YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

//  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.

//

// The following only applies to changes made to this file as part of YugaByte development.

//

// Portions Copyright (c) YugaByte, Inc.

//

// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except

// in compliance with the License.  You may obtain a copy of the License at

//

// http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software distributed under the License

// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express

// or implied.  See the License for the specific language governing permissions and limitations

// under the License.

//

// 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

namespace rocksdb {

class Comparator;

class InternalIterator;

class Env;

class Arena;

// Return an iterator that provided the union of the data in

// children[0,n-1].  Takes ownership of the child iterators and

// will delete them when the result iterator is deleted.

//

// The result does no duplicate suppression.  I.e., if a particular

// key is present in K child iterators, it will be yielded K times.

//

// REQUIRES: n >= 0

extern InternalIterator* NewMergingIterator(const Comparator* comparator,

                                            InternalIterator** children, int n,

                                            Arena* arena = nullptr);

class MergingIterator;

// A builder class to build a merging iterator by adding iterators one by one.

class MergeIteratorBuilder {

 public:

  // comparator: the comparator used in merging comparator

  // arena: where the merging iterator needs to be allocated from.

  explicit MergeIteratorBuilder(const Comparator* comparator, Arena* arena);

  ~MergeIteratorBuilder() {}

  // Add iter to the merging iterator.

  void AddIterator(InternalIterator* iter);

  // Get arena used to build the merging iterator. It is called one a child

  // iterator needs to be allocated.

  Arena* GetArena() { return arena; }

  // Return the result merging iterator.

  InternalIterator* Finish();

 private:

  MergingIterator* merge_iter;

  InternalIterator* first_iter;

  bool use_merging_iter;

  Arena* arena;

};

}  // namespace rocksdb