rocksdb/table/two_level_iterator.h

//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
//  This source code is licensed under the BSD-style license found in the
//  LICENSE file in the root directory of this source tree. An additional grant
//  of patent rights can be found in the PATENTS file in the same 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 "rocksdb/iterator.h"
#include "rocksdb/env.h"
#include "table/iterator_wrapper.h"

namespace rocksdb {

struct ReadOptions;
class InternalKeyComparator;
class Arena;

struct TwoLevelIteratorState {
  explicit TwoLevelIteratorState(bool _check_prefix_may_match)
      : check_prefix_may_match(_check_prefix_may_match) {}

  virtual ~TwoLevelIteratorState() {}
  virtual InternalIterator* NewSecondaryIterator(const Slice& handle) = 0;
  virtual bool PrefixMayMatch(const Slice& internal_key) = 0;

  // If call PrefixMayMatch()
  bool check_prefix_may_match;
};


// Return a new two level iterator.  A two-level iterator contains an
// index iterator whose values point to a sequence of blocks where
// each block is itself a sequence of key,value pairs.  The returned
// two-level iterator yields the concatenation of all key/value pairs
// in the sequence of blocks.  Takes ownership of "index_iter" and
// will delete it when no longer needed.
//
// Uses a supplied function to convert an index_iter value into
// an iterator over the contents of the corresponding block.
// arena: If not null, the arena is used to allocate the Iterator.
//        When destroying the iterator, the destructor will destroy
//        all the states but those allocated in arena.
// need_free_iter_and_state: free `state` and `first_level_iter` if
//                           true. Otherwise, just call destructor.
extern InternalIterator* NewTwoLevelIterator(
    TwoLevelIteratorState* state, InternalIterator* first_level_iter,
    Arena* arena = nullptr, bool need_free_iter_and_state = true);

}  // namespace rocksdb