersion() function above. Background threads carry
+  // the cfd->InstallSuperVersion() function. Background threads carry
  // deletion_state which can have new_superversion already allocated.
  void InstallSuperVersion(ColumnFamilyData* cfd,
                           DeletionState& deletion_state);
--- a/db/db_impl_readonly.cc
+++ b/db/db_impl_readonly.cc
@ -56,8 +56,8 @@ Status DBImplReadOnly::Get(const ReadOptions& options,
                           const ColumnFamilyHandle& column_family,
                           const Slice& key, std::string* value) {
  Status s;
-  MemTable* mem = GetDefaultColumnFamily()->mem;
-  Version* current = GetDefaultColumnFamily()->current;
+  MemTable* mem = GetDefaultColumnFamily()->mem();
+  Version* current = GetDefaultColumnFamily()->current();
  SequenceNumber snapshot = versions_->LastSequence();
  MergeContext merge_context;
  LookupKey lkey(key, snapshot);
--- a/db/db_stats_logger.cc
+++ b/db/db_stats_logger.cc
@ -65,7 +65,7 @@ void DBImpl::LogDBDeployStats() {

  uint64_t file_total_size = 0;
  uint32_t file_total_num = 0;
-  Version* current = default_cfd_->current;
+  Version* current = default_cfd_->current();
  for (int i = 0; i < current->NumberLevels(); i++) {
    file_total_num += current->NumLevelFiles(i);
    file_total_size += current->NumLevelBytes(i);
--- a/db/version_set.cc
+++ b/db/version_set.cc
@ -1390,7 +1390,7 @@ VersionSet::VersionSet(const std::string& dbname, const Options* options,

 VersionSet::~VersionSet() {
  for (auto cfd : *column_family_set_) {
-    cfd->current->Unref();
+    cfd->current()->Unref();
  }
  // we need to delete column_family_set_ because its destructor depends on
  // VersionSet
@ -1405,20 +1405,21 @@ void VersionSet::AppendVersion(ColumnFamilyData* column_family_data,
                               Version* v) {
  // Make "v" current
  assert(v->refs_ == 0);
-  assert(v != column_family_data->current);
-  if (column_family_data->current != nullptr) {
-    assert(column_family_data->current->refs_ > 0);
-    column_family_data->current->Unref();
+  Version* current = column_family_data->current();
+  assert(v != current);
+  if (current != nullptr) {
+    assert(current->refs_ > 0);
+    current->Unref();
  }
-  column_family_data->current = v;
+  column_family_data->SetCurrent(v);
  need_slowdown_for_num_level0_files_ =
      (options_->level0_slowdown_writes_trigger >= 0 &&
       v->NumLevelFiles(0) >= options_->level0_slowdown_writes_trigger);
  v->Ref();

  // Append to linked list
-  v->prev_ = column_family_data->dummy_versions->prev_;
-  v->next_ = column_family_data->dummy_versions;
+  v->prev_ = column_family_data->dummy_versions()->prev_;
+  v->next_ = column_family_data->dummy_versions();
  v->prev_->next_ = v;
  v->next_->prev_ = v;
 }
@ -1441,7 +1442,7 @@ Status VersionSet::LogAndApply(ColumnFamilyData* column_family_data,

  std::vector<VersionEdit*> batch_edits;
  Version* v = new Version(this, current_version_number_++);
-  Builder builder(this, column_family_data->current);
+  Builder builder(this, column_family_data->current());

  // process all requests in the queue
  ManifestWriter* last_writer = &w;
@ -1567,7 +1568,7 @@ Status VersionSet::LogAndApply(ColumnFamilyData* column_family_data,
    manifest_file_size_ = new_manifest_file_size;
    AppendVersion(column_family_data, v);
    log_number_ = edit->log_number_;
-    column_family_data->log_number = edit->log_number_;
+    column_family_data->SetLogNumber(edit->log_number_);
    prev_log_number_ = edit->prev_log_number_;

  } else {
@ -1676,7 +1677,7 @@ Status VersionSet::Recover(
  } else {
    ColumnFamilyData* default_cfd =
        CreateColumnFamily(default_cf_iter->second, &default_cf_edit);
-    builders.insert({0, new Builder(this, default_cfd->current)});
+    builders.insert({0, new Builder(this, default_cfd->current())});
  }

  {
@ -1722,7 +1723,7 @@ Status VersionSet::Recover(
          ColumnFamilyData* new_cfd =
              CreateColumnFamily(cf_options->second, &edit);
          builders.insert(
-              {edit.column_family_, new Builder(this, new_cfd->current)});
+              {edit.column_family_, new Builder(this, new_cfd->current())});
        }
      } else if (edit.is_column_family_drop_) {
        if (cf_in_builders) {
@ -1748,14 +1749,14 @@ Status VersionSet::Recover(
        auto cfd = column_family_set_->GetColumnFamily(edit.column_family_);
        // this should never happen since cf_in_builders is true
        assert(cfd != nullptr);
-        if (edit.max_level_ >= cfd->current->NumberLevels()) {
+        if (edit.max_level_ >= cfd->current()->NumberLevels()) {
          s = Status::InvalidArgument(
              "db has more levels than options.num_levels");
          break;
        }

        if (edit.has_log_number_) {
-          cfd->log_number = edit.log_number_;
+          cfd->SetLogNumber(edit.log_number_);
        }

        // if it is not column family add or column family drop,
@ -1817,7 +1818,7 @@ Status VersionSet::Recover(
  if (s.ok()) {
    for (auto cfd : *column_family_set_) {
      Version* v = new Version(this, current_version_number_++);
-      builders[cfd->id]->SaveTo(v);
+      builders[cfd->GetID()]->SaveTo(v);

      // Install recovered version
      std::vector<uint64_t> size_being_compacted(v->NumberLevels() - 1);
@ -1846,7 +1847,7 @@ Status VersionSet::Recover(

    for (auto cfd : *column_family_set_) {
      Log(options_->info_log, "Column family \"%s\", log number is %lu\n",
-          cfd->name.c_str(), cfd->log_number);
+          cfd->GetName().c_str(), cfd->GetLogNumber());
    }
  }

@ -1936,7 +1937,7 @@ Status VersionSet::ReduceNumberOfLevels(const std::string& dbname,
  }

  Version* current_version =
-      versions.GetColumnFamilySet()->GetDefault()->current;
+      versions.GetColumnFamilySet()->GetDefault()->current();
  int current_levels = current_version->NumberLevels();

  if (current_levels <= new_levels) {
@ -2009,7 +2010,8 @@ Status VersionSet::DumpManifest(Options& options, std::string& dscname,
  uint64_t prev_log_number = 0;
  int count = 0;
  // TODO works only for default column family currently
-  VersionSet::Builder builder(this, column_family_set_->GetDefault()->current);
+  VersionSet::Builder builder(this,
+                              column_family_set_->GetDefault()->current());

  {
    VersionSet::LogReporter reporter;
@ -2120,11 +2122,11 @@ Status VersionSet::WriteSnapshot(log::Writer* log) {
    {
      // Store column family info
      VersionEdit edit;
-      if (cfd->id != 0) {
+      if (cfd->GetID() != 0) {
        // default column family is always there,
        // no need to explicitly write it
-        edit.AddColumnFamily(cfd->name);
-        edit.SetColumnFamily(cfd->id);
+        edit.AddColumnFamily(cfd->GetName());
+        edit.SetColumnFamily(cfd->GetID());
        std::string record;
        edit.EncodeTo(&record);
        Status s = log->AddRecord(record);
@ -2137,10 +2139,10 @@ Status VersionSet::WriteSnapshot(log::Writer* log) {
    {
      // Save files
      VersionEdit edit;
-      edit.SetColumnFamily(cfd->id);
+      edit.SetColumnFamily(cfd->GetID());

      for (int level = 0; level < NumberLevels(); level++) {
-        for (const auto& f : cfd->current->files_[level]) {
+        for (const auto& f : cfd->current()->files_[level]) {
          edit.AddFile(level,
                       f->number,
                       f->file_size,
@ -2150,7 +2152,7 @@ Status VersionSet::WriteSnapshot(log::Writer* log) {
                       f->largest_seqno);
        }
      }
-      edit.SetLogNumber(cfd->log_number);
+      edit.SetLogNumber(cfd->GetLogNumber());
      std::string record;
      edit.EncodeTo(&record);
      Status s = log->AddRecord(record);
@ -2235,7 +2237,8 @@ void VersionSet::AddLiveFiles(std::vector<uint64_t>* live_list) {
  // pre-calculate space requirement
  int64_t total_files = 0;
  for (auto cfd : *column_family_set_) {
-    for (Version* v = cfd->dummy_versions->next_; v != cfd->dummy_versions;
+    Version* dummy_versions = cfd->dummy_versions();
+    for (Version* v = dummy_versions->next_; v != dummy_versions;
         v = v->next_) {
      for (int level = 0; level < v->NumberLevels(); level++) {
        total_files += v->files_[level].size();
@ -2247,7 +2250,8 @@ void VersionSet::AddLiveFiles(std::vector<uint64_t>* live_list) {
  live_list->reserve(live_list->size() + total_files);

  for (auto cfd : *column_family_set_) {
-    for (Version* v = cfd->dummy_versions->next_; v != cfd->dummy_versions;
+    Version* dummy_versions = cfd->dummy_versions();
+    for (Version* v = dummy_versions->next_; v != dummy_versions;
         v = v->next_) {
      for (int level = 0; level < v->NumberLevels(); level++) {
        for (const auto& f : v->files_[level]) {
@ -2260,7 +2264,7 @@ void VersionSet::AddLiveFiles(std::vector<uint64_t>* live_list) {

 Compaction* VersionSet::PickCompaction() {
  // TODO this only works for default column family now
-  Version* version = column_family_set_->GetDefault()->current;
+  Version* version = column_family_set_->GetDefault()->current();
  return compaction_picker_->PickCompaction(version);
 }

@ -2269,7 +2273,7 @@ Compaction* VersionSet::CompactRange(int input_level, int output_level,
                                     const InternalKey* end,
                                     InternalKey** compaction_end) {
  // TODO this only works for default column family now
-  Version* version = column_family_set_->GetDefault()->current;
+  Version* version = column_family_set_->GetDefault()->current();
  return compaction_picker_->CompactRange(version, input_level, output_level,
                                          begin, end, compaction_end);
 }
@ -2321,7 +2325,7 @@ uint64_t VersionSet::MaxFileSizeForLevel(int level) {
 bool VersionSet::VerifyCompactionFileConsistency(Compaction* c) {
 #ifndef NDEBUG
  // TODO this only works for default column family now
-  Version* version = column_family_set_->GetDefault()->current;
+  Version* version = column_family_set_->GetDefault()->current();
  if (c->input_version() != version) {
    Log(options_->info_log, "VerifyCompactionFileConsistency version mismatch");
  }
@ -2374,7 +2378,7 @@ Status VersionSet::GetMetadataForFile(uint64_t number, int* filelevel,
                                      FileMetaData* meta,
                                      ColumnFamilyData** cfd) {
  for (auto cfd_iter : *column_family_set_) {
-    Version* version = cfd_iter->current;
+    Version* version = cfd_iter->current();
    for (int level = 0; level < version->NumberLevels(); level++) {
      for (const auto& file : version->files_[level]) {
        if (file->number == number) {
@ -2392,7 +2396,7 @@ Status VersionSet::GetMetadataForFile(uint64_t number, int* filelevel,
 void VersionSet::GetLiveFilesMetaData(std::vector<LiveFileMetaData>* metadata) {
  for (auto cfd : *column_family_set_) {
    for (int level = 0; level < NumberLevels(); level++) {
-      for (const auto& file : cfd->current->files_[level]) {
+      for (const auto& file : cfd->current()->files_[level]) {
        LiveFileMetaData filemetadata;
        filemetadata.name = TableFileName("", file->number);
        filemetadata.level = level;
--- a/db/version_set.h
+++ b/db/version_set.h
@ -363,8 +363,8 @@ class VersionSet {
  uint64_t MinLogNumber() const {
    uint64_t min_log_num = 0;
    for (auto cfd : *column_family_set_) {
-      if (min_log_num == 0 || min_log_num > cfd->log_number) {
-        min_log_num = cfd->log_number;
+      if (min_log_num == 0 || min_log_num > cfd->GetLogNumber()) {
+        min_log_num = cfd->GetLogNumber();
      }
    }
    return min_log_num;
@ -448,7 +448,7 @@ class VersionSet {
  friend class Compaction;
  friend class Version;
  // TODO(icanadi) temporarily until we have what ColumnFamilyData needs (icmp_)
-  friend struct ColumnFamilyData;
+  friend class ColumnFamilyData;

  struct LogReporter : public log::Reader::Reporter {
    Status* status;
--- a/util/ldb_cmd.cc
+++ b/util/ldb_cmd.cc
@ -1028,7 +1028,7 @@ Status ReduceDBLevelsCommand::GetOldNumOfLevels(Options& opt,
  int max = -1;
  auto default_cfd = versions.GetColumnFamilySet()->GetDefault();
  for (int i = 0; i < versions.NumberLevels(); i++) {
-    if (default_cfd->current->NumLevelFiles(i)) {
+    if (default_cfd->current()->NumLevelFiles(i)) {
      max = i;
    }
  }