WritePrepared Txn: Refactor conf params

Summary:
Summary of changes:
- Move seq_per_batch out of Options
- Rename concurrent_prepare to two_write_queues
- Add allocate_seq_only_for_data_
Closes https://github.com/facebook/rocksdb/pull/3136

Differential Revision: D6304458

Pulled By: maysamyabandeh

fbshipit-source-id: 08e685bfa82bbc41b5b1c5eb7040a8ca6e05e58c

db/compaction_job_test.cc

@@ -143,7 +143,7 @@ class CompactionJobTest : public testing::Test {
   }
 
   void SetLastSequence(const SequenceNumber sequence_number) {
-    versions_->SetLastToBeWrittenSequence(sequence_number + 1);
+    versions_->SetLastAllocatedSequence(sequence_number + 1);
     versions_->SetLastSequence(sequence_number + 1);
   }
 

db/db_impl.cc

@@ -136,7 +136,8 @@ void DumpSupportInfo(Logger* logger) {
 int64_t kDefaultLowPriThrottledRate = 2 * 1024 * 1024;
 } // namespace
 
-DBImpl::DBImpl(const DBOptions& options, const std::string& dbname)
+DBImpl::DBImpl(const DBOptions& options, const std::string& dbname,
+               const bool seq_per_batch)
     : env_(options.env),
       dbname_(dbname),
       initial_db_options_(SanitizeOptions(dbname, options)),
@@ -185,18 +186,30 @@ DBImpl::DBImpl(const DBOptions& options, const std::string& dbname)
           env_options_, immutable_db_options_)),
       num_running_ingest_file_(0),
 #ifndef ROCKSDB_LITE
-      wal_manager_(immutable_db_options_, env_options_),
+      wal_manager_(immutable_db_options_, env_options_, seq_per_batch),
 #endif  // ROCKSDB_LITE
       event_logger_(immutable_db_options_.info_log.get()),
       bg_work_paused_(0),
       bg_compaction_paused_(0),
       refitting_level_(false),
       opened_successfully_(false),
-      concurrent_prepare_(options.concurrent_prepare),
+      two_write_queues_(options.two_write_queues),
       manual_wal_flush_(options.manual_wal_flush),
-      seq_per_batch_(options.seq_per_batch),
+      seq_per_batch_(seq_per_batch),
-      // TODO(myabandeh): revise this when we change options.seq_per_batch
+      // When two_write_queues_ and seq_per_batch_ are both enabled we
-      use_custom_gc_(options.seq_per_batch),
+      // sometimes allocate a seq also to indicate the commit timestmamp of a
+      // transaction. In such cases last_sequence_ would not indicate the last
+      // visible sequence number in memtable and should not be used for
+      // snapshots. It should use last_allocated_sequence_ instaed but also
+      // needs other mechanisms to exclude the data that after last_sequence_
+      // and before last_allocated_sequence_ from the snapshot. In
+      // WritePreparedTxn this property is ensured since such data are not
+      // committed yet.
+      allocate_seq_only_for_data_(!(seq_per_batch && options.two_write_queues)),
+      // Since seq_per_batch_ is currently set only by WritePreparedTxn which
+      // requires a custom gc for compaction, we use that to set use_custom_gc_
+      // as well.
+      use_custom_gc_(seq_per_batch),
       preserve_deletes_(options.preserve_deletes) {
   env_->GetAbsolutePath(dbname, &db_absolute_path_);
 
@@ -751,7 +764,7 @@ SequenceNumber DBImpl::GetLatestSequenceNumber() const {
 }
 
 SequenceNumber DBImpl::IncAndFetchSequenceNumber() {
-  return versions_->FetchAddLastToBeWrittenSequence(1ull) + 1ull;
+  return versions_->FetchAddLastAllocatedSequence(1ull) + 1ull;
 }
 
 bool DBImpl::SetPreserveDeletesSequenceNumber(SequenceNumber seqnum) {
@@ -977,9 +990,8 @@ Status DBImpl::GetImpl(const ReadOptions& read_options,
     // super versipon because a flush happening in between may compact
     // away data for the snapshot, but the snapshot is earlier than the
     // data overwriting it, so users may see wrong results.
-    snapshot = concurrent_prepare_ && seq_per_batch_
+    snapshot = allocate_seq_only_for_data_ ? versions_->LastSequence()
-                   ? versions_->LastToBeWrittenSequence()
+                                           : versions_->LastAllocatedSequence();
-                   : versions_->LastSequence();
   }
   TEST_SYNC_POINT("DBImpl::GetImpl:3");
   TEST_SYNC_POINT("DBImpl::GetImpl:4");
@@ -1070,9 +1082,8 @@ std::vector<Status> DBImpl::MultiGet(
     snapshot = reinterpret_cast<const SnapshotImpl*>(
         read_options.snapshot)->number_;
   } else {
-    snapshot = concurrent_prepare_ && seq_per_batch_
+    snapshot = allocate_seq_only_for_data_ ? versions_->LastSequence()
-                   ? versions_->LastToBeWrittenSequence()
+                                           : versions_->LastAllocatedSequence();
-                   : versions_->LastSequence();
   }
   for (auto mgd_iter : multiget_cf_data) {
     mgd_iter.second->super_version =
@@ -1478,8 +1489,9 @@ Iterator* DBImpl::NewIterator(const ReadOptions& read_options,
         read_callback);
 #endif
   } else {
-    // Note: no need to consider the special case of concurrent_prepare_ &&
+    // Note: no need to consider the special case of
-    // seq_per_batch_ since NewIterator is overridden in WritePreparedTxnDB
+    // allocate_seq_only_for_data_==false since NewIterator is overridden in
+    // WritePreparedTxnDB
     auto snapshot = read_options.snapshot != nullptr
                         ? read_options.snapshot->GetSequenceNumber()
                         : versions_->LastSequence();
@@ -1595,8 +1607,9 @@ Status DBImpl::NewIterators(
     }
 #endif
   } else {
-    // Note: no need to consider the special case of concurrent_prepare_ &&
+    // Note: no need to consider the special case of
-    // seq_per_batch_ since NewIterators is overridden in WritePreparedTxnDB
+    // allocate_seq_only_for_data_==false since NewIterators is overridden in
+    // WritePreparedTxnDB
     auto snapshot = read_options.snapshot != nullptr
                         ? read_options.snapshot->GetSequenceNumber()
                         : versions_->LastSequence();
@@ -1630,9 +1643,9 @@ const Snapshot* DBImpl::GetSnapshotImpl(bool is_write_conflict_boundary) {
     delete s;
     return nullptr;
   }
-  auto snapshot_seq = concurrent_prepare_ && seq_per_batch_
+  auto snapshot_seq = allocate_seq_only_for_data_
-                          ? versions_->LastToBeWrittenSequence()
+                          ? versions_->LastSequence()
-                          : versions_->LastSequence();
+                          : versions_->LastAllocatedSequence();
   return snapshots_.New(s, snapshot_seq, unix_time, is_write_conflict_boundary);
 }
 
@@ -1643,9 +1656,9 @@ void DBImpl::ReleaseSnapshot(const Snapshot* s) {
     snapshots_.Delete(casted_s);
     uint64_t oldest_snapshot;
     if (snapshots_.empty()) {
-      oldest_snapshot = concurrent_prepare_ && seq_per_batch_
+      oldest_snapshot = allocate_seq_only_for_data_
-                            ? versions_->LastToBeWrittenSequence()
+                            ? versions_->LastSequence()
-                            : versions_->LastSequence();
+                            : versions_->LastAllocatedSequence();
     } else {
       oldest_snapshot = snapshots_.oldest()->number_;
     }
@@ -2753,7 +2766,7 @@ Status DBImpl::IngestExternalFile(
     WriteThread::Writer w;
     write_thread_.EnterUnbatched(&w, &mutex_);
     WriteThread::Writer nonmem_w;
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       nonmem_write_thread_.EnterUnbatched(&nonmem_w, &mutex_);
     }
 
@@ -2796,7 +2809,7 @@ Status DBImpl::IngestExternalFile(
     }
 
     // Resume writes to the DB
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       nonmem_write_thread_.ExitUnbatched(&nonmem_w);
     }
     write_thread_.ExitUnbatched(&w);

db/db_impl.h

@@ -68,7 +68,8 @@ struct MemTableInfo;
 
 class DBImpl : public DB {
  public:
-  DBImpl(const DBOptions& options, const std::string& dbname);
+  DBImpl(const DBOptions& options, const std::string& dbname,
+         const bool seq_per_batch = false);
   virtual ~DBImpl();
 
   // Implementations of the DB interface
@@ -220,10 +221,10 @@ class DBImpl : public DB {
 
   virtual SequenceNumber GetLatestSequenceNumber() const override;
   virtual SequenceNumber IncAndFetchSequenceNumber();
-  // Returns LastToBeWrittenSequence in concurrent_prepare_ && seq_per_batch_
+  // Returns LastSequence in allocate_seq_only_for_data_
-  // mode and LastSequence otherwise. This is useful when visiblility depends
+  // mode and LastAllocatedSequence otherwise. This is useful when visiblility
-  // also on data written to the WAL but not to the memtable.
+  // depends also on data written to the WAL but not to the memtable.
-  SequenceNumber TEST_GetLatestVisibleSequenceNumber() const;
+  SequenceNumber TEST_GetLastVisibleSequence() const;
 
   virtual bool SetPreserveDeletesSequenceNumber(SequenceNumber seqnum) override;
 
@@ -606,6 +607,12 @@ class DBImpl : public DB {
 
   Status NewDB();
 
+  // This is to be used only by internal rocksdb classes.
+  static Status Open(const DBOptions& db_options, const std::string& name,
+                     const std::vector<ColumnFamilyDescriptor>& column_families,
+                     std::vector<ColumnFamilyHandle*>* handles, DB** dbptr,
+                     const bool seq_per_batch);
+
  protected:
   Env* const env_;
   const std::string dbname_;
@@ -905,12 +912,12 @@ class DBImpl : public DB {
   FileLock* db_lock_;
 
   // In addition to mutex_, log_write_mutex_ protected writes to logs_ and
-  // logfile_number_. With concurrent_prepare it also protects alive_log_files_,
+  // logfile_number_. With two_write_queues it also protects alive_log_files_,
   // and log_empty_. Refer to the definition of each variable below for more
   // details.
   InstrumentedMutex log_write_mutex_;
   // State below is protected by mutex_
-  // With concurrent_prepare enabled, some of the variables that accessed during
+  // With two_write_queues enabled, some of the variables that accessed during
   // WriteToWAL need different synchronization: log_empty_, alive_log_files_,
   // logs_, logfile_number_. Refer to the definition of each variable below for
   // more description.
@@ -935,10 +942,10 @@ class DBImpl : public DB {
   std::deque<uint64_t>
       log_recycle_files;  // a list of log files that we can recycle
   bool log_dir_synced_;
-  // Without concurrent_prepare, read and writes to log_empty_ are protected by
+  // Without two_write_queues, read and writes to log_empty_ are protected by
   // mutex_. Since it is currently updated/read only in write_thread_, it can be
   // accessed from the same write_thread_ without any locks. With
-  // concurrent_prepare writes, where it can be updated in different threads,
+  // two_write_queues writes, where it can be updated in different threads,
   // read and writes are protected by log_write_mutex_ instead. This is to avoid
   // expesnive mutex_ lock during WAL write, which update log_empty_.
   bool log_empty_;
@@ -975,10 +982,10 @@ class DBImpl : public DB {
     // true for some prefix of logs_
     bool getting_synced = false;
   };
-  // Without concurrent_prepare, read and writes to alive_log_files_ are
+  // Without two_write_queues, read and writes to alive_log_files_ are
   // protected by mutex_. However since back() is never popped, and push_back()
   // is done only from write_thread_, the same thread can access the item
-  // reffered by back() without mutex_. With concurrent_prepare_, writes
+  // reffered by back() without mutex_. With two_write_queues_, writes
   // are protected by locking both mutex_ and log_write_mutex_, and reads must
   // be under either mutex_ or log_write_mutex_.
   std::deque<LogFileNumberSize> alive_log_files_;
@@ -1003,7 +1010,7 @@ class DBImpl : public DB {
   // memtable on normal writes and hence improving the throughput. Each new
   // write of the state will replace the previous state entirely even if the
   // keys in the two consecuitive states do not overlap.
-  // It is protected by log_write_mutex_ when concurrent_prepare_ is enabled.
+  // It is protected by log_write_mutex_ when two_write_queues_ is enabled.
   // Otherwise only the heaad of write_thread_ can access it.
   WriteBatch cached_recoverable_state_;
   std::atomic<bool> cached_recoverable_state_empty_ = {true};
@@ -1319,9 +1326,22 @@ class DBImpl : public DB {
 
   // When set, we use a seprate queue for writes that dont write to memtable. In
   // 2PC these are the writes at Prepare phase.
-  const bool concurrent_prepare_;
+  const bool two_write_queues_;
   const bool manual_wal_flush_;
+  // Increase the sequence number after writing each batch, whether memtable is
+  // disabled for that or not. Otherwise the sequence number is increased after
+  // writing each key into memtable. This implies that when disable_memtable is
+  // set, the seq is not increased at all.
+  //
+  // Default: false
   const bool seq_per_batch_;
+  // A sequence number is allocated only for data written to DB. Otherwise it
+  // could also be allocated for operational purposes such as commit timestamp
+  // of a transaction.
+  const bool allocate_seq_only_for_data_;
+  // It indicates that a customized gc algorithm must be used for
+  // flush/compaction and if it is not provided vis SnapshotChecker, we should
+  // disable gc to be safe.
   const bool use_custom_gc_;
 
   // Clients must periodically call SetPreserveDeletesSequenceNumber()

db/db_impl_debug.cc

@@ -209,11 +209,11 @@ int DBImpl::TEST_BGFlushesAllowed() const {
   return GetBGJobLimits().max_flushes;
 }
 
-SequenceNumber DBImpl::TEST_GetLatestVisibleSequenceNumber() const {
+SequenceNumber DBImpl::TEST_GetLastVisibleSequence() const {
-  if (concurrent_prepare_ && seq_per_batch_) {
+  if (allocate_seq_only_for_data_) {
-    return versions_->LastToBeWrittenSequence();
-  } else {
     return versions_->LastSequence();
+  } else {
+    return versions_->LastAllocatedSequence();
   }
 }
 

db/db_impl_files.cc

@@ -252,11 +252,11 @@ void DBImpl::FindObsoleteFiles(JobContext* job_context, bool force,
       }
       job_context->size_log_to_delete += earliest.size;
       total_log_size_ -= earliest.size;
-      if (concurrent_prepare_) {
+      if (two_write_queues_) {
         log_write_mutex_.Lock();
       }
       alive_log_files_.pop_front();
-      if (concurrent_prepare_) {
+      if (two_write_queues_) {
         log_write_mutex_.Unlock();
       }
       // Current log should always stay alive since it can't have

db/db_impl_open.cc

@@ -592,9 +592,10 @@ Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
         // happen when we open and write to a corrupted DB, where sequence id
         // will start from the last sequence id we recovered.
         if (sequence == *next_sequence ||
-            // With seq_per_batch_, if previous run was with concurrent_prepare_
+            // With seq_per_batch_, if previous run was with two_write_queues_
-            // then gap in the sequence numbers is expected by the commits
+            // then allocate_seq_only_for_data_ was disabled and a gap in the
-            // without prepares.
+            // sequence numbers in the log is expected by the commits without
+            // prepares.
             (seq_per_batch_ && sequence >= *next_sequence)) {
           stop_replay_for_corruption = false;
         }
@@ -754,7 +755,7 @@ Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
     auto last_sequence = *next_sequence - 1;
     if ((*next_sequence != kMaxSequenceNumber) &&
         (versions_->LastSequence() <= last_sequence)) {
-      versions_->SetLastToBeWrittenSequence(last_sequence);
+      versions_->SetLastAllocatedSequence(last_sequence);
       versions_->SetLastSequence(last_sequence);
     }
   }
@@ -845,13 +846,13 @@ Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
   if (data_seen && !flushed) {
     // Mark these as alive so they'll be considered for deletion later by
     // FindObsoleteFiles()
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       log_write_mutex_.Lock();
     }
     for (auto log_number : log_numbers) {
       alive_log_files_.push_back(LogFileNumberSize(log_number));
     }
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       log_write_mutex_.Unlock();
     }
   }
@@ -966,6 +967,15 @@ Status DB::Open(const Options& options, const std::string& dbname, DB** dbptr) {
 Status DB::Open(const DBOptions& db_options, const std::string& dbname,
                 const std::vector<ColumnFamilyDescriptor>& column_families,
                 std::vector<ColumnFamilyHandle*>* handles, DB** dbptr) {
+  const bool seq_per_batch = true;
+  return DBImpl::Open(db_options, dbname, column_families, handles, dbptr,
+                      !seq_per_batch);
+}
+
+Status DBImpl::Open(const DBOptions& db_options, const std::string& dbname,
+                    const std::vector<ColumnFamilyDescriptor>& column_families,
+                    std::vector<ColumnFamilyHandle*>* handles, DB** dbptr,
+                    const bool seq_per_batch) {
   Status s = SanitizeOptionsByTable(db_options, column_families);
   if (!s.ok()) {
     return s;
@@ -985,7 +995,7 @@ Status DB::Open(const DBOptions& db_options, const std::string& dbname,
         std::max(max_write_buffer_size, cf.options.write_buffer_size);
   }
 
-  DBImpl* impl = new DBImpl(db_options, dbname);
+  DBImpl* impl = new DBImpl(db_options, dbname, seq_per_batch);
   s = impl->env_->CreateDirIfMissing(impl->immutable_db_options_.wal_dir);
   if (s.ok()) {
     for (auto db_path : impl->immutable_db_options_.db_paths) {
@@ -1070,12 +1080,12 @@ Status DB::Open(const DBOptions& db_options, const std::string& dbname,
             cfd, &sv_context, *cfd->GetLatestMutableCFOptions());
       }
       sv_context.Clean();
-      if (impl->concurrent_prepare_) {
+      if (impl->two_write_queues_) {
         impl->log_write_mutex_.Lock();
       }
       impl->alive_log_files_.push_back(
           DBImpl::LogFileNumberSize(impl->logfile_number_));
-      if (impl->concurrent_prepare_) {
+      if (impl->two_write_queues_) {
         impl->log_write_mutex_.Unlock();
       }
       impl->DeleteObsoleteFiles();

db/db_impl_write.cc

@@ -67,7 +67,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
   if (write_options.sync && write_options.disableWAL) {
     return Status::InvalidArgument("Sync writes has to enable WAL.");
   }
-  if (concurrent_prepare_ && immutable_db_options_.enable_pipelined_write) {
+  if (two_write_queues_ && immutable_db_options_.enable_pipelined_write) {
     return Status::NotSupported(
         "pipelined_writes is not compatible with concurrent prepares");
   }
@@ -87,7 +87,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
     }
   }
 
-  if (concurrent_prepare_ && disable_memtable) {
+  if (two_write_queues_ && disable_memtable) {
     return WriteImplWALOnly(write_options, my_batch, callback, log_used,
                             log_ref, seq_used);
   }
@@ -154,7 +154,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
   WriteThread::WriteGroup write_group;
   bool in_parallel_group = false;
   uint64_t last_sequence = kMaxSequenceNumber;
-  if (!concurrent_prepare_) {
+  if (!two_write_queues_) {
     last_sequence = versions_->LastSequence();
   }
 
@@ -162,7 +162,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
 
   bool need_log_sync = write_options.sync;
   bool need_log_dir_sync = need_log_sync && !log_dir_synced_;
-  if (!concurrent_prepare_ || !disable_memtable) {
+  if (!two_write_queues_ || !disable_memtable) {
     // With concurrent writes we do preprocess only in the write thread that
     // also does write to memtable to avoid sync issue on shared data structure
     // with the other thread
@@ -209,7 +209,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
     }
     size_t seq_inc = seq_per_batch_ ? write_group.size : total_count;
 
-    const bool concurrent_update = concurrent_prepare_;
+    const bool concurrent_update = two_write_queues_;
     // Update stats while we are an exclusive group leader, so we know
     // that nobody else can be writing to these particular stats.
     // We're optimistic, updating the stats before we successfully
@@ -237,7 +237,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
 
     PERF_TIMER_STOP(write_pre_and_post_process_time);
 
-    if (!concurrent_prepare_) {
+    if (!two_write_queues_) {
       if (status.ok() && !write_options.disableWAL) {
         PERF_TIMER_GUARD(write_wal_time);
         status = WriteToWAL(write_group, log_writer, log_used, need_log_sync,
@@ -246,13 +246,13 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
     } else {
       if (status.ok() && !write_options.disableWAL) {
         PERF_TIMER_GUARD(write_wal_time);
-        // LastToBeWrittenSequence is increased inside WriteToWAL under
+        // LastAllocatedSequence is increased inside WriteToWAL under
         // wal_write_mutex_ to ensure ordered events in WAL
         status = ConcurrentWriteToWAL(write_group, log_used, &last_sequence,
                                       seq_inc);
       } else {
         // Otherwise we inc seq number for memtable writes
-        last_sequence = versions_->FetchAddLastToBeWrittenSequence(seq_inc);
+        last_sequence = versions_->FetchAddLastAllocatedSequence(seq_inc);
       }
     }
     assert(last_sequence != kMaxSequenceNumber);
@@ -310,9 +310,9 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
     mutex_.Lock();
     MarkLogsSynced(logfile_number_, need_log_dir_sync, status);
     mutex_.Unlock();
-    // Requesting sync with concurrent_prepare_ is expected to be very rare. We
+    // Requesting sync with two_write_queues_ is expected to be very rare. We
     // hance provide a simple implementation that is not necessarily efficient.
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       if (manual_wal_flush_) {
         status = FlushWAL(true);
       } else {
@@ -532,7 +532,7 @@ Status DBImpl::WriteImplWALOnly(const WriteOptions& write_options,
   PERF_TIMER_STOP(write_pre_and_post_process_time);
 
   PERF_TIMER_GUARD(write_wal_time);
-  // LastToBeWrittenSequence is increased inside WriteToWAL under
+  // LastAllocatedSequence is increased inside WriteToWAL under
   // wal_write_mutex_ to ensure ordered events in WAL
   size_t seq_inc = seq_per_batch_ ? write_group.size : 0 /*total_count*/;
   status = ConcurrentWriteToWAL(write_group, log_used, &last_sequence, seq_inc);
@@ -548,7 +548,7 @@ Status DBImpl::WriteImplWALOnly(const WriteOptions& write_options,
     }
   }
   if (status.ok() && write_options.sync) {
-    // Requesting sync with concurrent_prepare_ is expected to be very rare. We
+    // Requesting sync with two_write_queues_ is expected to be very rare. We
     // hance provide a simple implementation that is not necessarily efficient.
     if (manual_wal_flush_) {
       status = FlushWAL(true);
@@ -719,7 +719,7 @@ WriteBatch* DBImpl::MergeBatch(const WriteThread::WriteGroup& write_group,
   return merged_batch;
 }
 
-// When concurrent_prepare_ is disabled, this function is called from the only
+// When two_write_queues_ is disabled, this function is called from the only
 // write thread. Otherwise this must be called holding log_write_mutex_.
 Status DBImpl::WriteToWAL(const WriteBatch& merged_batch,
                           log::Writer* log_writer, uint64_t* log_used,
@@ -828,7 +828,7 @@ Status DBImpl::ConcurrentWriteToWAL(const WriteThread::WriteGroup& write_group,
       writer->log_used = logfile_number_;
     }
   }
-  *last_sequence = versions_->FetchAddLastToBeWrittenSequence(seq_inc);
+  *last_sequence = versions_->FetchAddLastAllocatedSequence(seq_inc);
   auto sequence = *last_sequence + 1;
   WriteBatchInternal::SetSequence(merged_batch, sequence);
 
@@ -858,7 +858,7 @@ Status DBImpl::WriteRecoverableState() {
   if (!cached_recoverable_state_empty_) {
     bool dont_care_bool;
     SequenceNumber next_seq;
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       log_write_mutex_.Lock();
     }
     SequenceNumber seq = versions_->LastSequence();
@@ -869,7 +869,7 @@ Status DBImpl::WriteRecoverableState() {
         false /* concurrent_memtable_writes */, &next_seq, &dont_care_bool,
         seq_per_batch_);
     versions_->SetLastSequence(--next_seq);
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       log_write_mutex_.Unlock();
     }
     if (status.ok()) {
@@ -1109,7 +1109,7 @@ void DBImpl::NotifyOnMemTableSealed(ColumnFamilyData* cfd,
 Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
   mutex_.AssertHeld();
   WriteThread::Writer nonmem_w;
-  if (concurrent_prepare_) {
+  if (two_write_queues_) {
     // SwitchMemtable is a rare event. To simply the reasoning, we make sure
     // that there is no concurrent thread writing to WAL.
     nonmem_write_thread_.EnterUnbatched(&nonmem_w, &mutex_);
@@ -1135,11 +1135,11 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
   // Attempt to switch to a new memtable and trigger flush of old.
   // Do this without holding the dbmutex lock.
   assert(versions_->prev_log_number() == 0);
-  if (concurrent_prepare_) {
+  if (two_write_queues_) {
     log_write_mutex_.Lock();
   }
   bool creating_new_log = !log_empty_;
-  if (concurrent_prepare_) {
+  if (two_write_queues_) {
     log_write_mutex_.Unlock();
   }
   uint64_t recycle_log_number = 0;
@@ -1224,7 +1224,7 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
     assert(creating_new_log);
     assert(!new_mem);
     assert(!new_log);
-    if (concurrent_prepare_) {
+    if (two_write_queues_) {
       nonmem_write_thread_.ExitUnbatched(&nonmem_w);
     }
     return s;
@@ -1264,7 +1264,7 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
   cfd->SetMemtable(new_mem);
   InstallSuperVersionAndScheduleWork(cfd, &context->superversion_context,
                                      mutable_cf_options);
-  if (concurrent_prepare_) {
+  if (two_write_queues_) {
     nonmem_write_thread_.ExitUnbatched(&nonmem_w);
   }
   return s;

db/db_test_util.cc

@@ -486,7 +486,7 @@ Options DBTestBase::GetOptions(
     }
     case kConcurrentWALWrites: {
       // This options optimize 2PC commit path
-      options.concurrent_prepare = true;
+      options.two_write_queues = true;
       options.manual_wal_flush = true;
       break;
     }

db/db_wal_test.cc

@@ -730,7 +730,7 @@ class RecoveryTestHelper {
         batch.Put(key, value);
         WriteBatchInternal::SetSequence(&batch, seq);
         current_log_writer->AddRecord(WriteBatchInternal::Contents(&batch));
-        versions->SetLastToBeWrittenSequence(seq);
+        versions->SetLastAllocatedSequence(seq);
         versions->SetLastSequence(seq);
       }
     }

db/external_sst_file_ingestion_job.cc

@@ -164,7 +164,7 @@ Status ExternalSstFileIngestionJob::Run() {
     // if the dont overlap with any ranges since we have snapshots
     force_global_seqno = true;
   }
-  // It is safe to use this instead of LastToBeWrittenSequence since we are
+  // It is safe to use this instead of LastAllocatedSequence since we are
   // the only active writer, and hence they are equal
   const SequenceNumber last_seqno = versions_->LastSequence();
   SuperVersion* super_version = cfd_->GetSuperVersion();
@@ -199,7 +199,7 @@ Status ExternalSstFileIngestionJob::Run() {
   }
 
   if (consumed_seqno) {
-    versions_->SetLastToBeWrittenSequence(last_seqno + 1);
+    versions_->SetLastAllocatedSequence(last_seqno + 1);
     versions_->SetLastSequence(last_seqno + 1);
   }
 

db/repair.cc

@@ -546,7 +546,7 @@ class Repairer {
         max_sequence = tables_[i].max_sequence;
       }
     }
-    vset_.SetLastToBeWrittenSequence(max_sequence);
+    vset_.SetLastAllocatedSequence(max_sequence);
     vset_.SetLastSequence(max_sequence);
 
     for (const auto& cf_id_and_tables : cf_id_to_tables) {

db/transaction_log_impl.cc

@@ -19,7 +19,8 @@ TransactionLogIteratorImpl::TransactionLogIteratorImpl(
     const std::string& dir, const ImmutableDBOptions* options,
     const TransactionLogIterator::ReadOptions& read_options,
     const EnvOptions& soptions, const SequenceNumber seq,
-    std::unique_ptr<VectorLogPtr> files, VersionSet const* const versions)
+    std::unique_ptr<VectorLogPtr> files, VersionSet const* const versions,
+    const bool seq_per_batch)
     : dir_(dir),
       options_(options),
       read_options_(read_options),
@@ -31,7 +32,8 @@ TransactionLogIteratorImpl::TransactionLogIteratorImpl(
       currentFileIndex_(0),
       currentBatchSeq_(0),
       currentLastSeq_(0),
-      versions_(versions) {
+      versions_(versions),
+      seq_per_batch_(seq_per_batch) {
   assert(files_ != nullptr);
   assert(versions_ != nullptr);
 
@@ -241,12 +243,12 @@ void TransactionLogIteratorImpl::UpdateCurrentWriteBatch(const Slice& record) {
     }
     startingSequenceNumber_ = expectedSeq;
     // currentStatus_ will be set to Ok if reseek succeeds
-    // Note: this is still ok in seq_pre_batch_ && concurrent_preparep_ mode
+    // Note: this is still ok in seq_pre_batch_ && two_write_queuesp_ mode
     // that allows gaps in the WAL since it will still skip over the gap.
     currentStatus_ = Status::NotFound("Gap in sequence numbers");
-    // In seq_per_batch mode, gaps in the seq are possible so the strict mode
+    // In seq_per_batch_ mode, gaps in the seq are possible so the strict mode
     // should be disabled
-    return SeekToStartSequence(currentFileIndex_, !options_->seq_per_batch);
+    return SeekToStartSequence(currentFileIndex_, !seq_per_batch_);
   }
 
   struct BatchCounter : public WriteBatch::Handler {
@@ -284,7 +286,7 @@ void TransactionLogIteratorImpl::UpdateCurrentWriteBatch(const Slice& record) {
   };
 
   currentBatchSeq_ = WriteBatchInternal::Sequence(batch.get());
-  if (options_->seq_per_batch) {
+  if (seq_per_batch_) {
     BatchCounter counter(currentBatchSeq_);
     batch->Iterate(&counter);
     currentLastSeq_ = counter.sequence_;

db/transaction_log_impl.h

@@ -62,7 +62,8 @@ class TransactionLogIteratorImpl : public TransactionLogIterator {
       const std::string& dir, const ImmutableDBOptions* options,
       const TransactionLogIterator::ReadOptions& read_options,
       const EnvOptions& soptions, const SequenceNumber seqNum,
-      std::unique_ptr<VectorLogPtr> files, VersionSet const* const versions);
+      std::unique_ptr<VectorLogPtr> files, VersionSet const* const versions,
+      const bool seq_per_batch);
 
   virtual bool Valid() override;
 
@@ -103,7 +104,7 @@ class TransactionLogIteratorImpl : public TransactionLogIterator {
   // Used only to get latest seq. num
   // TODO(icanadi) can this be just a callback?
   VersionSet const* const versions_;
-
+  const bool seq_per_batch_;
   // Reads from transaction log only if the writebatch record has been written
   bool RestrictedRead(Slice* record, std::string* scratch);
   // Seeks to startingSequenceNumber reading from startFileIndex in files_.

db/version_set.cc

@@ -2414,7 +2414,7 @@ VersionSet::VersionSet(const std::string& dbname,
       manifest_file_number_(0),  // Filled by Recover()
       pending_manifest_file_number_(0),
       last_sequence_(0),
-      last_to_be_written_sequence_(0),
+      last_allocated_sequence_(0),
       prev_log_number_(0),
       current_version_number_(0),
       manifest_file_size_(0),
@@ -2754,9 +2754,8 @@ void VersionSet::LogAndApplyCFHelper(VersionEdit* edit) {
   // updated the last_sequence_ yet. It is also possible that the log has is
   // expecting some new data that is not written yet. Since LastSequence is an
   // upper bound on the sequence, it is ok to record
-  // last_to_be_written_sequence_ as the last sequence.
+  // last_allocated_sequence_ as the last sequence.
-  edit->SetLastSequence(db_options_->concurrent_prepare
+  edit->SetLastSequence(db_options_->two_write_queues ? last_allocated_sequence_
-                            ? last_to_be_written_sequence_
                                                       : last_sequence_);
   if (edit->is_column_family_drop_) {
     // if we drop column family, we have to make sure to save max column family,
@@ -2784,9 +2783,8 @@ void VersionSet::LogAndApplyHelper(ColumnFamilyData* cfd,
   // updated the last_sequence_ yet. It is also possible that the log has is
   // expecting some new data that is not written yet. Since LastSequence is an
   // upper bound on the sequence, it is ok to record
-  // last_to_be_written_sequence_ as the last sequence.
+  // last_allocated_sequence_ as the last sequence.
-  edit->SetLastSequence(db_options_->concurrent_prepare
+  edit->SetLastSequence(db_options_->two_write_queues ? last_allocated_sequence_
-                            ? last_to_be_written_sequence_
                                                       : last_sequence_);
 
   builder->Apply(edit);
@@ -3077,7 +3075,7 @@ Status VersionSet::Recover(
 
     manifest_file_size_ = current_manifest_file_size;
     next_file_number_.store(next_file + 1);
-    last_to_be_written_sequence_ = last_sequence;
+    last_allocated_sequence_ = last_sequence;
     last_sequence_ = last_sequence;
     prev_log_number_ = previous_log_number;
 
@@ -3448,7 +3446,7 @@ Status VersionSet::DumpManifest(Options& options, std::string& dscname,
     }
 
     next_file_number_.store(next_file + 1);
-    last_to_be_written_sequence_ = last_sequence;
+    last_allocated_sequence_ = last_sequence;
     last_sequence_ = last_sequence;
     prev_log_number_ = previous_log_number;
 

db/version_set.h

@@ -765,28 +765,27 @@ class VersionSet {
   }
 
   // Note: memory_order_acquire must be sufficient.
-  uint64_t LastToBeWrittenSequence() const {
+  uint64_t LastAllocatedSequence() const {
-    return last_to_be_written_sequence_.load(std::memory_order_seq_cst);
+    return last_allocated_sequence_.load(std::memory_order_seq_cst);
   }
 
   // Set the last sequence number to s.
   void SetLastSequence(uint64_t s) {
     assert(s >= last_sequence_);
     // Last visible seqeunce must always be less than last written seq
-    assert(!db_options_->concurrent_prepare ||
+    assert(!db_options_->two_write_queues || s <= last_allocated_sequence_);
-           s <= last_to_be_written_sequence_);
     last_sequence_.store(s, std::memory_order_release);
   }
 
   // Note: memory_order_release must be sufficient
-  void SetLastToBeWrittenSequence(uint64_t s) {
+  void SetLastAllocatedSequence(uint64_t s) {
-    assert(s >= last_to_be_written_sequence_);
+    assert(s >= last_allocated_sequence_);
-    last_to_be_written_sequence_.store(s, std::memory_order_seq_cst);
+    last_allocated_sequence_.store(s, std::memory_order_seq_cst);
   }
 
   // Note: memory_order_release must be sufficient
-  uint64_t FetchAddLastToBeWrittenSequence(uint64_t s) {
+  uint64_t FetchAddLastAllocatedSequence(uint64_t s) {
-    return last_to_be_written_sequence_.fetch_add(s, std::memory_order_seq_cst);
+    return last_allocated_sequence_.fetch_add(s, std::memory_order_seq_cst);
   }
 
   // Mark the specified file number as used.
@@ -894,8 +893,9 @@ class VersionSet {
   uint64_t pending_manifest_file_number_;
   // The last seq visible to reads
   std::atomic<uint64_t> last_sequence_;
-  // The last seq with which a writer has written/will write.
+  // The last seq that is already allocated. The seq might or might not have
-  std::atomic<uint64_t> last_to_be_written_sequence_;
+  // appreated in memtable.
+  std::atomic<uint64_t> last_allocated_sequence_;
   uint64_t prev_log_number_;  // 0 or backing store for memtable being compacted
 
   // Opened lazily

db/wal_manager.cc

@@ -115,7 +115,7 @@ Status WalManager::GetUpdatesSince(
   }
   iter->reset(new TransactionLogIteratorImpl(
       db_options_.wal_dir, &db_options_, read_options, env_options_, seq,
-      std::move(wal_files), version_set));
+      std::move(wal_files), version_set, seq_per_batch_));
   return (*iter)->status();
 }
 

db/wal_manager.h

@@ -31,11 +31,12 @@ namespace rocksdb {
 class WalManager {
  public:
   WalManager(const ImmutableDBOptions& db_options,
-             const EnvOptions& env_options)
+             const EnvOptions& env_options, const bool seq_per_batch = false)
       : db_options_(db_options),
         env_options_(env_options),
         env_(db_options.env),
-        purge_wal_files_last_run_(0) {}
+        purge_wal_files_last_run_(0),
+        seq_per_batch_(seq_per_batch) {}
 
   Status GetSortedWalFiles(VectorLogPtr& files);
 
@@ -86,6 +87,8 @@ class WalManager {
   // last time when PurgeObsoleteWALFiles ran.
   uint64_t purge_wal_files_last_run_;
 
+  bool seq_per_batch_;
+
   // obsolete files will be deleted every this seconds if ttl deletion is
   // enabled and archive size_limit is disabled.
   static const uint64_t kDefaultIntervalToDeleteObsoleteWAL = 600;

db/wal_manager_test.cc

@@ -67,7 +67,7 @@ class WalManagerTest : public testing::Test {
     batch.Put(key, value);
     WriteBatchInternal::SetSequence(&batch, seq);
     current_log_writer_->AddRecord(WriteBatchInternal::Contents(&batch));
-    versions_->SetLastToBeWrittenSequence(seq);
+    versions_->SetLastAllocatedSequence(seq);
     versions_->SetLastSequence(seq);
   }
 

db/write_callback_test.cc

@@ -136,9 +136,8 @@ TEST_F(WriteCallbackTest, WriteWithCallbackTest) {
               options.create_if_missing = true;
               options.allow_concurrent_memtable_write = allow_parallel;
               options.enable_pipelined_write = enable_pipelined_write;
-              options.concurrent_prepare = two_queues;
+              options.two_write_queues = two_queues;
-              if (options.enable_pipelined_write &&
+              if (options.enable_pipelined_write && options.two_write_queues) {
-                  options.concurrent_prepare) {
                 // This combination is not supported
                 continue;
               }

include/rocksdb/options.h

@@ -905,22 +905,12 @@ struct DBOptions {
   // allows the memtable writes not to lag behind other writes. It can be used
   // to optimize MySQL 2PC in which only the commits, which are serial, write to
   // memtable.
-  bool concurrent_prepare = false;
+  bool two_write_queues = false;
 
   // If true WAL is not flushed automatically after each write. Instead it
   // relies on manual invocation of FlushWAL to write the WAL buffer to its
   // file.
   bool manual_wal_flush = false;
-
-  // Increase the sequence number after writing each batch, whether memtable is
-  // disabled for that or not. Otherwise the sequence number is increased after
-  // writing each key into memtable. This implies that when memtable_disable is
-  // set, the seq is not increased at all.
-  //
-  // Default: false
-  // Note: This option is experimental and meant to be used only for internal
-  // projects.
-  bool seq_per_batch = false;
 };
 
 // Options to control the behavior of a database (passed to DB::Open)

options/db_options.cc

@@ -85,9 +85,8 @@ ImmutableDBOptions::ImmutableDBOptions(const DBOptions& options)
       avoid_flush_during_recovery(options.avoid_flush_during_recovery),
       allow_ingest_behind(options.allow_ingest_behind),
       preserve_deletes(options.preserve_deletes),
-      concurrent_prepare(options.concurrent_prepare),
+      two_write_queues(options.two_write_queues),
-      manual_wal_flush(options.manual_wal_flush),
+      manual_wal_flush(options.manual_wal_flush) {
-      seq_per_batch(options.seq_per_batch) {
 }
 
 void ImmutableDBOptions::Dump(Logger* log) const {
@@ -217,11 +216,10 @@ void ImmutableDBOptions::Dump(Logger* log) const {
                    allow_ingest_behind);
   ROCKS_LOG_HEADER(log, "            Options.preserve_deletes: %d",
                    preserve_deletes);
-  ROCKS_LOG_HEADER(log, "            Options.concurrent_prepare: %d",
+  ROCKS_LOG_HEADER(log, "            Options.two_write_queues: %d",
-                   concurrent_prepare);
+                   two_write_queues);
   ROCKS_LOG_HEADER(log, "            Options.manual_wal_flush: %d",
                    manual_wal_flush);
-  ROCKS_LOG_HEADER(log, "            Options.seq_per_batch: %d", seq_per_batch);
 }
 
 MutableDBOptions::MutableDBOptions()

options/db_options.h

@@ -77,9 +77,8 @@ struct ImmutableDBOptions {
   bool avoid_flush_during_recovery;
   bool allow_ingest_behind;
   bool preserve_deletes;
-  bool concurrent_prepare;
+  bool two_write_queues;
   bool manual_wal_flush;
-  bool seq_per_batch;
 };
 
 struct MutableDBOptions {

options/options_helper.h

@@ -360,18 +360,18 @@ static std::unordered_map<std::string, OptionTypeInfo> db_options_type_info = {
      {offsetof(struct DBOptions, preserve_deletes), OptionType::kBoolean,
       OptionVerificationType::kNormal, false,
       offsetof(struct ImmutableDBOptions, preserve_deletes)}},
-    {"concurrent_prepare",
+    {"concurrent_prepare",  // Deprecated by two_write_queues
-     {offsetof(struct DBOptions, concurrent_prepare), OptionType::kBoolean,
+     {0, OptionType::kBoolean, OptionVerificationType::kDeprecated, false, 0}},
+    {"two_write_queues",
+     {offsetof(struct DBOptions, two_write_queues), OptionType::kBoolean,
       OptionVerificationType::kNormal, false,
-      offsetof(struct ImmutableDBOptions, concurrent_prepare)}},
+      offsetof(struct ImmutableDBOptions, two_write_queues)}},
     {"manual_wal_flush",
      {offsetof(struct DBOptions, manual_wal_flush), OptionType::kBoolean,
       OptionVerificationType::kNormal, false,
       offsetof(struct ImmutableDBOptions, manual_wal_flush)}},
     {"seq_per_batch",
-     {offsetof(struct DBOptions, seq_per_batch), OptionType::kBoolean,
+     {0, OptionType::kBoolean, OptionVerificationType::kDeprecated, false, 0}}};
-      OptionVerificationType::kNormal, false,
-      offsetof(struct ImmutableDBOptions, seq_per_batch)}}};
 
 // offset_of is used to get the offset of a class data member
 // ex: offset_of(&ColumnFamilyOptions::num_levels)

options/options_settable_test.cc

@@ -284,6 +284,7 @@ TEST_F(OptionsSettableTest, DBOptionsAllFieldsSettable) {
                              "allow_ingest_behind=false;"
                              "preserve_deletes=false;"
                              "concurrent_prepare=false;"
+                             "two_write_queues=false;"
                              "manual_wal_flush=false;"
                              "seq_per_batch=false;",
                              new_options));

utilities/transactions/pessimistic_transaction_db.cc

@@ -189,12 +189,11 @@ Status TransactionDB::Open(
   std::vector<ColumnFamilyDescriptor> column_families_copy = column_families;
   std::vector<size_t> compaction_enabled_cf_indices;
   DBOptions db_options_2pc = db_options;
-  if (txn_db_options.write_policy == WRITE_PREPARED) {
-    db_options_2pc.seq_per_batch = true;
-  }
   PrepareWrap(&db_options_2pc, &column_families_copy,
               &compaction_enabled_cf_indices);
-  s = DB::Open(db_options_2pc, dbname, column_families_copy, handles, &db);
+  const bool use_seq_per_batch = txn_db_options.write_policy == WRITE_PREPARED;
+  s = DBImpl::Open(db_options_2pc, dbname, column_families_copy, handles, &db,
+                   use_seq_per_batch);
   if (s.ok()) {
     s = WrapDB(db, txn_db_options, compaction_enabled_cf_indices, *handles,
                dbptr);

utilities/transactions/transaction_test.cc

@@ -4856,12 +4856,12 @@ TEST_P(TransactionTest, SeqAdvanceTest) {
     auto seq = db_impl->GetLatestSequenceNumber();
     exp_seq = seq;
     txn_t0(0);
-    seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    seq = db_impl->TEST_GetLastVisibleSequence();
     ASSERT_EQ(exp_seq, seq);
 
     if (branch_do(n, &branch)) {
       db_impl->Flush(fopt);
-      seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+      seq = db_impl->TEST_GetLastVisibleSequence();
       ASSERT_EQ(exp_seq, seq);
     }
     if (branch_do(n, &branch)) {
@@ -4874,16 +4874,16 @@ TEST_P(TransactionTest, SeqAdvanceTest) {
 
     // Doing it twice might detect some bugs
     txn_t0(1);
-    seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    seq = db_impl->TEST_GetLastVisibleSequence();
     ASSERT_EQ(exp_seq, seq);
 
     txn_t1(0);
-    seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    seq = db_impl->TEST_GetLastVisibleSequence();
     ASSERT_EQ(exp_seq, seq);
 
     if (branch_do(n, &branch)) {
       db_impl->Flush(fopt);
-      seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+      seq = db_impl->TEST_GetLastVisibleSequence();
       ASSERT_EQ(exp_seq, seq);
     }
     if (branch_do(n, &branch)) {
@@ -4895,12 +4895,12 @@ TEST_P(TransactionTest, SeqAdvanceTest) {
     }
 
     txn_t3(0);
-    seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    seq = db_impl->TEST_GetLastVisibleSequence();
     ASSERT_EQ(exp_seq, seq);
 
     if (branch_do(n, &branch)) {
       db_impl->Flush(fopt);
-      seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+      seq = db_impl->TEST_GetLastVisibleSequence();
       ASSERT_EQ(exp_seq, seq);
     }
     if (branch_do(n, &branch)) {
@@ -4912,16 +4912,16 @@ TEST_P(TransactionTest, SeqAdvanceTest) {
     }
 
     txn_t0(0);
-    seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    seq = db_impl->TEST_GetLastVisibleSequence();
     ASSERT_EQ(exp_seq, seq);
 
     txn_t2(0);
-    seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    seq = db_impl->TEST_GetLastVisibleSequence();
     ASSERT_EQ(exp_seq, seq);
 
     if (branch_do(n, &branch)) {
       db_impl->Flush(fopt);
-      seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+      seq = db_impl->TEST_GetLastVisibleSequence();
       ASSERT_EQ(exp_seq, seq);
     }
     if (branch_do(n, &branch)) {

utilities/transactions/transaction_test.h

@@ -54,7 +54,7 @@ class TransactionTest : public ::testing::TestWithParam<
     options.merge_operator = MergeOperators::CreateFromStringId("stringappend");
     env = new FaultInjectionTestEnv(Env::Default());
     options.env = env;
-    options.concurrent_prepare = std::get<1>(GetParam());
+    options.two_write_queues = std::get<1>(GetParam());
     dbname = test::TmpDir() + "/transaction_testdb";
 
     DestroyDB(dbname, options);
@@ -113,11 +113,10 @@ class TransactionTest : public ::testing::TestWithParam<
     std::vector<ColumnFamilyHandle*> handles;
     DB* root_db;
     Options options_copy(options);
-    if (txn_db_options.write_policy == WRITE_PREPARED) {
+    const bool use_seq_per_batch =
-      options_copy.seq_per_batch = true;
+        txn_db_options.write_policy == WRITE_PREPARED;
-    }
+    Status s = DBImpl::Open(options_copy, dbname, column_families, &handles,
-    Status s =
+                            &root_db, use_seq_per_batch);
-        DB::Open(options_copy, dbname, column_families, &handles, &root_db);
     if (s.ok()) {
       assert(handles.size() == 1);
       s = TransactionDB::WrapStackableDB(
@@ -144,7 +143,7 @@ class TransactionTest : public ::testing::TestWithParam<
     } else {
       // Consume one seq per batch
       exp_seq++;
-      if (options.concurrent_prepare) {
+      if (options.two_write_queues) {
         // Consume one seq for commit
         exp_seq++;
       }
@@ -169,7 +168,7 @@ class TransactionTest : public ::testing::TestWithParam<
     } else {
       // Consume one seq per batch
       exp_seq++;
-      if (options.concurrent_prepare) {
+      if (options.two_write_queues) {
         // Consume one seq for commit
         exp_seq++;
       }
@@ -197,7 +196,7 @@ class TransactionTest : public ::testing::TestWithParam<
     } else {
       // Consume one seq per batch
       exp_seq++;
-      if (options.concurrent_prepare) {
+      if (options.two_write_queues) {
         // Consume one seq for commit
         exp_seq++;
       }

utilities/transactions/write_prepared_transaction_test.cc

@@ -625,7 +625,7 @@ TEST_P(WritePreparedTransactionTest, SeqAdvanceConcurrentTest) {
       printf("Tested %" ROCKSDB_PRIszt " cases so far\n", n);
     }
     DBImpl* db_impl = reinterpret_cast<DBImpl*>(db->GetRootDB());
-    auto seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    auto seq = db_impl->TEST_GetLastVisibleSequence();
     exp_seq = seq;
     // This is increased before writing the batch for commit
     commit_writes = 0;
@@ -693,17 +693,17 @@ TEST_P(WritePreparedTransactionTest, SeqAdvanceConcurrentTest) {
     for (auto& t : threads) {
       t.join();
     }
-    if (options.concurrent_prepare) {
+    if (options.two_write_queues) {
       // In this case none of the above scheduling tricks to deterministically
       // form merged bactches works because the writes go to saparte queues.
       // This would result in different write groups in each run of the test. We
       // still keep the test since althgouh non-deterministic and hard to debug,
       // it is still useful to have.
-      // TODO(myabandeh): Add a deterministic unit test for concurrent_prepare
+      // TODO(myabandeh): Add a deterministic unit test for two_write_queues
     }
 
     // Check if memtable inserts advanced seq number as expected
-    seq = db_impl->TEST_GetLatestVisibleSequenceNumber();
+    seq = db_impl->TEST_GetLastVisibleSequence();
     ASSERT_EQ(exp_seq, seq);
 
     rocksdb::SyncPoint::GetInstance()->DisableProcessing();
@@ -1258,7 +1258,7 @@ TEST_P(WritePreparedTransactionTest, DisableGCDuringRecoveryTest) {
     VerifyKeys({{"foo", v}});
     seq++;  // one for the key/value
     KeyVersion kv = {"foo", v, seq, kTypeValue};
-    if (options.concurrent_prepare) {
+    if (options.two_write_queues) {
       seq++;  // one for the commit
     }
     versions.emplace_back(kv);
@@ -1306,10 +1306,10 @@ TEST_P(WritePreparedTransactionTest, CompactionShouldKeepUncommittedKeys) {
   auto add_key = [&](std::function<Status()> func) {
     ASSERT_OK(func());
     expected_seq++;
-    if (options.concurrent_prepare) {
+    if (options.two_write_queues) {
       expected_seq++;  // 1 for commit
     }
-    ASSERT_EQ(expected_seq, db_impl->TEST_GetLatestVisibleSequenceNumber());
+    ASSERT_EQ(expected_seq, db_impl->TEST_GetLastVisibleSequence());
     snapshots.push_back(db->GetSnapshot());
   };
 
@@ -1397,7 +1397,7 @@ TEST_P(WritePreparedTransactionTest, CompactionShouldKeepSnapshotVisibleKeys) {
   ASSERT_EQ(++expected_seq, db->GetLatestSequenceNumber());
   ASSERT_OK(txn1->Commit());
   DBImpl* db_impl = reinterpret_cast<DBImpl*>(db->GetRootDB());
-  ASSERT_EQ(++expected_seq, db_impl->TEST_GetLatestVisibleSequenceNumber());
+  ASSERT_EQ(++expected_seq, db_impl->TEST_GetLastVisibleSequence());
   delete txn1;
   // Take a snapshots to avoid keys get evicted before compaction.
   const Snapshot* snapshot1 = db->GetSnapshot();
@@ -1410,24 +1410,24 @@ TEST_P(WritePreparedTransactionTest, CompactionShouldKeepSnapshotVisibleKeys) {
   // txn2 commit after snapshot2 and it is not visible.
   const Snapshot* snapshot2 = db->GetSnapshot();
   ASSERT_OK(txn2->Commit());
-  ASSERT_EQ(++expected_seq, db_impl->TEST_GetLatestVisibleSequenceNumber());
+  ASSERT_EQ(++expected_seq, db_impl->TEST_GetLastVisibleSequence());
   delete txn2;
   // Take a snapshots to avoid keys get evicted before compaction.
   const Snapshot* snapshot3 = db->GetSnapshot();
   ASSERT_OK(db->Put(WriteOptions(), "key1", "value1_2"));
   expected_seq++;  // 1 for write
   SequenceNumber seq1 = expected_seq;
-  if (options.concurrent_prepare) {
+  if (options.two_write_queues) {
     expected_seq++;  // 1 for commit
   }
-  ASSERT_EQ(expected_seq, db_impl->TEST_GetLatestVisibleSequenceNumber());
+  ASSERT_EQ(expected_seq, db_impl->TEST_GetLastVisibleSequence());
   ASSERT_OK(db->Put(WriteOptions(), "key2", "value2_2"));
   expected_seq++;  // 1 for write
   SequenceNumber seq2 = expected_seq;
-  if (options.concurrent_prepare) {
+  if (options.two_write_queues) {
     expected_seq++;  // 1 for commit
   }
-  ASSERT_EQ(expected_seq, db_impl->TEST_GetLatestVisibleSequenceNumber());
+  ASSERT_EQ(expected_seq, db_impl->TEST_GetLastVisibleSequence());
   ASSERT_OK(db->Flush(FlushOptions()));
   db->ReleaseSnapshot(snapshot1);
   db->ReleaseSnapshot(snapshot3);

utilities/transactions/write_prepared_txn.cc

@@ -90,7 +90,7 @@ Status WritePreparedTxn::CommitWithoutPrepareInternal() {
 }
 
 SequenceNumber WritePreparedTxn::GetACommitSeqNumber(SequenceNumber prep_seq) {
-  if (db_impl_->immutable_db_options().concurrent_prepare) {
+  if (db_impl_->immutable_db_options().two_write_queues) {
     return db_impl_->IncAndFetchSequenceNumber();
   } else {
     return prep_seq;

utilities/transactions/write_prepared_txn.h

@@ -46,7 +46,7 @@ class WritePreparedTxn : public PessimisticTransaction {
   virtual ~WritePreparedTxn() {}
 
   // To make WAL commit markers visible, the snapshot will be based on the last
-  // seq in the WAL, LastToBeWrittenSquence, as opposed to the last seq in the
+  // seq in the WAL, LastAllocatedSequence, as opposed to the last seq in the
   // memtable.
   using Transaction::Get;
   virtual Status Get(const ReadOptions& options,
@@ -54,7 +54,7 @@ class WritePreparedTxn : public PessimisticTransaction {
                      PinnableSlice* value) override;
 
   // To make WAL commit markers visible, the snapshot will be based on the last
-  // seq in the WAL, LastToBeWrittenSquence, as opposed to the last seq in the
+  // seq in the WAL, LastAllocatedSequence, as opposed to the last seq in the
   // memtable.
   using Transaction::GetIterator;
   virtual Iterator* GetIterator(const ReadOptions& options) override;
@@ -76,7 +76,7 @@ class WritePreparedTxn : public PessimisticTransaction {
   // commit entails writing only a commit marker in the WAL. The sequence number
   // of the commit marker is then the commit timestamp of the transaction. To
   // make the commit timestamp visible to readers, their snapshot is based on
-  // the last seq in the WAL, LastToBeWrittenSquence, as opposed to the last seq
+  // the last seq in the WAL, LastAllocatedSequence, as opposed to the last seq
   // in the memtable.
   Status CommitInternal() override;