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rocksdb/db/forward_iterator.cc
Peter Dillinger 54cb9c77d9 Prefer static_cast in place of most reinterpret_cast (#12308) 
Summary:
The following are risks associated with pointer-to-pointer reinterpret_cast:
* Can produce the "wrong result" (crash or memory corruption). IIRC, in theory this can happen for any up-cast or down-cast for a non-standard-layout type, though in practice would only happen for multiple inheritance cases (where the base class pointer might be "inside" the derived object). We don't use multiple inheritance a lot, but we do.
* Can mask useful compiler errors upon code change, including converting between unrelated pointer types that you are expecting to be related, and converting between pointer and scalar types unintentionally.

I can only think of some obscure cases where static_cast could be troublesome when it compiles as a replacement:
* Going through `void*` could plausibly cause unnecessary or broken pointer arithmetic. Suppose we have
`struct Derived: public Base1, public Base2`.  If we have `Derived*` -> `void*` -> `Base2*` -> `Derived*` through reinterpret casts, this could plausibly work (though technical UB) assuming the `Base2*` is not dereferenced. Changing to static cast could introduce breaking pointer arithmetic.
* Unnecessary (but safe) pointer arithmetic could arise in a case like `Derived*` -> `Base2*` -> `Derived*` where before the Base2 pointer might not have been dereferenced. This could potentially affect performance.

With some light scripting, I tried replacing pointer-to-pointer reinterpret_casts with static_cast and kept the cases that still compile. Most occurrences of reinterpret_cast have successfully been changed (except for java/ and third-party/). 294 changed, 257 remain.

A couple of related interventions included here:
* Previously Cache::Handle was not actually derived from in the implementations and just used as a `void*` stand-in with reinterpret_cast. Now there is a relationship to allow static_cast. In theory, this could introduce pointer arithmetic (as described above) but is unlikely without multiple inheritance AND non-empty Cache::Handle.
* Remove some unnecessary casts to void* as this is allowed to be implicit (for better or worse).

Most of the remaining reinterpret_casts are for converting to/from raw bytes of objects. We could consider better idioms for these patterns in follow-up work.

I wish there were a way to implement a template variant of static_cast that would only compile if no pointer arithmetic is generated, but best I can tell, this is not possible. AFAIK the best you could do is a dynamic check that the void* conversion after the static cast is unchanged.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/12308

Test Plan: existing tests, CI

Reviewed By: ltamasi

Differential Revision: D53204947

Pulled By: pdillinger

fbshipit-source-id: 9de23e618263b0d5b9820f4e15966876888a16e2
2024-02-07 10:44:11 -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/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 std::shared_ptr<const SliceTransform>& prefix_extractor,
bool allow_unprepared_value, uint8_t block_protection_bytes_per_key)
: 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),
block_protection_bytes_per_key_(block_protection_bytes_per_key) {
status_.PermitUncheckedError(); // Allow uninitialized status through
}
~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,
/*max_file_size_for_l0_meta_pin=*/0,
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr, allow_unprepared_value_,
block_protection_bytes_per_key_);
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_;
// Kept alive by ForwardIterator::sv_->mutable_cf_options
const std::shared_ptr<const SliceTransform>& prefix_extractor_;
const bool allow_unprepared_value_;
const uint8_t block_protection_bytes_per_key_;
};
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);
}
if (!CheckFSFeatureSupport(cfd_->ioptions()->env->GetFileSystem().get(),
FSSupportedOps::kAsyncIO)) {
read_options_.async_io = false;
}
// immutable_status_ is a local aggregation of the
// status of the immutable Iterators.
// We have to PermitUncheckedError in case it is never
// used, otherwise it will fail ASSERT_STATUS_CHECKED.
immutable_status_.PermitUncheckedError();
}
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;
};
} // anonymous namespace
// Used in PinnedIteratorsManager to release pinned SuperVersion
void ForwardIterator::DeferredSVCleanup(void* arg) {
auto d = static_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, false);
}
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, false);
if (read_options_.async_io) {
SeekInternal(internal_key, false, true);
}
}
// In case of async_io, SeekInternal is called twice with seek_after_async_io
// enabled in second call which only does seeking part to retrieve the blocks.
void ForwardIterator::SeekInternal(const Slice& internal_key,
bool seek_to_first,
bool seek_after_async_io) {
assert(mutable_iter_);
// mutable
if (!seek_after_async_io) {
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 || seek_after_async_io ||
NeedToSeekImmutable(internal_key)) {
if (!seek_after_async_io) {
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_after_async_io) {
if (!l0_iters_[i]->status().IsTryAgain()) {
continue;
}
}
if (seek_to_first) {
l0_iters_[i]->SeekToFirst();
} else {
// If the target key passes over the largest key, we are sure Next()
// won't go over this file.
if (seek_after_async_io == false &&
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().IsTryAgain()) {
assert(!seek_after_async_io);
continue;
} else 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;
}
if (seek_after_async_io) {
if (!level_iters_[level - 1]->status().IsTryAgain()) {
continue;
}
}
uint32_t f_idx = 0;
if (!seek_to_first && !seek_after_async_io) {
f_idx = FindFileInRange(level_files, internal_key, 0,
static_cast<uint32_t>(level_files.size()));
}
// Seek
if (seek_after_async_io || f_idx < level_files.size()) {
if (!seek_after_async_io) {
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().IsTryAgain()) {
assert(!seek_after_async_io);
continue;
} else 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_);
}
// For async_io, it should be updated when seek_after_async_io is true (in
// second call).
if (seek_to_first || !read_options_.async_io || seek_after_async_io) {
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, false);
if (read_options_.async_io) {
SeekInternal(old_key, false, true);
}
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 = std::to_string(sv_->version_number);
return Status::OK();
}
return Status::InvalidArgument("Unrecognized property: " + prop_name);
}
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(),
false /* immutable_memtable */));
range_del_agg.AddTombstones(std::move(range_del_iter));
// Always return Status::OK().
Status temp_s = sv_->imm->AddRangeTombstoneIterators(read_options_, &arena_,
&range_del_agg);
assert(temp_s.ok());
}
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,
/*table_reader_ptr=*/nullptr, /*file_read_hist=*/nullptr,
TableReaderCaller::kUserIterator, /*arena=*/nullptr,
/*skip_filters=*/false, /*level=*/-1,
MaxFileSizeForL0MetaPin(sv_->mutable_cf_options),
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr, allow_unprepared_value_,
sv_->mutable_cf_options.block_protection_bytes_per_key));
}
BuildLevelIterators(vstorage, sv_);
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(),
false /* immutable_memtable */));
range_del_agg.AddTombstones(std::move(range_del_iter));
// Always return Status::OK().
Status temp_s = svnew->imm->AddRangeTombstoneIterators(
read_options_, &arena_, &range_del_agg);
assert(temp_s.ok());
}
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,
/*table_reader_ptr=*/nullptr, /*file_read_hist=*/nullptr,
TableReaderCaller::kUserIterator, /*arena=*/nullptr,
/*skip_filters=*/false, /*level=*/-1,
MaxFileSizeForL0MetaPin(svnew->mutable_cf_options),
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr, allow_unprepared_value_,
svnew->mutable_cf_options.block_protection_bytes_per_key));
}
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, svnew);
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,
SuperVersion* sv) {
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, allow_unprepared_value_,
sv->mutable_cf_options.block_protection_bytes_per_key));
}
}
}
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,
/*table_reader_ptr=*/nullptr, /*file_read_hist=*/nullptr,
TableReaderCaller::kUserIterator, /*arena=*/nullptr,
/*skip_filters=*/false, /*level=*/-1,
MaxFileSizeForL0MetaPin(sv_->mutable_cf_options),
/*smallest_compaction_key=*/nullptr,
/*largest_compaction_key=*/nullptr, allow_unprepared_value_,
sv_->mutable_cf_options.block_protection_bytes_per_key);
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& k) -> bool {
return cfd_->internal_comparator().InternalKeyComparator::Compare(
f->largest.Encode(), k) < 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
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