VersionEdit not to take NumLevels()

Summary:
I will submit a sequence of diffs that are preparing master branch for column families. There are a lot of implicit assumptions in the code that are making column family implementation hard. If I make the change only in column family branch, it will make merging back to master impossible.

Most of the diffs will be simple code refactorings, so I hope we can have fast turnaround time. Feel free to grab me in person to discuss any of them.

This diff removes number of level check from VersionEdit. It is used only when VersionEdit is read, not written, but has to be set when it is written. I believe it is a right thing to make VersionEdit dumb and check consistency on the caller side. This will also make it much easier to implement Column Families, since different column families can have different number of levels.

Test Plan: make check

Reviewers: dhruba, haobo, sdong, kailiu

Reviewed By: kailiu

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15159

db/db_impl.cc

@@ -252,8 +252,8 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)
     : env_(options.env),
       dbname_(dbname),
       internal_comparator_(options.comparator),
-      options_(SanitizeOptions(
-          dbname, &internal_comparator_, &internal_filter_policy_, options)),
+      options_(SanitizeOptions(dbname, &internal_comparator_,
+                               &internal_filter_policy_, options)),
       internal_filter_policy_(options.filter_policy),
       owns_info_log_(options_.info_log != options.info_log),
       db_lock_(nullptr),
@@ -261,8 +261,7 @@ DBImpl::DBImpl(const Options& options, const std::string& dbname)
       shutting_down_(nullptr),
       bg_cv_(&mutex_),
       mem_rep_factory_(options_.memtable_factory.get()),
-      mem_(new MemTable(internal_comparator_, mem_rep_factory_,
-        NumberLevels(), options_)),
+      mem_(new MemTable(internal_comparator_, options_)),
       logfile_number_(0),
       super_version_(nullptr),
       tmp_batch_(),
@@ -408,7 +407,7 @@ uint64_t DBImpl::TEST_Current_Manifest_FileNo() {
 }
 
 Status DBImpl::NewDB() {
-  VersionEdit new_db(NumberLevels());
+  VersionEdit new_db;
   new_db.SetComparatorName(user_comparator()->Name());
   new_db.SetLogNumber(0);
   new_db.SetNextFile(2);
@@ -864,7 +863,7 @@ void DBImpl::PurgeObsoleteWALFiles() {
 // If externalTable is set, then apply recovered transactions
 // to that table. This is used for readonly mode.
 Status DBImpl::Recover(VersionEdit* edit, MemTable* external_table,
-    bool error_if_log_file_exist) {
+                       bool error_if_log_file_exist) {
   mutex_.AssertHeld();
 
   assert(db_lock_ == nullptr);
@@ -1031,8 +1030,7 @@ Status DBImpl::RecoverLogFile(uint64_t log_number,
     WriteBatchInternal::SetContents(&batch, record);
 
     if (mem == nullptr) {
-      mem = new MemTable(internal_comparator_, mem_rep_factory_,
-        NumberLevels(), options_);
+      mem = new MemTable(internal_comparator_, options_);
       mem->Ref();
     }
     status = WriteBatchInternal::InsertInto(&batch, mem, &options_);
@@ -1358,7 +1356,7 @@ void DBImpl::ReFitLevel(int level, int target_level) {
     Log(options_.info_log, "Before refitting:\n%s",
         versions_->current()->DebugString().data());
 
-    VersionEdit edit(NumberLevels());
+    VersionEdit edit;
     for (const auto& f : versions_->current()->files_[level]) {
       edit.DeleteFile(level, f->number);
       edit.AddFile(to_level, f->number, f->file_size, f->smallest, f->largest,
@@ -3289,17 +3287,13 @@ Status DBImpl::MakeRoomForWrite(bool force,
         EnvOptions soptions(storage_options_);
         soptions.use_mmap_writes = false;
         DelayLoggingAndReset();
-        s = env_->NewWritableFile(
-            LogFileName(options_.wal_dir, new_log_number),
-            &lfile,
-            soptions
-          );
+        s = env_->NewWritableFile(LogFileName(options_.wal_dir, new_log_number),
+                                  &lfile, soptions);
         if (s.ok()) {
           // Our final size should be less than write_buffer_size
           // (compression, etc) but err on the side of caution.
           lfile->SetPreallocationBlockSize(1.1 * options_.write_buffer_size);
-          memtmp = new MemTable(
-            internal_comparator_, mem_rep_factory_, NumberLevels(), options_);
+          memtmp = new MemTable(internal_comparator_, options_);
           new_superversion = new SuperVersion(options_.max_write_buffer_number);
         }
       }
@@ -3680,7 +3674,7 @@ Status DBImpl::DeleteFile(std::string name) {
   int level;
   FileMetaData metadata;
   int maxlevel = NumberLevels();
-  VersionEdit edit(maxlevel);
+  VersionEdit edit;
   DeletionState deletion_state(0, true);
   {
     MutexLock l(&mutex_);
@@ -3802,7 +3796,7 @@ Status DB::Open(const Options& options, const std::string& dbname, DB** dbptr) {
     return s;
   }
   impl->mutex_.Lock();
-  VersionEdit edit(impl->NumberLevels());
+  VersionEdit edit;
   s = impl->Recover(&edit); // Handles create_if_missing, error_if_exists
   if (s.ok()) {
     uint64_t new_log_number = impl->versions_->NewFileNumber();

db/db_impl_readonly.cc

@@ -86,7 +86,7 @@ Status DB::OpenForReadOnly(const Options& options, const std::string& dbname,
 
   DBImplReadOnly* impl = new DBImplReadOnly(options, dbname);
   impl->mutex_.Lock();
-  VersionEdit edit(impl->NumberLevels());
+  VersionEdit edit;
   Status s = impl->Recover(&edit, impl->GetMemTable(),
                            error_if_log_file_exist);
   impl->mutex_.Unlock();

db/db_test.cc

@@ -765,10 +765,9 @@ TEST(DBTest, LevelLimitReopen) {
   options.num_levels = 1;
   options.max_bytes_for_level_multiplier_additional.resize(1, 1);
   Status s = TryReopen(&options);
-  ASSERT_EQ(s.IsCorruption(), true);
+  ASSERT_EQ(s.IsInvalidArgument(), true);
   ASSERT_EQ(s.ToString(),
-            "Corruption: VersionEdit: db already has "
-            "more levels than options.num_levels");
+            "Invalid argument: db has more levels than options.num_levels");
 
   options.num_levels = 10;
   options.max_bytes_for_level_multiplier_additional.resize(10, 1);
@@ -4936,7 +4935,7 @@ void BM_LogAndApply(int iters, int num_base_files) {
   EnvOptions sopt;
   VersionSet vset(dbname, &options, sopt, nullptr, &cmp);
   ASSERT_OK(vset.Recover());
-  VersionEdit vbase(vset.NumberLevels());
+  VersionEdit vbase;
   uint64_t fnum = 1;
   for (int i = 0; i < num_base_files; i++) {
     InternalKey start(MakeKey(2*fnum), 1, kTypeValue);
@@ -4948,7 +4947,7 @@ void BM_LogAndApply(int iters, int num_base_files) {
   uint64_t start_micros = env->NowMicros();
 
   for (int i = 0; i < iters; i++) {
-    VersionEdit vedit(vset.NumberLevels());
+    VersionEdit vedit;
     vedit.DeleteFile(2, fnum);
     InternalKey start(MakeKey(2*fnum), 1, kTypeValue);
     InternalKey limit(MakeKey(2*fnum+1), 1, kTypeDeletion);

db/memtable.cc

@@ -33,24 +33,20 @@ struct hash<rocksdb::Slice> {
 
 namespace rocksdb {
 
-MemTable::MemTable(const InternalKeyComparator& cmp,
-                   MemTableRepFactory* table_factory,
-                   int numlevel,
-                   const Options& options)
+MemTable::MemTable(const InternalKeyComparator& cmp, const Options& options)
     : comparator_(cmp),
       refs_(0),
       arena_impl_(options.arena_block_size),
-      table_(table_factory->CreateMemTableRep(comparator_, &arena_impl_)),
+      table_(options.memtable_factory->CreateMemTableRep(comparator_,
+                                                         &arena_impl_)),
       flush_in_progress_(false),
       flush_completed_(false),
       file_number_(0),
-      edit_(numlevel),
       first_seqno_(0),
       mem_next_logfile_number_(0),
       mem_logfile_number_(0),
-      locks_(options.inplace_update_support
-             ? options.inplace_update_num_locks
-             : 0) { }
+      locks_(options.inplace_update_support ? options.inplace_update_num_locks
+                                            : 0) {}
 
 MemTable::~MemTable() {
   assert(refs_ == 0);
@@ -58,7 +54,7 @@ MemTable::~MemTable() {
 
 size_t MemTable::ApproximateMemoryUsage() {
   return arena_impl_.ApproximateMemoryUsage() +
-    table_->ApproximateMemoryUsage();
+         table_->ApproximateMemoryUsage();
 }
 
 int MemTable::KeyComparator::operator()(const char* aptr, const char* bptr)

db/memtable.h

@@ -34,11 +34,8 @@ class MemTable {
 
   // MemTables are reference counted.  The initial reference count
   // is zero and the caller must call Ref() at least once.
-  explicit MemTable(
-    const InternalKeyComparator& comparator,
-    MemTableRepFactory* table_factory,
-    int numlevel = 7,
-    const Options& options = Options());
+  explicit MemTable(const InternalKeyComparator& comparator,
+                    const Options& options = Options());
 
   ~MemTable();
 

db/repair.cc

@@ -58,7 +58,7 @@ class Repairer {
         next_file_number_(1) {
     // TableCache can be small since we expect each table to be opened once.
     table_cache_ = new TableCache(dbname_, &options_, storage_options_, 10);
-    edit_ = new VersionEdit(options.num_levels);
+    edit_ = new VersionEdit();
   }
 
   ~Repairer() {
@@ -196,8 +196,7 @@ class Repairer {
     std::string scratch;
     Slice record;
     WriteBatch batch;
-    MemTable* mem = new MemTable(icmp_, options_.memtable_factory.get(),
-      options_.num_levels);
+    MemTable* mem = new MemTable(icmp_, options_);
     mem->Ref();
     int counter = 0;
     while (reader.ReadRecord(&record, &scratch)) {

db/version_edit.cc

@@ -33,6 +33,7 @@ enum Tag {
 
 void VersionEdit::Clear() {
   comparator_.clear();
+  max_level_ = 0;
   log_number_ = 0;
   prev_log_number_ = 0;
   last_sequence_ = 0;
@@ -107,14 +108,13 @@ static bool GetInternalKey(Slice* input, InternalKey* dst) {
 
 bool VersionEdit::GetLevel(Slice* input, int* level, const char** msg) {
   uint32_t v;
-  if (GetVarint32(input, &v) &&
-      (int)v < number_levels_) {
+  if (GetVarint32(input, &v)) {
     *level = v;
+    if (max_level_ < *level) {
+      max_level_ = *level;
+    }
     return true;
   } else {
-    if ((int)v >= number_levels_) {
-      *msg = "db already has more levels than options.num_levels";
-    }
     return false;
   }
 }

db/version_edit.h

@@ -34,10 +34,7 @@ struct FileMetaData {
 
 class VersionEdit {
  public:
-  explicit VersionEdit(int number_levels) :
-      number_levels_(number_levels) {
-    Clear();
-  }
+  VersionEdit() { Clear(); }
   ~VersionEdit() { }
 
   void Clear();
@@ -108,7 +105,7 @@ class VersionEdit {
 
   bool GetLevel(Slice* input, int* level, const char** msg);
 
-  int number_levels_;
+  int max_level_;
   std::string comparator_;
   uint64_t log_number_;
   uint64_t prev_log_number_;
@@ -120,9 +117,9 @@ class VersionEdit {
   bool has_next_file_number_;
   bool has_last_sequence_;
 
-  std::vector< std::pair<int, InternalKey> > compact_pointers_;
+  std::vector<std::pair<int, InternalKey> > compact_pointers_;
   DeletedFileSet deleted_files_;
-  std::vector< std::pair<int, FileMetaData> > new_files_;
+  std::vector<std::pair<int, FileMetaData> > new_files_;
 };
 
 }  // namespace rocksdb

db/version_edit_test.cc

@@ -15,7 +15,7 @@ namespace rocksdb {
 static void TestEncodeDecode(const VersionEdit& edit) {
   std::string encoded, encoded2;
   edit.EncodeTo(&encoded);
-  VersionEdit parsed(7);
+  VersionEdit parsed();
   Status s = parsed.DecodeFrom(encoded);
   ASSERT_TRUE(s.ok()) << s.ToString();
   parsed.EncodeTo(&encoded2);
@@ -27,7 +27,7 @@ class VersionEditTest { };
 TEST(VersionEditTest, EncodeDecode) {
   static const uint64_t kBig = 1ull << 50;
 
-  VersionEdit edit(7);
+  VersionEdit edit();
   for (int i = 0; i < 4; i++) {
     TestEncodeDecode(edit);
     edit.AddFile(3, kBig + 300 + i, kBig + 400 + i,

db/version_set.cc

@@ -980,14 +980,12 @@ class VersionSet::Builder {
 #endif
   }
 
-  void CheckConsistencyForDeletes(
-    VersionEdit* edit,
-    unsigned int number,
-    int level) {
+  void CheckConsistencyForDeletes(VersionEdit* edit, unsigned int number,
+                                  int level) {
 #ifndef NDEBUG
       // a file to be deleted better exist in the previous version
       bool found = false;
-      for (int l = 0; !found && l < edit->number_levels_; l++) {
+      for (int l = 0; !found && l < vset_->NumberLevels(); l++) {
         const std::vector<FileMetaData*>& base_files = base_->files_[l];
         for (unsigned int i = 0; i < base_files.size(); i++) {
           FileMetaData* f = base_files[i];
@@ -1000,7 +998,7 @@ class VersionSet::Builder {
       // if the file did not exist in the previous version, then it
       // is possibly moved from lower level to higher level in current
       // version
-      for (int l = level+1; !found && l < edit->number_levels_; l++) {
+      for (int l = level+1; !found && l < vset_->NumberLevels(); l++) {
         const FileSet* added = levels_[l].added_files;
         for (FileSet::const_iterator added_iter = added->begin();
              added_iter != added->end(); ++added_iter) {
@@ -1213,7 +1211,7 @@ void VersionSet::AppendVersion(Version* v) {
 }
 
 Status VersionSet::LogAndApply(VersionEdit* edit, port::Mutex* mu,
-    bool new_descriptor_log) {
+                               bool new_descriptor_log) {
   mu->AssertHeld();
 
   // queue our request
@@ -1383,7 +1381,7 @@ Status VersionSet::LogAndApply(VersionEdit* edit, port::Mutex* mu,
 }
 
 void VersionSet::LogAndApplyHelper(Builder* builder, Version* v,
-  VersionEdit* edit, port::Mutex* mu) {
+                                   VersionEdit* edit, port::Mutex* mu) {
   mu->AssertHeld();
 
   if (edit->has_log_number_) {
@@ -1455,21 +1453,28 @@ Status VersionSet::Recover() {
     Slice record;
     std::string scratch;
     while (reader.ReadRecord(&record, &scratch) && s.ok()) {
-      VersionEdit edit(NumberLevels());
+      VersionEdit edit;
       s = edit.DecodeFrom(record);
-      if (s.ok()) {
-        if (edit.has_comparator_ &&
-            edit.comparator_ != icmp_.user_comparator()->Name()) {
-          s = Status::InvalidArgument(icmp_.user_comparator()->Name(),
-                                      "does not match existing comparator " +
-                                      edit.comparator_);
-        }
+      if (!s.ok()) {
+        break;
       }
 
-      if (s.ok()) {
-        builder.Apply(&edit);
+      if (edit.max_level_ >= NumberLevels()) {
+        s = Status::InvalidArgument(
+            "db has more levels than options.num_levels");
+        break;
       }
 
+      if (edit.has_comparator_ &&
+          edit.comparator_ != icmp_.user_comparator()->Name()) {
+        s = Status::InvalidArgument(icmp_.user_comparator()->Name(),
+            "does not match existing comparator " +
+            edit.comparator_);
+        break;
+      }
+
+      builder.Apply(&edit);
+
       if (edit.has_log_number_) {
         log_number = edit.log_number_;
         have_log_number = true;
@@ -1577,7 +1582,7 @@ Status VersionSet::DumpManifest(Options& options, std::string& dscname,
     Slice record;
     std::string scratch;
     while (reader.ReadRecord(&record, &scratch) && s.ok()) {
-      VersionEdit edit(NumberLevels());
+      VersionEdit edit;
       s = edit.DecodeFrom(record);
       if (s.ok()) {
         if (edit.has_comparator_ &&
@@ -1832,7 +1837,7 @@ Status VersionSet::WriteSnapshot(log::Writer* log) {
   // TODO: Break up into multiple records to reduce memory usage on recovery?
 
   // Save metadata
-  VersionEdit edit(NumberLevels());
+  VersionEdit edit;
   edit.SetComparatorName(icmp_.user_comparator()->Name());
 
   // Save compaction pointers
@@ -2994,7 +2999,7 @@ Compaction::Compaction(int level, int out_level, uint64_t target_file_size,
       bottommost_level_(false),
       is_full_compaction_(false),
       level_ptrs_(std::vector<size_t>(number_levels)) {
-  edit_ = new VersionEdit(number_levels_);
+  edit_ = new VersionEdit();
   for (int i = 0; i < number_levels_; i++) {
     level_ptrs_[i] = 0;
   }

db/version_set_reduce_num_levels.cc

@@ -72,8 +72,8 @@ Status VersionSet::ReduceNumberOfLevels(int new_levels, port::Mutex* mu) {
   num_levels_ = new_levels;
   compact_pointer_ = new std::string[new_levels];
   Init(new_levels);
-  VersionEdit ve(new_levels);
-  st = LogAndApply(&ve , mu, true);
+  VersionEdit ve;
+  st = LogAndApply(&ve, mu, true);
   return st;
 }