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rust-rocksdb/table/compaction_merging_iterator.h

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1.9 KiB

// Copyright (c) Meta Platforms, Inc. and affiliates.
//
// 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).
#pragma once
#include "db/range_del_aggregator.h"
#include "rocksdb/slice.h"
#include "rocksdb/types.h"
#include "table/merging_iterator.h"
namespace ROCKSDB_NAMESPACE {
/*
* This is a simplified version of MergingIterator and is specifically used for
* compaction. It merges the input `children` iterators into a sorted stream of
* keys. Range tombstone start keys are also emitted to prevent oversize
* compactions. For example, consider an L1 file with content [a, b), y, z,
* where [a, b) is a range tombstone and y and z are point keys. This could
* cause an oversize compaction as it can overlap with a wide range of key space
* in L2.
*
* CompactionMergingIterator emits range tombstone start keys from each LSM
* level's range tombstone iterator, and for each range tombstone
* [start,end)@seqno, the key will be start@seqno with op_type
* kTypeRangeDeletion unless truncated at file boundary (see detail in
* TruncatedRangeDelIterator::start_key()).
*
* Caller should use CompactionMergingIterator::IsDeleteRangeSentinelKey() to
* check if the current key is a range tombstone key.
* TODO(cbi): IsDeleteRangeSentinelKey() is used for two kinds of keys at
* different layers: file boundary and range tombstone keys. Separate them into
* two APIs for clarity.
*/
class CompactionMergingIterator;
InternalIterator* NewCompactionMergingIterator(
const InternalKeyComparator* comparator, InternalIterator** children, int n,
std::vector<std::pair<TruncatedRangeDelIterator*,
TruncatedRangeDelIterator***>>& range_tombstone_iters,
Arena* arena = nullptr);
} // namespace ROCKSDB_NAMESPACE