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// 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 "db/dbformat.h"
#include "rocksdb/types.h"
namespace ROCKSDB_NAMESPACE {
class Comparator;
class Env;
class Arena;
template <class TValue>
class InternalIteratorBase;
using InternalIterator = InternalIteratorBase<Slice>;
// 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 InternalKeyComparator* comparator, InternalIterator** children, int n,
Arena* arena = nullptr, bool prefix_seek_mode = false);
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 InternalKeyComparator* comparator,
Arena* arena, bool prefix_seek_mode = false);
~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_NAMESPACE
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