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diff --git a/src/rocksdb/db/range_tombstone_fragmenter.h b/src/rocksdb/db/range_tombstone_fragmenter.h
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+++ b/src/rocksdb/db/range_tombstone_fragmenter.h
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+//  Copyright (c) 2018-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).
+
+#pragma once
+
+#include <list>
+#include <memory>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "db/dbformat.h"
+#include "db/pinned_iterators_manager.h"
+#include "rocksdb/status.h"
+#include "table/internal_iterator.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+struct FragmentedRangeTombstoneList {
+ public:
+  // A compact representation of a "stack" of range tombstone fragments, which
+  // start and end at the same user keys but have different sequence numbers.
+  // The members seq_start_idx and seq_end_idx are intended to be parameters to
+  // seq_iter().
+  struct RangeTombstoneStack {
+    RangeTombstoneStack(const Slice& start, const Slice& end, size_t start_idx,
+                        size_t end_idx)
+        : start_key(start),
+          end_key(end),
+          seq_start_idx(start_idx),
+          seq_end_idx(end_idx) {}
+
+    Slice start_key;
+    Slice end_key;
+    size_t seq_start_idx;
+    size_t seq_end_idx;
+  };
+  FragmentedRangeTombstoneList(
+      std::unique_ptr<InternalIterator> unfragmented_tombstones,
+      const InternalKeyComparator& icmp, bool for_compaction = false,
+      const std::vector<SequenceNumber>& snapshots = {});
+
+  std::vector<RangeTombstoneStack>::const_iterator begin() const {
+    return tombstones_.begin();
+  }
+
+  std::vector<RangeTombstoneStack>::const_iterator end() const {
+    return tombstones_.end();
+  }
+
+  std::vector<SequenceNumber>::const_iterator seq_iter(size_t idx) const {
+    return std::next(tombstone_seqs_.begin(), idx);
+  }
+
+  std::vector<SequenceNumber>::const_iterator seq_begin() const {
+    return tombstone_seqs_.begin();
+  }
+
+  std::vector<SequenceNumber>::const_iterator seq_end() const {
+    return tombstone_seqs_.end();
+  }
+
+  bool empty() const { return tombstones_.empty(); }
+
+  // Returns true if the stored tombstones contain with one with a sequence
+  // number in [lower, upper].
+  bool ContainsRange(SequenceNumber lower, SequenceNumber upper) const;
+
+ private:
+  // Given an ordered range tombstone iterator unfragmented_tombstones,
+  // "fragment" the tombstones into non-overlapping pieces, and store them in
+  // tombstones_ and tombstone_seqs_.
+  void FragmentTombstones(
+      std::unique_ptr<InternalIterator> unfragmented_tombstones,
+      const InternalKeyComparator& icmp, bool for_compaction,
+      const std::vector<SequenceNumber>& snapshots);
+
+  std::vector<RangeTombstoneStack> tombstones_;
+  std::vector<SequenceNumber> tombstone_seqs_;
+  std::set<SequenceNumber> seq_set_;
+  std::list<std::string> pinned_slices_;
+  PinnedIteratorsManager pinned_iters_mgr_;
+};
+
+// FragmentedRangeTombstoneIterator converts an InternalIterator of a range-del
+// meta block into an iterator over non-overlapping tombstone fragments. The
+// tombstone fragmentation process should be more efficient than the range
+// tombstone collapsing algorithm in RangeDelAggregator because this leverages
+// the internal key ordering already provided by the input iterator, if
+// applicable (when the iterator is unsorted, a new sorted iterator is created
+// before proceeding). If there are few overlaps, creating a
+// FragmentedRangeTombstoneIterator should be O(n), while the RangeDelAggregator
+// tombstone collapsing is always O(n log n).
+class FragmentedRangeTombstoneIterator : public InternalIterator {
+ public:
+  FragmentedRangeTombstoneIterator(
+      const FragmentedRangeTombstoneList* tombstones,
+      const InternalKeyComparator& icmp, SequenceNumber upper_bound,
+      SequenceNumber lower_bound = 0);
+  FragmentedRangeTombstoneIterator(
+      const std::shared_ptr<const FragmentedRangeTombstoneList>& tombstones,
+      const InternalKeyComparator& icmp, SequenceNumber upper_bound,
+      SequenceNumber lower_bound = 0);
+
+  void SeekToFirst() override;
+  void SeekToLast() override;
+
+  void SeekToTopFirst();
+  void SeekToTopLast();
+
+  // NOTE: Seek and SeekForPrev do not behave in the way InternalIterator
+  // seeking should behave. This is OK because they are not currently used, but
+  // eventually FragmentedRangeTombstoneIterator should no longer implement
+  // InternalIterator.
+  //
+  // Seeks to the range tombstone that covers target at a seqnum in the
+  // snapshot. If no such tombstone exists, seek to the earliest tombstone in
+  // the snapshot that ends after target.
+  void Seek(const Slice& target) override;
+  // Seeks to the range tombstone that covers target at a seqnum in the
+  // snapshot. If no such tombstone exists, seek to the latest tombstone in the
+  // snapshot that starts before target.
+  void SeekForPrev(const Slice& target) override;
+
+  void Next() override;
+  void Prev() override;
+
+  void TopNext();
+  void TopPrev();
+
+  bool Valid() const override;
+  Slice key() const override {
+    MaybePinKey();
+    return current_start_key_.Encode();
+  }
+  Slice value() const override { return pos_->end_key; }
+  bool IsKeyPinned() const override { return false; }
+  bool IsValuePinned() const override { return true; }
+  Status status() const override { return Status::OK(); }
+
+  bool empty() const { return tombstones_->empty(); }
+  void Invalidate() {
+    pos_ = tombstones_->end();
+    seq_pos_ = tombstones_->seq_end();
+    pinned_pos_ = tombstones_->end();
+    pinned_seq_pos_ = tombstones_->seq_end();
+  }
+
+  RangeTombstone Tombstone() const {
+    return RangeTombstone(start_key(), end_key(), seq());
+  }
+  Slice start_key() const { return pos_->start_key; }
+  Slice end_key() const { return pos_->end_key; }
+  SequenceNumber seq() const { return *seq_pos_; }
+  ParsedInternalKey parsed_start_key() const {
+    return ParsedInternalKey(pos_->start_key, kMaxSequenceNumber,
+                             kTypeRangeDeletion);
+  }
+  ParsedInternalKey parsed_end_key() const {
+    return ParsedInternalKey(pos_->end_key, kMaxSequenceNumber,
+                             kTypeRangeDeletion);
+  }
+
+  SequenceNumber MaxCoveringTombstoneSeqnum(const Slice& user_key);
+
+  // Splits the iterator into n+1 iterators (where n is the number of
+  // snapshots), each providing a view over a "stripe" of sequence numbers. The
+  // iterators are keyed by the upper bound of their ranges (the provided
+  // snapshots + kMaxSequenceNumber).
+  //
+  // NOTE: the iterators in the returned map are no longer valid if their
+  // parent iterator is deleted, since they do not modify the refcount of the
+  // underlying tombstone list. Therefore, this map should be deleted before
+  // the parent iterator.
+  std::map<SequenceNumber, std::unique_ptr<FragmentedRangeTombstoneIterator>>
+  SplitBySnapshot(const std::vector<SequenceNumber>& snapshots);
+
+  SequenceNumber upper_bound() const { return upper_bound_; }
+  SequenceNumber lower_bound() const { return lower_bound_; }
+
+ private:
+  using RangeTombstoneStack = FragmentedRangeTombstoneList::RangeTombstoneStack;
+
+  struct RangeTombstoneStackStartComparator {
+    explicit RangeTombstoneStackStartComparator(const Comparator* c) : cmp(c) {}
+
+    bool operator()(const RangeTombstoneStack& a,
+                    const RangeTombstoneStack& b) const {
+      return cmp->Compare(a.start_key, b.start_key) < 0;
+    }
+
+    bool operator()(const RangeTombstoneStack& a, const Slice& b) const {
+      return cmp->Compare(a.start_key, b) < 0;
+    }
+
+    bool operator()(const Slice& a, const RangeTombstoneStack& b) const {
+      return cmp->Compare(a, b.start_key) < 0;
+    }
+
+    const Comparator* cmp;
+  };
+
+  struct RangeTombstoneStackEndComparator {
+    explicit RangeTombstoneStackEndComparator(const Comparator* c) : cmp(c) {}
+
+    bool operator()(const RangeTombstoneStack& a,
+                    const RangeTombstoneStack& b) const {
+      return cmp->Compare(a.end_key, b.end_key) < 0;
+    }
+
+    bool operator()(const RangeTombstoneStack& a, const Slice& b) const {
+      return cmp->Compare(a.end_key, b) < 0;
+    }
+
+    bool operator()(const Slice& a, const RangeTombstoneStack& b) const {
+      return cmp->Compare(a, b.end_key) < 0;
+    }
+
+    const Comparator* cmp;
+  };
+
+  void MaybePinKey() const {
+    if (pos_ != tombstones_->end() && seq_pos_ != tombstones_->seq_end() &&
+        (pinned_pos_ != pos_ || pinned_seq_pos_ != seq_pos_)) {
+      current_start_key_.Set(pos_->start_key, *seq_pos_, kTypeRangeDeletion);
+      pinned_pos_ = pos_;
+      pinned_seq_pos_ = seq_pos_;
+    }
+  }
+
+  void SeekToCoveringTombstone(const Slice& key);
+  void SeekForPrevToCoveringTombstone(const Slice& key);
+  void ScanForwardToVisibleTombstone();
+  void ScanBackwardToVisibleTombstone();
+  bool ValidPos() const {
+    return Valid() && seq_pos_ != tombstones_->seq_iter(pos_->seq_end_idx);
+  }
+
+  const RangeTombstoneStackStartComparator tombstone_start_cmp_;
+  const RangeTombstoneStackEndComparator tombstone_end_cmp_;
+  const InternalKeyComparator* icmp_;
+  const Comparator* ucmp_;
+  std::shared_ptr<const FragmentedRangeTombstoneList> tombstones_ref_;
+  const FragmentedRangeTombstoneList* tombstones_;
+  SequenceNumber upper_bound_;
+  SequenceNumber lower_bound_;
+  std::vector<RangeTombstoneStack>::const_iterator pos_;
+  std::vector<SequenceNumber>::const_iterator seq_pos_;
+  mutable std::vector<RangeTombstoneStack>::const_iterator pinned_pos_;
+  mutable std::vector<SequenceNumber>::const_iterator pinned_seq_pos_;
+  mutable InternalKey current_start_key_;
+};
+
+}  // namespace ROCKSDB_NAMESPACE