Adding upstream version 16.2.11+ds.upstream/16.2.11+dsupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2092 insertions, 0 deletions

diff --git a/src/rocksdb/db/write_batch.cc b/src/rocksdb/db/write_batch.cc
new file mode 100644
index 000000000..d578db59b
--- /dev/null
+++ b/src/rocksdb/db/write_batch.cc
@@ -0,0 +1,2092 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+//
+// WriteBatch::rep_ :=
+//    sequence: fixed64
+//    count: fixed32
+//    data: record[count]
+// record :=
+//    kTypeValue varstring varstring
+//    kTypeDeletion varstring
+//    kTypeSingleDeletion varstring
+//    kTypeRangeDeletion varstring varstring
+//    kTypeMerge varstring varstring
+//    kTypeColumnFamilyValue varint32 varstring varstring
+//    kTypeColumnFamilyDeletion varint32 varstring
+//    kTypeColumnFamilySingleDeletion varint32 varstring
+//    kTypeColumnFamilyRangeDeletion varint32 varstring varstring
+//    kTypeColumnFamilyMerge varint32 varstring varstring
+//    kTypeBeginPrepareXID varstring
+//    kTypeEndPrepareXID
+//    kTypeCommitXID varstring
+//    kTypeRollbackXID varstring
+//    kTypeBeginPersistedPrepareXID varstring
+//    kTypeBeginUnprepareXID varstring
+//    kTypeNoop
+// varstring :=
+//    len: varint32
+//    data: uint8[len]
+
+#include "rocksdb/write_batch.h"
+
+#include <map>
+#include <stack>
+#include <stdexcept>
+#include <type_traits>
+#include <unordered_map>
+#include <vector>
+
+#include "db/column_family.h"
+#include "db/db_impl/db_impl.h"
+#include "db/dbformat.h"
+#include "db/flush_scheduler.h"
+#include "db/memtable.h"
+#include "db/merge_context.h"
+#include "db/snapshot_impl.h"
+#include "db/trim_history_scheduler.h"
+#include "db/write_batch_internal.h"
+#include "monitoring/perf_context_imp.h"
+#include "monitoring/statistics.h"
+#include "rocksdb/merge_operator.h"
+#include "util/autovector.h"
+#include "util/cast_util.h"
+#include "util/coding.h"
+#include "util/duplicate_detector.h"
+#include "util/string_util.h"
+#include "util/util.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// anon namespace for file-local types
+namespace {
+
+enum ContentFlags : uint32_t {
+  DEFERRED = 1 << 0,
+  HAS_PUT = 1 << 1,
+  HAS_DELETE = 1 << 2,
+  HAS_SINGLE_DELETE = 1 << 3,
+  HAS_MERGE = 1 << 4,
+  HAS_BEGIN_PREPARE = 1 << 5,
+  HAS_END_PREPARE = 1 << 6,
+  HAS_COMMIT = 1 << 7,
+  HAS_ROLLBACK = 1 << 8,
+  HAS_DELETE_RANGE = 1 << 9,
+  HAS_BLOB_INDEX = 1 << 10,
+  HAS_BEGIN_UNPREPARE = 1 << 11,
+};
+
+struct BatchContentClassifier : public WriteBatch::Handler {
+  uint32_t content_flags = 0;
+
+  Status PutCF(uint32_t, const Slice&, const Slice&) override {
+    content_flags |= ContentFlags::HAS_PUT;
+    return Status::OK();
+  }
+
+  Status DeleteCF(uint32_t, const Slice&) override {
+    content_flags |= ContentFlags::HAS_DELETE;
+    return Status::OK();
+  }
+
+  Status SingleDeleteCF(uint32_t, const Slice&) override {
+    content_flags |= ContentFlags::HAS_SINGLE_DELETE;
+    return Status::OK();
+  }
+
+  Status DeleteRangeCF(uint32_t, const Slice&, const Slice&) override {
+    content_flags |= ContentFlags::HAS_DELETE_RANGE;
+    return Status::OK();
+  }
+
+  Status MergeCF(uint32_t, const Slice&, const Slice&) override {
+    content_flags |= ContentFlags::HAS_MERGE;
+    return Status::OK();
+  }
+
+  Status PutBlobIndexCF(uint32_t, const Slice&, const Slice&) override {
+    content_flags |= ContentFlags::HAS_BLOB_INDEX;
+    return Status::OK();
+  }
+
+  Status MarkBeginPrepare(bool unprepare) override {
+    content_flags |= ContentFlags::HAS_BEGIN_PREPARE;
+    if (unprepare) {
+      content_flags |= ContentFlags::HAS_BEGIN_UNPREPARE;
+    }
+    return Status::OK();
+  }
+
+  Status MarkEndPrepare(const Slice&) override {
+    content_flags |= ContentFlags::HAS_END_PREPARE;
+    return Status::OK();
+  }
+
+  Status MarkCommit(const Slice&) override {
+    content_flags |= ContentFlags::HAS_COMMIT;
+    return Status::OK();
+  }
+
+  Status MarkRollback(const Slice&) override {
+    content_flags |= ContentFlags::HAS_ROLLBACK;
+    return Status::OK();
+  }
+};
+
+class TimestampAssigner : public WriteBatch::Handler {
+ public:
+  explicit TimestampAssigner(const Slice& ts)
+      : timestamp_(ts), timestamps_(kEmptyTimestampList) {}
+  explicit TimestampAssigner(const std::vector<Slice>& ts_list)
+      : timestamps_(ts_list) {
+    SanityCheck();
+  }
+  ~TimestampAssigner() override {}
+
+  Status PutCF(uint32_t, const Slice& key, const Slice&) override {
+    AssignTimestamp(key);
+    ++idx_;
+    return Status::OK();
+  }
+
+  Status DeleteCF(uint32_t, const Slice& key) override {
+    AssignTimestamp(key);
+    ++idx_;
+    return Status::OK();
+  }
+
+  Status SingleDeleteCF(uint32_t, const Slice& key) override {
+    AssignTimestamp(key);
+    ++idx_;
+    return Status::OK();
+  }
+
+  Status DeleteRangeCF(uint32_t, const Slice& begin_key,
+                       const Slice& end_key) override {
+    AssignTimestamp(begin_key);
+    AssignTimestamp(end_key);
+    ++idx_;
+    return Status::OK();
+  }
+
+  Status MergeCF(uint32_t, const Slice& key, const Slice&) override {
+    AssignTimestamp(key);
+    ++idx_;
+    return Status::OK();
+  }
+
+  Status PutBlobIndexCF(uint32_t, const Slice&, const Slice&) override {
+    // TODO (yanqin): support blob db in the future.
+    return Status::OK();
+  }
+
+  Status MarkBeginPrepare(bool) override {
+    // TODO (yanqin): support in the future.
+    return Status::OK();
+  }
+
+  Status MarkEndPrepare(const Slice&) override {
+    // TODO (yanqin): support in the future.
+    return Status::OK();
+  }
+
+  Status MarkCommit(const Slice&) override {
+    // TODO (yanqin): support in the future.
+    return Status::OK();
+  }
+
+  Status MarkRollback(const Slice&) override {
+    // TODO (yanqin): support in the future.
+    return Status::OK();
+  }
+
+ private:
+  void SanityCheck() const {
+    assert(!timestamps_.empty());
+#ifndef NDEBUG
+    const size_t ts_sz = timestamps_[0].size();
+    for (size_t i = 1; i != timestamps_.size(); ++i) {
+      assert(ts_sz == timestamps_[i].size());
+    }
+#endif  // !NDEBUG
+  }
+
+  void AssignTimestamp(const Slice& key) {
+    assert(timestamps_.empty() || idx_ < timestamps_.size());
+    const Slice& ts = timestamps_.empty() ? timestamp_ : timestamps_[idx_];
+    size_t ts_sz = ts.size();
+    char* ptr = const_cast<char*>(key.data() + key.size() - ts_sz);
+    memcpy(ptr, ts.data(), ts_sz);
+  }
+
+  static const std::vector<Slice> kEmptyTimestampList;
+  const Slice timestamp_;
+  const std::vector<Slice>& timestamps_;
+  size_t idx_ = 0;
+
+  // No copy or move.
+  TimestampAssigner(const TimestampAssigner&) = delete;
+  TimestampAssigner(TimestampAssigner&&) = delete;
+  TimestampAssigner& operator=(const TimestampAssigner&) = delete;
+  TimestampAssigner&& operator=(TimestampAssigner&&) = delete;
+};
+const std::vector<Slice> TimestampAssigner::kEmptyTimestampList;
+
+}  // anon namespace
+
+struct SavePoints {
+  std::stack<SavePoint, autovector<SavePoint>> stack;
+};
+
+WriteBatch::WriteBatch(size_t reserved_bytes, size_t max_bytes)
+    : content_flags_(0), max_bytes_(max_bytes), rep_(), timestamp_size_(0) {
+  rep_.reserve((reserved_bytes > WriteBatchInternal::kHeader)
+                   ? reserved_bytes
+                   : WriteBatchInternal::kHeader);
+  rep_.resize(WriteBatchInternal::kHeader);
+}
+
+WriteBatch::WriteBatch(size_t reserved_bytes, size_t max_bytes, size_t ts_sz)
+    : content_flags_(0), max_bytes_(max_bytes), rep_(), timestamp_size_(ts_sz) {
+  rep_.reserve((reserved_bytes > WriteBatchInternal::kHeader) ?
+    reserved_bytes : WriteBatchInternal::kHeader);
+  rep_.resize(WriteBatchInternal::kHeader);
+}
+
+WriteBatch::WriteBatch(const std::string& rep)
+    : content_flags_(ContentFlags::DEFERRED),
+      max_bytes_(0),
+      rep_(rep),
+      timestamp_size_(0) {}
+
+WriteBatch::WriteBatch(std::string&& rep)
+    : content_flags_(ContentFlags::DEFERRED),
+      max_bytes_(0),
+      rep_(std::move(rep)),
+      timestamp_size_(0) {}
+
+WriteBatch::WriteBatch(const WriteBatch& src)
+    : wal_term_point_(src.wal_term_point_),
+      content_flags_(src.content_flags_.load(std::memory_order_relaxed)),
+      max_bytes_(src.max_bytes_),
+      rep_(src.rep_),
+      timestamp_size_(src.timestamp_size_) {
+  if (src.save_points_ != nullptr) {
+    save_points_.reset(new SavePoints());
+    save_points_->stack = src.save_points_->stack;
+  }
+}
+
+WriteBatch::WriteBatch(WriteBatch&& src) noexcept
+    : save_points_(std::move(src.save_points_)),
+      wal_term_point_(std::move(src.wal_term_point_)),
+      content_flags_(src.content_flags_.load(std::memory_order_relaxed)),
+      max_bytes_(src.max_bytes_),
+      rep_(std::move(src.rep_)),
+      timestamp_size_(src.timestamp_size_) {}
+
+WriteBatch& WriteBatch::operator=(const WriteBatch& src) {
+  if (&src != this) {
+    this->~WriteBatch();
+    new (this) WriteBatch(src);
+  }
+  return *this;
+}
+
+WriteBatch& WriteBatch::operator=(WriteBatch&& src) {
+  if (&src != this) {
+    this->~WriteBatch();
+    new (this) WriteBatch(std::move(src));
+  }
+  return *this;
+}
+
+WriteBatch::~WriteBatch() { }
+
+WriteBatch::Handler::~Handler() { }
+
+void WriteBatch::Handler::LogData(const Slice& /*blob*/) {
+  // If the user has not specified something to do with blobs, then we ignore
+  // them.
+}
+
+bool WriteBatch::Handler::Continue() {
+  return true;
+}
+
+void WriteBatch::Clear() {
+  rep_.clear();
+  rep_.resize(WriteBatchInternal::kHeader);
+
+  content_flags_.store(0, std::memory_order_relaxed);
+
+  if (save_points_ != nullptr) {
+    while (!save_points_->stack.empty()) {
+      save_points_->stack.pop();
+    }
+  }
+
+  wal_term_point_.clear();
+}
+
+uint32_t WriteBatch::Count() const { return WriteBatchInternal::Count(this); }
+
+uint32_t WriteBatch::ComputeContentFlags() const {
+  auto rv = content_flags_.load(std::memory_order_relaxed);
+  if ((rv & ContentFlags::DEFERRED) != 0) {
+    BatchContentClassifier classifier;
+    Iterate(&classifier);
+    rv = classifier.content_flags;
+
+    // this method is conceptually const, because it is performing a lazy
+    // computation that doesn't affect the abstract state of the batch.
+    // content_flags_ is marked mutable so that we can perform the
+    // following assignment
+    content_flags_.store(rv, std::memory_order_relaxed);
+  }
+  return rv;
+}
+
+void WriteBatch::MarkWalTerminationPoint() {
+  wal_term_point_.size = GetDataSize();
+  wal_term_point_.count = Count();
+  wal_term_point_.content_flags = content_flags_;
+}
+
+bool WriteBatch::HasPut() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_PUT) != 0;
+}
+
+bool WriteBatch::HasDelete() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_DELETE) != 0;
+}
+
+bool WriteBatch::HasSingleDelete() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_SINGLE_DELETE) != 0;
+}
+
+bool WriteBatch::HasDeleteRange() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_DELETE_RANGE) != 0;
+}
+
+bool WriteBatch::HasMerge() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_MERGE) != 0;
+}
+
+bool ReadKeyFromWriteBatchEntry(Slice* input, Slice* key, bool cf_record) {
+  assert(input != nullptr && key != nullptr);
+  // Skip tag byte
+  input->remove_prefix(1);
+
+  if (cf_record) {
+    // Skip column_family bytes
+    uint32_t cf;
+    if (!GetVarint32(input, &cf)) {
+      return false;
+    }
+  }
+
+  // Extract key
+  return GetLengthPrefixedSlice(input, key);
+}
+
+bool WriteBatch::HasBeginPrepare() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_BEGIN_PREPARE) != 0;
+}
+
+bool WriteBatch::HasEndPrepare() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_END_PREPARE) != 0;
+}
+
+bool WriteBatch::HasCommit() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_COMMIT) != 0;
+}
+
+bool WriteBatch::HasRollback() const {
+  return (ComputeContentFlags() & ContentFlags::HAS_ROLLBACK) != 0;
+}
+
+Status ReadRecordFromWriteBatch(Slice* input, char* tag,
+                                uint32_t* column_family, Slice* key,
+                                Slice* value, Slice* blob, Slice* xid) {
+  assert(key != nullptr && value != nullptr);
+  *tag = (*input)[0];
+  input->remove_prefix(1);
+  *column_family = 0;  // default
+  switch (*tag) {
+    case kTypeColumnFamilyValue:
+      if (!GetVarint32(input, column_family)) {
+        return Status::Corruption("bad WriteBatch Put");
+      }
+      FALLTHROUGH_INTENDED;
+    case kTypeValue:
+      if (!GetLengthPrefixedSlice(input, key) ||
+          !GetLengthPrefixedSlice(input, value)) {
+        return Status::Corruption("bad WriteBatch Put");
+      }
+      break;
+    case kTypeColumnFamilyDeletion:
+    case kTypeColumnFamilySingleDeletion:
+      if (!GetVarint32(input, column_family)) {
+        return Status::Corruption("bad WriteBatch Delete");
+      }
+      FALLTHROUGH_INTENDED;
+    case kTypeDeletion:
+    case kTypeSingleDeletion:
+      if (!GetLengthPrefixedSlice(input, key)) {
+        return Status::Corruption("bad WriteBatch Delete");
+      }
+      break;
+    case kTypeColumnFamilyRangeDeletion:
+      if (!GetVarint32(input, column_family)) {
+        return Status::Corruption("bad WriteBatch DeleteRange");
+      }
+      FALLTHROUGH_INTENDED;
+    case kTypeRangeDeletion:
+      // for range delete, "key" is begin_key, "value" is end_key
+      if (!GetLengthPrefixedSlice(input, key) ||
+          !GetLengthPrefixedSlice(input, value)) {
+        return Status::Corruption("bad WriteBatch DeleteRange");
+      }
+      break;
+    case kTypeColumnFamilyMerge:
+      if (!GetVarint32(input, column_family)) {
+        return Status::Corruption("bad WriteBatch Merge");
+      }
+      FALLTHROUGH_INTENDED;
+    case kTypeMerge:
+      if (!GetLengthPrefixedSlice(input, key) ||
+          !GetLengthPrefixedSlice(input, value)) {
+        return Status::Corruption("bad WriteBatch Merge");
+      }
+      break;
+    case kTypeColumnFamilyBlobIndex:
+      if (!GetVarint32(input, column_family)) {
+        return Status::Corruption("bad WriteBatch BlobIndex");
+      }
+      FALLTHROUGH_INTENDED;
+    case kTypeBlobIndex:
+      if (!GetLengthPrefixedSlice(input, key) ||
+          !GetLengthPrefixedSlice(input, value)) {
+        return Status::Corruption("bad WriteBatch BlobIndex");
+      }
+      break;
+    case kTypeLogData:
+      assert(blob != nullptr);
+      if (!GetLengthPrefixedSlice(input, blob)) {
+        return Status::Corruption("bad WriteBatch Blob");
+      }
+      break;
+    case kTypeNoop:
+    case kTypeBeginPrepareXID:
+      // This indicates that the prepared batch is also persisted in the db.
+      // This is used in WritePreparedTxn
+    case kTypeBeginPersistedPrepareXID:
+      // This is used in WriteUnpreparedTxn
+    case kTypeBeginUnprepareXID:
+      break;
+    case kTypeEndPrepareXID:
+      if (!GetLengthPrefixedSlice(input, xid)) {
+        return Status::Corruption("bad EndPrepare XID");
+      }
+      break;
+    case kTypeCommitXID:
+      if (!GetLengthPrefixedSlice(input, xid)) {
+        return Status::Corruption("bad Commit XID");
+      }
+      break;
+    case kTypeRollbackXID:
+      if (!GetLengthPrefixedSlice(input, xid)) {
+        return Status::Corruption("bad Rollback XID");
+      }
+      break;
+    default:
+      return Status::Corruption("unknown WriteBatch tag");
+  }
+  return Status::OK();
+}
+
+Status WriteBatch::Iterate(Handler* handler) const {
+  if (rep_.size() < WriteBatchInternal::kHeader) {
+    return Status::Corruption("malformed WriteBatch (too small)");
+  }
+
+  return WriteBatchInternal::Iterate(this, handler, WriteBatchInternal::kHeader,
+                                     rep_.size());
+}
+
+Status WriteBatchInternal::Iterate(const WriteBatch* wb,
+                                   WriteBatch::Handler* handler, size_t begin,
+                                   size_t end) {
+  if (begin > wb->rep_.size() || end > wb->rep_.size() || end < begin) {
+    return Status::Corruption("Invalid start/end bounds for Iterate");
+  }
+  assert(begin <= end);
+  Slice input(wb->rep_.data() + begin, static_cast<size_t>(end - begin));
+  bool whole_batch =
+      (begin == WriteBatchInternal::kHeader) && (end == wb->rep_.size());
+
+  Slice key, value, blob, xid;
+  // Sometimes a sub-batch starts with a Noop. We want to exclude such Noops as
+  // the batch boundary symbols otherwise we would mis-count the number of
+  // batches. We do that by checking whether the accumulated batch is empty
+  // before seeing the next Noop.
+  bool empty_batch = true;
+  uint32_t found = 0;
+  Status s;
+  char tag = 0;
+  uint32_t column_family = 0;  // default
+  bool last_was_try_again = false;
+  bool handler_continue = true;
+  while (((s.ok() && !input.empty()) || UNLIKELY(s.IsTryAgain()))) {
+    handler_continue = handler->Continue();
+    if (!handler_continue) {
+      break;
+    }
+
+    if (LIKELY(!s.IsTryAgain())) {
+      last_was_try_again = false;
+      tag = 0;
+      column_family = 0;  // default
+
+      s = ReadRecordFromWriteBatch(&input, &tag, &column_family, &key, &value,
+                                   &blob, &xid);
+      if (!s.ok()) {
+        return s;
+      }
+    } else {
+      assert(s.IsTryAgain());
+      assert(!last_was_try_again);  // to detect infinite loop bugs
+      if (UNLIKELY(last_was_try_again)) {
+        return Status::Corruption(
+            "two consecutive TryAgain in WriteBatch handler; this is either a "
+            "software bug or data corruption.");
+      }
+      last_was_try_again = true;
+      s = Status::OK();
+    }
+
+    switch (tag) {
+      case kTypeColumnFamilyValue:
+      case kTypeValue:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_PUT));
+        s = handler->PutCF(column_family, key, value);
+        if (LIKELY(s.ok())) {
+          empty_batch = false;
+          found++;
+        }
+        break;
+      case kTypeColumnFamilyDeletion:
+      case kTypeDeletion:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_DELETE));
+        s = handler->DeleteCF(column_family, key);
+        if (LIKELY(s.ok())) {
+          empty_batch = false;
+          found++;
+        }
+        break;
+      case kTypeColumnFamilySingleDeletion:
+      case kTypeSingleDeletion:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_SINGLE_DELETE));
+        s = handler->SingleDeleteCF(column_family, key);
+        if (LIKELY(s.ok())) {
+          empty_batch = false;
+          found++;
+        }
+        break;
+      case kTypeColumnFamilyRangeDeletion:
+      case kTypeRangeDeletion:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_DELETE_RANGE));
+        s = handler->DeleteRangeCF(column_family, key, value);
+        if (LIKELY(s.ok())) {
+          empty_batch = false;
+          found++;
+        }
+        break;
+      case kTypeColumnFamilyMerge:
+      case kTypeMerge:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_MERGE));
+        s = handler->MergeCF(column_family, key, value);
+        if (LIKELY(s.ok())) {
+          empty_batch = false;
+          found++;
+        }
+        break;
+      case kTypeColumnFamilyBlobIndex:
+      case kTypeBlobIndex:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_BLOB_INDEX));
+        s = handler->PutBlobIndexCF(column_family, key, value);
+        if (LIKELY(s.ok())) {
+          found++;
+        }
+        break;
+      case kTypeLogData:
+        handler->LogData(blob);
+        // A batch might have nothing but LogData. It is still a batch.
+        empty_batch = false;
+        break;
+      case kTypeBeginPrepareXID:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_BEGIN_PREPARE));
+        handler->MarkBeginPrepare();
+        empty_batch = false;
+        if (!handler->WriteAfterCommit()) {
+          s = Status::NotSupported(
+              "WriteCommitted txn tag when write_after_commit_ is disabled (in "
+              "WritePrepared/WriteUnprepared mode). If it is not due to "
+              "corruption, the WAL must be emptied before changing the "
+              "WritePolicy.");
+        }
+        if (handler->WriteBeforePrepare()) {
+          s = Status::NotSupported(
+              "WriteCommitted txn tag when write_before_prepare_ is enabled "
+              "(in WriteUnprepared mode). If it is not due to corruption, the "
+              "WAL must be emptied before changing the WritePolicy.");
+        }
+        break;
+      case kTypeBeginPersistedPrepareXID:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_BEGIN_PREPARE));
+        handler->MarkBeginPrepare();
+        empty_batch = false;
+        if (handler->WriteAfterCommit()) {
+          s = Status::NotSupported(
+              "WritePrepared/WriteUnprepared txn tag when write_after_commit_ "
+              "is enabled (in default WriteCommitted mode). If it is not due "
+              "to corruption, the WAL must be emptied before changing the "
+              "WritePolicy.");
+        }
+        break;
+      case kTypeBeginUnprepareXID:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_BEGIN_UNPREPARE));
+        handler->MarkBeginPrepare(true /* unprepared */);
+        empty_batch = false;
+        if (handler->WriteAfterCommit()) {
+          s = Status::NotSupported(
+              "WriteUnprepared txn tag when write_after_commit_ is enabled (in "
+              "default WriteCommitted mode). If it is not due to corruption, "
+              "the WAL must be emptied before changing the WritePolicy.");
+        }
+        if (!handler->WriteBeforePrepare()) {
+          s = Status::NotSupported(
+              "WriteUnprepared txn tag when write_before_prepare_ is disabled "
+              "(in WriteCommitted/WritePrepared mode). If it is not due to "
+              "corruption, the WAL must be emptied before changing the "
+              "WritePolicy.");
+        }
+        break;
+      case kTypeEndPrepareXID:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_END_PREPARE));
+        handler->MarkEndPrepare(xid);
+        empty_batch = true;
+        break;
+      case kTypeCommitXID:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_COMMIT));
+        handler->MarkCommit(xid);
+        empty_batch = true;
+        break;
+      case kTypeRollbackXID:
+        assert(wb->content_flags_.load(std::memory_order_relaxed) &
+               (ContentFlags::DEFERRED | ContentFlags::HAS_ROLLBACK));
+        handler->MarkRollback(xid);
+        empty_batch = true;
+        break;
+      case kTypeNoop:
+        handler->MarkNoop(empty_batch);
+        empty_batch = true;
+        break;
+      default:
+        return Status::Corruption("unknown WriteBatch tag");
+    }
+  }
+  if (!s.ok()) {
+    return s;
+  }
+  if (handler_continue && whole_batch &&
+      found != WriteBatchInternal::Count(wb)) {
+    return Status::Corruption("WriteBatch has wrong count");
+  } else {
+    return Status::OK();
+  }
+}
+
+bool WriteBatchInternal::IsLatestPersistentState(const WriteBatch* b) {
+  return b->is_latest_persistent_state_;
+}
+
+void WriteBatchInternal::SetAsLastestPersistentState(WriteBatch* b) {
+  b->is_latest_persistent_state_ = true;
+}
+
+uint32_t WriteBatchInternal::Count(const WriteBatch* b) {
+  return DecodeFixed32(b->rep_.data() + 8);
+}
+
+void WriteBatchInternal::SetCount(WriteBatch* b, uint32_t n) {
+  EncodeFixed32(&b->rep_[8], n);
+}
+
+SequenceNumber WriteBatchInternal::Sequence(const WriteBatch* b) {
+  return SequenceNumber(DecodeFixed64(b->rep_.data()));
+}
+
+void WriteBatchInternal::SetSequence(WriteBatch* b, SequenceNumber seq) {
+  EncodeFixed64(&b->rep_[0], seq);
+}
+
+size_t WriteBatchInternal::GetFirstOffset(WriteBatch* /*b*/) {
+  return WriteBatchInternal::kHeader;
+}
+
+Status WriteBatchInternal::Put(WriteBatch* b, uint32_t column_family_id,
+                               const Slice& key, const Slice& value) {
+  if (key.size() > size_t{port::kMaxUint32}) {
+    return Status::InvalidArgument("key is too large");
+  }
+  if (value.size() > size_t{port::kMaxUint32}) {
+    return Status::InvalidArgument("value is too large");
+  }
+
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeValue));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyValue));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  if (0 == b->timestamp_size_) {
+    PutLengthPrefixedSlice(&b->rep_, key);
+  } else {
+    PutVarint32(&b->rep_,
+                static_cast<uint32_t>(key.size() + b->timestamp_size_));
+    b->rep_.append(key.data(), key.size());
+    b->rep_.append(b->timestamp_size_, '\0');
+  }
+  PutLengthPrefixedSlice(&b->rep_, value);
+  b->content_flags_.store(
+      b->content_flags_.load(std::memory_order_relaxed) | ContentFlags::HAS_PUT,
+      std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::Put(ColumnFamilyHandle* column_family, const Slice& key,
+                       const Slice& value) {
+  return WriteBatchInternal::Put(this, GetColumnFamilyID(column_family), key,
+                                 value);
+}
+
+Status WriteBatchInternal::CheckSlicePartsLength(const SliceParts& key,
+                                                 const SliceParts& value) {
+  size_t total_key_bytes = 0;
+  for (int i = 0; i < key.num_parts; ++i) {
+    total_key_bytes += key.parts[i].size();
+  }
+  if (total_key_bytes >= size_t{port::kMaxUint32}) {
+    return Status::InvalidArgument("key is too large");
+  }
+
+  size_t total_value_bytes = 0;
+  for (int i = 0; i < value.num_parts; ++i) {
+    total_value_bytes += value.parts[i].size();
+  }
+  if (total_value_bytes >= size_t{port::kMaxUint32}) {
+    return Status::InvalidArgument("value is too large");
+  }
+  return Status::OK();
+}
+
+Status WriteBatchInternal::Put(WriteBatch* b, uint32_t column_family_id,
+                               const SliceParts& key, const SliceParts& value) {
+  Status s = CheckSlicePartsLength(key, value);
+  if (!s.ok()) {
+    return s;
+  }
+
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeValue));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyValue));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  if (0 == b->timestamp_size_) {
+    PutLengthPrefixedSliceParts(&b->rep_, key);
+  } else {
+    PutLengthPrefixedSlicePartsWithPadding(&b->rep_, key, b->timestamp_size_);
+  }
+  PutLengthPrefixedSliceParts(&b->rep_, value);
+  b->content_flags_.store(
+      b->content_flags_.load(std::memory_order_relaxed) | ContentFlags::HAS_PUT,
+      std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::Put(ColumnFamilyHandle* column_family, const SliceParts& key,
+                       const SliceParts& value) {
+  return WriteBatchInternal::Put(this, GetColumnFamilyID(column_family), key,
+                                 value);
+}
+
+Status WriteBatchInternal::InsertNoop(WriteBatch* b) {
+  b->rep_.push_back(static_cast<char>(kTypeNoop));
+  return Status::OK();
+}
+
+Status WriteBatchInternal::MarkEndPrepare(WriteBatch* b, const Slice& xid,
+                                          bool write_after_commit,
+                                          bool unprepared_batch) {
+  // a manually constructed batch can only contain one prepare section
+  assert(b->rep_[12] == static_cast<char>(kTypeNoop));
+
+  // all savepoints up to this point are cleared
+  if (b->save_points_ != nullptr) {
+    while (!b->save_points_->stack.empty()) {
+      b->save_points_->stack.pop();
+    }
+  }
+
+  // rewrite noop as begin marker
+  b->rep_[12] = static_cast<char>(
+      write_after_commit ? kTypeBeginPrepareXID
+                         : (unprepared_batch ? kTypeBeginUnprepareXID
+                                             : kTypeBeginPersistedPrepareXID));
+  b->rep_.push_back(static_cast<char>(kTypeEndPrepareXID));
+  PutLengthPrefixedSlice(&b->rep_, xid);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_END_PREPARE |
+                              ContentFlags::HAS_BEGIN_PREPARE,
+                          std::memory_order_relaxed);
+  if (unprepared_batch) {
+    b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                                ContentFlags::HAS_BEGIN_UNPREPARE,
+                            std::memory_order_relaxed);
+  }
+  return Status::OK();
+}
+
+Status WriteBatchInternal::MarkCommit(WriteBatch* b, const Slice& xid) {
+  b->rep_.push_back(static_cast<char>(kTypeCommitXID));
+  PutLengthPrefixedSlice(&b->rep_, xid);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_COMMIT,
+                          std::memory_order_relaxed);
+  return Status::OK();
+}
+
+Status WriteBatchInternal::MarkRollback(WriteBatch* b, const Slice& xid) {
+  b->rep_.push_back(static_cast<char>(kTypeRollbackXID));
+  PutLengthPrefixedSlice(&b->rep_, xid);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_ROLLBACK,
+                          std::memory_order_relaxed);
+  return Status::OK();
+}
+
+Status WriteBatchInternal::Delete(WriteBatch* b, uint32_t column_family_id,
+                                  const Slice& key) {
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeDeletion));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyDeletion));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSlice(&b->rep_, key);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_DELETE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::Delete(ColumnFamilyHandle* column_family, const Slice& key) {
+  return WriteBatchInternal::Delete(this, GetColumnFamilyID(column_family),
+                                    key);
+}
+
+Status WriteBatchInternal::Delete(WriteBatch* b, uint32_t column_family_id,
+                                  const SliceParts& key) {
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeDeletion));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyDeletion));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSliceParts(&b->rep_, key);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_DELETE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::Delete(ColumnFamilyHandle* column_family,
+                          const SliceParts& key) {
+  return WriteBatchInternal::Delete(this, GetColumnFamilyID(column_family),
+                                    key);
+}
+
+Status WriteBatchInternal::SingleDelete(WriteBatch* b,
+                                        uint32_t column_family_id,
+                                        const Slice& key) {
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeSingleDeletion));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilySingleDeletion));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSlice(&b->rep_, key);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_SINGLE_DELETE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::SingleDelete(ColumnFamilyHandle* column_family,
+                                const Slice& key) {
+  return WriteBatchInternal::SingleDelete(
+      this, GetColumnFamilyID(column_family), key);
+}
+
+Status WriteBatchInternal::SingleDelete(WriteBatch* b,
+                                        uint32_t column_family_id,
+                                        const SliceParts& key) {
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeSingleDeletion));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilySingleDeletion));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSliceParts(&b->rep_, key);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_SINGLE_DELETE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::SingleDelete(ColumnFamilyHandle* column_family,
+                                const SliceParts& key) {
+  return WriteBatchInternal::SingleDelete(
+      this, GetColumnFamilyID(column_family), key);
+}
+
+Status WriteBatchInternal::DeleteRange(WriteBatch* b, uint32_t column_family_id,
+                                       const Slice& begin_key,
+                                       const Slice& end_key) {
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeRangeDeletion));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyRangeDeletion));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSlice(&b->rep_, begin_key);
+  PutLengthPrefixedSlice(&b->rep_, end_key);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_DELETE_RANGE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::DeleteRange(ColumnFamilyHandle* column_family,
+                               const Slice& begin_key, const Slice& end_key) {
+  return WriteBatchInternal::DeleteRange(this, GetColumnFamilyID(column_family),
+                                         begin_key, end_key);
+}
+
+Status WriteBatchInternal::DeleteRange(WriteBatch* b, uint32_t column_family_id,
+                                       const SliceParts& begin_key,
+                                       const SliceParts& end_key) {
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeRangeDeletion));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyRangeDeletion));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSliceParts(&b->rep_, begin_key);
+  PutLengthPrefixedSliceParts(&b->rep_, end_key);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_DELETE_RANGE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::DeleteRange(ColumnFamilyHandle* column_family,
+                               const SliceParts& begin_key,
+                               const SliceParts& end_key) {
+  return WriteBatchInternal::DeleteRange(this, GetColumnFamilyID(column_family),
+                                         begin_key, end_key);
+}
+
+Status WriteBatchInternal::Merge(WriteBatch* b, uint32_t column_family_id,
+                                 const Slice& key, const Slice& value) {
+  if (key.size() > size_t{port::kMaxUint32}) {
+    return Status::InvalidArgument("key is too large");
+  }
+  if (value.size() > size_t{port::kMaxUint32}) {
+    return Status::InvalidArgument("value is too large");
+  }
+
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeMerge));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyMerge));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSlice(&b->rep_, key);
+  PutLengthPrefixedSlice(&b->rep_, value);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_MERGE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::Merge(ColumnFamilyHandle* column_family, const Slice& key,
+                         const Slice& value) {
+  return WriteBatchInternal::Merge(this, GetColumnFamilyID(column_family), key,
+                                   value);
+}
+
+Status WriteBatchInternal::Merge(WriteBatch* b, uint32_t column_family_id,
+                                 const SliceParts& key,
+                                 const SliceParts& value) {
+  Status s = CheckSlicePartsLength(key, value);
+  if (!s.ok()) {
+    return s;
+  }
+
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeMerge));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyMerge));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSliceParts(&b->rep_, key);
+  PutLengthPrefixedSliceParts(&b->rep_, value);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_MERGE,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::Merge(ColumnFamilyHandle* column_family,
+                         const SliceParts& key, const SliceParts& value) {
+  return WriteBatchInternal::Merge(this, GetColumnFamilyID(column_family), key,
+                                   value);
+}
+
+Status WriteBatchInternal::PutBlobIndex(WriteBatch* b,
+                                        uint32_t column_family_id,
+                                        const Slice& key, const Slice& value) {
+  LocalSavePoint save(b);
+  WriteBatchInternal::SetCount(b, WriteBatchInternal::Count(b) + 1);
+  if (column_family_id == 0) {
+    b->rep_.push_back(static_cast<char>(kTypeBlobIndex));
+  } else {
+    b->rep_.push_back(static_cast<char>(kTypeColumnFamilyBlobIndex));
+    PutVarint32(&b->rep_, column_family_id);
+  }
+  PutLengthPrefixedSlice(&b->rep_, key);
+  PutLengthPrefixedSlice(&b->rep_, value);
+  b->content_flags_.store(b->content_flags_.load(std::memory_order_relaxed) |
+                              ContentFlags::HAS_BLOB_INDEX,
+                          std::memory_order_relaxed);
+  return save.commit();
+}
+
+Status WriteBatch::PutLogData(const Slice& blob) {
+  LocalSavePoint save(this);
+  rep_.push_back(static_cast<char>(kTypeLogData));
+  PutLengthPrefixedSlice(&rep_, blob);
+  return save.commit();
+}
+
+void WriteBatch::SetSavePoint() {
+  if (save_points_ == nullptr) {
+    save_points_.reset(new SavePoints());
+  }
+  // Record length and count of current batch of writes.
+  save_points_->stack.push(SavePoint(
+      GetDataSize(), Count(), content_flags_.load(std::memory_order_relaxed)));
+}
+
+Status WriteBatch::RollbackToSavePoint() {
+  if (save_points_ == nullptr || save_points_->stack.size() == 0) {
+    return Status::NotFound();
+  }
+
+  // Pop the most recent savepoint off the stack
+  SavePoint savepoint = save_points_->stack.top();
+  save_points_->stack.pop();
+
+  assert(savepoint.size <= rep_.size());
+  assert(static_cast<uint32_t>(savepoint.count) <= Count());
+
+  if (savepoint.size == rep_.size()) {
+    // No changes to rollback
+  } else if (savepoint.size == 0) {
+    // Rollback everything
+    Clear();
+  } else {
+    rep_.resize(savepoint.size);
+    WriteBatchInternal::SetCount(this, savepoint.count);
+    content_flags_.store(savepoint.content_flags, std::memory_order_relaxed);
+  }
+
+  return Status::OK();
+}
+
+Status WriteBatch::PopSavePoint() {
+  if (save_points_ == nullptr || save_points_->stack.size() == 0) {
+    return Status::NotFound();
+  }
+
+  // Pop the most recent savepoint off the stack
+  save_points_->stack.pop();
+
+  return Status::OK();
+}
+
+Status WriteBatch::AssignTimestamp(const Slice& ts) {
+  TimestampAssigner ts_assigner(ts);
+  return Iterate(&ts_assigner);
+}
+
+Status WriteBatch::AssignTimestamps(const std::vector<Slice>& ts_list) {
+  TimestampAssigner ts_assigner(ts_list);
+  return Iterate(&ts_assigner);
+}
+
+class MemTableInserter : public WriteBatch::Handler {
+
+  SequenceNumber sequence_;
+  ColumnFamilyMemTables* const cf_mems_;
+  FlushScheduler* const flush_scheduler_;
+  TrimHistoryScheduler* const trim_history_scheduler_;
+  const bool ignore_missing_column_families_;
+  const uint64_t recovering_log_number_;
+  // log number that all Memtables inserted into should reference
+  uint64_t log_number_ref_;
+  DBImpl* db_;
+  const bool concurrent_memtable_writes_;
+  bool       post_info_created_;
+
+  bool* has_valid_writes_;
+  // On some (!) platforms just default creating
+  // a map is too expensive in the Write() path as they
+  // cause memory allocations though unused.
+  // Make creation optional but do not incur
+  // std::unique_ptr additional allocation
+  using MemPostInfoMap = std::map<MemTable*, MemTablePostProcessInfo>;
+  using PostMapType = std::aligned_storage<sizeof(MemPostInfoMap)>::type;
+  PostMapType mem_post_info_map_;
+  // current recovered transaction we are rebuilding (recovery)
+  WriteBatch* rebuilding_trx_;
+  SequenceNumber rebuilding_trx_seq_;
+  // Increase seq number once per each write batch. Otherwise increase it once
+  // per key.
+  bool seq_per_batch_;
+  // Whether the memtable write will be done only after the commit
+  bool write_after_commit_;
+  // Whether memtable write can be done before prepare
+  bool write_before_prepare_;
+  // Whether this batch was unprepared or not
+  bool unprepared_batch_;
+  using DupDetector = std::aligned_storage<sizeof(DuplicateDetector)>::type;
+  DupDetector       duplicate_detector_;
+  bool              dup_dectector_on_;
+
+  bool hint_per_batch_;
+  bool hint_created_;
+  // Hints for this batch
+  using HintMap = std::unordered_map<MemTable*, void*>;
+  using HintMapType = std::aligned_storage<sizeof(HintMap)>::type;
+  HintMapType hint_;
+
+  HintMap& GetHintMap() {
+    assert(hint_per_batch_);
+    if (!hint_created_) {
+      new (&hint_) HintMap();
+      hint_created_ = true;
+    }
+    return *reinterpret_cast<HintMap*>(&hint_);
+  }
+
+  MemPostInfoMap& GetPostMap() {
+    assert(concurrent_memtable_writes_);
+    if(!post_info_created_) {
+      new (&mem_post_info_map_) MemPostInfoMap();
+      post_info_created_ = true;
+    }
+    return *reinterpret_cast<MemPostInfoMap*>(&mem_post_info_map_);
+  }
+
+  bool IsDuplicateKeySeq(uint32_t column_family_id, const Slice& key) {
+    assert(!write_after_commit_);
+    assert(rebuilding_trx_ != nullptr);
+    if (!dup_dectector_on_) {
+      new (&duplicate_detector_) DuplicateDetector(db_);
+      dup_dectector_on_ = true;
+    }
+    return reinterpret_cast<DuplicateDetector*>
+      (&duplicate_detector_)->IsDuplicateKeySeq(column_family_id, key, sequence_);
+  }
+
+ protected:
+  bool WriteBeforePrepare() const override { return write_before_prepare_; }
+  bool WriteAfterCommit() const override { return write_after_commit_; }
+
+ public:
+  // cf_mems should not be shared with concurrent inserters
+  MemTableInserter(SequenceNumber _sequence, ColumnFamilyMemTables* cf_mems,
+                   FlushScheduler* flush_scheduler,
+                   TrimHistoryScheduler* trim_history_scheduler,
+                   bool ignore_missing_column_families,
+                   uint64_t recovering_log_number, DB* db,
+                   bool concurrent_memtable_writes,
+                   bool* has_valid_writes = nullptr, bool seq_per_batch = false,
+                   bool batch_per_txn = true, bool hint_per_batch = false)
+      : sequence_(_sequence),
+        cf_mems_(cf_mems),
+        flush_scheduler_(flush_scheduler),
+        trim_history_scheduler_(trim_history_scheduler),
+        ignore_missing_column_families_(ignore_missing_column_families),
+        recovering_log_number_(recovering_log_number),
+        log_number_ref_(0),
+        db_(static_cast_with_check<DBImpl, DB>(db)),
+        concurrent_memtable_writes_(concurrent_memtable_writes),
+        post_info_created_(false),
+        has_valid_writes_(has_valid_writes),
+        rebuilding_trx_(nullptr),
+        rebuilding_trx_seq_(0),
+        seq_per_batch_(seq_per_batch),
+        // Write after commit currently uses one seq per key (instead of per
+        // batch). So seq_per_batch being false indicates write_after_commit
+        // approach.
+        write_after_commit_(!seq_per_batch),
+        // WriteUnprepared can write WriteBatches per transaction, so
+        // batch_per_txn being false indicates write_before_prepare.
+        write_before_prepare_(!batch_per_txn),
+        unprepared_batch_(false),
+        duplicate_detector_(),
+        dup_dectector_on_(false),
+        hint_per_batch_(hint_per_batch),
+        hint_created_(false) {
+    assert(cf_mems_);
+  }
+
+  ~MemTableInserter() override {
+    if (dup_dectector_on_) {
+      reinterpret_cast<DuplicateDetector*>
+        (&duplicate_detector_)->~DuplicateDetector();
+    }
+    if (post_info_created_) {
+      reinterpret_cast<MemPostInfoMap*>
+        (&mem_post_info_map_)->~MemPostInfoMap();
+    }
+    if (hint_created_) {
+      for (auto iter : GetHintMap()) {
+        delete[] reinterpret_cast<char*>(iter.second);
+      }
+      reinterpret_cast<HintMap*>(&hint_)->~HintMap();
+    }
+    delete rebuilding_trx_;
+  }
+
+  MemTableInserter(const MemTableInserter&) = delete;
+  MemTableInserter& operator=(const MemTableInserter&) = delete;
+
+  // The batch seq is regularly restarted; In normal mode it is set when
+  // MemTableInserter is constructed in the write thread and in recovery mode it
+  // is set when a batch, which is tagged with seq, is read from the WAL.
+  // Within a sequenced batch, which could be a merge of multiple batches, we
+  // have two policies to advance the seq: i) seq_per_key (default) and ii)
+  // seq_per_batch. To implement the latter we need to mark the boundary between
+  // the individual batches. The approach is this: 1) Use the terminating
+  // markers to indicate the boundary (kTypeEndPrepareXID, kTypeCommitXID,
+  // kTypeRollbackXID) 2) Terminate a batch with kTypeNoop in the absence of a
+  // natural boundary marker.
+  void MaybeAdvanceSeq(bool batch_boundry = false) {
+    if (batch_boundry == seq_per_batch_) {
+      sequence_++;
+    }
+  }
+
+  void set_log_number_ref(uint64_t log) { log_number_ref_ = log; }
+
+  SequenceNumber sequence() const { return sequence_; }
+
+  void PostProcess() {
+    assert(concurrent_memtable_writes_);
+    // If post info was not created there is nothing
+    // to process and no need to create on demand
+    if(post_info_created_) {
+      for (auto& pair : GetPostMap()) {
+        pair.first->BatchPostProcess(pair.second);
+      }
+    }
+  }
+
+  bool SeekToColumnFamily(uint32_t column_family_id, Status* s) {
+    // If we are in a concurrent mode, it is the caller's responsibility
+    // to clone the original ColumnFamilyMemTables so that each thread
+    // has its own instance.  Otherwise, it must be guaranteed that there
+    // is no concurrent access
+    bool found = cf_mems_->Seek(column_family_id);
+    if (!found) {
+      if (ignore_missing_column_families_) {
+        *s = Status::OK();
+      } else {
+        *s = Status::InvalidArgument(
+            "Invalid column family specified in write batch");
+      }
+      return false;
+    }
+    if (recovering_log_number_ != 0 &&
+        recovering_log_number_ < cf_mems_->GetLogNumber()) {
+      // This is true only in recovery environment (recovering_log_number_ is
+      // always 0 in
+      // non-recovery, regular write code-path)
+      // * If recovering_log_number_ < cf_mems_->GetLogNumber(), this means that
+      // column
+      // family already contains updates from this log. We can't apply updates
+      // twice because of update-in-place or merge workloads -- ignore the
+      // update
+      *s = Status::OK();
+      return false;
+    }
+
+    if (has_valid_writes_ != nullptr) {
+      *has_valid_writes_ = true;
+    }
+
+    if (log_number_ref_ > 0) {
+      cf_mems_->GetMemTable()->RefLogContainingPrepSection(log_number_ref_);
+    }
+
+    return true;
+  }
+
+  Status PutCFImpl(uint32_t column_family_id, const Slice& key,
+                   const Slice& value, ValueType value_type) {
+    // optimize for non-recovery mode
+    if (UNLIKELY(write_after_commit_ && rebuilding_trx_ != nullptr)) {
+      WriteBatchInternal::Put(rebuilding_trx_, column_family_id, key, value);
+      return Status::OK();
+      // else insert the values to the memtable right away
+    }
+
+    Status seek_status;
+    if (UNLIKELY(!SeekToColumnFamily(column_family_id, &seek_status))) {
+      bool batch_boundry = false;
+      if (rebuilding_trx_ != nullptr) {
+        assert(!write_after_commit_);
+        // The CF is probably flushed and hence no need for insert but we still
+        // need to keep track of the keys for upcoming rollback/commit.
+        WriteBatchInternal::Put(rebuilding_trx_, column_family_id, key, value);
+        batch_boundry = IsDuplicateKeySeq(column_family_id, key);
+      }
+      MaybeAdvanceSeq(batch_boundry);
+      return seek_status;
+    }
+    Status ret_status;
+
+    MemTable* mem = cf_mems_->GetMemTable();
+    auto* moptions = mem->GetImmutableMemTableOptions();
+    // inplace_update_support is inconsistent with snapshots, and therefore with
+    // any kind of transactions including the ones that use seq_per_batch
+    assert(!seq_per_batch_ || !moptions->inplace_update_support);
+    if (!moptions->inplace_update_support) {
+      bool mem_res =
+          mem->Add(sequence_, value_type, key, value,
+                   concurrent_memtable_writes_, get_post_process_info(mem),
+                   hint_per_batch_ ? &GetHintMap()[mem] : nullptr);
+      if (UNLIKELY(!mem_res)) {
+        assert(seq_per_batch_);
+        ret_status = Status::TryAgain("key+seq exists");
+        const bool BATCH_BOUNDRY = true;
+        MaybeAdvanceSeq(BATCH_BOUNDRY);
+      }
+    } else if (moptions->inplace_callback == nullptr) {
+      assert(!concurrent_memtable_writes_);
+      mem->Update(sequence_, key, value);
+    } else {
+      assert(!concurrent_memtable_writes_);
+      if (mem->UpdateCallback(sequence_, key, value)) {
+      } else {
+        // key not found in memtable. Do sst get, update, add
+        SnapshotImpl read_from_snapshot;
+        read_from_snapshot.number_ = sequence_;
+        ReadOptions ropts;
+        // it's going to be overwritten for sure, so no point caching data block
+        // containing the old version
+        ropts.fill_cache = false;
+        ropts.snapshot = &read_from_snapshot;
+
+        std::string prev_value;
+        std::string merged_value;
+
+        auto cf_handle = cf_mems_->GetColumnFamilyHandle();
+        Status s = Status::NotSupported();
+        if (db_ != nullptr && recovering_log_number_ == 0) {
+          if (cf_handle == nullptr) {
+            cf_handle = db_->DefaultColumnFamily();
+          }
+          s = db_->Get(ropts, cf_handle, key, &prev_value);
+        }
+
+        char* prev_buffer = const_cast<char*>(prev_value.c_str());
+        uint32_t prev_size = static_cast<uint32_t>(prev_value.size());
+        auto status = moptions->inplace_callback(s.ok() ? prev_buffer : nullptr,
+                                                 s.ok() ? &prev_size : nullptr,
+                                                 value, &merged_value);
+        if (status == UpdateStatus::UPDATED_INPLACE) {
+          // prev_value is updated in-place with final value.
+          bool mem_res __attribute__((__unused__));
+          mem_res = mem->Add(
+              sequence_, value_type, key, Slice(prev_buffer, prev_size));
+          assert(mem_res);
+          RecordTick(moptions->statistics, NUMBER_KEYS_WRITTEN);
+        } else if (status == UpdateStatus::UPDATED) {
+          // merged_value contains the final value.
+          bool mem_res __attribute__((__unused__));
+          mem_res =
+              mem->Add(sequence_, value_type, key, Slice(merged_value));
+          assert(mem_res);
+          RecordTick(moptions->statistics, NUMBER_KEYS_WRITTEN);
+        }
+      }
+    }
+    // optimize for non-recovery mode
+    if (UNLIKELY(!ret_status.IsTryAgain() && rebuilding_trx_ != nullptr)) {
+      assert(!write_after_commit_);
+      // If the ret_status is TryAgain then let the next try to add the ky to
+      // the rebuilding transaction object.
+      WriteBatchInternal::Put(rebuilding_trx_, column_family_id, key, value);
+    }
+    // Since all Puts are logged in transaction logs (if enabled), always bump
+    // sequence number. Even if the update eventually fails and does not result
+    // in memtable add/update.
+    MaybeAdvanceSeq();
+    CheckMemtableFull();
+    return ret_status;
+  }
+
+  Status PutCF(uint32_t column_family_id, const Slice& key,
+               const Slice& value) override {
+    return PutCFImpl(column_family_id, key, value, kTypeValue);
+  }
+
+  Status DeleteImpl(uint32_t /*column_family_id*/, const Slice& key,
+                    const Slice& value, ValueType delete_type) {
+    Status ret_status;
+    MemTable* mem = cf_mems_->GetMemTable();
+    bool mem_res =
+        mem->Add(sequence_, delete_type, key, value,
+                 concurrent_memtable_writes_, get_post_process_info(mem),
+                 hint_per_batch_ ? &GetHintMap()[mem] : nullptr);
+    if (UNLIKELY(!mem_res)) {
+      assert(seq_per_batch_);
+      ret_status = Status::TryAgain("key+seq exists");
+      const bool BATCH_BOUNDRY = true;
+      MaybeAdvanceSeq(BATCH_BOUNDRY);
+    }
+    MaybeAdvanceSeq();
+    CheckMemtableFull();
+    return ret_status;
+  }
+
+  Status DeleteCF(uint32_t column_family_id, const Slice& key) override {
+    // optimize for non-recovery mode
+    if (UNLIKELY(write_after_commit_ && rebuilding_trx_ != nullptr)) {
+      WriteBatchInternal::Delete(rebuilding_trx_, column_family_id, key);
+      return Status::OK();
+      // else insert the values to the memtable right away
+    }
+
+    Status seek_status;
+    if (UNLIKELY(!SeekToColumnFamily(column_family_id, &seek_status))) {
+      bool batch_boundry = false;
+      if (rebuilding_trx_ != nullptr) {
+        assert(!write_after_commit_);
+        // The CF is probably flushed and hence no need for insert but we still
+        // need to keep track of the keys for upcoming rollback/commit.
+        WriteBatchInternal::Delete(rebuilding_trx_, column_family_id, key);
+        batch_boundry = IsDuplicateKeySeq(column_family_id, key);
+      }
+      MaybeAdvanceSeq(batch_boundry);
+      return seek_status;
+    }
+
+    auto ret_status = DeleteImpl(column_family_id, key, Slice(), kTypeDeletion);
+    // optimize for non-recovery mode
+    if (UNLIKELY(!ret_status.IsTryAgain() && rebuilding_trx_ != nullptr)) {
+      assert(!write_after_commit_);
+      // If the ret_status is TryAgain then let the next try to add the ky to
+      // the rebuilding transaction object.
+      WriteBatchInternal::Delete(rebuilding_trx_, column_family_id, key);
+    }
+    return ret_status;
+  }
+
+  Status SingleDeleteCF(uint32_t column_family_id, const Slice& key) override {
+    // optimize for non-recovery mode
+    if (UNLIKELY(write_after_commit_ && rebuilding_trx_ != nullptr)) {
+      WriteBatchInternal::SingleDelete(rebuilding_trx_, column_family_id, key);
+      return Status::OK();
+      // else insert the values to the memtable right away
+    }
+
+    Status seek_status;
+    if (UNLIKELY(!SeekToColumnFamily(column_family_id, &seek_status))) {
+      bool batch_boundry = false;
+      if (rebuilding_trx_ != nullptr) {
+        assert(!write_after_commit_);
+        // The CF is probably flushed and hence no need for insert but we still
+        // need to keep track of the keys for upcoming rollback/commit.
+        WriteBatchInternal::SingleDelete(rebuilding_trx_, column_family_id,
+                                         key);
+        batch_boundry = IsDuplicateKeySeq(column_family_id, key);
+      }
+      MaybeAdvanceSeq(batch_boundry);
+      return seek_status;
+    }
+
+    auto ret_status =
+        DeleteImpl(column_family_id, key, Slice(), kTypeSingleDeletion);
+    // optimize for non-recovery mode
+    if (UNLIKELY(!ret_status.IsTryAgain() && rebuilding_trx_ != nullptr)) {
+      assert(!write_after_commit_);
+      // If the ret_status is TryAgain then let the next try to add the ky to
+      // the rebuilding transaction object.
+      WriteBatchInternal::SingleDelete(rebuilding_trx_, column_family_id, key);
+    }
+    return ret_status;
+  }
+
+  Status DeleteRangeCF(uint32_t column_family_id, const Slice& begin_key,
+                       const Slice& end_key) override {
+    // optimize for non-recovery mode
+    if (UNLIKELY(write_after_commit_ && rebuilding_trx_ != nullptr)) {
+      WriteBatchInternal::DeleteRange(rebuilding_trx_, column_family_id,
+                                      begin_key, end_key);
+      return Status::OK();
+      // else insert the values to the memtable right away
+    }
+
+    Status seek_status;
+    if (UNLIKELY(!SeekToColumnFamily(column_family_id, &seek_status))) {
+      bool batch_boundry = false;
+      if (rebuilding_trx_ != nullptr) {
+        assert(!write_after_commit_);
+        // The CF is probably flushed and hence no need for insert but we still
+        // need to keep track of the keys for upcoming rollback/commit.
+        WriteBatchInternal::DeleteRange(rebuilding_trx_, column_family_id,
+                                        begin_key, end_key);
+        // TODO(myabandeh): when transactional DeleteRange support is added,
+        // check if end_key must also be added.
+        batch_boundry = IsDuplicateKeySeq(column_family_id, begin_key);
+      }
+      MaybeAdvanceSeq(batch_boundry);
+      return seek_status;
+    }
+    if (db_ != nullptr) {
+      auto cf_handle = cf_mems_->GetColumnFamilyHandle();
+      if (cf_handle == nullptr) {
+        cf_handle = db_->DefaultColumnFamily();
+      }
+      auto* cfd = reinterpret_cast<ColumnFamilyHandleImpl*>(cf_handle)->cfd();
+      if (!cfd->is_delete_range_supported()) {
+        return Status::NotSupported(
+            std::string("DeleteRange not supported for table type ") +
+            cfd->ioptions()->table_factory->Name() + " in CF " +
+            cfd->GetName());
+      }
+    }
+
+    auto ret_status =
+        DeleteImpl(column_family_id, begin_key, end_key, kTypeRangeDeletion);
+    // optimize for non-recovery mode
+    if (UNLIKELY(!ret_status.IsTryAgain() && rebuilding_trx_ != nullptr)) {
+      assert(!write_after_commit_);
+      // If the ret_status is TryAgain then let the next try to add the ky to
+      // the rebuilding transaction object.
+      WriteBatchInternal::DeleteRange(rebuilding_trx_, column_family_id,
+                                      begin_key, end_key);
+    }
+    return ret_status;
+  }
+
+  Status MergeCF(uint32_t column_family_id, const Slice& key,
+                 const Slice& value) override {
+    // optimize for non-recovery mode
+    if (UNLIKELY(write_after_commit_ && rebuilding_trx_ != nullptr)) {
+      WriteBatchInternal::Merge(rebuilding_trx_, column_family_id, key, value);
+      return Status::OK();
+      // else insert the values to the memtable right away
+    }
+
+    Status seek_status;
+    if (UNLIKELY(!SeekToColumnFamily(column_family_id, &seek_status))) {
+      bool batch_boundry = false;
+      if (rebuilding_trx_ != nullptr) {
+        assert(!write_after_commit_);
+        // The CF is probably flushed and hence no need for insert but we still
+        // need to keep track of the keys for upcoming rollback/commit.
+        WriteBatchInternal::Merge(rebuilding_trx_, column_family_id, key,
+                                  value);
+        batch_boundry = IsDuplicateKeySeq(column_family_id, key);
+      }
+      MaybeAdvanceSeq(batch_boundry);
+      return seek_status;
+    }
+
+    Status ret_status;
+    MemTable* mem = cf_mems_->GetMemTable();
+    auto* moptions = mem->GetImmutableMemTableOptions();
+    bool perform_merge = false;
+    assert(!concurrent_memtable_writes_ ||
+           moptions->max_successive_merges == 0);
+
+    // If we pass DB through and options.max_successive_merges is hit
+    // during recovery, Get() will be issued which will try to acquire
+    // DB mutex and cause deadlock, as DB mutex is already held.
+    // So we disable merge in recovery
+    if (moptions->max_successive_merges > 0 && db_ != nullptr &&
+        recovering_log_number_ == 0) {
+      assert(!concurrent_memtable_writes_);
+      LookupKey lkey(key, sequence_);
+
+      // Count the number of successive merges at the head
+      // of the key in the memtable
+      size_t num_merges = mem->CountSuccessiveMergeEntries(lkey);
+
+      if (num_merges >= moptions->max_successive_merges) {
+        perform_merge = true;
+      }
+    }
+
+    if (perform_merge) {
+      // 1) Get the existing value
+      std::string get_value;
+
+      // Pass in the sequence number so that we also include previous merge
+      // operations in the same batch.
+      SnapshotImpl read_from_snapshot;
+      read_from_snapshot.number_ = sequence_;
+      ReadOptions read_options;
+      read_options.snapshot = &read_from_snapshot;
+
+      auto cf_handle = cf_mems_->GetColumnFamilyHandle();
+      if (cf_handle == nullptr) {
+        cf_handle = db_->DefaultColumnFamily();
+      }
+      db_->Get(read_options, cf_handle, key, &get_value);
+      Slice get_value_slice = Slice(get_value);
+
+      // 2) Apply this merge
+      auto merge_operator = moptions->merge_operator;
+      assert(merge_operator);
+
+      std::string new_value;
+
+      Status merge_status = MergeHelper::TimedFullMerge(
+          merge_operator, key, &get_value_slice, {value}, &new_value,
+          moptions->info_log, moptions->statistics, Env::Default());
+
+      if (!merge_status.ok()) {
+        // Failed to merge!
+        // Store the delta in memtable
+        perform_merge = false;
+      } else {
+        // 3) Add value to memtable
+        assert(!concurrent_memtable_writes_);
+        bool mem_res = mem->Add(sequence_, kTypeValue, key, new_value);
+        if (UNLIKELY(!mem_res)) {
+          assert(seq_per_batch_);
+          ret_status = Status::TryAgain("key+seq exists");
+          const bool BATCH_BOUNDRY = true;
+          MaybeAdvanceSeq(BATCH_BOUNDRY);
+        }
+      }
+    }
+
+    if (!perform_merge) {
+      // Add merge operator to memtable
+      bool mem_res =
+          mem->Add(sequence_, kTypeMerge, key, value,
+                   concurrent_memtable_writes_, get_post_process_info(mem));
+      if (UNLIKELY(!mem_res)) {
+        assert(seq_per_batch_);
+        ret_status = Status::TryAgain("key+seq exists");
+        const bool BATCH_BOUNDRY = true;
+        MaybeAdvanceSeq(BATCH_BOUNDRY);
+      }
+    }
+
+    // optimize for non-recovery mode
+    if (UNLIKELY(!ret_status.IsTryAgain() && rebuilding_trx_ != nullptr)) {
+      assert(!write_after_commit_);
+      // If the ret_status is TryAgain then let the next try to add the ky to
+      // the rebuilding transaction object.
+      WriteBatchInternal::Merge(rebuilding_trx_, column_family_id, key, value);
+    }
+    MaybeAdvanceSeq();
+    CheckMemtableFull();
+    return ret_status;
+  }
+
+  Status PutBlobIndexCF(uint32_t column_family_id, const Slice& key,
+                        const Slice& value) override {
+    // Same as PutCF except for value type.
+    return PutCFImpl(column_family_id, key, value, kTypeBlobIndex);
+  }
+
+  void CheckMemtableFull() {
+    if (flush_scheduler_ != nullptr) {
+      auto* cfd = cf_mems_->current();
+      assert(cfd != nullptr);
+      if (cfd->mem()->ShouldScheduleFlush() &&
+          cfd->mem()->MarkFlushScheduled()) {
+        // MarkFlushScheduled only returns true if we are the one that
+        // should take action, so no need to dedup further
+        flush_scheduler_->ScheduleWork(cfd);
+      }
+    }
+    // check if memtable_list size exceeds max_write_buffer_size_to_maintain
+    if (trim_history_scheduler_ != nullptr) {
+      auto* cfd = cf_mems_->current();
+
+      assert(cfd);
+      assert(cfd->ioptions());
+
+      const size_t size_to_maintain = static_cast<size_t>(
+          cfd->ioptions()->max_write_buffer_size_to_maintain);
+
+      if (size_to_maintain > 0) {
+        MemTableList* const imm = cfd->imm();
+        assert(imm);
+
+        if (imm->HasHistory()) {
+          const MemTable* const mem = cfd->mem();
+          assert(mem);
+
+          if (mem->ApproximateMemoryUsageFast() +
+                      imm->ApproximateMemoryUsageExcludingLast() >=
+                  size_to_maintain &&
+              imm->MarkTrimHistoryNeeded()) {
+            trim_history_scheduler_->ScheduleWork(cfd);
+          }
+        }
+      }
+    }
+  }
+
+  // The write batch handler calls MarkBeginPrepare with unprepare set to true
+  // if it encounters the kTypeBeginUnprepareXID marker.
+  Status MarkBeginPrepare(bool unprepare) override {
+    assert(rebuilding_trx_ == nullptr);
+    assert(db_);
+
+    if (recovering_log_number_ != 0) {
+      // during recovery we rebuild a hollow transaction
+      // from all encountered prepare sections of the wal
+      if (db_->allow_2pc() == false) {
+        return Status::NotSupported(
+            "WAL contains prepared transactions. Open with "
+            "TransactionDB::Open().");
+      }
+
+      // we are now iterating through a prepared section
+      rebuilding_trx_ = new WriteBatch();
+      rebuilding_trx_seq_ = sequence_;
+      // Verify that we have matching MarkBeginPrepare/MarkEndPrepare markers.
+      // unprepared_batch_ should be false because it is false by default, and
+      // gets reset to false in MarkEndPrepare.
+      assert(!unprepared_batch_);
+      unprepared_batch_ = unprepare;
+
+      if (has_valid_writes_ != nullptr) {
+        *has_valid_writes_ = true;
+      }
+    }
+
+    return Status::OK();
+  }
+
+  Status MarkEndPrepare(const Slice& name) override {
+    assert(db_);
+    assert((rebuilding_trx_ != nullptr) == (recovering_log_number_ != 0));
+
+    if (recovering_log_number_ != 0) {
+      assert(db_->allow_2pc());
+      size_t batch_cnt =
+          write_after_commit_
+              ? 0  // 0 will disable further checks
+              : static_cast<size_t>(sequence_ - rebuilding_trx_seq_ + 1);
+      db_->InsertRecoveredTransaction(recovering_log_number_, name.ToString(),
+                                      rebuilding_trx_, rebuilding_trx_seq_,
+                                      batch_cnt, unprepared_batch_);
+      unprepared_batch_ = false;
+      rebuilding_trx_ = nullptr;
+    } else {
+      assert(rebuilding_trx_ == nullptr);
+    }
+    const bool batch_boundry = true;
+    MaybeAdvanceSeq(batch_boundry);
+
+    return Status::OK();
+  }
+
+  Status MarkNoop(bool empty_batch) override {
+    // A hack in pessimistic transaction could result into a noop at the start
+    // of the write batch, that should be ignored.
+    if (!empty_batch) {
+      // In the absence of Prepare markers, a kTypeNoop tag indicates the end of
+      // a batch. This happens when write batch commits skipping the prepare
+      // phase.
+      const bool batch_boundry = true;
+      MaybeAdvanceSeq(batch_boundry);
+    }
+    return Status::OK();
+  }
+
+  Status MarkCommit(const Slice& name) override {
+    assert(db_);
+
+    Status s;
+
+    if (recovering_log_number_ != 0) {
+      // in recovery when we encounter a commit marker
+      // we lookup this transaction in our set of rebuilt transactions
+      // and commit.
+      auto trx = db_->GetRecoveredTransaction(name.ToString());
+
+      // the log containing the prepared section may have
+      // been released in the last incarnation because the
+      // data was flushed to L0
+      if (trx != nullptr) {
+        // at this point individual CF lognumbers will prevent
+        // duplicate re-insertion of values.
+        assert(log_number_ref_ == 0);
+        if (write_after_commit_) {
+          // write_after_commit_ can only have one batch in trx.
+          assert(trx->batches_.size() == 1);
+          const auto& batch_info = trx->batches_.begin()->second;
+          // all inserts must reference this trx log number
+          log_number_ref_ = batch_info.log_number_;
+          s = batch_info.batch_->Iterate(this);
+          log_number_ref_ = 0;
+        }
+        // else the values are already inserted before the commit
+
+        if (s.ok()) {
+          db_->DeleteRecoveredTransaction(name.ToString());
+        }
+        if (has_valid_writes_ != nullptr) {
+          *has_valid_writes_ = true;
+        }
+      }
+    } else {
+      // When writes are not delayed until commit, there is no disconnect
+      // between a memtable write and the WAL that supports it. So the commit
+      // need not reference any log as the only log to which it depends.
+      assert(!write_after_commit_ || log_number_ref_ > 0);
+    }
+    const bool batch_boundry = true;
+    MaybeAdvanceSeq(batch_boundry);
+
+    return s;
+  }
+
+  Status MarkRollback(const Slice& name) override {
+    assert(db_);
+
+    if (recovering_log_number_ != 0) {
+      auto trx = db_->GetRecoveredTransaction(name.ToString());
+
+      // the log containing the transactions prep section
+      // may have been released in the previous incarnation
+      // because we knew it had been rolled back
+      if (trx != nullptr) {
+        db_->DeleteRecoveredTransaction(name.ToString());
+      }
+    } else {
+      // in non recovery we simply ignore this tag
+    }
+
+    const bool batch_boundry = true;
+    MaybeAdvanceSeq(batch_boundry);
+
+    return Status::OK();
+  }
+
+ private:
+  MemTablePostProcessInfo* get_post_process_info(MemTable* mem) {
+    if (!concurrent_memtable_writes_) {
+      // No need to batch counters locally if we don't use concurrent mode.
+      return nullptr;
+    }
+    return &GetPostMap()[mem];
+  }
+};
+
+// This function can only be called in these conditions:
+// 1) During Recovery()
+// 2) During Write(), in a single-threaded write thread
+// 3) During Write(), in a concurrent context where memtables has been cloned
+// The reason is that it calls memtables->Seek(), which has a stateful cache
+Status WriteBatchInternal::InsertInto(
+    WriteThread::WriteGroup& write_group, SequenceNumber sequence,
+    ColumnFamilyMemTables* memtables, FlushScheduler* flush_scheduler,
+    TrimHistoryScheduler* trim_history_scheduler,
+    bool ignore_missing_column_families, uint64_t recovery_log_number, DB* db,
+    bool concurrent_memtable_writes, bool seq_per_batch, bool batch_per_txn) {
+  MemTableInserter inserter(
+      sequence, memtables, flush_scheduler, trim_history_scheduler,
+      ignore_missing_column_families, recovery_log_number, db,
+      concurrent_memtable_writes, nullptr /*has_valid_writes*/, seq_per_batch,
+      batch_per_txn);
+  for (auto w : write_group) {
+    if (w->CallbackFailed()) {
+      continue;
+    }
+    w->sequence = inserter.sequence();
+    if (!w->ShouldWriteToMemtable()) {
+      // In seq_per_batch_ mode this advances the seq by one.
+      inserter.MaybeAdvanceSeq(true);
+      continue;
+    }
+    SetSequence(w->batch, inserter.sequence());
+    inserter.set_log_number_ref(w->log_ref);
+    w->status = w->batch->Iterate(&inserter);
+    if (!w->status.ok()) {
+      return w->status;
+    }
+    assert(!seq_per_batch || w->batch_cnt != 0);
+    assert(!seq_per_batch || inserter.sequence() - w->sequence == w->batch_cnt);
+  }
+  return Status::OK();
+}
+
+Status WriteBatchInternal::InsertInto(
+    WriteThread::Writer* writer, SequenceNumber sequence,
+    ColumnFamilyMemTables* memtables, FlushScheduler* flush_scheduler,
+    TrimHistoryScheduler* trim_history_scheduler,
+    bool ignore_missing_column_families, uint64_t log_number, DB* db,
+    bool concurrent_memtable_writes, bool seq_per_batch, size_t batch_cnt,
+    bool batch_per_txn, bool hint_per_batch) {
+#ifdef NDEBUG
+  (void)batch_cnt;
+#endif
+  assert(writer->ShouldWriteToMemtable());
+  MemTableInserter inserter(
+      sequence, memtables, flush_scheduler, trim_history_scheduler,
+      ignore_missing_column_families, log_number, db,
+      concurrent_memtable_writes, nullptr /*has_valid_writes*/, seq_per_batch,
+      batch_per_txn, hint_per_batch);
+  SetSequence(writer->batch, sequence);
+  inserter.set_log_number_ref(writer->log_ref);
+  Status s = writer->batch->Iterate(&inserter);
+  assert(!seq_per_batch || batch_cnt != 0);
+  assert(!seq_per_batch || inserter.sequence() - sequence == batch_cnt);
+  if (concurrent_memtable_writes) {
+    inserter.PostProcess();
+  }
+  return s;
+}
+
+Status WriteBatchInternal::InsertInto(
+    const WriteBatch* batch, ColumnFamilyMemTables* memtables,
+    FlushScheduler* flush_scheduler,
+    TrimHistoryScheduler* trim_history_scheduler,
+    bool ignore_missing_column_families, uint64_t log_number, DB* db,
+    bool concurrent_memtable_writes, SequenceNumber* next_seq,
+    bool* has_valid_writes, bool seq_per_batch, bool batch_per_txn) {
+  MemTableInserter inserter(Sequence(batch), memtables, flush_scheduler,
+                            trim_history_scheduler,
+                            ignore_missing_column_families, log_number, db,
+                            concurrent_memtable_writes, has_valid_writes,
+                            seq_per_batch, batch_per_txn);
+  Status s = batch->Iterate(&inserter);
+  if (next_seq != nullptr) {
+    *next_seq = inserter.sequence();
+  }
+  if (concurrent_memtable_writes) {
+    inserter.PostProcess();
+  }
+  return s;
+}
+
+Status WriteBatchInternal::SetContents(WriteBatch* b, const Slice& contents) {
+  assert(contents.size() >= WriteBatchInternal::kHeader);
+  b->rep_.assign(contents.data(), contents.size());
+  b->content_flags_.store(ContentFlags::DEFERRED, std::memory_order_relaxed);
+  return Status::OK();
+}
+
+Status WriteBatchInternal::Append(WriteBatch* dst, const WriteBatch* src,
+                                  const bool wal_only) {
+  size_t src_len;
+  int src_count;
+  uint32_t src_flags;
+
+  const SavePoint& batch_end = src->GetWalTerminationPoint();
+
+  if (wal_only && !batch_end.is_cleared()) {
+    src_len = batch_end.size - WriteBatchInternal::kHeader;
+    src_count = batch_end.count;
+    src_flags = batch_end.content_flags;
+  } else {
+    src_len = src->rep_.size() - WriteBatchInternal::kHeader;
+    src_count = Count(src);
+    src_flags = src->content_flags_.load(std::memory_order_relaxed);
+  }
+
+  SetCount(dst, Count(dst) + src_count);
+  assert(src->rep_.size() >= WriteBatchInternal::kHeader);
+  dst->rep_.append(src->rep_.data() + WriteBatchInternal::kHeader, src_len);
+  dst->content_flags_.store(
+      dst->content_flags_.load(std::memory_order_relaxed) | src_flags,
+      std::memory_order_relaxed);
+  return Status::OK();
+}
+
+size_t WriteBatchInternal::AppendedByteSize(size_t leftByteSize,
+                                            size_t rightByteSize) {
+  if (leftByteSize == 0 || rightByteSize == 0) {
+    return leftByteSize + rightByteSize;
+  } else {
+    return leftByteSize + rightByteSize - WriteBatchInternal::kHeader;
+  }
+}
+
+}  // namespace ROCKSDB_NAMESPACE