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rocksdb/db/forward_iterator.cc
Venkatesh Radhakrishnan 4d28a7d8ab Add a whitebox test for deleted file iterators. 
Summary:
We have earlier added a feature to delete file iterators when the
current key is over the iterate upper bound. We now add a whitebox test
to check if the file iterators were actually deleted.

Test Plan: Add check for a range which has deleted iterators.

Reviewers: sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D45321
2015-08-25 13:40:58 -07:00

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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
#ifndef ROCKSDB_LITE
#include "db/forward_iterator.h"
#include <limits>
#include <string>
#include <utility>
#include "db/job_context.h"
#include "db/db_impl.h"
#include "db/db_iter.h"
#include "db/column_family.h"
#include "rocksdb/env.h"
#include "rocksdb/slice.h"
#include "rocksdb/slice_transform.h"
#include "table/merger.h"
#include "db/dbformat.h"
#include "util/sync_point.h"
namespace rocksdb {
// Usage:
// LevelIterator iter;
// iter.SetFileIndex(file_index);
// iter.Seek(target);
// iter.Next()
class LevelIterator : public Iterator {
public:
LevelIterator(const ColumnFamilyData* const cfd,
const ReadOptions& read_options,
const std::vector<FileMetaData*>& files)
: cfd_(cfd), read_options_(read_options), files_(files), valid_(false),
file_index_(std::numeric_limits<uint32_t>::max()) {}
void SetFileIndex(uint32_t file_index) {
assert(file_index < files_.size());
if (file_index != file_index_) {
file_index_ = file_index;
Reset();
}
valid_ = false;
}
void Reset() {
assert(file_index_ < files_.size());
file_iter_.reset(cfd_->table_cache()->NewIterator(
read_options_, *(cfd_->soptions()), cfd_->internal_comparator(),
files_[file_index_]->fd, nullptr /* table_reader_ptr */, nullptr,
false));
}
void SeekToLast() override {
status_ = Status::NotSupported("LevelIterator::SeekToLast()");
valid_ = false;
}
void Prev() override {
status_ = Status::NotSupported("LevelIterator::Prev()");
valid_ = false;
}
bool Valid() const override {
return valid_;
}
void SeekToFirst() override {
SetFileIndex(0);
file_iter_->SeekToFirst();
valid_ = file_iter_->Valid();
}
void Seek(const Slice& internal_key) override {
assert(file_iter_ != nullptr);
file_iter_->Seek(internal_key);
valid_ = file_iter_->Valid();
}
void Next() override {
assert(valid_);
file_iter_->Next();
for (;;) {
if (file_iter_->status().IsIncomplete() || file_iter_->Valid()) {
valid_ = !file_iter_->status().IsIncomplete();
return;
}
if (file_index_ + 1 >= files_.size()) {
valid_ = false;
return;
}
SetFileIndex(file_index_ + 1);
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_ && !file_iter_->status().ok()) {
return file_iter_->status();
}
return Status::OK();
}
private:
const ColumnFamilyData* const cfd_;
const ReadOptions& read_options_;
const std::vector<FileMetaData*>& files_;
bool valid_;
uint32_t file_index_;
Status status_;
std::unique_ptr<Iterator> file_iter_;
};
ForwardIterator::ForwardIterator(DBImpl* db, const ReadOptions& read_options,
ColumnFamilyData* cfd,
SuperVersion* current_sv)
: db_(db),
read_options_(read_options),
cfd_(cfd),
prefix_extractor_(cfd->ioptions()->prefix_extractor),
user_comparator_(cfd->user_comparator()),
immutable_min_heap_(MinIterComparator(&cfd_->internal_comparator())),
sv_(current_sv),
mutable_iter_(nullptr),
current_(nullptr),
status_(Status::OK()),
immutable_status_(Status::OK()),
valid_(false),
has_iter_trimmed_for_upper_bound_(false),
is_prev_set_(false),
is_prev_inclusive_(false) {
if (sv_) {
RebuildIterators(false);
}
}
ForwardIterator::~ForwardIterator() {
Cleanup(true);
}
void ForwardIterator::Cleanup(bool release_sv) {
if (mutable_iter_ != nullptr) {
mutable_iter_->~Iterator();
}
for (auto* m : imm_iters_) {
m->~Iterator();
}
imm_iters_.clear();
for (auto* f : l0_iters_) {
delete f;
}
l0_iters_.clear();
for (auto* l : level_iters_) {
delete l;
}
level_iters_.clear();
if (release_sv) {
if (sv_ != nullptr && 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);
db_->mutex_.Unlock();
delete sv_;
if (job_context.HaveSomethingToDelete()) {
db_->PurgeObsoleteFiles(job_context);
}
job_context.Clean();
}
}
}
bool ForwardIterator::Valid() const {
return valid_;
}
void ForwardIterator::SeekToFirst() {
if (sv_ == nullptr ||
sv_ ->version_number != cfd_->GetSuperVersionNumber()) {
RebuildIterators(true);
} 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 (IsOverUpperBound(internal_key)) {
valid_ = false;
}
if (sv_ == nullptr ||
sv_ ->version_number != cfd_->GetSuperVersionNumber()) {
RebuildIterators(true);
} 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 (NeedToRebuildTrimmed(internal_key)) {
// 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];
if (!m) {
continue;
}
seek_to_first ? m->SeekToFirst() : m->Seek(internal_key);
if (!m->status().ok()) {
immutable_status_ = m->status();
} else if (m->Valid()) {
if (!IsOverUpperBound(m->key())) {
immutable_min_heap_.push(m);
} else {
has_iter_trimmed_for_upper_bound_ = true;
delete m;
imm_iters_[i] = nullptr;
}
}
}
Slice user_key;
if (!seek_to_first) {
user_key = ExtractUserKey(internal_key);
}
const VersionStorageInfo* vstorage = sv_->current->storage_info();
const std::vector<FileMetaData*>& l0 = vstorage->LevelFiles(0);
for (uint32_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(user_key,
l0[i]->largest.user_key()) > 0) {
if (read_options_.iterate_upper_bound != nullptr) {
has_iter_trimmed_for_upper_bound_ = true;
delete 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()) {
if (!IsOverUpperBound(l0_iters_[i]->key())) {
immutable_min_heap_.push(l0_iters_[i]);
} else {
has_iter_trimmed_for_upper_bound_ = true;
delete l0_iters_[i];
l0_iters_[i] = nullptr;
}
}
}
int32_t search_left_bound = 0;
int32_t search_right_bound = FileIndexer::kLevelMaxIndex;
for (int32_t level = 1; level < vstorage->num_levels(); ++level) {
const std::vector<FileMetaData*>& level_files =
vstorage->LevelFiles(level);
if (level_files.empty()) {
search_left_bound = 0;
search_right_bound = FileIndexer::kLevelMaxIndex;
continue;
}
if (level_iters_[level - 1] == nullptr) {
continue;
}
uint32_t f_idx = 0;
const auto& indexer = vstorage->file_indexer();
if (!seek_to_first) {
if (search_left_bound == search_right_bound) {
f_idx = search_left_bound;
} else if (search_left_bound < search_right_bound) {
f_idx =
FindFileInRange(level_files, internal_key, search_left_bound,
search_right_bound == FileIndexer::kLevelMaxIndex
? static_cast<uint32_t>(level_files.size())
: search_right_bound);
} else {
// search_left_bound > search_right_bound
// There are only 2 cases this can happen:
// (1) target key is smaller than left most file
// (2) target key is larger than right most file
assert(search_left_bound == (int32_t)level_files.size() ||
search_right_bound == -1);
if (search_right_bound == -1) {
assert(search_left_bound == 0);
f_idx = 0;
} else {
indexer.GetNextLevelIndex(
level, level_files.size() - 1,
1, 1, &search_left_bound, &search_right_bound);
continue;
}
}
// Prepare hints for the next level
if (f_idx < level_files.size()) {
int cmp_smallest = user_comparator_->Compare(
user_key, level_files[f_idx]->smallest.user_key());
int cmp_largest = -1;
if (cmp_smallest >= 0) {
cmp_smallest = user_comparator_->Compare(
user_key, level_files[f_idx]->smallest.user_key());
}
indexer.GetNextLevelIndex(level, f_idx,
cmp_smallest, cmp_largest,
&search_left_bound, &search_right_bound);
} else {
indexer.GetNextLevelIndex(
level, level_files.size() - 1,
1, 1, &search_left_bound, &search_right_bound);
}
}
// 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()) {
if (!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;
delete level_iters_[level - 1];
level_iters_[level - 1] = nullptr;
}
}
}
}
if (seek_to_first) {
is_prev_set_ = false;
} else {
prev_key_.SetKey(internal_key);
is_prev_set_ = true;
is_prev_inclusive_ = true;
}
} 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());
RebuildIterators(true);
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_.GetKey()).compare(
prefix_extractor_->Transform(current_->key())) == 0;
} else {
update_prev_key = true;
}
if (update_prev_key) {
prev_key_.SetKey(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 ((!mutable_iter_->Valid()) && update_prev_key) {
mutable_iter_->Seek(prev_key_.GetKey());
}
}
}
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_;
}
void ForwardIterator::RebuildIterators(bool refresh_sv) {
// Clean up
Cleanup(refresh_sv);
if (refresh_sv) {
// New
sv_ = cfd_->GetReferencedSuperVersion(&(db_->mutex_));
}
mutable_iter_ = sv_->mem->NewIterator(read_options_, &arena_);
sv_->imm->AddIterators(read_options_, &imm_iters_, &arena_);
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) {
has_iter_trimmed_for_upper_bound_ = true;
l0_iters_.push_back(nullptr);
continue;
}
l0_iters_.push_back(cfd_->table_cache()->NewIterator(
read_options_, *cfd_->soptions(), cfd_->internal_comparator(), l0->fd));
}
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 LevelIterator(cfd_, read_options_, level_files));
}
}
current_ = nullptr;
is_prev_set_ = false;
}
void ForwardIterator::ResetIncompleteIterators() {
const auto& l0_files = sv_->current->storage_info()->LevelFiles(0);
for (uint32_t i = 0; i < l0_iters_.size(); ++i) {
assert(i < l0_files.size());
if (!l0_iters_[i] || !l0_iters_[i]->status().IsIncomplete()) {
continue;
}
delete l0_iters_[i];
l0_iters_[i] = cfd_->table_cache()->NewIterator(
read_options_, *cfd_->soptions(), cfd_->internal_comparator(),
l0_files[i]->fd);
}
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);
if (!status_.ok()) {
status_ = Status::OK();
}
if (valid_ && IsOverUpperBound(current_->key())) {
valid_ = false;
current_ = nullptr;
}
}
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_.GetKey();
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;
}
bool ForwardIterator::NeedToRebuildTrimmed(const Slice& target) {
if (!has_iter_trimmed_for_upper_bound_) {
return false;
}
if (!valid_ || !current_ || !is_prev_set_ || !immutable_status_.ok()) {
return true;
}
Slice prev_key = prev_key_.GetKey();
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;
}
return false;
}
void ForwardIterator::DeleteCurrentIter() {
for (size_t i = 0; i < imm_iters_.size(); i++) {
auto& m = imm_iters_[i];
if (!m) {
continue;
}
if (m == current_) {
has_iter_trimmed_for_upper_bound_ = true;
delete m;
m = nullptr;
return;
}
}
const VersionStorageInfo* vstorage = sv_->current->storage_info();
const std::vector<FileMetaData*>& l0 = vstorage->LevelFiles(0);
for (uint32_t i = 0; i < l0.size(); ++i) {
if (!l0_iters_[i]) {
continue;
}
if (l0_iters_[i] == current_) {
has_iter_trimmed_for_upper_bound_ = true;
delete 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;
delete level_iters_[level - 1];
level_iters_[level - 1] = nullptr;
}
}
}
bool ForwardIterator::TEST_CheckDeletedIters() {
if (!has_iter_trimmed_for_upper_bound_) {
return false;
}
for (size_t i = 0; i < imm_iters_.size(); i++) {
auto& m = imm_iters_[i];
if (!m) {
return true;
}
}
const VersionStorageInfo* vstorage = sv_->current->storage_info();
const std::vector<FileMetaData*>& l0 = vstorage->LevelFiles(0);
for (uint32_t i = 0; i < l0.size(); ++i) {
if (!l0_iters_[i]) {
return true;
}
}
for (int32_t level = 1; level < vstorage->num_levels(); ++level) {
if ((level_iters_[level - 1] == nullptr) &&
(!vstorage->LevelFiles(level).empty())) {
return true;
}
}
return false;
}
uint32_t ForwardIterator::FindFileInRange(
const std::vector<FileMetaData*>& files, const Slice& internal_key,
uint32_t left, uint32_t right) {
while (left < right) {
uint32_t mid = (left + right) / 2;
const FileMetaData* f = files[mid];
if (cfd_->internal_comparator().InternalKeyComparator::Compare(
f->largest.Encode(), internal_key) < 0) {
// Key at "mid.largest" is < "target". Therefore all
// files at or before "mid" are uninteresting.
left = mid + 1;
} else {
// Key at "mid.largest" is >= "target". Therefore all files
// after "mid" are uninteresting.
right = mid;
}
}
return right;
}
} // namespace rocksdb
#endif // ROCKSDB_LITE
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