andreacavalli/rocksdb
0
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity
920386f2b7
rocksdb/db/compaction/compaction_iterator.cc
Levi Tamasi dc5de45af8 Support readahead during compaction for blob files (#9187) 
Summary:
The patch adds a new BlobDB configuration option `blob_compaction_readahead_size`
that can be used to enable prefetching data from blob files during compaction.
This is important when using storage with higher latencies like HDDs or remote filesystems.
If enabled, prefetching is used for all cases when blobs are read during compaction,
namely garbage collection, compaction filters (when the existing value has to be read from
a blob file), and `Merge` (when the value of the base `Put` is stored in a blob file).

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9187

Test Plan: Ran `make check` and the stress/crash test.

Reviewed By: riversand963

Differential Revision: D32565512

Pulled By: ltamasi

fbshipit-source-id: 87be9cebc3aa01cc227bec6b5f64d827b8164f5d
2021-11-19 17:53:47 -08:00

1214 lines
47 KiB
C++
Raw Blame History

// 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_fetcher.h"
#include "db/blob/blob_file_builder.h"
#include "db/blob/blob_index.h"
#include "db/blob/prefetch_buffer_collection.h"
#include "db/snapshot_checker.h"
#include "logging/logging.h"
#include "port/likely.h"
#include "rocksdb/listener.h"
#include "table/internal_iterator.h"
#include "test_util/sync_point.h"
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::atomic<bool>* manual_compaction_canceled,
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, manual_compaction_canceled, 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::atomic<bool>* manual_compaction_canceled,
const std::shared_ptr<Logger> info_log,
const std::string* full_history_ts_low)
: input_(input, cmp,
!compaction || compaction->DoesInputReferenceBlobFiles()),
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().get()),
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),
manual_compaction_canceled_(manual_compaction_canceled),
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())),
blob_fetcher_(CreateBlobFetcherIfNeeded(compaction_.get())),
prefetch_buffers_(
CreatePrefetchBufferCollectionIfNeeded(compaction_.get())),
current_key_committed_(false),
cmp_with_history_ts_low_(0),
level_(compaction_ == nullptr ? 0 : compaction_->level()) {
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_ Iterator 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_) {
AdvanceInputIter();
}
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_ ||
(ikey_.type != kTypeValue && ikey_.type != kTypeBlobIndex)) {
return true;
}
bool error = false;
// 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 = CompactionFilter::Decision::kUndetermined;
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.
assert(compaction_filter_);
Slice& filter_key =
(ikey_.type == kTypeValue ||
!compaction_filter_->IsStackedBlobDbInternalCompactionFilter())
? ikey_.user_key
: key_;
{
StopWatchNano timer(clock_, report_detailed_time_);
if (kTypeBlobIndex == ikey_.type) {
blob_value_.Reset();
filter = compaction_filter_->FilterBlobByKey(
level_, filter_key, &compaction_filter_value_,
compaction_filter_skip_until_.rep());
if (CompactionFilter::Decision::kUndetermined == filter &&
!compaction_filter_->IsStackedBlobDbInternalCompactionFilter()) {
if (compaction_ == nullptr) {
status_ =
Status::Corruption("Unexpected blob index outside of compaction");
valid_ = false;
return false;
}
// For integrated BlobDB impl, CompactionIterator reads blob value.
// For Stacked BlobDB impl, the corresponding CompactionFilter's
// FilterV2 method should read the blob value.
BlobIndex blob_index;
Status s = blob_index.DecodeFrom(value_);
if (!s.ok()) {
status_ = s;
valid_ = false;
return false;
}
FilePrefetchBuffer* prefetch_buffer =
prefetch_buffers_ ? prefetch_buffers_->GetOrCreatePrefetchBuffer(
blob_index.file_number())
: nullptr;
uint64_t bytes_read = 0;
assert(blob_fetcher_);
s = blob_fetcher_->FetchBlob(ikey_.user_key, blob_index,
prefetch_buffer, &blob_value_,
&bytes_read);
if (!s.ok()) {
status_ = s;
valid_ = false;
return false;
}
++iter_stats_.num_blobs_read;
iter_stats_.total_blob_bytes_read += bytes_read;
value_type = CompactionFilter::ValueType::kValue;
}
}
if (CompactionFilter::Decision::kUndetermined == filter) {
filter = compaction_filter_->FilterV2(
level_, filter_key, value_type,
blob_value_.empty() ? value_ : blob_value_, &compaction_filter_value_,
compaction_filter_skip_until_.rep());
}
iter_stats_.total_filter_time +=
env_ != nullptr && report_detailed_time_ ? timer.ElapsedNanos() : 0;
}
if (CompactionFilter::Decision::kUndetermined == filter) {
// Should not reach here, since FilterV2 should never return kUndetermined.
status_ =
Status::NotSupported("FilterV2() should never return kUndetermined");
valid_ = false;
return false;
}
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) {
// Only the StackableDB-based BlobDB impl's compaction filter should return
// kChangeBlobIndex. Decision about rewriting blob and changing blob index
// in the integrated BlobDB impl is made in subsequent call to
// PrepareOutput() and its callees.
if (!compaction_filter_->IsStackedBlobDbInternalCompactionFilter()) {
status_ = Status::NotSupported(
"Only stacked BlobDB's internal compaction filter can return "
"kChangeBlobIndex.");
valid_ = false;
return false;
}
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) {
if (!compaction_filter_->IsStackedBlobDbInternalCompactionFilter()) {
status_ = Status::NotSupported(
"CompactionFilter for integrated BlobDB should not return kIOError");
valid_ = false;
return false;
}
status_ = Status::IOError("Failed to access blob during compaction filter");
error = true;
}
return !error;
}
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;
bool user_key_equal_without_ts = false;
int cmp_ts = 0;
if (has_current_user_key_) {
user_key_equal_without_ts =
cmp_->EqualWithoutTimestamp(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_ || !user_key_equal_without_ts || cmp_ts != 0) {
// First occurrence of this user key
// Copy key for output
key_ = current_key_.SetInternalKey(key_, &ikey_);
int prev_cmp_with_ts_low =
!full_history_ts_low_ ? 0
: curr_ts_.empty()
? 0
: cmp_->CompareTimestamp(curr_ts_, *full_history_ts_low_);
// 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_, OR
// (6) timestamp is the largest one 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_ ||
!user_key_equal_without_ts || cmp_with_history_ts_low_ >= 0 ||
prev_cmp_with_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;
last_key_seq_zeroed_ = 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.
//
// A note about 2) above:
// we try to determine whether there is any earlier write conflict
// checking snapshot by calling DefinitelyInSnapshot() with seq and
// earliest_write_conflict_snapshot as arguments. For write-prepared
// and write-unprepared transactions, if earliest_write_conflict_snapshot
// is evicted from WritePreparedTxnDB::commit_cache, then
// DefinitelyInSnapshot(seq, earliest_write_conflict_snapshot) returns
// false, even if the seq is actually visible within
// earliest_write_conflict_snapshot. Consequently, CompactionIterator
// may try to zero out its sequence number, thus hitting assertion error
// in debug mode or cause incorrect DBIter return result.
// We observe that earliest_write_conflict_snapshot >= earliest_snapshot,
// and the seq zeroing logic depends on
// DefinitelyInSnapshot(seq, earliest_snapshot). Therefore, if we cannot
// determine whether seq is **definitely** in
// earliest_write_conflict_snapshot, then we can additionally check if
// seq is definitely in earliest_snapshot. If the latter holds, then the
// former holds too.
//
// 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.
//
// Note: If timestamp is enabled, then record will be eligible for
// deletion, only if, along with above conditions (Rule 1 and Rule 2)
// full_history_ts_low_ is specified and timestamp for that key is less
// than *full_history_ts_low_. If it's not eligible for deletion, then we
// will output the SingleDelete. For Optimization 3 also, if
// full_history_ts_low_ is specified and timestamp for the key is less
// than *full_history_ts_low_ then only optimization will be applied.
// The easiest way to process a SingleDelete during iteration is to peek
// ahead at the next key.
const bool is_timestamp_eligible_for_gc =
(timestamp_size_ == 0 ||
(full_history_ts_low_ && cmp_with_history_ts_low_ < 0));
ParsedInternalKey next_ikey;
AdvanceInputIter();
// 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_->EqualWithoutTimestamp(ikey_.user_key, next_ikey.user_key)) {
#ifndef NDEBUG
const Compaction* c =
compaction_ ? compaction_->real_compaction() : nullptr;
#endif
TEST_SYNC_POINT_CALLBACK(
"CompactionIterator::NextFromInput:SingleDelete:1",
const_cast<Compaction*>(c));
if (last_key_seq_zeroed_) {
++iter_stats_.num_record_drop_hidden;
++iter_stats_.num_record_drop_obsolete;
assert(bottommost_level_);
AdvanceInputIter();
} else if (prev_snapshot == 0 ||
DefinitelyNotInSnapshot(next_ikey.sequence, prev_snapshot)) {
// Check whether the next key belongs to the same snapshot as the
// SingleDelete.
TEST_SYNC_POINT_CALLBACK(
"CompactionIterator::NextFromInput:SingleDelete:2", nullptr);
if (next_ikey.type == kTypeSingleDeletion ||
next_ikey.type == kTypeDeletion) {
// We encountered two SingleDeletes for same key in a row. This
// could be due to unexpected user input. If write-(un)prepared
// transaction is used, this could also be due to releasing an old
// snapshot between a Put and its matching SingleDelete.
// Furthermore, if write-(un)prepared transaction is rolled back
// after prepare, we will write a Delete to cancel a prior Put. If
// old snapshot is released between a later Put and its matching
// SingleDelete, we will end up with a Delete followed by
// SingleDelete.
// Skip the first SingleDelete and let the next iteration decide
// how to handle the second SingleDelete or Delete.
// 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 (!is_timestamp_eligible_for_gc) {
// We cannot drop the SingleDelete as timestamp is enabled, and
// timestamp of this key is greater than or equal to
// *full_history_ts_low_. We will output the SingleDelete.
valid_ = true;
} else if (has_outputted_key_ ||
DefinitelyInSnapshot(ikey_.sequence,
earliest_write_conflict_snapshot_) ||
(earliest_snapshot_ < earliest_write_conflict_snapshot_ &&
DefinitelyInSnapshot(ikey_.sequence,
earliest_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.
AdvanceInputIter();
} 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;
TEST_SYNC_POINT_CALLBACK(
"CompactionIterator::NextFromInput:KeepSDForWW",
/*arg=*/nullptr);
}
} else {
// We hit the next snapshot without hitting a put, so the iterator
// returns the single delete.
valid_ = true;
TEST_SYNC_POINT_CALLBACK(
"CompactionIterator::NextFromInput:SingleDelete:3",
const_cast<Compaction*>(c));
}
} 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 &&
DefinitelyInSnapshot(ikey_.sequence, earliest_snapshot_) &&
compaction_->KeyNotExistsBeyondOutputLevel(ikey_.user_key,
&level_ptrs_) &&
is_timestamp_eligible_for_gc) {
// 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 if (last_key_seq_zeroed_) {
// Skip.
++iter_stats_.num_record_drop_hidden;
++iter_stats_.num_record_drop_obsolete;
assert(bottommost_level_);
} 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)
AdvanceInputIter();
} else if (compaction_ != nullptr &&
(ikey_.type == kTypeDeletion ||
(ikey_.type == kTypeDeletionWithTimestamp &&
cmp_with_history_ts_low_ < 0)) &&
DefinitelyInSnapshot(ikey_.sequence, earliest_snapshot_) &&
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;
}
AdvanceInputIter();
} 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;
AdvanceInputIter();
#ifndef NDEBUG
const Compaction* c =
compaction_ ? compaction_->real_compaction() : nullptr;
#endif
TEST_SYNC_POINT_CALLBACK(
"CompactionIterator::NextFromInput:BottommostDelete:1",
const_cast<Compaction*>(c));
// 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()) &&
cmp_->EqualWithoutTimestamp(ikey_.user_key, next_ikey.user_key) &&
(prev_snapshot == 0 ||
DefinitelyNotInSnapshot(next_ikey.sequence, prev_snapshot))) {
AdvanceInputIter();
}
// 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()) &&
cmp_->EqualWithoutTimestamp(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_, blob_fetcher_.get(), prefetch_buffers_.get(),
&iter_stats_);
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;
AdvanceInputIter();
} else {
valid_ = true;
}
}
if (need_skip) {
SkipUntil(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.file_number() >=
blob_garbage_collection_cutoff_file_number_) {
return;
}
FilePrefetchBuffer* prefetch_buffer =
prefetch_buffers_ ? prefetch_buffers_->GetOrCreatePrefetchBuffer(
blob_index.file_number())
: nullptr;
uint64_t bytes_read = 0;
{
assert(blob_fetcher_);
const Status s = blob_fetcher_->FetchBlob(
user_key(), blob_index, prefetch_buffer, &blob_value_, &bytes_read);
if (!s.ok()) {
status_ = s;
valid_ = false;
return;
}
}
++iter_stats_.num_blobs_read;
iter_stats_.total_blob_bytes_read += bytes_read;
++iter_stats_.num_blobs_relocated;
iter_stats_.total_blob_bytes_relocated += blob_index.size();
value_ = blob_value_;
if (ExtractLargeValueIfNeededImpl()) {
return;
}
ikey_.type = kTypeValue;
current_key_.UpdateInternalKey(ikey_.sequence, ikey_.type);
return;
}
// GC for stacked BlobDB
if (compaction_filter_ &&
compaction_filter_->IsStackedBlobDbInternalCompactionFilter()) {
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_ &&
DefinitelyInSnapshot(ikey_.sequence, earliest_snapshot_) &&
ikey_.type != kTypeMerge) {
assert(ikey_.type != kTypeDeletion);
assert(ikey_.type != kTypeSingleDeletion ||
(timestamp_size_ || full_history_ts_low_));
if (ikey_.type == kTypeDeletion ||
(ikey_.type == kTypeSingleDeletion &&
(!timestamp_size_ || !full_history_ts_low_))) {
ROCKS_LOG_FATAL(info_log_,
"Unexpected key type %d for seq-zero optimization",
ikey_.type);
}
ikey_.sequence = 0;
last_key_seq_zeroed_ = true;
TEST_SYNC_POINT_CALLBACK("CompactionIterator::PrepareOutput:ZeroingSeq",
&ikey_);
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_);
}
uint64_t CompactionIterator::ComputeBlobGarbageCollectionCutoffFileNumber(
const CompactionProxy* compaction) {
if (!compaction) {
return 0;
}
if (!compaction->enable_blob_garbage_collection()) {
return 0;
}
const 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();
}
std::unique_ptr<BlobFetcher> CompactionIterator::CreateBlobFetcherIfNeeded(
const CompactionProxy* compaction) {
if (!compaction) {
return nullptr;
}
const Version* const version = compaction->input_version();
if (!version) {
return nullptr;
}
return std::unique_ptr<BlobFetcher>(new BlobFetcher(version, ReadOptions()));
}
std::unique_ptr<PrefetchBufferCollection>
CompactionIterator::CreatePrefetchBufferCollectionIfNeeded(
const CompactionProxy* compaction) {
if (!compaction) {
return nullptr;
}
if (!compaction->input_version()) {
return nullptr;
}
if (compaction->allow_mmap_reads()) {
return nullptr;
}
const uint64_t readahead_size = compaction->blob_compaction_readahead_size();
if (!readahead_size) {
return nullptr;
}
return std::unique_ptr<PrefetchBufferCollection>(
new PrefetchBufferCollection(readahead_size));
}
} // namespace ROCKSDB_NAMESPACE
Reference in New Issue View Git Blame Copy Permalink