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rocksdb/db/db_iter.cc
Mike Kolupaev 236d4c67e9 Less linear search in DBIter::Seek() when keys are overwritten a lot 
Summary:
In one deployment we saw high latencies (presumably from slow iterator operations) and a lot of CPU time reported by perf with this stack:

```
  rocksdb::MergingIterator::Next
  rocksdb::DBIter::FindNextUserEntryInternal
  rocksdb::DBIter::Seek
```

I think what's happening is:
1. we create a snapshot iterator,
2. we do lots of Put()s for the same key x; this creates lots of entries in memtable,
3. we seek the iterator to a key slightly smaller than x,
4. the seek walks over lots of entries in memtable for key x, skipping them because of high sequence numbers.

CC IslamAbdelRahman
Closes https://github.com/facebook/rocksdb/pull/1413

Differential Revision: D4083879

Pulled By: IslamAbdelRahman

fbshipit-source-id: a83ddae
2016-11-28 10:24:11 -08:00

1127 lines
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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/merge_helper.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,
bool total_order_seek = false)
: arena_mode_(arena_mode),
env_(env),
logger_(ioptions.info_log),
user_comparator_(cmp),
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),
total_order_seek_(total_order_seek),
range_del_agg_(ioptions.internal_comparator, s) {
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
if (pinned_iters_mgr_.PinningEnabled()) {
pinned_iters_mgr_.ReleasePinnedData();
}
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 RangeDelAggregator* GetRangeDelAggregator() {
return &range_del_agg_;
}
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_) {
// If pinned_value_ is set then the result of merge operator is one of
// the merge operands and we should return it.
return pinned_value_.data() ? pinned_value_ : 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 SeekForPrev(const Slice& target) override;
virtual void SeekToFirst() override;
virtual void SeekToLast() override;
private:
void ReverseToForward();
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_.PinningEnabled()) {
pinned_iters_mgr_.ReleasePinnedData();
}
}
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 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_;
// for prefix seek mode to support prev()
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_;
const bool total_order_seek_;
// List of operands for merge operator.
MergeContext merge_context_;
RangeDelAggregator range_del_agg_;
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_);
// Release temporarily pinned blocks from last operation
ReleaseTempPinnedData();
if (direction_ == kReverse) {
ReverseToForward();
} 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 or a sequence number higher than sequence_
//
// 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;
// How many times in a row we have skipped an entry with user key less than
// or equal to saved_key_. We could skip these entries either because
// sequence numbers were too high or because skipping = true.
// What saved_key_ contains throughout this method:
// - if skipping : saved_key_ contains the key that we need to skip,
// and we haven't seen any keys greater than that,
// - if num_skipped > 0 : saved_key_ contains the key that we have skipped
// num_skipped times, and we haven't seen any keys
// greater than that,
// - none of the above : saved_key_ can contain anything, it doesn't matter.
uint64_t num_skipped = 0;
do {
ParsedInternalKey ikey;
if (!ParseKey(&ikey)) {
// Skip corrupted keys.
iter_->Next();
continue;
}
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 {
skipping = false; // ikey > saved_key_, i.e. saved_key_ is skipped
num_skipped = 0;
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;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
break;
case kTypeValue:
saved_key_.SetKey(
ikey.user_key,
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
if (range_del_agg_.ShouldDelete(ikey)) {
// Arrange to skip all upcoming entries for this key since
// they are hidden by this deletion.
skipping = true;
num_skipped = 0;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
} else {
valid_ = true;
return;
}
break;
case kTypeMerge:
saved_key_.SetKey(
ikey.user_key,
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
if (range_del_agg_.ShouldDelete(ikey)) {
// Arrange to skip all upcoming entries for this key since
// they are hidden by this deletion.
skipping = true;
num_skipped = 0;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
} else {
// By now, we are sure the current ikey is going to yield a
// value
current_entry_is_merged_ = true;
valid_ = true;
MergeValuesNewToOld(); // Go to a different state machine
return;
}
break;
default:
assert(false);
break;
}
}
} else {
// This key was inserted after our snapshot was taken.
PERF_COUNTER_ADD(internal_recent_skipped_count, 1);
// Here saved_key_ may contain some old key, or the default empty key, or
// key assigned by some random other method. We don't care.
if (user_comparator_->Compare(ikey.user_key, saved_key_.GetKey()) <= 0) {
num_skipped++;
} else {
saved_key_.SetKey(
ikey.user_key,
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
skipping = false;
num_skipped = 0;
}
}
// If we have sequentially iterated via numerous equal keys, then it's
// better to seek so that we can avoid too many key comparisons.
if (num_skipped > max_skip_) {
num_skipped = 0;
std::string last_key;
if (skipping) {
// We're looking for the next user-key but all we see are the same
// user-key with decreasing sequence numbers. Fast forward to
// sequence number 0 and type deletion (the smallest type).
AppendInternalKey(&last_key, ParsedInternalKey(saved_key_.GetKey(), 0,
kTypeDeletion));
// Don't set skipping = false because we may still see more user-keys
// equal to saved_key_.
} else {
// We saw multiple entries with this user key and sequence numbers
// higher than sequence_. Fast forward to sequence_.
// Note that this only covers a case when a higher key was overwritten
// many times since our snapshot was taken, not the case when a lot of
// different keys were inserted after our snapshot was taken.
AppendInternalKey(&last_key,
ParsedInternalKey(saved_key_.GetKey(), sequence_,
kValueTypeForSeek));
}
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 (!merge_operator_) {
Log(InfoLogLevel::ERROR_LEVEL,
logger_, "Options::merge_operator is null.");
status_ = Status::InvalidArgument("merge_operator_ must be set.");
valid_ = false;
return;
}
// Temporarily pin the blocks that hold merge operands
TempPinData();
merge_context_.Clear();
// Start the merge process by pushing the first operand
merge_context_.PushOperand(iter_->value(),
iter_->IsValuePinned() /* operand_pinned */);
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 ||
range_del_agg_.ShouldDelete(ikey)) {
// 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();
MergeHelper::TimedFullMerge(merge_operator_, ikey.user_key, &val,
merge_context_.GetOperands(), &saved_value_,
logger_, statistics_, env_, &pinned_value_);
// 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.
merge_context_.PushOperand(iter_->value(),
iter_->IsValuePinned() /* operand_pinned */);
PERF_COUNTER_ADD(internal_merge_count, 1);
} else {
assert(false);
}
}
// 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.
MergeHelper::TimedFullMerge(merge_operator_, saved_key_.GetKey(), nullptr,
merge_context_.GetOperands(), &saved_value_,
logger_, statistics_, env_, &pinned_value_);
}
void DBIter::Prev() {
assert(valid_);
ReleaseTempPinnedData();
if (direction_ == kForward) {
ReverseToBackward();
}
PrevInternal();
if (statistics_ != nullptr) {
local_stats_.prev_count_++;
if (valid_) {
local_stats_.prev_found_count_++;
local_stats_.bytes_read_ += (key().size() + value().size());
}
}
}
void DBIter::ReverseToForward() {
if (prefix_extractor_ != nullptr && !total_order_seek_) {
IterKey last_key;
last_key.SetInternalKey(ParsedInternalKey(
saved_key_.GetKey(), kMaxSequenceNumber, kValueTypeForSeek));
iter_->Seek(last_key.GetKey());
}
FindNextUserKey();
direction_ = kForward;
if (!iter_->Valid()) {
iter_->SeekToFirst();
}
}
void DBIter::ReverseToBackward() {
if (prefix_extractor_ != nullptr && !total_order_seek_) {
IterKey last_key;
last_key.SetInternalKey(
ParsedInternalKey(saved_key_.GetKey(), 0, kValueTypeForSeekForPrev));
iter_->SeekForPrev(last_key.GetKey());
}
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) {
if (ikey.sequence > sequence_) {
PERF_COUNTER_ADD(internal_recent_skipped_count, 1);
} else {
PERF_COUNTER_ADD(internal_key_skipped_count, 1);
}
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();
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_ &&
prefix_extractor_->Transform(saved_key_.GetKey())
.compare(prefix_start_key_) != 0) {
valid_ = false;
}
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
// Or the prefix is different than start prefix
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);
// Temporarily pin blocks that hold (merge operands / the value)
ReleaseTempPinnedData();
TempPinData();
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:
if (range_del_agg_.ShouldDelete(ikey)) {
last_key_entry_type = kTypeRangeDeletion;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
} else {
assert(iter_->IsValuePinned());
pinned_value_ = iter_->value();
}
merge_context_.Clear();
last_not_merge_type = last_key_entry_type;
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:
if (range_del_agg_.ShouldDelete(ikey)) {
merge_context_.Clear();
last_key_entry_type = kTypeRangeDeletion;
last_not_merge_type = last_key_entry_type;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
} else {
assert(merge_operator_ != nullptr);
merge_context_.PushOperandBack(
iter_->value(), iter_->IsValuePinned() /* operand_pinned */);
PERF_COUNTER_ADD(internal_merge_count, 1);
}
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:
case kTypeRangeDeletion:
valid_ = false;
return false;
case kTypeMerge:
current_entry_is_merged_ = true;
if (last_not_merge_type == kTypeDeletion ||
last_not_merge_type == kTypeSingleDeletion ||
last_not_merge_type == kTypeRangeDeletion) {
MergeHelper::TimedFullMerge(merge_operator_, saved_key_.GetKey(),
nullptr, merge_context_.GetOperands(),
&saved_value_, logger_, statistics_, env_,
&pinned_value_);
} else {
assert(last_not_merge_type == kTypeValue);
MergeHelper::TimedFullMerge(merge_operator_, saved_key_.GetKey(),
&pinned_value_,
merge_context_.GetOperands(), &saved_value_,
logger_, statistics_, env_, &pinned_value_);
}
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() {
// FindValueForCurrentKey will enable pinning before calling
// FindValueForCurrentKeyUsingSeek()
assert(pinned_iters_mgr_.PinningEnabled());
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 == kTypeDeletion || ikey.type == kTypeSingleDeletion ||
range_del_agg_.ShouldDelete(ikey)) {
valid_ = false;
return false;
}
if (ikey.type == kTypeValue) {
assert(iter_->IsValuePinned());
pinned_value_ = iter_->value();
valid_ = true;
return true;
}
// 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 && !range_del_agg_.ShouldDelete(ikey)) {
merge_context_.PushOperand(iter_->value(),
iter_->IsValuePinned() /* operand_pinned */);
PERF_COUNTER_ADD(internal_merge_count, 1);
iter_->Next();
FindParseableKey(&ikey, kForward);
}
if (!iter_->Valid() ||
!user_comparator_->Equal(ikey.user_key, saved_key_.GetKey()) ||
ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion ||
range_del_agg_.ShouldDelete(ikey)) {
MergeHelper::TimedFullMerge(merge_operator_, saved_key_.GetKey(), nullptr,
merge_context_.GetOperands(), &saved_value_,
logger_, statistics_, env_, &pinned_value_);
// 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();
MergeHelper::TimedFullMerge(merge_operator_, saved_key_.GetKey(), &val,
merge_context_.GetOperands(), &saved_value_,
logger_, statistics_, env_, &pinned_value_);
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;
}
}
if (ikey.sequence > sequence_) {
PERF_COUNTER_ADD(internal_recent_skipped_count, 1);
} else {
PERF_COUNTER_ADD(internal_key_skipped_count, 1);
}
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::SeekForPrev(const Slice& target) {
StopWatch sw(env_, statistics_, DB_SEEK);
ReleaseTempPinnedData();
saved_key_.Clear();
// now saved_key is used to store internal key.
saved_key_.SetInternalKey(target, 0 /* sequence_number */,
kValueTypeForSeekForPrev);
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->SeekForPrev(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_ = kReverse;
ClearSavedValue();
PrevInternal();
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) {
SeekForPrev(*iterate_upper_bound_);
if (!Valid()) {
return;
} else if (user_comparator_->Equal(*iterate_upper_bound_, key())) {
Prev();
}
} else {
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, bool total_order_seek) {
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, total_order_seek);
return db_iter;
}
ArenaWrappedDBIter::~ArenaWrappedDBIter() { db_iter_->~DBIter(); }
void ArenaWrappedDBIter::SetDBIter(DBIter* iter) { db_iter_ = iter; }
RangeDelAggregator* ArenaWrappedDBIter::GetRangeDelAggregator() {
return db_iter_->GetRangeDelAggregator();
}
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::SeekForPrev(const Slice& target) {
db_iter_->SeekForPrev(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,
bool total_order_seek) {
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, total_order_seek);
iter->SetDBIter(db_iter);
return iter;
}
} // namespace rocksdb
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