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rust-rocksdb/db/range_tombstone_fragmenter.cc

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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).
#include "db/range_tombstone_fragmenter.h"
#include <algorithm>
#include <cinttypes>
#include <cstdio>
#include <functional>
#include <set>
#include "util/autovector.h"
#include "util/kv_map.h"
#include "util/vector_iterator.h"
namespace ROCKSDB_NAMESPACE {
FragmentedRangeTombstoneList::FragmentedRangeTombstoneList(
std::unique_ptr<InternalIterator> unfragmented_tombstones,
const InternalKeyComparator& icmp, bool for_compaction,
const std::vector<SequenceNumber>& snapshots) {
if (unfragmented_tombstones == nullptr) {
return;
}
bool is_sorted = true;
InternalKey pinned_last_start_key;
Slice last_start_key;
num_unfragmented_tombstones_ = 0;
total_tombstone_payload_bytes_ = 0;
for (unfragmented_tombstones->SeekToFirst(); unfragmented_tombstones->Valid();
unfragmented_tombstones->Next(), num_unfragmented_tombstones_++) {
total_tombstone_payload_bytes_ += unfragmented_tombstones->key().size() +
unfragmented_tombstones->value().size();
if (num_unfragmented_tombstones_ > 0 &&
icmp.Compare(last_start_key, unfragmented_tombstones->key()) > 0) {
is_sorted = false;
break;
}
if (unfragmented_tombstones->IsKeyPinned()) {
last_start_key = unfragmented_tombstones->key();
} else {
pinned_last_start_key.DecodeFrom(unfragmented_tombstones->key());
last_start_key = pinned_last_start_key.Encode();
}
}
if (is_sorted) {
FragmentTombstones(std::move(unfragmented_tombstones), icmp, for_compaction,
snapshots);
return;
}
// Sort the tombstones before fragmenting them.
std::vector<std::string> keys, values;
keys.reserve(num_unfragmented_tombstones_);
values.reserve(num_unfragmented_tombstones_);
// Reset the counter to zero for the next iteration over keys.
total_tombstone_payload_bytes_ = 0;
for (unfragmented_tombstones->SeekToFirst(); unfragmented_tombstones->Valid();
unfragmented_tombstones->Next()) {
total_tombstone_payload_bytes_ += unfragmented_tombstones->key().size() +
unfragmented_tombstones->value().size();
keys.emplace_back(unfragmented_tombstones->key().data(),
unfragmented_tombstones->key().size());
values.emplace_back(unfragmented_tombstones->value().data(),
unfragmented_tombstones->value().size());
}
// VectorIterator implicitly sorts by key during construction.
auto iter = std::make_unique<VectorIterator>(std::move(keys),
std::move(values), &icmp);
FragmentTombstones(std::move(iter), icmp, for_compaction, snapshots);
}
void FragmentedRangeTombstoneList::FragmentTombstones(
std::unique_ptr<InternalIterator> unfragmented_tombstones,
const InternalKeyComparator& icmp, bool for_compaction,
const std::vector<SequenceNumber>& snapshots) {
Slice cur_start_key(nullptr, 0);
auto cmp = ParsedInternalKeyComparator(&icmp);
// Stores the end keys and sequence numbers of range tombstones with a start
// key less than or equal to cur_start_key. Provides an ordering by end key
// for use in flush_current_tombstones.
std::set<ParsedInternalKey, ParsedInternalKeyComparator> cur_end_keys(cmp);
size_t ts_sz = icmp.user_comparator()->timestamp_size();
// Given the next start key in unfragmented_tombstones,
// flush_current_tombstones writes every tombstone fragment that starts
// and ends with a key before next_start_key, and starts with a key greater
// than or equal to cur_start_key.
auto flush_current_tombstones = [&](const Slice& next_start_key) {
auto it = cur_end_keys.begin();
bool reached_next_start_key = false;
for (; it != cur_end_keys.end() && !reached_next_start_key; ++it) {
Slice cur_end_key = it->user_key;
if (icmp.user_comparator()->CompareWithoutTimestamp(cur_start_key,
cur_end_key) == 0) {
// Empty tombstone.
continue;
}
if (icmp.user_comparator()->CompareWithoutTimestamp(next_start_key,
cur_end_key) <= 0) {
// All the end keys in [it, cur_end_keys.end()) are after
// next_start_key, so the tombstones they represent can be used in
// fragments that start with keys greater than or equal to
// next_start_key. However, the end keys we already passed will not be
// used in any more tombstone fragments.
//
// Remove the fully fragmented tombstones and stop iteration after a
// final round of flushing to preserve the tombstones we can create more
// fragments from.
reached_next_start_key = true;
cur_end_keys.erase(cur_end_keys.begin(), it);
cur_end_key = next_start_key;
}
// Flush a range tombstone fragment [cur_start_key, cur_end_key), which
// should not overlap with the last-flushed tombstone fragment.
assert(tombstones_.empty() ||
icmp.user_comparator()->CompareWithoutTimestamp(
tombstones_.back().end_key, cur_start_key) <= 0);
// Sort the sequence numbers of the tombstones being fragmented in
// descending order, and then flush them in that order.
autovector<SequenceNumber> seqnums_to_flush;
autovector<Slice> timestamps_to_flush;
for (auto flush_it = it; flush_it != cur_end_keys.end(); ++flush_it) {
seqnums_to_flush.push_back(flush_it->sequence);
if (ts_sz) {
timestamps_to_flush.push_back(
ExtractTimestampFromUserKey(flush_it->user_key, ts_sz));
}
}
// TODO: bind the two sorting together to be more efficient
std::sort(seqnums_to_flush.begin(), seqnums_to_flush.end(),
std::greater<SequenceNumber>());
if (ts_sz) {
std::sort(timestamps_to_flush.begin(), timestamps_to_flush.end(),
[icmp](const Slice& ts1, const Slice& ts2) {
return icmp.user_comparator()->CompareTimestamp(ts1, ts2) >
0;
});
}
size_t start_idx = tombstone_seqs_.size();
size_t end_idx = start_idx + seqnums_to_flush.size();
// If user-defined timestamp is enabled, we should not drop tombstones
// from any snapshot stripe. Garbage collection of range tombstones
// happens in CompactionOutputs::AddRangeDels().
if (for_compaction && ts_sz == 0) {
// Drop all tombstone seqnums that are not preserved by a snapshot.
SequenceNumber next_snapshot = kMaxSequenceNumber;
for (auto seq : seqnums_to_flush) {
if (seq <= next_snapshot) {
// This seqnum is visible by a lower snapshot.
tombstone_seqs_.push_back(seq);
auto upper_bound_it =
std::lower_bound(snapshots.begin(), snapshots.end(), seq);
if (upper_bound_it == snapshots.begin()) {
// This seqnum is the topmost one visible by the earliest
// snapshot. None of the seqnums below it will be visible, so we
// can skip them.
break;
}
next_snapshot = *std::prev(upper_bound_it);
}
}
end_idx = tombstone_seqs_.size();
} else {
// The fragmentation is being done for reads, so preserve all seqnums.
tombstone_seqs_.insert(tombstone_seqs_.end(), seqnums_to_flush.begin(),
seqnums_to_flush.end());
if (ts_sz) {
tombstone_timestamps_.insert(tombstone_timestamps_.end(),
timestamps_to_flush.begin(),
timestamps_to_flush.end());
}
}
assert(start_idx < end_idx);
if (ts_sz) {
std::string start_key_with_max_ts;
AppendUserKeyWithMaxTimestamp(&start_key_with_max_ts, cur_start_key,
ts_sz);
pinned_slices_.emplace_back(std::move(start_key_with_max_ts));
Slice start_key = pinned_slices_.back();
std::string end_key_with_max_ts;
AppendUserKeyWithMaxTimestamp(&end_key_with_max_ts, cur_end_key, ts_sz);
pinned_slices_.emplace_back(std::move(end_key_with_max_ts));
Slice end_key = pinned_slices_.back();
// RangeTombstoneStack expects start_key and end_key to have max
// timestamp.
tombstones_.emplace_back(start_key, end_key, start_idx, end_idx);
} else {
tombstones_.emplace_back(cur_start_key, cur_end_key, start_idx,
end_idx);
}
cur_start_key = cur_end_key;
}
if (!reached_next_start_key) {
// There is a gap between the last flushed tombstone fragment and
// the next tombstone's start key. Remove all the end keys in
// the working set, since we have fully fragmented their corresponding
// tombstones.
cur_end_keys.clear();
}
cur_start_key = next_start_key;
};
pinned_iters_mgr_.StartPinning();
bool no_tombstones = true;
for (unfragmented_tombstones->SeekToFirst(); unfragmented_tombstones->Valid();
unfragmented_tombstones->Next()) {
const Slice& ikey = unfragmented_tombstones->key();
Slice tombstone_start_key = ExtractUserKey(ikey);
SequenceNumber tombstone_seq = GetInternalKeySeqno(ikey);
if (!unfragmented_tombstones->IsKeyPinned()) {
pinned_slices_.emplace_back(tombstone_start_key.data(),
tombstone_start_key.size());
tombstone_start_key = pinned_slices_.back();
}
no_tombstones = false;
Slice tombstone_end_key = unfragmented_tombstones->value();
if (!unfragmented_tombstones->IsValuePinned()) {
pinned_slices_.emplace_back(tombstone_end_key.data(),
tombstone_end_key.size());
tombstone_end_key = pinned_slices_.back();
}
if (!cur_end_keys.empty() &&
icmp.user_comparator()->CompareWithoutTimestamp(
cur_start_key, tombstone_start_key) != 0) {
// The start key has changed. Flush all tombstones that start before
// this new start key.
flush_current_tombstones(tombstone_start_key);
}
cur_start_key = tombstone_start_key;
cur_end_keys.emplace(tombstone_end_key, tombstone_seq, kTypeRangeDeletion);
}
if (!cur_end_keys.empty()) {
ParsedInternalKey last_end_key = *std::prev(cur_end_keys.end());
flush_current_tombstones(last_end_key.user_key);
}
if (!no_tombstones) {
pinned_iters_mgr_.PinIterator(unfragmented_tombstones.release(),
false /* arena */);
}
}
bool FragmentedRangeTombstoneList::ContainsRange(SequenceNumber lower,
SequenceNumber upper) {
std::call_once(seq_set_init_once_flag_, [this]() {
for (auto s : tombstone_seqs_) {
seq_set_.insert(s);
}
});
auto seq_it = seq_set_.lower_bound(lower);
return seq_it != seq_set_.end() && *seq_it <= upper;
}
FragmentedRangeTombstoneIterator::FragmentedRangeTombstoneIterator(
FragmentedRangeTombstoneList* tombstones, const InternalKeyComparator& icmp,
SequenceNumber _upper_bound, const Slice* ts_upper_bound,
SequenceNumber _lower_bound)
: tombstone_start_cmp_(icmp.user_comparator()),
tombstone_end_cmp_(icmp.user_comparator()),
icmp_(&icmp),
ucmp_(icmp.user_comparator()),
tombstones_(tombstones),
upper_bound_(_upper_bound),
lower_bound_(_lower_bound),
ts_upper_bound_(ts_upper_bound) {
assert(tombstones_ != nullptr);
Invalidate();
}
FragmentedRangeTombstoneIterator::FragmentedRangeTombstoneIterator(
const std::shared_ptr<FragmentedRangeTombstoneList>& tombstones,
const InternalKeyComparator& icmp, SequenceNumber _upper_bound,
const Slice* ts_upper_bound, SequenceNumber _lower_bound)
: tombstone_start_cmp_(icmp.user_comparator()),
tombstone_end_cmp_(icmp.user_comparator()),
icmp_(&icmp),
ucmp_(icmp.user_comparator()),
tombstones_ref_(tombstones),
tombstones_(tombstones_ref_.get()),
upper_bound_(_upper_bound),
lower_bound_(_lower_bound),
ts_upper_bound_(ts_upper_bound) {
assert(tombstones_ != nullptr);
Invalidate();
}
FragmentedRangeTombstoneIterator::FragmentedRangeTombstoneIterator(
const std::shared_ptr<FragmentedRangeTombstoneListCache>& tombstones_cache,
const InternalKeyComparator& icmp, SequenceNumber _upper_bound,
const Slice* ts_upper_bound, SequenceNumber _lower_bound)
: tombstone_start_cmp_(icmp.user_comparator()),
tombstone_end_cmp_(icmp.user_comparator()),
icmp_(&icmp),
ucmp_(icmp.user_comparator()),
tombstones_cache_ref_(tombstones_cache),
tombstones_(tombstones_cache_ref_->tombstones.get()),
upper_bound_(_upper_bound),
lower_bound_(_lower_bound) {
assert(tombstones_ != nullptr);
if (!ts_upper_bound || ts_upper_bound->empty()) {
ts_upper_bound_ = nullptr;
} else {
ts_upper_bound_ = ts_upper_bound;
}
Invalidate();
}
void FragmentedRangeTombstoneIterator::SeekToFirst() {
pos_ = tombstones_->begin();
seq_pos_ = tombstones_->seq_begin();
}
void FragmentedRangeTombstoneIterator::SeekToTopFirst() {
if (tombstones_->empty()) {
Invalidate();
return;
}
pos_ = tombstones_->begin();
SetMaxVisibleSeqAndTimestamp();
ScanForwardToVisibleTombstone();
}
void FragmentedRangeTombstoneIterator::SeekToLast() {
pos_ = std::prev(tombstones_->end());
seq_pos_ = std::prev(tombstones_->seq_end());
}
void FragmentedRangeTombstoneIterator::SeekToTopLast() {
if (tombstones_->empty()) {
Invalidate();
return;
}
pos_ = std::prev(tombstones_->end());
SetMaxVisibleSeqAndTimestamp();
ScanBackwardToVisibleTombstone();
}
// @param `target` is a user key, with timestamp if user-defined timestamp is
// enabled.
void FragmentedRangeTombstoneIterator::Seek(const Slice& target) {
if (tombstones_->empty()) {
Invalidate();
return;
}
SeekToCoveringTombstone(target);
ScanForwardToVisibleTombstone();
}
void FragmentedRangeTombstoneIterator::SeekForPrev(const Slice& target) {
if (tombstones_->empty()) {
Invalidate();
return;
}
SeekForPrevToCoveringTombstone(target);
ScanBackwardToVisibleTombstone();
}
void FragmentedRangeTombstoneIterator::SeekToCoveringTombstone(
const Slice& target) {
pos_ = std::upper_bound(tombstones_->begin(), tombstones_->end(), target,
tombstone_end_cmp_);
if (pos_ == tombstones_->end()) {
// All tombstones end before target.
seq_pos_ = tombstones_->seq_end();
return;
}
SetMaxVisibleSeqAndTimestamp();
}
void FragmentedRangeTombstoneIterator::SeekForPrevToCoveringTombstone(
const Slice& target) {
if (tombstones_->empty()) {
Invalidate();
return;
}
pos_ = std::upper_bound(tombstones_->begin(), tombstones_->end(), target,
tombstone_start_cmp_);
if (pos_ == tombstones_->begin()) {
// All tombstones start after target.
Invalidate();
return;
}
--pos_;
SetMaxVisibleSeqAndTimestamp();
}
void FragmentedRangeTombstoneIterator::ScanForwardToVisibleTombstone() {
while (pos_ != tombstones_->end() &&
(seq_pos_ == tombstones_->seq_iter(pos_->seq_end_idx) ||
*seq_pos_ < lower_bound_)) {
++pos_;
if (pos_ == tombstones_->end()) {
Invalidate();
return;
}
SetMaxVisibleSeqAndTimestamp();
}
}
void FragmentedRangeTombstoneIterator::ScanBackwardToVisibleTombstone() {
while (pos_ != tombstones_->end() &&
(seq_pos_ == tombstones_->seq_iter(pos_->seq_end_idx) ||
*seq_pos_ < lower_bound_)) {
if (pos_ == tombstones_->begin()) {
Invalidate();
return;
}
--pos_;
SetMaxVisibleSeqAndTimestamp();
}
}
void FragmentedRangeTombstoneIterator::Next() {
++seq_pos_;
if (seq_pos_ == tombstones_->seq_iter(pos_->seq_end_idx)) {
++pos_;
}
}
void FragmentedRangeTombstoneIterator::TopNext() {
++pos_;
if (pos_ == tombstones_->end()) {
return;
}
SetMaxVisibleSeqAndTimestamp();
ScanForwardToVisibleTombstone();
}
void FragmentedRangeTombstoneIterator::Prev() {
if (seq_pos_ == tombstones_->seq_begin()) {
Invalidate();
return;
}
--seq_pos_;
if (pos_ == tombstones_->end() ||
seq_pos_ == tombstones_->seq_iter(pos_->seq_start_idx - 1)) {
--pos_;
}
}
void FragmentedRangeTombstoneIterator::TopPrev() {
if (pos_ == tombstones_->begin()) {
Invalidate();
return;
}
--pos_;
SetMaxVisibleSeqAndTimestamp();
ScanBackwardToVisibleTombstone();
}
bool FragmentedRangeTombstoneIterator::Valid() const {
return tombstones_ != nullptr && pos_ != tombstones_->end();
}
SequenceNumber FragmentedRangeTombstoneIterator::MaxCoveringTombstoneSeqnum(
const Slice& target_user_key) {
SeekToCoveringTombstone(target_user_key);
return ValidPos() && ucmp_->CompareWithoutTimestamp(start_key(),
target_user_key) <= 0
? seq()
: 0;
}
std::map<SequenceNumber, std::unique_ptr<FragmentedRangeTombstoneIterator>>
FragmentedRangeTombstoneIterator::SplitBySnapshot(
const std::vector<SequenceNumber>& snapshots) {
std::map<SequenceNumber, std::unique_ptr<FragmentedRangeTombstoneIterator>>
splits;
SequenceNumber lower = 0;
SequenceNumber upper;
for (size_t i = 0; i <= snapshots.size(); i++) {
if (i >= snapshots.size()) {
upper = kMaxSequenceNumber;
} else {
upper = snapshots[i];
}
if (tombstones_->ContainsRange(lower, upper)) {
splits.emplace(upper,
std::make_unique<FragmentedRangeTombstoneIterator>(
tombstones_, *icmp_, upper, ts_upper_bound_, lower));
}
lower = upper + 1;
}
return splits;
}
} // namespace ROCKSDB_NAMESPACE