https://github.com/facebook/rocksdb
Tip revision: 913c664f25782fbe1689df542f7aa8f0a9535f48 authored by sdong on 16 December 2019, 22:54:02 UTC
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Tip revision: 913c664
range_tombstone_fragmenter.h
// 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 {
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