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rocksdb/db/forward_iterator.cc
Mike Kolupaev e45673dece Properly report IO errors when IndexType::kBinarySearchWithFirstKey is used (#6621) 
Summary:
Context: Index type `kBinarySearchWithFirstKey` added the ability for sst file iterator to sometimes report a key from index without reading the corresponding data block. This is useful when sst blocks are cut at some meaningful boundaries (e.g. one block per key prefix), and many seeks land between blocks (e.g. for each prefix, the ranges of keys in different sst files are nearly disjoint, so a typical seek needs to read a data block from only one file even if all files have the prefix). But this added a new error condition, which rocksdb code was really not equipped to deal with: `InternalIterator::value()` may fail with an IO error or Status::Incomplete, but it's just a method returning a Slice, with no way to report error instead. Before this PR, this type of error wasn't handled at all (an empty slice was returned), and kBinarySearchWithFirstKey implementation was considered a prototype.

Now that we (LogDevice) have experimented with kBinarySearchWithFirstKey for a while and confirmed that it's really useful, this PR is adding the missing error handling.

It's a pretty inconvenient situation implementation-wise. The error needs to be reported from InternalIterator when trying to access value. But there are ~700 call sites of `InternalIterator::value()`, most of which either can't hit the error condition (because the iterator is reading from memtable or from index or something) or wouldn't benefit from the deferred loading of the value (e.g. compaction iterator that reads all values anyway). Adding error handling to all these call sites would needlessly bloat the code. So instead I made the deferred value loading optional: only the call sites that may use deferred loading have to call the new method `PrepareValue()` before calling `value()`. The feature is enabled with a new bool argument `allow_unprepared_value` to a bunch of methods that create iterators (it wouldn't make sense to put it in ReadOptions because it's completely internal to iterators, with virtually no user-visible effect). Lmk if you have better ideas.

Note that the deferred value loading only happens for *internal* iterators. The user-visible iterator (DBIter) always prepares the value before returning from Seek/Next/etc. We could go further and add an API to defer that value loading too, but that's most likely not useful for LogDevice, so it doesn't seem worth the complexity for now.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6621

Test Plan: make -j5 check . Will also deploy to some logdevice test clusters and look at stats.

Reviewed By: siying

Differential Revision: D20786930

Pulled By: al13n321

fbshipit-source-id: 6da77d918bad3780522e918f17f4d5513d3e99ee
2020-04-15 17:40:44 -07:00

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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).
#ifndef ROCKSDB_LITE
#include "db/forward_iterator.h"
#include <limits>
#include <string>
#include <utility>
#include "db/column_family.h"
#include "db/db_impl/db_impl.h"
#include "db/db_iter.h"
#include "db/dbformat.h"
#include "db/job_context.h"
#include "db/range_del_aggregator.h"
#include "db/range_tombstone_fragmenter.h"
#include "rocksdb/env.h"
#include "rocksdb/slice.h"
#include "rocksdb/slice_transform.h"
#include "table/merging_iterator.h"
#include "test_util/sync_point.h"
#include "util/string_util.h"
namespace ROCKSDB_NAMESPACE {
// Usage:
// ForwardLevelIterator iter;
// iter.SetFileIndex(file_index);
// iter.Seek(target); // or iter.SeekToFirst();
// iter.Next()
class ForwardLevelIterator : public InternalIterator {
public:
ForwardLevelIterator(const ColumnFamilyData* const cfd,
const ReadOptions& read_options,
const std::vector<FileMetaData*>& files,
const SliceTransform* prefix_extractor,
bool allow_unprepared_value)
: cfd_(cfd),
read_options_(read_options),
files_(files),
valid_(false),
file_index_(std::numeric_limits<uint32_t>::max()),
file_iter_(nullptr),
pinned_iters_mgr_(nullptr),
prefix_extractor_(prefix_extractor),
allow_unprepared_value_(allow_unprepared_value) {}
~ForwardLevelIterator() override {
// Reset current pointer
if (pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled()) {
pinned_iters_mgr_->PinIterator(file_iter_);
} else {
delete file_iter_;
}
}
void SetFileIndex(uint32_t file_index) {
assert(file_index < files_.size());
status_ = Status::OK();
if (file_index != file_index_) {
file_index_ = file_index;
Reset();
}
}
void Reset() {
assert(file_index_ < files_.size());
// Reset current pointer
if (pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled()) {
pinned_iters_mgr_->PinIterator(file_iter_);
} else {
delete file_iter_;
}
ReadRangeDelAggregator range_del_agg(&cfd_->internal_comparator(),
kMaxSequenceNumber /* upper_bound */);
file_iter_ = cfd_->table_cache()->NewIterator(
read_options_, *(cfd_->soptions()), cfd_->internal_comparator(),
*files_[file_index_],
read_options_.ignore_range_deletions ? nullptr : &range_del_agg,
prefix_extractor_, /*table_reader_ptr=*/nullptr,
/*file_read_hist=*/nullptr, TableReaderCaller::kUserIterator,
/*arena=*/nullptr, /*skip_filters=*/false, /*level=*/-1,
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr,
allow_unprepared_value_);
file_iter_->SetPinnedItersMgr(pinned_iters_mgr_);
valid_ = false;
if (!range_del_agg.IsEmpty()) {
status_ = Status::NotSupported(
"Range tombstones unsupported with ForwardIterator");
}
}
void SeekToLast() override {
status_ = Status::NotSupported("ForwardLevelIterator::SeekToLast()");
valid_ = false;
}
void Prev() override {
status_ = Status::NotSupported("ForwardLevelIterator::Prev()");
valid_ = false;
}
bool Valid() const override {
return valid_;
}
void SeekToFirst() override {
assert(file_iter_ != nullptr);
if (!status_.ok()) {
assert(!valid_);
return;
}
file_iter_->SeekToFirst();
valid_ = file_iter_->Valid();
}
void Seek(const Slice& internal_key) override {
assert(file_iter_ != nullptr);
// This deviates from the usual convention for InternalIterator::Seek() in
// that it doesn't discard pre-existing error status. That's because this
// Seek() is only supposed to be called immediately after SetFileIndex()
// (which discards pre-existing error status), and SetFileIndex() may set
// an error status, which we shouldn't discard.
if (!status_.ok()) {
assert(!valid_);
return;
}
file_iter_->Seek(internal_key);
valid_ = file_iter_->Valid();
}
void SeekForPrev(const Slice& /*internal_key*/) override {
status_ = Status::NotSupported("ForwardLevelIterator::SeekForPrev()");
valid_ = false;
}
void Next() override {
assert(valid_);
file_iter_->Next();
for (;;) {
valid_ = file_iter_->Valid();
if (!file_iter_->status().ok()) {
assert(!valid_);
return;
}
if (valid_) {
return;
}
if (file_index_ + 1 >= files_.size()) {
valid_ = false;
return;
}
SetFileIndex(file_index_ + 1);
if (!status_.ok()) {
assert(!valid_);
return;
}
file_iter_->SeekToFirst();
}
}
Slice key() const override {
assert(valid_);
return file_iter_->key();
}
Slice value() const override {
assert(valid_);
return file_iter_->value();
}
Status status() const override {
if (!status_.ok()) {
return status_;
} else if (file_iter_) {
return file_iter_->status();
}
return Status::OK();
}
bool PrepareValue() override {
assert(valid_);
if (file_iter_->PrepareValue()) {
return true;
}
assert(!file_iter_->Valid());
valid_ = false;
return false;
}
bool IsKeyPinned() const override {
return pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled() &&
file_iter_->IsKeyPinned();
}
bool IsValuePinned() const override {
return pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled() &&
file_iter_->IsValuePinned();
}
void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) override {
pinned_iters_mgr_ = pinned_iters_mgr;
if (file_iter_) {
file_iter_->SetPinnedItersMgr(pinned_iters_mgr_);
}
}
private:
const ColumnFamilyData* const cfd_;
const ReadOptions& read_options_;
const std::vector<FileMetaData*>& files_;
bool valid_;
uint32_t file_index_;
Status status_;
InternalIterator* file_iter_;
PinnedIteratorsManager* pinned_iters_mgr_;
const SliceTransform* prefix_extractor_;
const bool allow_unprepared_value_;
};
ForwardIterator::ForwardIterator(DBImpl* db, const ReadOptions& read_options,
ColumnFamilyData* cfd,
SuperVersion* current_sv,
bool allow_unprepared_value)
: db_(db),
read_options_(read_options),
cfd_(cfd),
prefix_extractor_(current_sv->mutable_cf_options.prefix_extractor.get()),
user_comparator_(cfd->user_comparator()),
allow_unprepared_value_(allow_unprepared_value),
immutable_min_heap_(MinIterComparator(&cfd_->internal_comparator())),
sv_(current_sv),
mutable_iter_(nullptr),
current_(nullptr),
valid_(false),
status_(Status::OK()),
immutable_status_(Status::OK()),
has_iter_trimmed_for_upper_bound_(false),
current_over_upper_bound_(false),
is_prev_set_(false),
is_prev_inclusive_(false),
pinned_iters_mgr_(nullptr) {
if (sv_) {
RebuildIterators(false);
}
}
ForwardIterator::~ForwardIterator() {
Cleanup(true);
}
void ForwardIterator::SVCleanup(DBImpl* db, SuperVersion* sv,
bool background_purge_on_iterator_cleanup) {
if (sv->Unref()) {
// Job id == 0 means that this is not our background process, but rather
// user thread
JobContext job_context(0);
db->mutex_.Lock();
sv->Cleanup();
db->FindObsoleteFiles(&job_context, false, true);
if (background_purge_on_iterator_cleanup) {
db->ScheduleBgLogWriterClose(&job_context);
db->AddSuperVersionsToFreeQueue(sv);
db->SchedulePurge();
}
db->mutex_.Unlock();
if (!background_purge_on_iterator_cleanup) {
delete sv;
}
if (job_context.HaveSomethingToDelete()) {
db->PurgeObsoleteFiles(job_context, background_purge_on_iterator_cleanup);
}
job_context.Clean();
}
}
namespace {
struct SVCleanupParams {
DBImpl* db;
SuperVersion* sv;
bool background_purge_on_iterator_cleanup;
};
}
// Used in PinnedIteratorsManager to release pinned SuperVersion
void ForwardIterator::DeferredSVCleanup(void* arg) {
auto d = reinterpret_cast<SVCleanupParams*>(arg);
ForwardIterator::SVCleanup(
d->db, d->sv, d->background_purge_on_iterator_cleanup);
delete d;
}
void ForwardIterator::SVCleanup() {
if (sv_ == nullptr) {
return;
}
bool background_purge =
read_options_.background_purge_on_iterator_cleanup ||
db_->immutable_db_options().avoid_unnecessary_blocking_io;
if (pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled()) {
// pinned_iters_mgr_ tells us to make sure that all visited key-value slices
// are alive until pinned_iters_mgr_->ReleasePinnedData() is called.
// The slices may point into some memtables owned by sv_, so we need to keep
// sv_ referenced until pinned_iters_mgr_ unpins everything.
auto p = new SVCleanupParams{db_, sv_, background_purge};
pinned_iters_mgr_->PinPtr(p, &ForwardIterator::DeferredSVCleanup);
} else {
SVCleanup(db_, sv_, background_purge);
}
}
void ForwardIterator::Cleanup(bool release_sv) {
if (mutable_iter_ != nullptr) {
DeleteIterator(mutable_iter_, true /* is_arena */);
}
for (auto* m : imm_iters_) {
DeleteIterator(m, true /* is_arena */);
}
imm_iters_.clear();
for (auto* f : l0_iters_) {
DeleteIterator(f);
}
l0_iters_.clear();
for (auto* l : level_iters_) {
DeleteIterator(l);
}
level_iters_.clear();
if (release_sv) {
SVCleanup();
}
}
bool ForwardIterator::Valid() const {
// See UpdateCurrent().
return valid_ ? !current_over_upper_bound_ : false;
}
void ForwardIterator::SeekToFirst() {
if (sv_ == nullptr) {
RebuildIterators(true);
} else if (sv_->version_number != cfd_->GetSuperVersionNumber()) {
RenewIterators();
} else if (immutable_status_.IsIncomplete()) {
ResetIncompleteIterators();
}
SeekInternal(Slice(), true);
}
bool ForwardIterator::IsOverUpperBound(const Slice& internal_key) const {
return !(read_options_.iterate_upper_bound == nullptr ||
cfd_->internal_comparator().user_comparator()->Compare(
ExtractUserKey(internal_key),
*read_options_.iterate_upper_bound) < 0);
}
void ForwardIterator::Seek(const Slice& internal_key) {
if (sv_ == nullptr) {
RebuildIterators(true);
} else if (sv_->version_number != cfd_->GetSuperVersionNumber()) {
RenewIterators();
} else if (immutable_status_.IsIncomplete()) {
ResetIncompleteIterators();
}
SeekInternal(internal_key, false);
}
void ForwardIterator::SeekInternal(const Slice& internal_key,
bool seek_to_first) {
assert(mutable_iter_);
// mutable
seek_to_first ? mutable_iter_->SeekToFirst() :
mutable_iter_->Seek(internal_key);
// immutable
// TODO(ljin): NeedToSeekImmutable has negative impact on performance
// if it turns to need to seek immutable often. We probably want to have
// an option to turn it off.
if (seek_to_first || NeedToSeekImmutable(internal_key)) {
immutable_status_ = Status::OK();
if (has_iter_trimmed_for_upper_bound_ &&
(
// prev_ is not set yet
is_prev_set_ == false ||
// We are doing SeekToFirst() and internal_key.size() = 0
seek_to_first ||
// prev_key_ > internal_key
cfd_->internal_comparator().InternalKeyComparator::Compare(
prev_key_.GetInternalKey(), internal_key) > 0)) {
// Some iterators are trimmed. Need to rebuild.
RebuildIterators(true);
// Already seeked mutable iter, so seek again
seek_to_first ? mutable_iter_->SeekToFirst()
: mutable_iter_->Seek(internal_key);
}
{
auto tmp = MinIterHeap(MinIterComparator(&cfd_->internal_comparator()));
immutable_min_heap_.swap(tmp);
}
for (size_t i = 0; i < imm_iters_.size(); i++) {
auto* m = imm_iters_[i];
seek_to_first ? m->SeekToFirst() : m->Seek(internal_key);
if (!m->status().ok()) {
immutable_status_ = m->status();
} else if (m->Valid()) {
immutable_min_heap_.push(m);
}
}
Slice target_user_key;
if (!seek_to_first) {
target_user_key = ExtractUserKey(internal_key);
}
const VersionStorageInfo* vstorage = sv_->current->storage_info();
const std::vector<FileMetaData*>& l0 = vstorage->LevelFiles(0);
for (size_t i = 0; i < l0.size(); ++i) {
if (!l0_iters_[i]) {
continue;
}
if (seek_to_first) {
l0_iters_[i]->SeekToFirst();
} else {
// If the target key passes over the larget key, we are sure Next()
// won't go over this file.
if (user_comparator_->Compare(target_user_key,
l0[i]->largest.user_key()) > 0) {
if (read_options_.iterate_upper_bound != nullptr) {
has_iter_trimmed_for_upper_bound_ = true;
DeleteIterator(l0_iters_[i]);
l0_iters_[i] = nullptr;
}
continue;
}
l0_iters_[i]->Seek(internal_key);
}
if (!l0_iters_[i]->status().ok()) {
immutable_status_ = l0_iters_[i]->status();
} else if (l0_iters_[i]->Valid() &&
!IsOverUpperBound(l0_iters_[i]->key())) {
immutable_min_heap_.push(l0_iters_[i]);
} else {
has_iter_trimmed_for_upper_bound_ = true;
DeleteIterator(l0_iters_[i]);
l0_iters_[i] = nullptr;
}
}
for (int32_t level = 1; level < vstorage->num_levels(); ++level) {
const std::vector<FileMetaData*>& level_files =
vstorage->LevelFiles(level);
if (level_files.empty()) {
continue;
}
if (level_iters_[level - 1] == nullptr) {
continue;
}
uint32_t f_idx = 0;
if (!seek_to_first) {
f_idx = FindFileInRange(level_files, internal_key, 0,
static_cast<uint32_t>(level_files.size()));
}
// Seek
if (f_idx < level_files.size()) {
level_iters_[level - 1]->SetFileIndex(f_idx);
seek_to_first ? level_iters_[level - 1]->SeekToFirst() :
level_iters_[level - 1]->Seek(internal_key);
if (!level_iters_[level - 1]->status().ok()) {
immutable_status_ = level_iters_[level - 1]->status();
} else if (level_iters_[level - 1]->Valid() &&
!IsOverUpperBound(level_iters_[level - 1]->key())) {
immutable_min_heap_.push(level_iters_[level - 1]);
} else {
// Nothing in this level is interesting. Remove.
has_iter_trimmed_for_upper_bound_ = true;
DeleteIterator(level_iters_[level - 1]);
level_iters_[level - 1] = nullptr;
}
}
}
if (seek_to_first) {
is_prev_set_ = false;
} else {
prev_key_.SetInternalKey(internal_key);
is_prev_set_ = true;
is_prev_inclusive_ = true;
}
TEST_SYNC_POINT_CALLBACK("ForwardIterator::SeekInternal:Immutable", this);
} else if (current_ && current_ != mutable_iter_) {
// current_ is one of immutable iterators, push it back to the heap
immutable_min_heap_.push(current_);
}
UpdateCurrent();
TEST_SYNC_POINT_CALLBACK("ForwardIterator::SeekInternal:Return", this);
}
void ForwardIterator::Next() {
assert(valid_);
bool update_prev_key = false;
if (sv_ == nullptr ||
sv_->version_number != cfd_->GetSuperVersionNumber()) {
std::string current_key = key().ToString();
Slice old_key(current_key.data(), current_key.size());
if (sv_ == nullptr) {
RebuildIterators(true);
} else {
RenewIterators();
}
SeekInternal(old_key, false);
if (!valid_ || key().compare(old_key) != 0) {
return;
}
} else if (current_ != mutable_iter_) {
// It is going to advance immutable iterator
if (is_prev_set_ && prefix_extractor_) {
// advance prev_key_ to current_ only if they share the same prefix
update_prev_key =
prefix_extractor_->Transform(prev_key_.GetUserKey())
.compare(prefix_extractor_->Transform(current_->key())) == 0;
} else {
update_prev_key = true;
}
if (update_prev_key) {
prev_key_.SetInternalKey(current_->key());
is_prev_set_ = true;
is_prev_inclusive_ = false;
}
}
current_->Next();
if (current_ != mutable_iter_) {
if (!current_->status().ok()) {
immutable_status_ = current_->status();
} else if ((current_->Valid()) && (!IsOverUpperBound(current_->key()))) {
immutable_min_heap_.push(current_);
} else {
if ((current_->Valid()) && (IsOverUpperBound(current_->key()))) {
// remove the current iterator
DeleteCurrentIter();
current_ = nullptr;
}
if (update_prev_key) {
mutable_iter_->Seek(prev_key_.GetInternalKey());
}
}
}
UpdateCurrent();
TEST_SYNC_POINT_CALLBACK("ForwardIterator::Next:Return", this);
}
Slice ForwardIterator::key() const {
assert(valid_);
return current_->key();
}
Slice ForwardIterator::value() const {
assert(valid_);
return current_->value();
}
Status ForwardIterator::status() const {
if (!status_.ok()) {
return status_;
} else if (!mutable_iter_->status().ok()) {
return mutable_iter_->status();
}
return immutable_status_;
}
bool ForwardIterator::PrepareValue() {
assert(valid_);
if (current_->PrepareValue()) {
return true;
}
assert(!current_->Valid());
assert(!current_->status().ok());
assert(current_ != mutable_iter_); // memtable iterator can't fail
assert(immutable_status_.ok());
valid_ = false;
immutable_status_ = current_->status();
return false;
}
Status ForwardIterator::GetProperty(std::string prop_name, std::string* prop) {
assert(prop != nullptr);
if (prop_name == "rocksdb.iterator.super-version-number") {
*prop = ToString(sv_->version_number);
return Status::OK();
}
return Status::InvalidArgument();
}
void ForwardIterator::SetPinnedItersMgr(
PinnedIteratorsManager* pinned_iters_mgr) {
pinned_iters_mgr_ = pinned_iters_mgr;
UpdateChildrenPinnedItersMgr();
}
void ForwardIterator::UpdateChildrenPinnedItersMgr() {
// Set PinnedIteratorsManager for mutable memtable iterator.
if (mutable_iter_) {
mutable_iter_->SetPinnedItersMgr(pinned_iters_mgr_);
}
// Set PinnedIteratorsManager for immutable memtable iterators.
for (InternalIterator* child_iter : imm_iters_) {
if (child_iter) {
child_iter->SetPinnedItersMgr(pinned_iters_mgr_);
}
}
// Set PinnedIteratorsManager for L0 files iterators.
for (InternalIterator* child_iter : l0_iters_) {
if (child_iter) {
child_iter->SetPinnedItersMgr(pinned_iters_mgr_);
}
}
// Set PinnedIteratorsManager for L1+ levels iterators.
for (ForwardLevelIterator* child_iter : level_iters_) {
if (child_iter) {
child_iter->SetPinnedItersMgr(pinned_iters_mgr_);
}
}
}
bool ForwardIterator::IsKeyPinned() const {
return pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled() &&
current_->IsKeyPinned();
}
bool ForwardIterator::IsValuePinned() const {
return pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled() &&
current_->IsValuePinned();
}
void ForwardIterator::RebuildIterators(bool refresh_sv) {
// Clean up
Cleanup(refresh_sv);
if (refresh_sv) {
// New
sv_ = cfd_->GetReferencedSuperVersion(db_);
}
ReadRangeDelAggregator range_del_agg(&cfd_->internal_comparator(),
kMaxSequenceNumber /* upper_bound */);
mutable_iter_ = sv_->mem->NewIterator(read_options_, &arena_);
sv_->imm->AddIterators(read_options_, &imm_iters_, &arena_);
if (!read_options_.ignore_range_deletions) {
std::unique_ptr<FragmentedRangeTombstoneIterator> range_del_iter(
sv_->mem->NewRangeTombstoneIterator(
read_options_, sv_->current->version_set()->LastSequence()));
range_del_agg.AddTombstones(std::move(range_del_iter));
sv_->imm->AddRangeTombstoneIterators(read_options_, &arena_,
&range_del_agg);
}
has_iter_trimmed_for_upper_bound_ = false;
const auto* vstorage = sv_->current->storage_info();
const auto& l0_files = vstorage->LevelFiles(0);
l0_iters_.reserve(l0_files.size());
for (const auto* l0 : l0_files) {
if ((read_options_.iterate_upper_bound != nullptr) &&
cfd_->internal_comparator().user_comparator()->Compare(
l0->smallest.user_key(), *read_options_.iterate_upper_bound) > 0) {
// No need to set has_iter_trimmed_for_upper_bound_: this ForwardIterator
// will never be interested in files with smallest key above
// iterate_upper_bound, since iterate_upper_bound can't be changed.
l0_iters_.push_back(nullptr);
continue;
}
l0_iters_.push_back(cfd_->table_cache()->NewIterator(
read_options_, *cfd_->soptions(), cfd_->internal_comparator(), *l0,
read_options_.ignore_range_deletions ? nullptr : &range_del_agg,
sv_->mutable_cf_options.prefix_extractor.get(),
/*table_reader_ptr=*/nullptr, /*file_read_hist=*/nullptr,
TableReaderCaller::kUserIterator, /*arena=*/nullptr,
/*skip_filters=*/false, /*level=*/-1,
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr,
allow_unprepared_value_));
}
BuildLevelIterators(vstorage);
current_ = nullptr;
is_prev_set_ = false;
UpdateChildrenPinnedItersMgr();
if (!range_del_agg.IsEmpty()) {
status_ = Status::NotSupported(
"Range tombstones unsupported with ForwardIterator");
valid_ = false;
}
}
void ForwardIterator::RenewIterators() {
SuperVersion* svnew;
assert(sv_);
svnew = cfd_->GetReferencedSuperVersion(db_);
if (mutable_iter_ != nullptr) {
DeleteIterator(mutable_iter_, true /* is_arena */);
}
for (auto* m : imm_iters_) {
DeleteIterator(m, true /* is_arena */);
}
imm_iters_.clear();
mutable_iter_ = svnew->mem->NewIterator(read_options_, &arena_);
svnew->imm->AddIterators(read_options_, &imm_iters_, &arena_);
ReadRangeDelAggregator range_del_agg(&cfd_->internal_comparator(),
kMaxSequenceNumber /* upper_bound */);
if (!read_options_.ignore_range_deletions) {
std::unique_ptr<FragmentedRangeTombstoneIterator> range_del_iter(
svnew->mem->NewRangeTombstoneIterator(
read_options_, sv_->current->version_set()->LastSequence()));
range_del_agg.AddTombstones(std::move(range_del_iter));
svnew->imm->AddRangeTombstoneIterators(read_options_, &arena_,
&range_del_agg);
}
const auto* vstorage = sv_->current->storage_info();
const auto& l0_files = vstorage->LevelFiles(0);
const auto* vstorage_new = svnew->current->storage_info();
const auto& l0_files_new = vstorage_new->LevelFiles(0);
size_t iold, inew;
bool found;
std::vector<InternalIterator*> l0_iters_new;
l0_iters_new.reserve(l0_files_new.size());
for (inew = 0; inew < l0_files_new.size(); inew++) {
found = false;
for (iold = 0; iold < l0_files.size(); iold++) {
if (l0_files[iold] == l0_files_new[inew]) {
found = true;
break;
}
}
if (found) {
if (l0_iters_[iold] == nullptr) {
l0_iters_new.push_back(nullptr);
TEST_SYNC_POINT_CALLBACK("ForwardIterator::RenewIterators:Null", this);
} else {
l0_iters_new.push_back(l0_iters_[iold]);
l0_iters_[iold] = nullptr;
TEST_SYNC_POINT_CALLBACK("ForwardIterator::RenewIterators:Copy", this);
}
continue;
}
l0_iters_new.push_back(cfd_->table_cache()->NewIterator(
read_options_, *cfd_->soptions(), cfd_->internal_comparator(),
*l0_files_new[inew],
read_options_.ignore_range_deletions ? nullptr : &range_del_agg,
svnew->mutable_cf_options.prefix_extractor.get(),
/*table_reader_ptr=*/nullptr, /*file_read_hist=*/nullptr,
TableReaderCaller::kUserIterator, /*arena=*/nullptr,
/*skip_filters=*/false, /*level=*/-1,
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr,
allow_unprepared_value_));
}
for (auto* f : l0_iters_) {
DeleteIterator(f);
}
l0_iters_.clear();
l0_iters_ = l0_iters_new;
for (auto* l : level_iters_) {
DeleteIterator(l);
}
level_iters_.clear();
BuildLevelIterators(vstorage_new);
current_ = nullptr;
is_prev_set_ = false;
SVCleanup();
sv_ = svnew;
UpdateChildrenPinnedItersMgr();
if (!range_del_agg.IsEmpty()) {
status_ = Status::NotSupported(
"Range tombstones unsupported with ForwardIterator");
valid_ = false;
}
}
void ForwardIterator::BuildLevelIterators(const VersionStorageInfo* vstorage) {
level_iters_.reserve(vstorage->num_levels() - 1);
for (int32_t level = 1; level < vstorage->num_levels(); ++level) {
const auto& level_files = vstorage->LevelFiles(level);
if ((level_files.empty()) ||
((read_options_.iterate_upper_bound != nullptr) &&
(user_comparator_->Compare(*read_options_.iterate_upper_bound,
level_files[0]->smallest.user_key()) <
0))) {
level_iters_.push_back(nullptr);
if (!level_files.empty()) {
has_iter_trimmed_for_upper_bound_ = true;
}
} else {
level_iters_.push_back(new ForwardLevelIterator(
cfd_, read_options_, level_files,
sv_->mutable_cf_options.prefix_extractor.get(),
allow_unprepared_value_));
}
}
}
void ForwardIterator::ResetIncompleteIterators() {
const auto& l0_files = sv_->current->storage_info()->LevelFiles(0);
for (size_t i = 0; i < l0_iters_.size(); ++i) {
assert(i < l0_files.size());
if (!l0_iters_[i] || !l0_iters_[i]->status().IsIncomplete()) {
continue;
}
DeleteIterator(l0_iters_[i]);
l0_iters_[i] = cfd_->table_cache()->NewIterator(
read_options_, *cfd_->soptions(), cfd_->internal_comparator(),
*l0_files[i], /*range_del_agg=*/nullptr,
sv_->mutable_cf_options.prefix_extractor.get(),
/*table_reader_ptr=*/nullptr, /*file_read_hist=*/nullptr,
TableReaderCaller::kUserIterator, /*arena=*/nullptr,
/*skip_filters=*/false, /*level=*/-1,
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr,
allow_unprepared_value_);
l0_iters_[i]->SetPinnedItersMgr(pinned_iters_mgr_);
}
for (auto* level_iter : level_iters_) {
if (level_iter && level_iter->status().IsIncomplete()) {
level_iter->Reset();
}
}
current_ = nullptr;
is_prev_set_ = false;
}
void ForwardIterator::UpdateCurrent() {
if (immutable_min_heap_.empty() && !mutable_iter_->Valid()) {
current_ = nullptr;
} else if (immutable_min_heap_.empty()) {
current_ = mutable_iter_;
} else if (!mutable_iter_->Valid()) {
current_ = immutable_min_heap_.top();
immutable_min_heap_.pop();
} else {
current_ = immutable_min_heap_.top();
assert(current_ != nullptr);
assert(current_->Valid());
int cmp = cfd_->internal_comparator().InternalKeyComparator::Compare(
mutable_iter_->key(), current_->key());
assert(cmp != 0);
if (cmp > 0) {
immutable_min_heap_.pop();
} else {
current_ = mutable_iter_;
}
}
valid_ = current_ != nullptr && immutable_status_.ok();
if (!status_.ok()) {
status_ = Status::OK();
}
// Upper bound doesn't apply to the memtable iterator. We want Valid() to
// return false when all iterators are over iterate_upper_bound, but can't
// just set valid_ to false, as that would effectively disable the tailing
// optimization (Seek() would be called on all immutable iterators regardless
// of whether the target key is greater than prev_key_).
current_over_upper_bound_ = valid_ && IsOverUpperBound(current_->key());
}
bool ForwardIterator::NeedToSeekImmutable(const Slice& target) {
// We maintain the interval (prev_key_, immutable_min_heap_.top()->key())
// such that there are no records with keys within that range in
// immutable_min_heap_. Since immutable structures (SST files and immutable
// memtables) can't change in this version, we don't need to do a seek if
// 'target' belongs to that interval (immutable_min_heap_.top() is already
// at the correct position).
if (!valid_ || !current_ || !is_prev_set_ || !immutable_status_.ok()) {
return true;
}
Slice prev_key = prev_key_.GetInternalKey();
if (prefix_extractor_ && prefix_extractor_->Transform(target).compare(
prefix_extractor_->Transform(prev_key)) != 0) {
return true;
}
if (cfd_->internal_comparator().InternalKeyComparator::Compare(
prev_key, target) >= (is_prev_inclusive_ ? 1 : 0)) {
return true;
}
if (immutable_min_heap_.empty() && current_ == mutable_iter_) {
// Nothing to seek on.
return false;
}
if (cfd_->internal_comparator().InternalKeyComparator::Compare(
target, current_ == mutable_iter_ ? immutable_min_heap_.top()->key()
: current_->key()) > 0) {
return true;
}
return false;
}
void ForwardIterator::DeleteCurrentIter() {
const VersionStorageInfo* vstorage = sv_->current->storage_info();
const std::vector<FileMetaData*>& l0 = vstorage->LevelFiles(0);
for (size_t i = 0; i < l0.size(); ++i) {
if (!l0_iters_[i]) {
continue;
}
if (l0_iters_[i] == current_) {
has_iter_trimmed_for_upper_bound_ = true;
DeleteIterator(l0_iters_[i]);
l0_iters_[i] = nullptr;
return;
}
}
for (int32_t level = 1; level < vstorage->num_levels(); ++level) {
if (level_iters_[level - 1] == nullptr) {
continue;
}
if (level_iters_[level - 1] == current_) {
has_iter_trimmed_for_upper_bound_ = true;
DeleteIterator(level_iters_[level - 1]);
level_iters_[level - 1] = nullptr;
}
}
}
bool ForwardIterator::TEST_CheckDeletedIters(int* pdeleted_iters,
int* pnum_iters) {
bool retval = false;
int deleted_iters = 0;
int num_iters = 0;
const VersionStorageInfo* vstorage = sv_->current->storage_info();
const std::vector<FileMetaData*>& l0 = vstorage->LevelFiles(0);
for (size_t i = 0; i < l0.size(); ++i) {
if (!l0_iters_[i]) {
retval = true;
deleted_iters++;
} else {
num_iters++;
}
}
for (int32_t level = 1; level < vstorage->num_levels(); ++level) {
if ((level_iters_[level - 1] == nullptr) &&
(!vstorage->LevelFiles(level).empty())) {
retval = true;
deleted_iters++;
} else if (!vstorage->LevelFiles(level).empty()) {
num_iters++;
}
}
if ((!retval) && num_iters <= 1) {
retval = true;
}
if (pdeleted_iters) {
*pdeleted_iters = deleted_iters;
}
if (pnum_iters) {
*pnum_iters = num_iters;
}
return retval;
}
uint32_t ForwardIterator::FindFileInRange(
const std::vector<FileMetaData*>& files, const Slice& internal_key,
uint32_t left, uint32_t right) {
auto cmp = [&](const FileMetaData* f, const Slice& key) -> bool {
return cfd_->internal_comparator().InternalKeyComparator::Compare(
f->largest.Encode(), key) < 0;
};
const auto &b = files.begin();
return static_cast<uint32_t>(std::lower_bound(b + left,
b + right, internal_key, cmp) - b);
}
void ForwardIterator::DeleteIterator(InternalIterator* iter, bool is_arena) {
if (iter == nullptr) {
return;
}
if (pinned_iters_mgr_ && pinned_iters_mgr_->PinningEnabled()) {
pinned_iters_mgr_->PinIterator(iter, is_arena);
} else {
if (is_arena) {
iter->~InternalIterator();
} else {
delete iter;
}
}
}
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE
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