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rocksdb/db/compaction/compaction_iterator.cc
Levi Tamasi e5311a8ea4 Fix a SingleDelete related optimization for blob indexes (#7904) 
Summary:
There is a small `SingleDelete` related optimization in the
`CompactionIterator` code: when a `SingleDelete`-`Put` pair is preserved
solely for the purposes of transaction conflict checking, the value
itself gets cleared. (This is referred to as "optimization 3" in the
`CompactionIterator` code.) Though the rest of the code got updated to
support `SingleDelete`'ing blob indexes, this chunk was apparently
missed, resulting in an assertion failure (or `ROCKS_LOG_FATAL` in release
builds) when triggered. Note: in addition to clearing the value, we also
need to update the type of the KV to regular value when dealing with
blob indexes here.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7904

Test Plan: `make check`

Reviewed By: ajkr

Differential Revision: D26118009

Pulled By: ltamasi

fbshipit-source-id: 6bf78043d20265e2b15c2e1ab8865025040c42ae
2021-01-29 12:41:25 -08:00

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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).
#include "db/compaction/compaction_iterator.h"
#include <iterator>
#include <limits>
#include "db/blob/blob_file_builder.h"
#include "db/blob/blob_index.h"
#include "db/snapshot_checker.h"
#include "port/likely.h"
#include "rocksdb/listener.h"
#include "table/internal_iterator.h"
#include "test_util/sync_point.h"
#define DEFINITELY_IN_SNAPSHOT(seq, snapshot) \
((seq) <= (snapshot) && \
(snapshot_checker_ == nullptr || \
LIKELY(snapshot_checker_->CheckInSnapshot((seq), (snapshot)) == \
SnapshotCheckerResult::kInSnapshot)))
#define DEFINITELY_NOT_IN_SNAPSHOT(seq, snapshot) \
((seq) > (snapshot) || \
(snapshot_checker_ != nullptr && \
UNLIKELY(snapshot_checker_->CheckInSnapshot((seq), (snapshot)) == \
SnapshotCheckerResult::kNotInSnapshot)))
#define IN_EARLIEST_SNAPSHOT(seq) \
((seq) <= earliest_snapshot_ && \
(snapshot_checker_ == nullptr || LIKELY(IsInEarliestSnapshot(seq))))
namespace ROCKSDB_NAMESPACE {
CompactionIterator::CompactionIterator(
InternalIterator* input, const Comparator* cmp, MergeHelper* merge_helper,
SequenceNumber last_sequence, std::vector<SequenceNumber>* snapshots,
SequenceNumber earliest_write_conflict_snapshot,
const SnapshotChecker* snapshot_checker, Env* env,
bool report_detailed_time, bool expect_valid_internal_key,
CompactionRangeDelAggregator* range_del_agg,
BlobFileBuilder* blob_file_builder, bool allow_data_in_errors,
const Compaction* compaction, const CompactionFilter* compaction_filter,
const std::atomic<bool>* shutting_down,
const SequenceNumber preserve_deletes_seqnum,
const std::atomic<int>* manual_compaction_paused,
const std::shared_ptr<Logger> info_log,
const std::string* full_history_ts_low)
: CompactionIterator(
input, cmp, merge_helper, last_sequence, snapshots,
earliest_write_conflict_snapshot, snapshot_checker, env,
report_detailed_time, expect_valid_internal_key, range_del_agg,
blob_file_builder, allow_data_in_errors,
std::unique_ptr<CompactionProxy>(
compaction ? new RealCompaction(compaction) : nullptr),
compaction_filter, shutting_down, preserve_deletes_seqnum,
manual_compaction_paused, info_log, full_history_ts_low) {}
CompactionIterator::CompactionIterator(
InternalIterator* input, const Comparator* cmp, MergeHelper* merge_helper,
SequenceNumber /*last_sequence*/, std::vector<SequenceNumber>* snapshots,
SequenceNumber earliest_write_conflict_snapshot,
const SnapshotChecker* snapshot_checker, Env* env,
bool report_detailed_time, bool expect_valid_internal_key,
CompactionRangeDelAggregator* range_del_agg,
BlobFileBuilder* blob_file_builder, bool allow_data_in_errors,
std::unique_ptr<CompactionProxy> compaction,
const CompactionFilter* compaction_filter,
const std::atomic<bool>* shutting_down,
const SequenceNumber preserve_deletes_seqnum,
const std::atomic<int>* manual_compaction_paused,
const std::shared_ptr<Logger> info_log,
const std::string* full_history_ts_low)
: input_(input),
cmp_(cmp),
merge_helper_(merge_helper),
snapshots_(snapshots),
earliest_write_conflict_snapshot_(earliest_write_conflict_snapshot),
snapshot_checker_(snapshot_checker),
env_(env),
clock_(env_->GetSystemClock()),
report_detailed_time_(report_detailed_time),
expect_valid_internal_key_(expect_valid_internal_key),
range_del_agg_(range_del_agg),
blob_file_builder_(blob_file_builder),
compaction_(std::move(compaction)),
compaction_filter_(compaction_filter),
shutting_down_(shutting_down),
manual_compaction_paused_(manual_compaction_paused),
preserve_deletes_seqnum_(preserve_deletes_seqnum),
info_log_(info_log),
allow_data_in_errors_(allow_data_in_errors),
timestamp_size_(cmp_ ? cmp_->timestamp_size() : 0),
full_history_ts_low_(full_history_ts_low),
current_user_key_sequence_(0),
current_user_key_snapshot_(0),
merge_out_iter_(merge_helper_),
blob_garbage_collection_cutoff_file_number_(
ComputeBlobGarbageCollectionCutoffFileNumber(compaction_.get())),
current_key_committed_(false),
cmp_with_history_ts_low_(0) {
assert(compaction_filter_ == nullptr || compaction_ != nullptr);
assert(snapshots_ != nullptr);
bottommost_level_ = compaction_ == nullptr
? false
: compaction_->bottommost_level() &&
!compaction_->allow_ingest_behind();
if (compaction_ != nullptr) {
level_ptrs_ = std::vector<size_t>(compaction_->number_levels(), 0);
}
if (snapshots_->size() == 0) {
// optimize for fast path if there are no snapshots
visible_at_tip_ = true;
earliest_snapshot_iter_ = snapshots_->end();
earliest_snapshot_ = kMaxSequenceNumber;
latest_snapshot_ = 0;
} else {
visible_at_tip_ = false;
earliest_snapshot_iter_ = snapshots_->begin();
earliest_snapshot_ = snapshots_->at(0);
latest_snapshot_ = snapshots_->back();
}
#ifndef NDEBUG
// findEarliestVisibleSnapshot assumes this ordering.
for (size_t i = 1; i < snapshots_->size(); ++i) {
assert(snapshots_->at(i - 1) < snapshots_->at(i));
}
assert(timestamp_size_ == 0 || !full_history_ts_low_ ||
timestamp_size_ == full_history_ts_low_->size());
#endif
input_->SetPinnedItersMgr(&pinned_iters_mgr_);
TEST_SYNC_POINT_CALLBACK("CompactionIterator:AfterInit", compaction_.get());
}
CompactionIterator::~CompactionIterator() {
// input_ Iteartor lifetime is longer than pinned_iters_mgr_ lifetime
input_->SetPinnedItersMgr(nullptr);
}
void CompactionIterator::ResetRecordCounts() {
iter_stats_.num_record_drop_user = 0;
iter_stats_.num_record_drop_hidden = 0;
iter_stats_.num_record_drop_obsolete = 0;
iter_stats_.num_record_drop_range_del = 0;
iter_stats_.num_range_del_drop_obsolete = 0;
iter_stats_.num_optimized_del_drop_obsolete = 0;
}
void CompactionIterator::SeekToFirst() {
NextFromInput();
PrepareOutput();
}
void CompactionIterator::Next() {
// If there is a merge output, return it before continuing to process the
// input.
if (merge_out_iter_.Valid()) {
merge_out_iter_.Next();
// Check if we returned all records of the merge output.
if (merge_out_iter_.Valid()) {
key_ = merge_out_iter_.key();
value_ = merge_out_iter_.value();
Status s = ParseInternalKey(key_, &ikey_, allow_data_in_errors_);
// MergeUntil stops when it encounters a corrupt key and does not
// include them in the result, so we expect the keys here to be valid.
assert(s.ok());
if (!s.ok()) {
ROCKS_LOG_FATAL(info_log_, "Invalid key in compaction. %s",
s.getState());
}
// Keep current_key_ in sync.
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
key_ = current_key_.GetInternalKey();
ikey_.user_key = current_key_.GetUserKey();
valid_ = true;
} else {
// We consumed all pinned merge operands, release pinned iterators
pinned_iters_mgr_.ReleasePinnedData();
// MergeHelper moves the iterator to the first record after the merged
// records, so even though we reached the end of the merge output, we do
// not want to advance the iterator.
NextFromInput();
}
} else {
// Only advance the input iterator if there is no merge output and the
// iterator is not already at the next record.
if (!at_next_) {
input_->Next();
}
NextFromInput();
}
if (valid_) {
// Record that we've outputted a record for the current key.
has_outputted_key_ = true;
}
PrepareOutput();
}
bool CompactionIterator::InvokeFilterIfNeeded(bool* need_skip,
Slice* skip_until) {
if (compaction_filter_ != nullptr &&
(ikey_.type == kTypeValue || ikey_.type == kTypeBlobIndex)) {
// If the user has specified a compaction filter and the sequence
// number is greater than any external snapshot, then invoke the
// filter. If the return value of the compaction filter is true,
// replace the entry with a deletion marker.
CompactionFilter::Decision filter;
compaction_filter_value_.clear();
compaction_filter_skip_until_.Clear();
CompactionFilter::ValueType value_type =
ikey_.type == kTypeValue ? CompactionFilter::ValueType::kValue
: CompactionFilter::ValueType::kBlobIndex;
// Hack: pass internal key to BlobIndexCompactionFilter since it needs
// to get sequence number.
Slice& filter_key = ikey_.type == kTypeValue ? ikey_.user_key : key_;
{
StopWatchNano timer(clock_, report_detailed_time_);
filter = compaction_filter_->FilterV2(
compaction_->level(), filter_key, value_type, value_,
&compaction_filter_value_, compaction_filter_skip_until_.rep());
iter_stats_.total_filter_time +=
env_ != nullptr && report_detailed_time_ ? timer.ElapsedNanos() : 0;
}
if (filter == CompactionFilter::Decision::kRemoveAndSkipUntil &&
cmp_->Compare(*compaction_filter_skip_until_.rep(), ikey_.user_key) <=
0) {
// Can't skip to a key smaller than the current one.
// Keep the key as per FilterV2 documentation.
filter = CompactionFilter::Decision::kKeep;
}
if (filter == CompactionFilter::Decision::kRemove) {
// convert the current key to a delete; key_ is pointing into
// current_key_ at this point, so updating current_key_ updates key()
ikey_.type = kTypeDeletion;
current_key_.UpdateInternalKey(ikey_.sequence, kTypeDeletion);
// no value associated with delete
value_.clear();
iter_stats_.num_record_drop_user++;
} else if (filter == CompactionFilter::Decision::kChangeValue) {
if (ikey_.type == kTypeBlobIndex) {
// value transfer from blob file to inlined data
ikey_.type = kTypeValue;
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
}
value_ = compaction_filter_value_;
} else if (filter == CompactionFilter::Decision::kRemoveAndSkipUntil) {
*need_skip = true;
compaction_filter_skip_until_.ConvertFromUserKey(kMaxSequenceNumber,
kValueTypeForSeek);
*skip_until = compaction_filter_skip_until_.Encode();
} else if (filter == CompactionFilter::Decision::kChangeBlobIndex) {
if (ikey_.type == kTypeValue) {
// value transfer from inlined data to blob file
ikey_.type = kTypeBlobIndex;
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
}
value_ = compaction_filter_value_;
} else if (filter == CompactionFilter::Decision::kIOError) {
status_ =
Status::IOError("Failed to access blob during compaction filter");
return false;
}
}
return true;
}
void CompactionIterator::NextFromInput() {
at_next_ = false;
valid_ = false;
while (!valid_ && input_->Valid() && !IsPausingManualCompaction() &&
!IsShuttingDown()) {
key_ = input_->key();
value_ = input_->value();
iter_stats_.num_input_records++;
Status pik_status = ParseInternalKey(key_, &ikey_, allow_data_in_errors_);
if (!pik_status.ok()) {
iter_stats_.num_input_corrupt_records++;
// If `expect_valid_internal_key_` is false, return the corrupted key
// and let the caller decide what to do with it.
if (expect_valid_internal_key_) {
status_ = pik_status;
return;
}
key_ = current_key_.SetInternalKey(key_);
has_current_user_key_ = false;
current_user_key_sequence_ = kMaxSequenceNumber;
current_user_key_snapshot_ = 0;
valid_ = true;
break;
}
TEST_SYNC_POINT_CALLBACK("CompactionIterator:ProcessKV", &ikey_);
// Update input statistics
if (ikey_.type == kTypeDeletion || ikey_.type == kTypeSingleDeletion ||
ikey_.type == kTypeDeletionWithTimestamp) {
iter_stats_.num_input_deletion_records++;
}
iter_stats_.total_input_raw_key_bytes += key_.size();
iter_stats_.total_input_raw_value_bytes += value_.size();
// If need_skip is true, we should seek the input iterator
// to internal key skip_until and continue from there.
bool need_skip = false;
// Points either into compaction_filter_skip_until_ or into
// merge_helper_->compaction_filter_skip_until_.
Slice skip_until;
int cmp_user_key_without_ts = 0;
int cmp_ts = 0;
if (has_current_user_key_) {
cmp_user_key_without_ts =
timestamp_size_
? cmp_->CompareWithoutTimestamp(ikey_.user_key, current_user_key_)
: cmp_->Compare(ikey_.user_key, current_user_key_);
// if timestamp_size_ > 0, then curr_ts_ has been initialized by a
// previous key.
cmp_ts = timestamp_size_ ? cmp_->CompareTimestamp(
ExtractTimestampFromUserKey(
ikey_.user_key, timestamp_size_),
curr_ts_)
: 0;
}
// Check whether the user key changed. After this if statement current_key_
// is a copy of the current input key (maybe converted to a delete by the
// compaction filter). ikey_.user_key is pointing to the copy.
if (!has_current_user_key_ || cmp_user_key_without_ts != 0 || cmp_ts != 0) {
// First occurrence of this user key
// Copy key for output
key_ = current_key_.SetInternalKey(key_, &ikey_);
// If timestamp_size_ > 0, then copy from ikey_ to curr_ts_ for the use
// in next iteration to compare with the timestamp of next key.
UpdateTimestampAndCompareWithFullHistoryLow();
// If
// (1) !has_current_user_key_, OR
// (2) timestamp is disabled, OR
// (3) all history will be preserved, OR
// (4) user key (excluding timestamp) is different from previous key, OR
// (5) timestamp is NO older than *full_history_ts_low_
// then current_user_key_ must be treated as a different user key.
// This means, if a user key (excluding ts) is the same as the previous
// user key, and its ts is older than *full_history_ts_low_, then we
// consider this key for GC, e.g. it may be dropped if certain conditions
// match.
if (!has_current_user_key_ || !timestamp_size_ || !full_history_ts_low_ ||
0 != cmp_user_key_without_ts || cmp_with_history_ts_low_ >= 0) {
// Initialize for future comparison for rule (A) and etc.
current_user_key_sequence_ = kMaxSequenceNumber;
current_user_key_snapshot_ = 0;
has_current_user_key_ = true;
}
current_user_key_ = ikey_.user_key;
has_outputted_key_ = false;
current_key_committed_ = KeyCommitted(ikey_.sequence);
// Apply the compaction filter to the first committed version of the user
// key.
if (current_key_committed_ &&
!InvokeFilterIfNeeded(&need_skip, &skip_until)) {
break;
}
} else {
// Update the current key to reflect the new sequence number/type without
// copying the user key.
// TODO(rven): Compaction filter does not process keys in this path
// Need to have the compaction filter process multiple versions
// if we have versions on both sides of a snapshot
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
key_ = current_key_.GetInternalKey();
ikey_.user_key = current_key_.GetUserKey();
// Note that newer version of a key is ordered before older versions. If a
// newer version of a key is committed, so as the older version. No need
// to query snapshot_checker_ in that case.
if (UNLIKELY(!current_key_committed_)) {
assert(snapshot_checker_ != nullptr);
current_key_committed_ = KeyCommitted(ikey_.sequence);
// Apply the compaction filter to the first committed version of the
// user key.
if (current_key_committed_ &&
!InvokeFilterIfNeeded(&need_skip, &skip_until)) {
break;
}
}
}
if (UNLIKELY(!current_key_committed_)) {
assert(snapshot_checker_ != nullptr);
valid_ = true;
break;
}
// If there are no snapshots, then this kv affect visibility at tip.
// Otherwise, search though all existing snapshots to find the earliest
// snapshot that is affected by this kv.
SequenceNumber last_sequence = current_user_key_sequence_;
current_user_key_sequence_ = ikey_.sequence;
SequenceNumber last_snapshot = current_user_key_snapshot_;
SequenceNumber prev_snapshot = 0; // 0 means no previous snapshot
current_user_key_snapshot_ =
visible_at_tip_
? earliest_snapshot_
: findEarliestVisibleSnapshot(ikey_.sequence, &prev_snapshot);
if (need_skip) {
// This case is handled below.
} else if (clear_and_output_next_key_) {
// In the previous iteration we encountered a single delete that we could
// not compact out. We will keep this Put, but can drop it's data.
// (See Optimization 3, below.)
assert(ikey_.type == kTypeValue || ikey_.type == kTypeBlobIndex);
if (ikey_.type != kTypeValue && ikey_.type != kTypeBlobIndex) {
ROCKS_LOG_FATAL(info_log_,
"Unexpected key type %d for compaction output",
ikey_.type);
}
assert(current_user_key_snapshot_ == last_snapshot);
if (current_user_key_snapshot_ != last_snapshot) {
ROCKS_LOG_FATAL(info_log_,
"current_user_key_snapshot_ (%" PRIu64
") != last_snapshot (%" PRIu64 ")",
current_user_key_snapshot_, last_snapshot);
}
if (ikey_.type == kTypeBlobIndex) {
ikey_.type = kTypeValue;
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
}
value_.clear();
valid_ = true;
clear_and_output_next_key_ = false;
} else if (ikey_.type == kTypeSingleDeletion) {
// We can compact out a SingleDelete if:
// 1) We encounter the corresponding PUT -OR- we know that this key
// doesn't appear past this output level
// =AND=
// 2) We've already returned a record in this snapshot -OR-
// there are no earlier earliest_write_conflict_snapshot.
//
// Rule 1 is needed for SingleDelete correctness. Rule 2 is needed to
// allow Transactions to do write-conflict checking (if we compacted away
// all keys, then we wouldn't know that a write happened in this
// snapshot). If there is no earlier snapshot, then we know that there
// are no active transactions that need to know about any writes.
//
// Optimization 3:
// If we encounter a SingleDelete followed by a PUT and Rule 2 is NOT
// true, then we must output a SingleDelete. In this case, we will decide
// to also output the PUT. While we are compacting less by outputting the
// PUT now, hopefully this will lead to better compaction in the future
// when Rule 2 is later true (Ie, We are hoping we can later compact out
// both the SingleDelete and the Put, while we couldn't if we only
// outputted the SingleDelete now).
// In this case, we can save space by removing the PUT's value as it will
// never be read.
//
// Deletes and Merges are not supported on the same key that has a
// SingleDelete as it is not possible to correctly do any partial
// compaction of such a combination of operations. The result of mixing
// those operations for a given key is documented as being undefined. So
// we can choose how to handle such a combinations of operations. We will
// try to compact out as much as we can in these cases.
// We will report counts on these anomalous cases.
// The easiest way to process a SingleDelete during iteration is to peek
// ahead at the next key.
ParsedInternalKey next_ikey;
input_->Next();
// Check whether the next key exists, is not corrupt, and is the same key
// as the single delete.
if (input_->Valid() &&
ParseInternalKey(input_->key(), &next_ikey, allow_data_in_errors_)
.ok() &&
cmp_->Equal(ikey_.user_key, next_ikey.user_key)) {
// Check whether the next key belongs to the same snapshot as the
// SingleDelete.
if (prev_snapshot == 0 ||
DEFINITELY_NOT_IN_SNAPSHOT(next_ikey.sequence, prev_snapshot)) {
if (next_ikey.type == kTypeSingleDeletion) {
// We encountered two SingleDeletes in a row. This could be due to
// unexpected user input.
// Skip the first SingleDelete and let the next iteration decide how
// to handle the second SingleDelete
// First SingleDelete has been skipped since we already called
// input_->Next().
++iter_stats_.num_record_drop_obsolete;
++iter_stats_.num_single_del_mismatch;
} else if (has_outputted_key_ ||
DEFINITELY_IN_SNAPSHOT(
ikey_.sequence, earliest_write_conflict_snapshot_)) {
// Found a matching value, we can drop the single delete and the
// value. It is safe to drop both records since we've already
// outputted a key in this snapshot, or there is no earlier
// snapshot (Rule 2 above).
// Note: it doesn't matter whether the second key is a Put or if it
// is an unexpected Merge or Delete. We will compact it out
// either way. We will maintain counts of how many mismatches
// happened
if (next_ikey.type != kTypeValue &&
next_ikey.type != kTypeBlobIndex) {
++iter_stats_.num_single_del_mismatch;
}
++iter_stats_.num_record_drop_hidden;
++iter_stats_.num_record_drop_obsolete;
// Already called input_->Next() once. Call it a second time to
// skip past the second key.
input_->Next();
} else {
// Found a matching value, but we cannot drop both keys since
// there is an earlier snapshot and we need to leave behind a record
// to know that a write happened in this snapshot (Rule 2 above).
// Clear the value and output the SingleDelete. (The value will be
// outputted on the next iteration.)
// Setting valid_ to true will output the current SingleDelete
valid_ = true;
// Set up the Put to be outputted in the next iteration.
// (Optimization 3).
clear_and_output_next_key_ = true;
}
} else {
// We hit the next snapshot without hitting a put, so the iterator
// returns the single delete.
valid_ = true;
}
} else {
// We are at the end of the input, could not parse the next key, or hit
// a different key. The iterator returns the single delete if the key
// possibly exists beyond the current output level. We set
// has_current_user_key to false so that if the iterator is at the next
// key, we do not compare it again against the previous key at the next
// iteration. If the next key is corrupt, we return before the
// comparison, so the value of has_current_user_key does not matter.
has_current_user_key_ = false;
if (compaction_ != nullptr && IN_EARLIEST_SNAPSHOT(ikey_.sequence) &&
compaction_->KeyNotExistsBeyondOutputLevel(ikey_.user_key,
&level_ptrs_)) {
// Key doesn't exist outside of this range.
// Can compact out this SingleDelete.
++iter_stats_.num_record_drop_obsolete;
++iter_stats_.num_single_del_fallthru;
if (!bottommost_level_) {
++iter_stats_.num_optimized_del_drop_obsolete;
}
} else {
// Output SingleDelete
valid_ = true;
}
}
if (valid_) {
at_next_ = true;
}
} else if (last_snapshot == current_user_key_snapshot_ ||
(last_snapshot > 0 &&
last_snapshot < current_user_key_snapshot_)) {
// If the earliest snapshot is which this key is visible in
// is the same as the visibility of a previous instance of the
// same key, then this kv is not visible in any snapshot.
// Hidden by an newer entry for same user key
//
// Note: Dropping this key will not affect TransactionDB write-conflict
// checking since there has already been a record returned for this key
// in this snapshot.
assert(last_sequence >= current_user_key_sequence_);
if (last_sequence < current_user_key_sequence_) {
ROCKS_LOG_FATAL(info_log_,
"last_sequence (%" PRIu64
") < current_user_key_sequence_ (%" PRIu64 ")",
last_sequence, current_user_key_sequence_);
}
++iter_stats_.num_record_drop_hidden; // rule (A)
input_->Next();
} else if (compaction_ != nullptr &&
(ikey_.type == kTypeDeletion ||
(ikey_.type == kTypeDeletionWithTimestamp &&
cmp_with_history_ts_low_ < 0)) &&
IN_EARLIEST_SNAPSHOT(ikey_.sequence) &&
ikeyNotNeededForIncrementalSnapshot() &&
compaction_->KeyNotExistsBeyondOutputLevel(ikey_.user_key,
&level_ptrs_)) {
// TODO(noetzli): This is the only place where we use compaction_
// (besides the constructor). We should probably get rid of this
// dependency and find a way to do similar filtering during flushes.
//
// For this user key:
// (1) there is no data in higher levels
// (2) data in lower levels will have larger sequence numbers
// (3) data in layers that are being compacted here and have
// smaller sequence numbers will be dropped in the next
// few iterations of this loop (by rule (A) above).
// Therefore this deletion marker is obsolete and can be dropped.
//
// Note: Dropping this Delete will not affect TransactionDB
// write-conflict checking since it is earlier than any snapshot.
//
// It seems that we can also drop deletion later than earliest snapshot
// given that:
// (1) The deletion is earlier than earliest_write_conflict_snapshot, and
// (2) No value exist earlier than the deletion.
//
// Note also that a deletion marker of type kTypeDeletionWithTimestamp
// will be treated as a different user key unless the timestamp is older
// than *full_history_ts_low_.
++iter_stats_.num_record_drop_obsolete;
if (!bottommost_level_) {
++iter_stats_.num_optimized_del_drop_obsolete;
}
input_->Next();
} else if ((ikey_.type == kTypeDeletion ||
(ikey_.type == kTypeDeletionWithTimestamp &&
cmp_with_history_ts_low_ < 0)) &&
bottommost_level_ && ikeyNotNeededForIncrementalSnapshot()) {
// Handle the case where we have a delete key at the bottom most level
// We can skip outputting the key iff there are no subsequent puts for this
// key
assert(!compaction_ || compaction_->KeyNotExistsBeyondOutputLevel(
ikey_.user_key, &level_ptrs_));
ParsedInternalKey next_ikey;
input_->Next();
// Skip over all versions of this key that happen to occur in the same
// snapshot range as the delete.
//
// Note that a deletion marker of type kTypeDeletionWithTimestamp will be
// considered to have a different user key unless the timestamp is older
// than *full_history_ts_low_.
while (!IsPausingManualCompaction() && !IsShuttingDown() &&
input_->Valid() &&
(ParseInternalKey(input_->key(), &next_ikey, allow_data_in_errors_)
.ok()) &&
0 == cmp_->CompareWithoutTimestamp(ikey_.user_key,
next_ikey.user_key) &&
(prev_snapshot == 0 ||
DEFINITELY_NOT_IN_SNAPSHOT(next_ikey.sequence, prev_snapshot))) {
input_->Next();
}
// If you find you still need to output a row with this key, we need to output the
// delete too
if (input_->Valid() &&
(ParseInternalKey(input_->key(), &next_ikey, allow_data_in_errors_)
.ok()) &&
0 == cmp_->CompareWithoutTimestamp(ikey_.user_key,
next_ikey.user_key)) {
valid_ = true;
at_next_ = true;
}
} else if (ikey_.type == kTypeMerge) {
if (!merge_helper_->HasOperator()) {
status_ = Status::InvalidArgument(
"merge_operator is not properly initialized.");
return;
}
pinned_iters_mgr_.StartPinning();
// We know the merge type entry is not hidden, otherwise we would
// have hit (A)
// We encapsulate the merge related state machine in a different
// object to minimize change to the existing flow.
Status s =
merge_helper_->MergeUntil(input_, range_del_agg_, prev_snapshot,
bottommost_level_, allow_data_in_errors_);
merge_out_iter_.SeekToFirst();
if (!s.ok() && !s.IsMergeInProgress()) {
status_ = s;
return;
} else if (merge_out_iter_.Valid()) {
// NOTE: key, value, and ikey_ refer to old entries.
// These will be correctly set below.
key_ = merge_out_iter_.key();
value_ = merge_out_iter_.value();
pik_status = ParseInternalKey(key_, &ikey_, allow_data_in_errors_);
// MergeUntil stops when it encounters a corrupt key and does not
// include them in the result, so we expect the keys here to valid.
assert(pik_status.ok());
if (!pik_status.ok()) {
ROCKS_LOG_FATAL(info_log_, "Invalid key in compaction. %s",
pik_status.getState());
}
// Keep current_key_ in sync.
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
key_ = current_key_.GetInternalKey();
ikey_.user_key = current_key_.GetUserKey();
valid_ = true;
} else {
// all merge operands were filtered out. reset the user key, since the
// batch consumed by the merge operator should not shadow any keys
// coming after the merges
has_current_user_key_ = false;
pinned_iters_mgr_.ReleasePinnedData();
if (merge_helper_->FilteredUntil(&skip_until)) {
need_skip = true;
}
}
} else {
// 1. new user key -OR-
// 2. different snapshot stripe
bool should_delete = range_del_agg_->ShouldDelete(
key_, RangeDelPositioningMode::kForwardTraversal);
if (should_delete) {
++iter_stats_.num_record_drop_hidden;
++iter_stats_.num_record_drop_range_del;
input_->Next();
} else {
valid_ = true;
}
}
if (need_skip) {
input_->Seek(skip_until);
}
}
if (!valid_ && IsShuttingDown()) {
status_ = Status::ShutdownInProgress();
}
if (IsPausingManualCompaction()) {
status_ = Status::Incomplete(Status::SubCode::kManualCompactionPaused);
}
}
bool CompactionIterator::ExtractLargeValueIfNeededImpl() {
if (!blob_file_builder_) {
return false;
}
blob_index_.clear();
const Status s = blob_file_builder_->Add(user_key(), value_, &blob_index_);
if (!s.ok()) {
status_ = s;
valid_ = false;
return false;
}
if (blob_index_.empty()) {
return false;
}
value_ = blob_index_;
return true;
}
void CompactionIterator::ExtractLargeValueIfNeeded() {
assert(ikey_.type == kTypeValue);
if (!ExtractLargeValueIfNeededImpl()) {
return;
}
ikey_.type = kTypeBlobIndex;
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
}
void CompactionIterator::GarbageCollectBlobIfNeeded() {
assert(ikey_.type == kTypeBlobIndex);
if (!compaction_) {
return;
}
// GC for integrated BlobDB
if (compaction_->enable_blob_garbage_collection()) {
BlobIndex blob_index;
{
const Status s = blob_index.DecodeFrom(value_);
if (!s.ok()) {
status_ = s;
valid_ = false;
return;
}
}
if (blob_index.IsInlined() || blob_index.HasTTL()) {
status_ = Status::Corruption("Unexpected TTL/inlined blob index");
valid_ = false;
return;
}
if (blob_index.file_number() >=
blob_garbage_collection_cutoff_file_number_) {
return;
}
const Version* const version = compaction_->input_version();
assert(version);
{
const Status s =
version->GetBlob(ReadOptions(), user_key(), blob_index, &blob_value_);
if (!s.ok()) {
status_ = s;
valid_ = false;
return;
}
}
value_ = blob_value_;
if (ExtractLargeValueIfNeededImpl()) {
return;
}
ikey_.type = kTypeValue;
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
return;
}
// GC for stacked BlobDB
if (compaction_filter_) {
const auto blob_decision = compaction_filter_->PrepareBlobOutput(
user_key(), value_, &compaction_filter_value_);
if (blob_decision == CompactionFilter::BlobDecision::kCorruption) {
status_ =
Status::Corruption("Corrupted blob reference encountered during GC");
valid_ = false;
return;
}
if (blob_decision == CompactionFilter::BlobDecision::kIOError) {
status_ = Status::IOError("Could not relocate blob during GC");
valid_ = false;
return;
}
if (blob_decision == CompactionFilter::BlobDecision::kChangeValue) {
value_ = compaction_filter_value_;
return;
}
}
}
void CompactionIterator::PrepareOutput() {
if (valid_) {
if (ikey_.type == kTypeValue) {
ExtractLargeValueIfNeeded();
} else if (ikey_.type == kTypeBlobIndex) {
GarbageCollectBlobIfNeeded();
}
// Zeroing out the sequence number leads to better compression.
// If this is the bottommost level (no files in lower levels)
// and the earliest snapshot is larger than this seqno
// and the userkey differs from the last userkey in compaction
// then we can squash the seqno to zero.
//
// This is safe for TransactionDB write-conflict checking since transactions
// only care about sequence number larger than any active snapshots.
//
// Can we do the same for levels above bottom level as long as
// KeyNotExistsBeyondOutputLevel() return true?
if (valid_ && compaction_ != nullptr &&
!compaction_->allow_ingest_behind() &&
ikeyNotNeededForIncrementalSnapshot() && bottommost_level_ &&
IN_EARLIEST_SNAPSHOT(ikey_.sequence) && ikey_.type != kTypeMerge) {
assert(ikey_.type != kTypeDeletion && ikey_.type != kTypeSingleDeletion);
if (ikey_.type == kTypeDeletion || ikey_.type == kTypeSingleDeletion) {
ROCKS_LOG_FATAL(info_log_,
"Unexpected key type %d for seq-zero optimization",
ikey_.type);
}
ikey_.sequence = 0;
if (!timestamp_size_) {
current_key_.UpdateInternalKey(0, ikey_.type);
} else if (full_history_ts_low_ && cmp_with_history_ts_low_ < 0) {
// We can also zero out timestamp for better compression.
// For the same user key (excluding timestamp), the timestamp-based
// history can be collapsed to save some space if the timestamp is
// older than *full_history_ts_low_.
const std::string kTsMin(timestamp_size_, static_cast<char>(0));
const Slice ts_slice = kTsMin;
ikey_.SetTimestamp(ts_slice);
current_key_.UpdateInternalKey(0, ikey_.type, &ts_slice);
}
}
}
}
inline SequenceNumber CompactionIterator::findEarliestVisibleSnapshot(
SequenceNumber in, SequenceNumber* prev_snapshot) {
assert(snapshots_->size());
if (snapshots_->size() == 0) {
ROCKS_LOG_FATAL(info_log_,
"No snapshot left in findEarliestVisibleSnapshot");
}
auto snapshots_iter = std::lower_bound(
snapshots_->begin(), snapshots_->end(), in);
if (snapshots_iter == snapshots_->begin()) {
*prev_snapshot = 0;
} else {
*prev_snapshot = *std::prev(snapshots_iter);
assert(*prev_snapshot < in);
if (*prev_snapshot >= in) {
ROCKS_LOG_FATAL(info_log_,
"*prev_snapshot >= in in findEarliestVisibleSnapshot");
}
}
if (snapshot_checker_ == nullptr) {
return snapshots_iter != snapshots_->end()
? *snapshots_iter : kMaxSequenceNumber;
}
bool has_released_snapshot = !released_snapshots_.empty();
for (; snapshots_iter != snapshots_->end(); ++snapshots_iter) {
auto cur = *snapshots_iter;
assert(in <= cur);
if (in > cur) {
ROCKS_LOG_FATAL(info_log_, "in > cur in findEarliestVisibleSnapshot");
}
// Skip if cur is in released_snapshots.
if (has_released_snapshot && released_snapshots_.count(cur) > 0) {
continue;
}
auto res = snapshot_checker_->CheckInSnapshot(in, cur);
if (res == SnapshotCheckerResult::kInSnapshot) {
return cur;
} else if (res == SnapshotCheckerResult::kSnapshotReleased) {
released_snapshots_.insert(cur);
}
*prev_snapshot = cur;
}
return kMaxSequenceNumber;
}
// used in 2 places - prevents deletion markers to be dropped if they may be
// needed and disables seqnum zero-out in PrepareOutput for recent keys.
inline bool CompactionIterator::ikeyNotNeededForIncrementalSnapshot() {
return (!compaction_->preserve_deletes()) ||
(ikey_.sequence < preserve_deletes_seqnum_);
}
bool CompactionIterator::IsInEarliestSnapshot(SequenceNumber sequence) {
assert(snapshot_checker_ != nullptr);
bool pre_condition = (earliest_snapshot_ == kMaxSequenceNumber ||
(earliest_snapshot_iter_ != snapshots_->end() &&
*earliest_snapshot_iter_ == earliest_snapshot_));
assert(pre_condition);
if (!pre_condition) {
ROCKS_LOG_FATAL(info_log_,
"Pre-Condition is not hold in IsInEarliestSnapshot");
}
auto in_snapshot =
snapshot_checker_->CheckInSnapshot(sequence, earliest_snapshot_);
while (UNLIKELY(in_snapshot == SnapshotCheckerResult::kSnapshotReleased)) {
// Avoid the the current earliest_snapshot_ being return as
// earliest visible snapshot for the next value. So if a value's sequence
// is zero-ed out by PrepareOutput(), the next value will be compact out.
released_snapshots_.insert(earliest_snapshot_);
earliest_snapshot_iter_++;
if (earliest_snapshot_iter_ == snapshots_->end()) {
earliest_snapshot_ = kMaxSequenceNumber;
} else {
earliest_snapshot_ = *earliest_snapshot_iter_;
}
in_snapshot =
snapshot_checker_->CheckInSnapshot(sequence, earliest_snapshot_);
}
assert(in_snapshot != SnapshotCheckerResult::kSnapshotReleased);
if (in_snapshot == SnapshotCheckerResult::kSnapshotReleased) {
ROCKS_LOG_FATAL(info_log_,
"Unexpected released snapshot in IsInEarliestSnapshot");
}
return in_snapshot == SnapshotCheckerResult::kInSnapshot;
}
uint64_t CompactionIterator::ComputeBlobGarbageCollectionCutoffFileNumber(
const CompactionProxy* compaction) {
if (!compaction) {
return 0;
}
if (!compaction->enable_blob_garbage_collection()) {
return 0;
}
Version* const version = compaction->input_version();
assert(version);
const VersionStorageInfo* const storage_info = version->storage_info();
assert(storage_info);
const auto& blob_files = storage_info->GetBlobFiles();
auto it = blob_files.begin();
std::advance(
it, compaction->blob_garbage_collection_age_cutoff() * blob_files.size());
return it != blob_files.end() ? it->first
: std::numeric_limits<uint64_t>::max();
}
} // namespace ROCKSDB_NAMESPACE
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