1 files changed, 112 insertions, 0 deletions
diff --git a/src/rocksdb/db/arena_wrapped_db_iter.h b/src/rocksdb/db/arena_wrapped_db_iter.h
new file mode 100644
index 000000000..0c135f857
--- /dev/null
+++ b/src/rocksdb/db/arena_wrapped_db_iter.h
@@ -0,0 +1,112 @@
+//  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.
+
+#pragma once
+#include <stdint.h>
+#include <string>
+#include "db/db_impl/db_impl.h"
+#include "db/db_iter.h"
+#include "db/dbformat.h"
+#include "db/range_del_aggregator.h"
+#include "memory/arena.h"
+#include "options/cf_options.h"
+#include "rocksdb/db.h"
+#include "rocksdb/iterator.h"
+#include "util/autovector.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class Arena;
+
+// A wrapper iterator which wraps DB Iterator and the arena, with which the DB
+// iterator is supposed to be allocated. This class is used as an entry point of
+// a iterator hierarchy whose memory can be allocated inline. In that way,
+// accessing the iterator tree can be more cache friendly. It is also faster
+// to allocate.
+// When using the class's Iterator interface, the behavior is exactly
+// the same as the inner DBIter.
+class ArenaWrappedDBIter : public Iterator {
+ public:
+  virtual ~ArenaWrappedDBIter() { db_iter_->~DBIter(); }
+
+  // Get the arena to be used to allocate memory for DBIter to be wrapped,
+  // as well as child iterators in it.
+  virtual Arena* GetArena() { return &arena_; }
+  virtual ReadRangeDelAggregator* GetRangeDelAggregator() {
+    return db_iter_->GetRangeDelAggregator();
+  }
+
+  // Set the internal iterator wrapped inside the DB Iterator. Usually it is
+  // a merging iterator.
+  virtual void SetIterUnderDBIter(InternalIterator* iter) {
+    db_iter_->SetIter(iter);
+  }
+
+  bool Valid() const override { return db_iter_->Valid(); }
+  void SeekToFirst() override { db_iter_->SeekToFirst(); }
+  void SeekToLast() override { db_iter_->SeekToLast(); }
+  void Seek(const Slice& target) override { db_iter_->Seek(target); }
+  void SeekForPrev(const Slice& target) override {
+    db_iter_->SeekForPrev(target);
+  }
+  void Next() override { db_iter_->Next(); }
+  void Prev() override { db_iter_->Prev(); }
+  Slice key() const override { return db_iter_->key(); }
+  Slice value() const override { return db_iter_->value(); }
+  Status status() const override { return db_iter_->status(); }
+  bool IsBlob() const { return db_iter_->IsBlob(); }
+
+  Status GetProperty(std::string prop_name, std::string* prop) override;
+
+  Status Refresh() override;
+
+  void Init(Env* env, const ReadOptions& read_options,
+            const ImmutableCFOptions& cf_options,
+            const MutableCFOptions& mutable_cf_options,
+            const SequenceNumber& sequence,
+            uint64_t max_sequential_skip_in_iterations, uint64_t version_number,
+            ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd,
+            bool allow_blob, bool allow_refresh);
+
+  // Store some parameters so we can refresh the iterator at a later point
+  // with these same params
+  void StoreRefreshInfo(const ReadOptions& read_options, DBImpl* db_impl,
+                        ColumnFamilyData* cfd, ReadCallback* read_callback,
+                        bool allow_blob) {
+    read_options_ = read_options;
+    db_impl_ = db_impl;
+    cfd_ = cfd;
+    read_callback_ = read_callback;
+    allow_blob_ = allow_blob;
+  }
+
+ private:
+  DBIter* db_iter_;
+  Arena arena_;
+  uint64_t sv_number_;
+  ColumnFamilyData* cfd_ = nullptr;
+  DBImpl* db_impl_ = nullptr;
+  ReadOptions read_options_;
+  ReadCallback* read_callback_;
+  bool allow_blob_ = false;
+  bool allow_refresh_ = true;
+};
+
+// Generate the arena wrapped iterator class.
+// `db_impl` and `cfd` are used for reneweal. If left null, renewal will not
+// be supported.
+extern ArenaWrappedDBIter* NewArenaWrappedDbIterator(
+    Env* env, const ReadOptions& read_options,
+    const ImmutableCFOptions& cf_options,
+    const MutableCFOptions& mutable_cf_options, const SequenceNumber& sequence,
+    uint64_t max_sequential_skip_in_iterations, uint64_t version_number,
+    ReadCallback* read_callback, DBImpl* db_impl = nullptr,
+    ColumnFamilyData* cfd = nullptr, bool allow_blob = false,
+    bool allow_refresh = true);
+}  // namespace ROCKSDB_NAMESPACE