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rocksdb/db/db_iter.cc
Islam AbdelRahman ff4b3fb5b4 Fix Iterator::Prev memory pinning bug 
Summary: We should not use IterKey::SetKey with copy = false except if we are pinning the iterator thru it's life time, otherwise we may release the temporarily pinned blocks and in this case the IterKey will be pointing to freed memory

Test Plan: added a new test

Reviewers: sdong, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D57561
2016-05-03 16:50:01 -07:00

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// Copyright (c) 2011-present, 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.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "db/db_iter.h"
#include <stdexcept>
#include <deque>
#include <string>
#include <limits>
#include "db/dbformat.h"
#include "db/filename.h"
#include "db/merge_context.h"
#include "db/pinned_iterators_manager.h"
#include "port/port.h"
#include "rocksdb/env.h"
#include "rocksdb/iterator.h"
#include "rocksdb/merge_operator.h"
#include "rocksdb/options.h"
#include "table/internal_iterator.h"
#include "util/arena.h"
#include "util/logging.h"
#include "util/mutexlock.h"
#include "util/perf_context_imp.h"
#include "util/string_util.h"
namespace rocksdb {
#if 0
static void DumpInternalIter(Iterator* iter) {
for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
ParsedInternalKey k;
if (!ParseInternalKey(iter->key(), &k)) {
fprintf(stderr, "Corrupt '%s'\n", EscapeString(iter->key()).c_str());
} else {
fprintf(stderr, "@ '%s'\n", k.DebugString().c_str());
}
}
}
#endif
// Memtables and sstables that make the DB representation contain
// (userkey,seq,type) => uservalue entries. DBIter
// combines multiple entries for the same userkey found in the DB
// representation into a single entry while accounting for sequence
// numbers, deletion markers, overwrites, etc.
class DBIter: public Iterator {
public:
// The following is grossly complicated. TODO: clean it up
// Which direction is the iterator currently moving?
// (1) When moving forward, the internal iterator is positioned at
// the exact entry that yields this->key(), this->value()
// (2) When moving backwards, the internal iterator is positioned
// just before all entries whose user key == this->key().
enum Direction {
kForward,
kReverse
};
// LocalStatistics contain Statistics counters that will be aggregated per
// each iterator instance and then will be sent to the global statistics when
// the iterator is destroyed.
//
// The purpose of this approach is to avoid perf regression happening
// when multiple threads bump the atomic counters from a DBIter::Next().
struct LocalStatistics {
explicit LocalStatistics() { ResetCounters(); }
void ResetCounters() {
next_count_ = 0;
next_found_count_ = 0;
prev_count_ = 0;
prev_found_count_ = 0;
bytes_read_ = 0;
}
void BumpGlobalStatistics(Statistics* global_statistics) {
RecordTick(global_statistics, NUMBER_DB_NEXT, next_count_);
RecordTick(global_statistics, NUMBER_DB_NEXT_FOUND, next_found_count_);
RecordTick(global_statistics, NUMBER_DB_PREV, prev_count_);
RecordTick(global_statistics, NUMBER_DB_PREV_FOUND, prev_found_count_);
RecordTick(global_statistics, ITER_BYTES_READ, bytes_read_);
ResetCounters();
}
// Map to Tickers::NUMBER_DB_NEXT
uint64_t next_count_;
// Map to Tickers::NUMBER_DB_NEXT_FOUND
uint64_t next_found_count_;
// Map to Tickers::NUMBER_DB_PREV
uint64_t prev_count_;
// Map to Tickers::NUMBER_DB_PREV_FOUND
uint64_t prev_found_count_;
// Map to Tickers::ITER_BYTES_READ
uint64_t bytes_read_;
};
DBIter(Env* env, const ImmutableCFOptions& ioptions, const Comparator* cmp,
InternalIterator* iter, SequenceNumber s, bool arena_mode,
uint64_t max_sequential_skip_in_iterations, uint64_t version_number,
const Slice* iterate_upper_bound = nullptr,
bool prefix_same_as_start = false, bool pin_data = false)
: arena_mode_(arena_mode),
env_(env),
logger_(ioptions.info_log),
user_comparator_(cmp),
user_merge_operator_(ioptions.merge_operator),
iter_(iter),
sequence_(s),
direction_(kForward),
valid_(false),
current_entry_is_merged_(false),
statistics_(ioptions.statistics),
version_number_(version_number),
iterate_upper_bound_(iterate_upper_bound),
prefix_same_as_start_(prefix_same_as_start),
pin_thru_lifetime_(pin_data) {
RecordTick(statistics_, NO_ITERATORS);
prefix_extractor_ = ioptions.prefix_extractor;
max_skip_ = max_sequential_skip_in_iterations;
if (pin_thru_lifetime_) {
pinned_iters_mgr_.StartPinning();
}
if (iter_) {
iter_->SetPinnedItersMgr(&pinned_iters_mgr_);
}
}
virtual ~DBIter() {
// Release pinned data if any
pinned_iters_mgr_.ReleasePinnedIterators();
RecordTick(statistics_, NO_ITERATORS, -1);
local_stats_.BumpGlobalStatistics(statistics_);
if (!arena_mode_) {
delete iter_;
} else {
iter_->~InternalIterator();
}
}
virtual void SetIter(InternalIterator* iter) {
assert(iter_ == nullptr);
iter_ = iter;
iter_->SetPinnedItersMgr(&pinned_iters_mgr_);
}
virtual bool Valid() const override { return valid_; }
virtual Slice key() const override {
assert(valid_);
return saved_key_.GetKey();
}
virtual Slice value() const override {
assert(valid_);
if (current_entry_is_merged_) {
return saved_value_;
} else if (direction_ == kReverse) {
return pinned_value_;
} else {
return iter_->value();
}
}
virtual Status status() const override {
if (status_.ok()) {
return iter_->status();
} else {
return status_;
}
}
virtual Status GetProperty(std::string prop_name,
std::string* prop) override {
if (prop == nullptr) {
return Status::InvalidArgument("prop is nullptr");
}
if (prop_name == "rocksdb.iterator.super-version-number") {
// First try to pass the value returned from inner iterator.
if (!iter_->GetProperty(prop_name, prop).ok()) {
*prop = ToString(version_number_);
}
return Status::OK();
} else if (prop_name == "rocksdb.iterator.is-key-pinned") {
if (valid_) {
*prop = (pin_thru_lifetime_ && saved_key_.IsKeyPinned()) ? "1" : "0";
} else {
*prop = "Iterator is not valid.";
}
return Status::OK();
}
return Status::InvalidArgument("Undentified property.");
}
virtual void Next() override;
virtual void Prev() override;
virtual void Seek(const Slice& target) override;
virtual void SeekToFirst() override;
virtual void SeekToLast() override;
private:
void ReverseToBackward();
void PrevInternal();
void FindParseableKey(ParsedInternalKey* ikey, Direction direction);
bool FindValueForCurrentKey();
bool FindValueForCurrentKeyUsingSeek();
void FindPrevUserKey();
void FindNextUserKey();
inline void FindNextUserEntry(bool skipping, bool prefix_check);
void FindNextUserEntryInternal(bool skipping, bool prefix_check);
bool ParseKey(ParsedInternalKey* key);
void MergeValuesNewToOld();
// Temporarily pin the blocks that we encounter until ReleaseTempPinnedData()
// is called
void TempPinData() {
if (!pin_thru_lifetime_) {
pinned_iters_mgr_.StartPinning();
}
}
// Release blocks pinned by TempPinData()
void ReleaseTempPinnedData() {
if (!pin_thru_lifetime_) {
pinned_iters_mgr_.ReleasePinnedIterators();
}
}
inline void ClearSavedValue() {
if (saved_value_.capacity() > 1048576) {
std::string empty;
swap(empty, saved_value_);
} else {
saved_value_.clear();
}
}
const SliceTransform* prefix_extractor_;
bool arena_mode_;
Env* const env_;
Logger* logger_;
const Comparator* const user_comparator_;
const MergeOperator* const user_merge_operator_;
InternalIterator* iter_;
SequenceNumber const sequence_;
Status status_;
IterKey saved_key_;
std::string saved_value_;
Slice pinned_value_;
Direction direction_;
bool valid_;
bool current_entry_is_merged_;
Statistics* statistics_;
uint64_t max_skip_;
uint64_t version_number_;
const Slice* iterate_upper_bound_;
IterKey prefix_start_buf_;
Slice prefix_start_key_;
const bool prefix_same_as_start_;
// Means that we will pin all data blocks we read as long the Iterator
// is not deleted, will be true if ReadOptions::pin_data is true
const bool pin_thru_lifetime_;
// List of operands for merge operator.
MergeContext merge_context_;
LocalStatistics local_stats_;
PinnedIteratorsManager pinned_iters_mgr_;
// No copying allowed
DBIter(const DBIter&);
void operator=(const DBIter&);
};
inline bool DBIter::ParseKey(ParsedInternalKey* ikey) {
if (!ParseInternalKey(iter_->key(), ikey)) {
status_ = Status::Corruption("corrupted internal key in DBIter");
Log(InfoLogLevel::ERROR_LEVEL,
logger_, "corrupted internal key in DBIter: %s",
iter_->key().ToString(true).c_str());
return false;
} else {
return true;
}
}
void DBIter::Next() {
assert(valid_);
if (direction_ == kReverse) {
// We only pin blocks when doing kReverse
ReleaseTempPinnedData();
FindNextUserKey();
direction_ = kForward;
if (!iter_->Valid()) {
iter_->SeekToFirst();
}
} else if (iter_->Valid() && !current_entry_is_merged_) {
// If the current value is not a merge, the iter position is the
// current key, which is already returned. We can safely issue a
// Next() without checking the current key.
// If the current key is a merge, very likely iter already points
// to the next internal position.
iter_->Next();
PERF_COUNTER_ADD(internal_key_skipped_count, 1);
}
if (statistics_ != nullptr) {
local_stats_.next_count_++;
}
// Now we point to the next internal position, for both of merge and
// not merge cases.
if (!iter_->Valid()) {
valid_ = false;
return;
}
FindNextUserEntry(true /* skipping the current user key */, prefix_same_as_start_);
if (statistics_ != nullptr && valid_) {
local_stats_.next_found_count_++;
local_stats_.bytes_read_ += (key().size() + value().size());
}
}
// PRE: saved_key_ has the current user key if skipping
// POST: saved_key_ should have the next user key if valid_,
// if the current entry is a result of merge
// current_entry_is_merged_ => true
// saved_value_ => the merged value
//
// NOTE: In between, saved_key_ can point to a user key that has
// a delete marker
//
// The prefix_check parameter controls whether we check the iterated
// keys against the prefix of the seeked key. Set to false when
// performing a seek without a key (e.g. SeekToFirst). Set to
// prefix_same_as_start_ for other iterations.
inline void DBIter::FindNextUserEntry(bool skipping, bool prefix_check) {
PERF_TIMER_GUARD(find_next_user_entry_time);
FindNextUserEntryInternal(skipping, prefix_check);
}
// Actual implementation of DBIter::FindNextUserEntry()
void DBIter::FindNextUserEntryInternal(bool skipping, bool prefix_check) {
// Loop until we hit an acceptable entry to yield
assert(iter_->Valid());
assert(direction_ == kForward);
current_entry_is_merged_ = false;
uint64_t num_skipped = 0;
do {
ParsedInternalKey ikey;
if (ParseKey(&ikey)) {
if (iterate_upper_bound_ != nullptr &&
user_comparator_->Compare(ikey.user_key, *iterate_upper_bound_) >= 0) {
break;
}
if (prefix_extractor_ && prefix_check &&
prefix_extractor_->Transform(ikey.user_key).compare(prefix_start_key_) != 0) {
break;
}
if (ikey.sequence <= sequence_) {
if (skipping &&
user_comparator_->Compare(ikey.user_key, saved_key_.GetKey()) <= 0) {
num_skipped++; // skip this entry
PERF_COUNTER_ADD(internal_key_skipped_count, 1);
} else {
switch (ikey.type) {
case kTypeDeletion:
case kTypeSingleDeletion:
// Arrange to skip all upcoming entries for this key since
// they are hidden by this deletion.
saved_key_.SetKey(
ikey.user_key,
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
skipping = true;
num_skipped = 0;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
break;
case kTypeValue:
valid_ = true;
saved_key_.SetKey(
ikey.user_key,
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
return;
case kTypeMerge:
// By now, we are sure the current ikey is going to yield a value
saved_key_.SetKey(
ikey.user_key,
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
current_entry_is_merged_ = true;
valid_ = true;
MergeValuesNewToOld(); // Go to a different state machine
return;
default:
assert(false);
break;
}
}
}
}
// If we have sequentially iterated via numerous keys and still not
// found the next user-key, then it is better to seek so that we can
// avoid too many key comparisons. We seek to the last occurrence of
// our current key by looking for sequence number 0 and type deletion
// (the smallest type).
if (skipping && num_skipped > max_skip_) {
num_skipped = 0;
std::string last_key;
AppendInternalKey(&last_key, ParsedInternalKey(saved_key_.GetKey(), 0,
kTypeDeletion));
iter_->Seek(last_key);
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
} else {
iter_->Next();
}
} while (iter_->Valid());
valid_ = false;
}
// Merge values of the same user key starting from the current iter_ position
// Scan from the newer entries to older entries.
// PRE: iter_->key() points to the first merge type entry
// saved_key_ stores the user key
// POST: saved_value_ has the merged value for the user key
// iter_ points to the next entry (or invalid)
void DBIter::MergeValuesNewToOld() {
if (!user_merge_operator_) {
Log(InfoLogLevel::ERROR_LEVEL,
logger_, "Options::merge_operator is null.");
status_ = Status::InvalidArgument("user_merge_operator_ must be set.");
valid_ = false;
return;
}
merge_context_.Clear();
// Start the merge process by pushing the first operand
merge_context_.PushOperand(iter_->value());
ParsedInternalKey ikey;
for (iter_->Next(); iter_->Valid(); iter_->Next()) {
if (!ParseKey(&ikey)) {
// skip corrupted key
continue;
}
if (!user_comparator_->Equal(ikey.user_key, saved_key_.GetKey())) {
// hit the next user key, stop right here
break;
} else if (kTypeDeletion == ikey.type || kTypeSingleDeletion == ikey.type) {
// hit a delete with the same user key, stop right here
// iter_ is positioned after delete
iter_->Next();
break;
} else if (kTypeValue == ikey.type) {
// hit a put, merge the put value with operands and store the
// final result in saved_value_. We are done!
// ignore corruption if there is any.
const Slice val = iter_->value();
{
StopWatchNano timer(env_, statistics_ != nullptr);
PERF_TIMER_GUARD(merge_operator_time_nanos);
user_merge_operator_->FullMerge(ikey.user_key, &val,
merge_context_.GetOperands(),
&saved_value_, logger_);
RecordTick(statistics_, MERGE_OPERATION_TOTAL_TIME,
timer.ElapsedNanos());
}
// iter_ is positioned after put
iter_->Next();
return;
} else if (kTypeMerge == ikey.type) {
// hit a merge, add the value as an operand and run associative merge.
// when complete, add result to operands and continue.
const Slice& val = iter_->value();
merge_context_.PushOperand(val);
} else {
assert(false);
}
}
{
StopWatchNano timer(env_, statistics_ != nullptr);
PERF_TIMER_GUARD(merge_operator_time_nanos);
// we either exhausted all internal keys under this user key, or hit
// a deletion marker.
// feed null as the existing value to the merge operator, such that
// client can differentiate this scenario and do things accordingly.
user_merge_operator_->FullMerge(saved_key_.GetKey(), nullptr,
merge_context_.GetOperands(), &saved_value_,
logger_);
RecordTick(statistics_, MERGE_OPERATION_TOTAL_TIME, timer.ElapsedNanos());
}
}
void DBIter::Prev() {
assert(valid_);
if (direction_ == kForward) {
ReverseToBackward();
}
ReleaseTempPinnedData();
PrevInternal();
if (statistics_ != nullptr) {
local_stats_.prev_count_++;
if (valid_) {
local_stats_.prev_found_count_++;
local_stats_.bytes_read_ += (key().size() + value().size());
}
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_ &&
prefix_extractor_->Transform(saved_key_.GetKey())
.compare(prefix_start_key_) != 0) {
valid_ = false;
}
}
void DBIter::ReverseToBackward() {
if (current_entry_is_merged_) {
// Not placed in the same key. Need to call Prev() until finding the
// previous key.
if (!iter_->Valid()) {
iter_->SeekToLast();
}
ParsedInternalKey ikey;
FindParseableKey(&ikey, kReverse);
while (iter_->Valid() &&
user_comparator_->Compare(ikey.user_key, saved_key_.GetKey()) > 0) {
iter_->Prev();
FindParseableKey(&ikey, kReverse);
}
}
#ifndef NDEBUG
if (iter_->Valid()) {
ParsedInternalKey ikey;
assert(ParseKey(&ikey));
assert(user_comparator_->Compare(ikey.user_key, saved_key_.GetKey()) <= 0);
}
#endif
FindPrevUserKey();
direction_ = kReverse;
}
void DBIter::PrevInternal() {
if (!iter_->Valid()) {
valid_ = false;
return;
}
ParsedInternalKey ikey;
while (iter_->Valid()) {
saved_key_.SetKey(ExtractUserKey(iter_->key()),
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
if (FindValueForCurrentKey()) {
valid_ = true;
if (!iter_->Valid()) {
return;
}
FindParseableKey(&ikey, kReverse);
if (user_comparator_->Equal(ikey.user_key, saved_key_.GetKey())) {
FindPrevUserKey();
}
return;
}
if (!iter_->Valid()) {
break;
}
FindParseableKey(&ikey, kReverse);
if (user_comparator_->Equal(ikey.user_key, saved_key_.GetKey())) {
FindPrevUserKey();
}
}
// We haven't found any key - iterator is not valid
assert(!iter_->Valid());
valid_ = false;
}
// This function checks, if the entry with biggest sequence_number <= sequence_
// is non kTypeDeletion or kTypeSingleDeletion. If it's not, we save value in
// saved_value_
bool DBIter::FindValueForCurrentKey() {
assert(iter_->Valid());
merge_context_.Clear();
current_entry_is_merged_ = false;
// last entry before merge (could be kTypeDeletion, kTypeSingleDeletion or
// kTypeValue)
ValueType last_not_merge_type = kTypeDeletion;
ValueType last_key_entry_type = kTypeDeletion;
ParsedInternalKey ikey;
FindParseableKey(&ikey, kReverse);
size_t num_skipped = 0;
while (iter_->Valid() && ikey.sequence <= sequence_ &&
user_comparator_->Equal(ikey.user_key, saved_key_.GetKey())) {
// We iterate too much: let's use Seek() to avoid too much key comparisons
if (num_skipped >= max_skip_) {
return FindValueForCurrentKeyUsingSeek();
}
last_key_entry_type = ikey.type;
switch (last_key_entry_type) {
case kTypeValue:
merge_context_.Clear();
ReleaseTempPinnedData();
TempPinData();
pinned_value_ = iter_->value();
last_not_merge_type = kTypeValue;
break;
case kTypeDeletion:
case kTypeSingleDeletion:
merge_context_.Clear();
last_not_merge_type = last_key_entry_type;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
break;
case kTypeMerge:
assert(user_merge_operator_ != nullptr);
merge_context_.PushOperandBack(iter_->value());
break;
default:
assert(false);
}
PERF_COUNTER_ADD(internal_key_skipped_count, 1);
assert(user_comparator_->Equal(ikey.user_key, saved_key_.GetKey()));
iter_->Prev();
++num_skipped;
FindParseableKey(&ikey, kReverse);
}
switch (last_key_entry_type) {
case kTypeDeletion:
case kTypeSingleDeletion:
valid_ = false;
return false;
case kTypeMerge:
current_entry_is_merged_ = true;
if (last_not_merge_type == kTypeDeletion) {
StopWatchNano timer(env_, statistics_ != nullptr);
PERF_TIMER_GUARD(merge_operator_time_nanos);
user_merge_operator_->FullMerge(saved_key_.GetKey(), nullptr,
merge_context_.GetOperands(),
&saved_value_, logger_);
RecordTick(statistics_, MERGE_OPERATION_TOTAL_TIME,
timer.ElapsedNanos());
} else {
assert(last_not_merge_type == kTypeValue);
{
StopWatchNano timer(env_, statistics_ != nullptr);
PERF_TIMER_GUARD(merge_operator_time_nanos);
user_merge_operator_->FullMerge(saved_key_.GetKey(), &pinned_value_,
merge_context_.GetOperands(),
&saved_value_, logger_);
RecordTick(statistics_, MERGE_OPERATION_TOTAL_TIME,
timer.ElapsedNanos());
}
}
break;
case kTypeValue:
// do nothing - we've already has value in saved_value_
break;
default:
assert(false);
break;
}
valid_ = true;
return true;
}
// This function is used in FindValueForCurrentKey.
// We use Seek() function instead of Prev() to find necessary value
bool DBIter::FindValueForCurrentKeyUsingSeek() {
std::string last_key;
AppendInternalKey(&last_key, ParsedInternalKey(saved_key_.GetKey(), sequence_,
kValueTypeForSeek));
iter_->Seek(last_key);
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
// assume there is at least one parseable key for this user key
ParsedInternalKey ikey;
FindParseableKey(&ikey, kForward);
if (ikey.type == kTypeValue || ikey.type == kTypeDeletion ||
ikey.type == kTypeSingleDeletion) {
if (ikey.type == kTypeValue) {
ReleaseTempPinnedData();
TempPinData();
pinned_value_ = iter_->value();
valid_ = true;
return true;
}
valid_ = false;
return false;
}
// kTypeMerge. We need to collect all kTypeMerge values and save them
// in operands
current_entry_is_merged_ = true;
merge_context_.Clear();
while (iter_->Valid() &&
user_comparator_->Equal(ikey.user_key, saved_key_.GetKey()) &&
ikey.type == kTypeMerge) {
merge_context_.PushOperand(iter_->value());
iter_->Next();
FindParseableKey(&ikey, kForward);
}
if (!iter_->Valid() ||
!user_comparator_->Equal(ikey.user_key, saved_key_.GetKey()) ||
ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion) {
{
StopWatchNano timer(env_, statistics_ != nullptr);
PERF_TIMER_GUARD(merge_operator_time_nanos);
user_merge_operator_->FullMerge(saved_key_.GetKey(), nullptr,
merge_context_.GetOperands(),
&saved_value_, logger_);
RecordTick(statistics_, MERGE_OPERATION_TOTAL_TIME, timer.ElapsedNanos());
}
// Make iter_ valid and point to saved_key_
if (!iter_->Valid() ||
!user_comparator_->Equal(ikey.user_key, saved_key_.GetKey())) {
iter_->Seek(last_key);
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
}
valid_ = true;
return true;
}
const Slice& val = iter_->value();
{
StopWatchNano timer(env_, statistics_ != nullptr);
PERF_TIMER_GUARD(merge_operator_time_nanos);
user_merge_operator_->FullMerge(saved_key_.GetKey(), &val,
merge_context_.GetOperands(), &saved_value_,
logger_);
RecordTick(statistics_, MERGE_OPERATION_TOTAL_TIME, timer.ElapsedNanos());
}
valid_ = true;
return true;
}
// Used in Next to change directions
// Go to next user key
// Don't use Seek(),
// because next user key will be very close
void DBIter::FindNextUserKey() {
if (!iter_->Valid()) {
return;
}
ParsedInternalKey ikey;
FindParseableKey(&ikey, kForward);
while (iter_->Valid() &&
!user_comparator_->Equal(ikey.user_key, saved_key_.GetKey())) {
iter_->Next();
FindParseableKey(&ikey, kForward);
}
}
// Go to previous user_key
void DBIter::FindPrevUserKey() {
if (!iter_->Valid()) {
return;
}
size_t num_skipped = 0;
ParsedInternalKey ikey;
FindParseableKey(&ikey, kReverse);
int cmp;
while (iter_->Valid() && ((cmp = user_comparator_->Compare(
ikey.user_key, saved_key_.GetKey())) == 0 ||
(cmp > 0 && ikey.sequence > sequence_))) {
if (cmp == 0) {
if (num_skipped >= max_skip_) {
num_skipped = 0;
IterKey last_key;
last_key.SetInternalKey(ParsedInternalKey(
saved_key_.GetKey(), kMaxSequenceNumber, kValueTypeForSeek));
iter_->Seek(last_key.GetKey());
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
} else {
++num_skipped;
}
}
iter_->Prev();
FindParseableKey(&ikey, kReverse);
}
}
// Skip all unparseable keys
void DBIter::FindParseableKey(ParsedInternalKey* ikey, Direction direction) {
while (iter_->Valid() && !ParseKey(ikey)) {
if (direction == kReverse) {
iter_->Prev();
} else {
iter_->Next();
}
}
}
void DBIter::Seek(const Slice& target) {
StopWatch sw(env_, statistics_, DB_SEEK);
ReleaseTempPinnedData();
saved_key_.Clear();
// now savved_key is used to store internal key.
saved_key_.SetInternalKey(target, sequence_);
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->Seek(saved_key_.GetKey());
}
RecordTick(statistics_, NUMBER_DB_SEEK);
if (iter_->Valid()) {
if (prefix_extractor_ && prefix_same_as_start_) {
prefix_start_key_ = prefix_extractor_->Transform(target);
}
direction_ = kForward;
ClearSavedValue();
FindNextUserEntry(false /* not skipping */, prefix_same_as_start_);
if (!valid_) {
prefix_start_key_.clear();
}
if (statistics_ != nullptr) {
if (valid_) {
RecordTick(statistics_, NUMBER_DB_SEEK_FOUND);
RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size());
}
}
} else {
valid_ = false;
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_) {
prefix_start_buf_.SetKey(prefix_start_key_);
prefix_start_key_ = prefix_start_buf_.GetKey();
}
}
void DBIter::SeekToFirst() {
// Don't use iter_::Seek() if we set a prefix extractor
// because prefix seek will be used.
if (prefix_extractor_ != nullptr) {
max_skip_ = std::numeric_limits<uint64_t>::max();
}
direction_ = kForward;
ReleaseTempPinnedData();
ClearSavedValue();
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->SeekToFirst();
}
RecordTick(statistics_, NUMBER_DB_SEEK);
if (iter_->Valid()) {
FindNextUserEntry(false /* not skipping */, false /* no prefix check */);
if (statistics_ != nullptr) {
if (valid_) {
RecordTick(statistics_, NUMBER_DB_SEEK_FOUND);
RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size());
}
}
} else {
valid_ = false;
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_) {
prefix_start_buf_.SetKey(prefix_extractor_->Transform(saved_key_.GetKey()));
prefix_start_key_ = prefix_start_buf_.GetKey();
}
}
void DBIter::SeekToLast() {
// Don't use iter_::Seek() if we set a prefix extractor
// because prefix seek will be used.
if (prefix_extractor_ != nullptr) {
max_skip_ = std::numeric_limits<uint64_t>::max();
}
direction_ = kReverse;
ReleaseTempPinnedData();
ClearSavedValue();
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->SeekToLast();
}
// When the iterate_upper_bound is set to a value,
// it will seek to the last key before the
// ReadOptions.iterate_upper_bound
if (iter_->Valid() && iterate_upper_bound_ != nullptr) {
saved_key_.SetKey(*iterate_upper_bound_, false /* copy */);
std::string last_key;
AppendInternalKey(&last_key,
ParsedInternalKey(saved_key_.GetKey(), kMaxSequenceNumber,
kValueTypeForSeek));
iter_->Seek(last_key);
if (!iter_->Valid()) {
iter_->SeekToLast();
} else {
iter_->Prev();
if (!iter_->Valid()) {
valid_ = false;
return;
}
}
}
PrevInternal();
if (statistics_ != nullptr) {
RecordTick(statistics_, NUMBER_DB_SEEK);
if (valid_) {
RecordTick(statistics_, NUMBER_DB_SEEK_FOUND);
RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size());
}
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_) {
prefix_start_buf_.SetKey(prefix_extractor_->Transform(saved_key_.GetKey()));
prefix_start_key_ = prefix_start_buf_.GetKey();
}
}
Iterator* NewDBIterator(Env* env, const ImmutableCFOptions& ioptions,
const Comparator* user_key_comparator,
InternalIterator* internal_iter,
const SequenceNumber& sequence,
uint64_t max_sequential_skip_in_iterations,
uint64_t version_number,
const Slice* iterate_upper_bound,
bool prefix_same_as_start, bool pin_data) {
DBIter* db_iter =
new DBIter(env, ioptions, user_key_comparator, internal_iter, sequence,
false, max_sequential_skip_in_iterations, version_number,
iterate_upper_bound, prefix_same_as_start, pin_data);
return db_iter;
}
ArenaWrappedDBIter::~ArenaWrappedDBIter() { db_iter_->~DBIter(); }
void ArenaWrappedDBIter::SetDBIter(DBIter* iter) { db_iter_ = iter; }
void ArenaWrappedDBIter::SetIterUnderDBIter(InternalIterator* iter) {
static_cast<DBIter*>(db_iter_)->SetIter(iter);
}
inline bool ArenaWrappedDBIter::Valid() const { return db_iter_->Valid(); }
inline void ArenaWrappedDBIter::SeekToFirst() { db_iter_->SeekToFirst(); }
inline void ArenaWrappedDBIter::SeekToLast() { db_iter_->SeekToLast(); }
inline void ArenaWrappedDBIter::Seek(const Slice& target) {
db_iter_->Seek(target);
}
inline void ArenaWrappedDBIter::Next() { db_iter_->Next(); }
inline void ArenaWrappedDBIter::Prev() { db_iter_->Prev(); }
inline Slice ArenaWrappedDBIter::key() const { return db_iter_->key(); }
inline Slice ArenaWrappedDBIter::value() const { return db_iter_->value(); }
inline Status ArenaWrappedDBIter::status() const { return db_iter_->status(); }
inline Status ArenaWrappedDBIter::GetProperty(std::string prop_name,
std::string* prop) {
return db_iter_->GetProperty(prop_name, prop);
}
void ArenaWrappedDBIter::RegisterCleanup(CleanupFunction function, void* arg1,
void* arg2) {
db_iter_->RegisterCleanup(function, arg1, arg2);
}
ArenaWrappedDBIter* NewArenaWrappedDbIterator(
Env* env, const ImmutableCFOptions& ioptions,
const Comparator* user_key_comparator, const SequenceNumber& sequence,
uint64_t max_sequential_skip_in_iterations, uint64_t version_number,
const Slice* iterate_upper_bound, bool prefix_same_as_start,
bool pin_data) {
ArenaWrappedDBIter* iter = new ArenaWrappedDBIter();
Arena* arena = iter->GetArena();
auto mem = arena->AllocateAligned(sizeof(DBIter));
DBIter* db_iter =
new (mem) DBIter(env, ioptions, user_key_comparator, nullptr, sequence,
true, max_sequential_skip_in_iterations, version_number,
iterate_upper_bound, prefix_same_as_start, pin_data);
iter->SetDBIter(db_iter);
return iter;
}
} // namespace rocksdb
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