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rocksdb/db/db_iter.cc

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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).
//
// 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 <string>
#include <iostream>
#include <limits>
#include "db/dbformat.h"
#include "db/merge_context.h"
#include "db/merge_helper.h"
#include "db/pinned_iterators_manager.h"
#include "monitoring/perf_context_imp.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/filename.h"
#include "util/logging.h"
#include "util/mutexlock.h"
#include "util/string_util.h"
#include "util/trace_replay.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 final: public Iterator {
public:
// The following is grossly complicated. TODO: clean it up
// Which direction is the iterator currently moving?
// (1) When moving forward:
// (1a) if current_entry_is_merged_ = false, the internal iterator is
// positioned at the exact entry that yields this->key(), this->value()
// (1b) if current_entry_is_merged_ = true, the internal iterator is
// positioned immediately after the last entry that contributed to the
// current this->value(). That entry may or may not have key equal to
// this->key().
// (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;
skip_count_ = 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_);
RecordTick(global_statistics, NUMBER_ITER_SKIP, skip_count_);
PERF_COUNTER_ADD(iter_read_bytes, 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_;
// Map to Tickers::NUMBER_ITER_SKIP
uint64_t skip_count_;
};
DBIter(Env* _env, const ReadOptions& read_options,
const ImmutableCFOptions& cf_options,
const MutableCFOptions& mutable_cf_options, const Comparator* cmp,
InternalIterator* iter, SequenceNumber s, bool arena_mode,
uint64_t max_sequential_skip_in_iterations,
ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd,
bool allow_blob)
: arena_mode_(arena_mode),
env_(_env),
logger_(cf_options.info_log),
user_comparator_(cmp),
merge_operator_(cf_options.merge_operator),
iter_(iter),
sequence_(s),
direction_(kForward),
valid_(false),
current_entry_is_merged_(false),
statistics_(cf_options.statistics),
num_internal_keys_skipped_(0),
iterate_lower_bound_(read_options.iterate_lower_bound),
iterate_upper_bound_(read_options.iterate_upper_bound),
prefix_same_as_start_(read_options.prefix_same_as_start),
pin_thru_lifetime_(read_options.pin_data),
total_order_seek_(read_options.total_order_seek),
range_del_agg_(cf_options.internal_comparator, s,
true /* collapse_deletions */),
read_callback_(read_callback),
db_impl_(db_impl),
cfd_(cfd),
allow_blob_(allow_blob),
is_blob_(false),
start_seqnum_(read_options.iter_start_seqnum) {
RecordTick(statistics_, NO_ITERATOR_CREATED);
prefix_extractor_ = mutable_cf_options.prefix_extractor.get();
max_skip_ = max_sequential_skip_in_iterations;
max_skippable_internal_keys_ = read_options.max_skippable_internal_keys;
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_ITERATOR_DELETED);
ResetInternalKeysSkippedCounter();
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_);
if(start_seqnum_ > 0) {
return saved_key_.GetInternalKey();
} else {
return saved_key_.GetUserKey();
}
}
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 {
assert(!valid_);
return status_;
}
}
bool IsBlob() const {
assert(valid_ && (allow_blob_ || !is_blob_));
return is_blob_;
}
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.
return iter_->GetProperty(prop_name, prop);
} 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();
} else if (prop_name == "rocksdb.iterator.internal-key") {
*prop = saved_key_.GetUserKey().ToString();
return Status::OK();
}
return Status::InvalidArgument("Unidentified 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;
Env* env() { return env_; }
void set_sequence(uint64_t s) { sequence_ = s; }
void set_valid(bool v) { valid_ = v; }
private:
// For all methods in this block:
// PRE: iter_->Valid() && status_.ok()
// Return false if there was an error, and status() is non-ok, valid_ = false;
// in this case callers would usually stop what they were doing and return.
bool ReverseToForward();
bool ReverseToBackward();
bool FindValueForCurrentKey();
bool FindValueForCurrentKeyUsingSeek();
bool FindUserKeyBeforeSavedKey();
inline bool FindNextUserEntry(bool skipping, bool prefix_check);
bool FindNextUserEntryInternal(bool skipping, bool prefix_check);
bool ParseKey(ParsedInternalKey* key);
bool MergeValuesNewToOld();
void PrevInternal();
bool TooManyInternalKeysSkipped(bool increment = true);
bool IsVisible(SequenceNumber sequence);
// CanReseekToSkip() returns whether the iterator can use the optimization
// where it reseek by sequence number to get the next key when there are too
// many versions. This is disabled for write unprepared because seeking to
// sequence number does not guarantee that it is visible.
inline bool CanReseekToSkip();
// MaxVisibleSequenceNumber() returns the maximum visible sequence number
// for this snapshot. This sequence number may be greater than snapshot
// seqno because uncommitted data written to DB for write unprepared will
// have a higher sequence number.
inline SequenceNumber MaxVisibleSequenceNumber();
// 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();
}
}
inline void ResetInternalKeysSkippedCounter() {
local_stats_.skip_count_ += num_internal_keys_skipped_;
if (valid_) {
local_stats_.skip_count_--;
}
num_internal_keys_skipped_ = 0;
}
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 sequence_;
Status status_;
IterKey saved_key_;
// Reusable internal key data structure. This is only used inside one function
// and should not be used across functions. Reusing this object can reduce
// overhead of calling construction of the function if creating it each time.
ParsedInternalKey ikey_;
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 max_skippable_internal_keys_;
uint64_t num_internal_keys_skipped_;
const Slice* iterate_lower_bound_;
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_;
ReadCallback* read_callback_;
DBImpl* db_impl_;
ColumnFamilyData* cfd_;
bool allow_blob_;
bool is_blob_;
// for diff snapshots we want the lower bound on the seqnum;
// if this value > 0 iterator will return internal keys
SequenceNumber start_seqnum_;
// 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");
valid_ = false;
ROCKS_LOG_ERROR(logger_, "corrupted internal key in DBIter: %s",
iter_->key().ToString(true).c_str());
return false;
} else {
return true;
}
}
void DBIter::Next() {
assert(valid_);
assert(status_.ok());
// Release temporarily pinned blocks from last operation
ReleaseTempPinnedData();
ResetInternalKeysSkippedCounter();
bool ok = true;
if (direction_ == kReverse) {
if (!ReverseToForward()) {
ok = false;
}
} 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_++;
}
if (ok && iter_->Valid()) {
FindNextUserEntry(true /* skipping the current user key */,
prefix_same_as_start_);
} else {
valid_ = false;
}
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_
// saved_key_ MUST have a proper user_key before calling this function
//
// 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 bool DBIter::FindNextUserEntry(bool skipping, bool prefix_check) {
PERF_TIMER_GUARD(find_next_user_entry_time);
return FindNextUserEntryInternal(skipping, prefix_check);
}
// Actual implementation of DBIter::FindNextUserEntry()
bool DBIter::FindNextUserEntryInternal(bool skipping, bool prefix_check) {
// Loop until we hit an acceptable entry to yield
assert(iter_->Valid());
assert(status_.ok());
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;
is_blob_ = false;
do {
if (!ParseKey(&ikey_)) {
return false;
}
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 (TooManyInternalKeysSkipped()) {
return false;
}
if (IsVisible(ikey_.sequence)) {
if (skipping && user_comparator_->Compare(ikey_.user_key,
saved_key_.GetUserKey()) <= 0) {
num_skipped++; // skip this entry
PERF_COUNTER_ADD(internal_key_skipped_count, 1);
} else {
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.
// if iterartor specified start_seqnum we
// 1) return internal key, including the type
// 2) return ikey only if ikey.seqnum >= start_seqnum_
// note that if deletion seqnum is < start_seqnum_ we
// just skip it like in normal iterator.
if (start_seqnum_ > 0 && ikey_.sequence >= start_seqnum_) {
saved_key_.SetInternalKey(ikey_);
valid_ = true;
return true;
} else {
saved_key_.SetUserKey(
ikey_.user_key,
!pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */);
skipping = true;
PERF_COUNTER_ADD(internal_delete_skipped_count, 1);
}
break;
case kTypeValue:
case kTypeBlobIndex:
if (start_seqnum_ > 0) {
// we are taking incremental snapshot here
// incremental snapshots aren't supported on DB with range deletes
assert(!(
(ikey_.type == kTypeBlobIndex) && (start_seqnum_ > 0)
));
if (ikey_.sequence >= start_seqnum_) {
saved_key_.SetInternalKey(ikey_);
valid_ = true;
return true;
} else {
// this key and all previous versions shouldn't be included,
// skipping
saved_key_.SetUserKey(ikey_.user_key,
!pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */);
skipping = true;
}
} else {
saved_key_.SetUserKey(
ikey_.user_key,
!pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */);
if (range_del_agg_.ShouldDelete(
ikey_, RangeDelPositioningMode::kForwardTraversal)) {
// 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 if (ikey_.type == kTypeBlobIndex) {
if (!allow_blob_) {
ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index.");
status_ = Status::NotSupported(
"Encounter unexpected blob index. Please open DB with "
"rocksdb::blob_db::BlobDB instead.");
valid_ = false;
return false;
}
is_blob_ = true;
valid_ = true;
return true;
} else {
valid_ = true;
return true;
}
}
break;
case kTypeMerge:
saved_key_.SetUserKey(
ikey_.user_key,
!pin_thru_lifetime_ || !iter_->IsKeyPinned() /* copy */);
if (range_del_agg_.ShouldDelete(
ikey_, RangeDelPositioningMode::kForwardTraversal)) {
// 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;
return MergeValuesNewToOld(); // Go to a different state machine
}
break;
default:
assert(false);
break;
}
}
} else {
PERF_COUNTER_ADD(internal_recent_skipped_count, 1);
// This key was inserted after our snapshot was taken.
// If this happens too many times in a row for the same user key, we want
// to seek to the target sequence number.
int cmp =
user_comparator_->Compare(ikey_.user_key, saved_key_.GetUserKey());
if (cmp == 0 || (skipping && cmp <= 0)) {
num_skipped++;
} else {
saved_key_.SetUserKey(
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_ && CanReseekToSkip()) {
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_.GetUserKey(),
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_.GetUserKey(), sequence_,
kValueTypeForSeek));
}
iter_->Seek(last_key);
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
} else {
iter_->Next();
}
} while (iter_->Valid());
valid_ = false;
return iter_->status().ok();
}
// 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)
bool DBIter::MergeValuesNewToOld() {
if (!merge_operator_) {
ROCKS_LOG_ERROR(logger_, "Options::merge_operator is null.");
status_ = Status::InvalidArgument("merge_operator_ must be set.");
valid_ = false;
return false;
}
// 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 */);
TEST_SYNC_POINT("DBIter::MergeValuesNewToOld:PushedFirstOperand");
ParsedInternalKey ikey;
Status s;
for (iter_->Next(); iter_->Valid(); iter_->Next()) {
TEST_SYNC_POINT("DBIter::MergeValuesNewToOld:SteppedToNextOperand");
if (!ParseKey(&ikey)) {
return false;
}
if (!user_comparator_->Equal(ikey.user_key, saved_key_.GetUserKey())) {
// hit the next user key, stop right here
break;
} else if (kTypeDeletion == ikey.type || kTypeSingleDeletion == ikey.type ||
range_del_agg_.ShouldDelete(
ikey, RangeDelPositioningMode::kForwardTraversal)) {
// 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!
const Slice val = iter_->value();
s = MergeHelper::TimedFullMerge(
merge_operator_, ikey.user_key, &val, merge_context_.GetOperands(),
&saved_value_, logger_, statistics_, env_, &pinned_value_, true);
if (!s.ok()) {
valid_ = false;
status_ = s;
return false;
}
// iter_ is positioned after put
iter_->Next();
if (!iter_->status().ok()) {
valid_ = false;
return false;
}
return true;
} 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 if (kTypeBlobIndex == ikey.type) {
if (!allow_blob_) {
ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index.");
status_ = Status::NotSupported(
"Encounter unexpected blob index. Please open DB with "
"rocksdb::blob_db::BlobDB instead.");
} else {
status_ =
Status::NotSupported("Blob DB does not support merge operator.");
}
valid_ = false;
return false;
} else {
assert(false);
}
}
if (!iter_->status().ok()) {
valid_ = false;
return 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.
s = MergeHelper::TimedFullMerge(merge_operator_, saved_key_.GetUserKey(),
nullptr, merge_context_.GetOperands(),
&saved_value_, logger_, statistics_, env_,
&pinned_value_, true);
if (!s.ok()) {
valid_ = false;
status_ = s;
return false;
}
assert(status_.ok());
return true;
}
void DBIter::Prev() {
assert(valid_);
assert(status_.ok());
ReleaseTempPinnedData();
ResetInternalKeysSkippedCounter();
bool ok = true;
if (direction_ == kForward) {
if (!ReverseToBackward()) {
ok = false;
}
}
if (ok) {
PrevInternal();
}
if (statistics_ != nullptr) {
local_stats_.prev_count_++;
if (valid_) {
local_stats_.prev_found_count_++;
local_stats_.bytes_read_ += (key().size() + value().size());
}
}
}
bool DBIter::ReverseToForward() {
assert(iter_->status().ok());
// When moving backwards, iter_ is positioned on _previous_ key, which may
// not exist or may have different prefix than the current key().
// If that's the case, seek iter_ to current key.
if ((prefix_extractor_ != nullptr && !total_order_seek_) || !iter_->Valid()) {
IterKey last_key;
last_key.SetInternalKey(ParsedInternalKey(
saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek));
iter_->Seek(last_key.GetInternalKey());
}
direction_ = kForward;
// Skip keys less than the current key() (a.k.a. saved_key_).
while (iter_->Valid()) {
ParsedInternalKey ikey;
if (!ParseKey(&ikey)) {
return false;
}
if (user_comparator_->Compare(ikey.user_key, saved_key_.GetUserKey()) >=
0) {
return true;
}
iter_->Next();
}
if (!iter_->status().ok()) {
valid_ = false;
return false;
}
return true;
}
// Move iter_ to the key before saved_key_.
bool DBIter::ReverseToBackward() {
assert(iter_->status().ok());
// When current_entry_is_merged_ is true, iter_ may be positioned on the next
// key, which may not exist or may have prefix different from current.
// If that's the case, seek to saved_key_.
if (current_entry_is_merged_ &&
((prefix_extractor_ != nullptr && !total_order_seek_) ||
!iter_->Valid())) {
IterKey last_key;
// Using kMaxSequenceNumber and kValueTypeForSeek
// (not kValueTypeForSeekForPrev) to seek to a key strictly smaller
// than saved_key_.
last_key.SetInternalKey(ParsedInternalKey(
saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek));
if (prefix_extractor_ != nullptr && !total_order_seek_) {
iter_->SeekForPrev(last_key.GetInternalKey());
} else {
// Some iterators may not support SeekForPrev(), so we avoid using it
// when prefix seek mode is disabled. This is somewhat expensive
// (an extra Prev(), as well as an extra change of direction of iter_),
// so we may need to reconsider it later.
iter_->Seek(last_key.GetInternalKey());
if (!iter_->Valid() && iter_->status().ok()) {
iter_->SeekToLast();
}
}
}
direction_ = kReverse;
return FindUserKeyBeforeSavedKey();
}
void DBIter::PrevInternal() {
while (iter_->Valid()) {
saved_key_.SetUserKey(
ExtractUserKey(iter_->key()),
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
if (prefix_extractor_ && prefix_same_as_start_ &&
prefix_extractor_->Transform(saved_key_.GetUserKey())
.compare(prefix_start_key_) != 0) {
// Current key does not have the same prefix as start
valid_ = false;
return;
}
if (iterate_lower_bound_ != nullptr &&
user_comparator_->Compare(saved_key_.GetUserKey(),
*iterate_lower_bound_) < 0) {
// We've iterated earlier than the user-specified lower bound.
valid_ = false;
return;
}
if (!FindValueForCurrentKey()) { // assigns valid_
return;
}
// Whether or not we found a value for current key, we need iter_ to end up
// on a smaller key.
if (!FindUserKeyBeforeSavedKey()) {
return;
}
if (valid_) {
// Found the value.
return;
}
if (TooManyInternalKeysSkipped(false)) {
return;
}
}
// We haven't found any key - iterator is not valid
valid_ = false;
}
// Used for backwards iteration.
// Looks at the entries with user key saved_key_ and finds the most up-to-date
// value for it, or executes a merge, or determines that the value was deleted.
// Sets valid_ to true if the value is found and is ready to be presented to
// the user through value().
// Sets valid_ to false if the value was deleted, and we should try another key.
// Returns false if an error occurred, and !status().ok() and !valid_.
//
// PRE: iter_ is positioned on the last entry with user key equal to saved_key_.
// POST: iter_ is positioned on one of the entries equal to saved_key_, or on
// the entry just before them, or on the entry just after them.
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;
// Temporarily pin blocks that hold (merge operands / the value)
ReleaseTempPinnedData();
TempPinData();
size_t num_skipped = 0;
while (iter_->Valid()) {
ParsedInternalKey ikey;
if (!ParseKey(&ikey)) {
return false;
}
if (!IsVisible(ikey.sequence) ||
!user_comparator_->Equal(ikey.user_key, saved_key_.GetUserKey())) {
break;
}
if (TooManyInternalKeysSkipped()) {
return false;
}
// This user key has lots of entries.
// We're going from old to new, and it's taking too long. Let's do a Seek()
// and go from new to old. This helps when a key was overwritten many times.
if (num_skipped >= max_skip_ && CanReseekToSkip()) {
return FindValueForCurrentKeyUsingSeek();
}
last_key_entry_type = ikey.type;
switch (last_key_entry_type) {
case kTypeValue:
case kTypeBlobIndex:
if (range_del_agg_.ShouldDelete(
ikey, RangeDelPositioningMode::kBackwardTraversal)) {
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, RangeDelPositioningMode::kBackwardTraversal)) {
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);
iter_->Prev();
++num_skipped;
}
if (!iter_->status().ok()) {
valid_ = false;
return false;
}
Status s;
is_blob_ = false;
switch (last_key_entry_type) {
case kTypeDeletion:
case kTypeSingleDeletion:
case kTypeRangeDeletion:
valid_ = false;
return true;
case kTypeMerge:
current_entry_is_merged_ = true;
if (last_not_merge_type == kTypeDeletion ||
last_not_merge_type == kTypeSingleDeletion ||
last_not_merge_type == kTypeRangeDeletion) {
s = MergeHelper::TimedFullMerge(
merge_operator_, saved_key_.GetUserKey(), nullptr,
merge_context_.GetOperands(), &saved_value_, logger_, statistics_,
env_, &pinned_value_, true);
} else if (last_not_merge_type == kTypeBlobIndex) {
if (!allow_blob_) {
ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index.");
status_ = Status::NotSupported(
"Encounter unexpected blob index. Please open DB with "
"rocksdb::blob_db::BlobDB instead.");
} else {
status_ =
Status::NotSupported("Blob DB does not support merge operator.");
}
valid_ = false;
return false;
} else {
assert(last_not_merge_type == kTypeValue);
s = MergeHelper::TimedFullMerge(
merge_operator_, saved_key_.GetUserKey(), &pinned_value_,
merge_context_.GetOperands(), &saved_value_, logger_, statistics_,
env_, &pinned_value_, true);
}
break;
case kTypeValue:
// do nothing - we've already has value in pinned_value_
break;
case kTypeBlobIndex:
if (!allow_blob_) {
ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index.");
status_ = Status::NotSupported(
"Encounter unexpected blob index. Please open DB with "
"rocksdb::blob_db::BlobDB instead.");
valid_ = false;
return false;
}
is_blob_ = true;
break;
default:
assert(false);
break;
}
if (!s.ok()) {
valid_ = false;
status_ = s;
return false;
}
valid_ = true;
return true;
}
// This function is used in FindValueForCurrentKey.
// We use Seek() function instead of Prev() to find necessary value
// TODO: This is very similar to FindNextUserEntry() and MergeValuesNewToOld().
// Would be nice to reuse some code.
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_.GetUserKey(),
sequence_, kValueTypeForSeek));
iter_->Seek(last_key);
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
// In case read_callback presents, the value we seek to may not be visible.
// Find the next value that's visible.
ParsedInternalKey ikey;
while (true) {
if (!iter_->Valid()) {
valid_ = false;
return iter_->status().ok();
}
if (!ParseKey(&ikey)) {
return false;
}
if (!user_comparator_->Equal(ikey.user_key, saved_key_.GetUserKey())) {
// No visible values for this key, even though FindValueForCurrentKey()
// has seen some. This is possible if we're using a tailing iterator, and
// the entries were discarded in a compaction.
valid_ = false;
return true;
}
if (IsVisible(ikey.sequence)) {
break;
}
iter_->Next();
}
if (ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion ||
range_del_agg_.ShouldDelete(
ikey, RangeDelPositioningMode::kBackwardTraversal)) {
valid_ = false;
return true;
}
if (ikey.type == kTypeBlobIndex && !allow_blob_) {
ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index.");
status_ = Status::NotSupported(
"Encounter unexpected blob index. Please open DB with "
"rocksdb::blob_db::BlobDB instead.");
valid_ = false;
return false;
}
if (ikey.type == kTypeValue || ikey.type == kTypeBlobIndex) {
assert(iter_->IsValuePinned());
pinned_value_ = iter_->value();
valid_ = true;
return true;
}
// kTypeMerge. We need to collect all kTypeMerge values and save them
// in operands
assert(ikey.type == kTypeMerge);
current_entry_is_merged_ = true;
merge_context_.Clear();
merge_context_.PushOperand(iter_->value(),
iter_->IsValuePinned() /* operand_pinned */);
while (true) {
iter_->Next();
if (!iter_->Valid()) {
if (!iter_->status().ok()) {
valid_ = false;
return false;
}
break;
}
if (!ParseKey(&ikey)) {
return false;
}
if (!user_comparator_->Equal(ikey.user_key, saved_key_.GetUserKey())) {
break;
}
if (ikey.type == kTypeDeletion || ikey.type == kTypeSingleDeletion ||
range_del_agg_.ShouldDelete(
ikey, RangeDelPositioningMode::kForwardTraversal)) {
break;
} else if (ikey.type == kTypeValue) {
const Slice val = iter_->value();
Status s = MergeHelper::TimedFullMerge(
merge_operator_, saved_key_.GetUserKey(), &val,
merge_context_.GetOperands(), &saved_value_, logger_, statistics_,
env_, &pinned_value_, true);
if (!s.ok()) {
valid_ = false;
status_ = s;
return false;
}
valid_ = true;
return true;
} else if (ikey.type == kTypeMerge) {
merge_context_.PushOperand(iter_->value(),
iter_->IsValuePinned() /* operand_pinned */);
PERF_COUNTER_ADD(internal_merge_count, 1);
} else if (ikey.type == kTypeBlobIndex) {
if (!allow_blob_) {
ROCKS_LOG_ERROR(logger_, "Encounter unexpected blob index.");
status_ = Status::NotSupported(
"Encounter unexpected blob index. Please open DB with "
"rocksdb::blob_db::BlobDB instead.");
} else {
status_ =
Status::NotSupported("Blob DB does not support merge operator.");
}
valid_ = false;
return false;
} else {
assert(false);
}
}
Status s = MergeHelper::TimedFullMerge(
merge_operator_, saved_key_.GetUserKey(), nullptr,
merge_context_.GetOperands(), &saved_value_, logger_, statistics_, env_,
&pinned_value_, true);
if (!s.ok()) {
valid_ = false;
status_ = s;
return false;
}
// Make sure we leave iter_ in a good state. If it's valid and we don't care
// about prefixes, that's already good enough. Otherwise it needs to be
// seeked to the current key.
if ((prefix_extractor_ != nullptr && !total_order_seek_) || !iter_->Valid()) {
if (prefix_extractor_ != nullptr && !total_order_seek_) {
iter_->SeekForPrev(last_key);
} else {
iter_->Seek(last_key);
if (!iter_->Valid() && iter_->status().ok()) {
iter_->SeekToLast();
}
}
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
}
valid_ = true;
return true;
}
// Move backwards until the key smaller than saved_key_.
// Changes valid_ only if return value is false.
bool DBIter::FindUserKeyBeforeSavedKey() {
assert(status_.ok());
size_t num_skipped = 0;
while (iter_->Valid()) {
ParsedInternalKey ikey;
if (!ParseKey(&ikey)) {
return false;
}
if (user_comparator_->Compare(ikey.user_key, saved_key_.GetUserKey()) < 0) {
return true;
}
if (TooManyInternalKeysSkipped()) {
return false;
}
assert(ikey.sequence != kMaxSequenceNumber);
if (!IsVisible(ikey.sequence)) {
PERF_COUNTER_ADD(internal_recent_skipped_count, 1);
} else {
PERF_COUNTER_ADD(internal_key_skipped_count, 1);
}
if (num_skipped >= max_skip_ && CanReseekToSkip()) {
num_skipped = 0;
IterKey last_key;
last_key.SetInternalKey(ParsedInternalKey(
saved_key_.GetUserKey(), kMaxSequenceNumber, kValueTypeForSeek));
// It would be more efficient to use SeekForPrev() here, but some
// iterators may not support it.
iter_->Seek(last_key.GetInternalKey());
RecordTick(statistics_, NUMBER_OF_RESEEKS_IN_ITERATION);
if (!iter_->Valid()) {
break;
}
} else {
++num_skipped;
}
iter_->Prev();
}
if (!iter_->status().ok()) {
valid_ = false;
return false;
}
return true;
}
bool DBIter::TooManyInternalKeysSkipped(bool increment) {
if ((max_skippable_internal_keys_ > 0) &&
(num_internal_keys_skipped_ > max_skippable_internal_keys_)) {
valid_ = false;
status_ = Status::Incomplete("Too many internal keys skipped.");
return true;
} else if (increment) {
num_internal_keys_skipped_++;
}
return false;
}
bool DBIter::IsVisible(SequenceNumber sequence) {
return sequence <= MaxVisibleSequenceNumber() &&
(read_callback_ == nullptr || read_callback_->IsVisible(sequence));
}
bool DBIter::CanReseekToSkip() {
return read_callback_ == nullptr ||
read_callback_->MaxUnpreparedSequenceNumber() == 0;
}
SequenceNumber DBIter::MaxVisibleSequenceNumber() {
if (read_callback_ == nullptr) {
return sequence_;
}
return std::max(sequence_, read_callback_->MaxUnpreparedSequenceNumber());
}
void DBIter::Seek(const Slice& target) {
StopWatch sw(env_, statistics_, DB_SEEK);
status_ = Status::OK();
ReleaseTempPinnedData();
ResetInternalKeysSkippedCounter();
SequenceNumber seq = MaxVisibleSequenceNumber();
saved_key_.Clear();
saved_key_.SetInternalKey(target, seq);
#ifndef ROCKSDB_LITE
if (db_impl_ != nullptr && cfd_ != nullptr) {
db_impl_->TraceIteratorSeek(cfd_->GetID(), target);
}
#endif // ROCKSDB_LITE
if (iterate_lower_bound_ != nullptr &&
user_comparator_->Compare(saved_key_.GetUserKey(),
*iterate_lower_bound_) < 0) {
saved_key_.Clear();
saved_key_.SetInternalKey(*iterate_lower_bound_, seq);
}
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->Seek(saved_key_.GetInternalKey());
range_del_agg_.InvalidateRangeDelMapPositions();
}
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_) {
// Decrement since we don't want to count this key as skipped
RecordTick(statistics_, NUMBER_DB_SEEK_FOUND);
RecordTick(statistics_, ITER_BYTES_READ, key().size() + value().size());
PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size());
}
}
} else {
valid_ = false;
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_) {
prefix_start_buf_.SetUserKey(prefix_start_key_);
prefix_start_key_ = prefix_start_buf_.GetUserKey();
}
}
void DBIter::SeekForPrev(const Slice& target) {
StopWatch sw(env_, statistics_, DB_SEEK);
status_ = Status::OK();
ReleaseTempPinnedData();
ResetInternalKeysSkippedCounter();
saved_key_.Clear();
// now saved_key is used to store internal key.
saved_key_.SetInternalKey(target, 0 /* sequence_number */,
kValueTypeForSeekForPrev);
if (iterate_upper_bound_ != nullptr &&
user_comparator_->Compare(saved_key_.GetUserKey(),
*iterate_upper_bound_) >= 0) {
saved_key_.Clear();
saved_key_.SetInternalKey(*iterate_upper_bound_, kMaxSequenceNumber);
}
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->SeekForPrev(saved_key_.GetInternalKey());
range_del_agg_.InvalidateRangeDelMapPositions();
}
#ifndef ROCKSDB_LITE
if (db_impl_ != nullptr && cfd_ != nullptr) {
db_impl_->TraceIteratorSeekForPrev(cfd_->GetID(), target);
}
#endif // ROCKSDB_LITE
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());
PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size());
}
}
} else {
valid_ = false;
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_) {
prefix_start_buf_.SetUserKey(prefix_start_key_);
prefix_start_key_ = prefix_start_buf_.GetUserKey();
}
}
void DBIter::SeekToFirst() {
if (iterate_lower_bound_ != nullptr) {
Seek(*iterate_lower_bound_);
return;
}
// Don't use iter_::Seek() if we set a prefix extractor
// because prefix seek will be used.
if (prefix_extractor_ != nullptr && !total_order_seek_) {
max_skip_ = std::numeric_limits<uint64_t>::max();
}
status_ = Status::OK();
direction_ = kForward;
ReleaseTempPinnedData();
ResetInternalKeysSkippedCounter();
ClearSavedValue();
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->SeekToFirst();
range_del_agg_.InvalidateRangeDelMapPositions();
}
RecordTick(statistics_, NUMBER_DB_SEEK);
if (iter_->Valid()) {
saved_key_.SetUserKey(
ExtractUserKey(iter_->key()),
!iter_->IsKeyPinned() || !pin_thru_lifetime_ /* copy */);
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());
PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size());
}
}
} else {
valid_ = false;
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_) {
prefix_start_buf_.SetUserKey(
prefix_extractor_->Transform(saved_key_.GetUserKey()));
prefix_start_key_ = prefix_start_buf_.GetUserKey();
}
}
void DBIter::SeekToLast() {
if (iterate_upper_bound_ != nullptr) {
// Seek to last key strictly less than ReadOptions.iterate_upper_bound.
SeekForPrev(*iterate_upper_bound_);
if (Valid() && user_comparator_->Equal(*iterate_upper_bound_, key())) {
ReleaseTempPinnedData();
PrevInternal();
}
return;
}
// Don't use iter_::Seek() if we set a prefix extractor
// because prefix seek will be used.
if (prefix_extractor_ != nullptr && !total_order_seek_) {
max_skip_ = std::numeric_limits<uint64_t>::max();
}
status_ = Status::OK();
direction_ = kReverse;
ReleaseTempPinnedData();
ResetInternalKeysSkippedCounter();
ClearSavedValue();
{
PERF_TIMER_GUARD(seek_internal_seek_time);
iter_->SeekToLast();
range_del_agg_.InvalidateRangeDelMapPositions();
}
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());
PERF_COUNTER_ADD(iter_read_bytes, key().size() + value().size());
}
}
if (valid_ && prefix_extractor_ && prefix_same_as_start_) {
prefix_start_buf_.SetUserKey(
prefix_extractor_->Transform(saved_key_.GetUserKey()));
prefix_start_key_ = prefix_start_buf_.GetUserKey();
}
}
Iterator* NewDBIterator(Env* env, const ReadOptions& read_options,
const ImmutableCFOptions& cf_options,
const MutableCFOptions& mutable_cf_options,
const Comparator* user_key_comparator,
InternalIterator* internal_iter,
const SequenceNumber& sequence,
uint64_t max_sequential_skip_in_iterations,
ReadCallback* read_callback, DBImpl* db_impl,
ColumnFamilyData* cfd, bool allow_blob) {
DBIter* db_iter = new DBIter(
env, read_options, cf_options, mutable_cf_options, user_key_comparator,
internal_iter, sequence, false, max_sequential_skip_in_iterations,
read_callback, db_impl, cfd, allow_blob);
return db_iter;
}
ArenaWrappedDBIter::~ArenaWrappedDBIter() { db_iter_->~DBIter(); }
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(); }
bool ArenaWrappedDBIter::IsBlob() const { return db_iter_->IsBlob(); }
inline Status ArenaWrappedDBIter::GetProperty(std::string prop_name,
std::string* prop) {
if (prop_name == "rocksdb.iterator.super-version-number") {
// First try to pass the value returned from inner iterator.
if (!db_iter_->GetProperty(prop_name, prop).ok()) {
*prop = ToString(sv_number_);
}
return Status::OK();
}
return db_iter_->GetProperty(prop_name, prop);
}
void ArenaWrappedDBIter::Init(Env* env, const ReadOptions& read_options,
const ImmutableCFOptions& cf_options,
const MutableCFOptions& mutable_cf_options,
const SequenceNumber& sequence,
uint64_t max_sequential_skip_in_iteration,
uint64_t version_number,
ReadCallback* read_callback, DBImpl* db_impl,
ColumnFamilyData* cfd, bool allow_blob,
bool allow_refresh) {
auto mem = arena_.AllocateAligned(sizeof(DBIter));
db_iter_ = new (mem) DBIter(env, read_options, cf_options, mutable_cf_options,
cf_options.user_comparator, nullptr, sequence,
true, max_sequential_skip_in_iteration,
read_callback, db_impl, cfd, allow_blob);
sv_number_ = version_number;
allow_refresh_ = allow_refresh;
}
Status ArenaWrappedDBIter::Refresh() {
if (cfd_ == nullptr || db_impl_ == nullptr || !allow_refresh_) {
return Status::NotSupported("Creating renew iterator is not allowed.");
}
assert(db_iter_ != nullptr);
// TODO(yiwu): For last_seq_same_as_publish_seq_==false, this is not the
// correct behavior. Will be corrected automatically when we take a snapshot
// here for the case of WritePreparedTxnDB.
SequenceNumber latest_seq = db_impl_->GetLatestSequenceNumber();
uint64_t cur_sv_number = cfd_->GetSuperVersionNumber();
if (sv_number_ != cur_sv_number) {
Env* env = db_iter_->env();
db_iter_->~DBIter();
arena_.~Arena();
new (&arena_) Arena();
SuperVersion* sv = cfd_->GetReferencedSuperVersion(db_impl_->mutex());
Init(env, read_options_, *(cfd_->ioptions()), sv->mutable_cf_options,
latest_seq, sv->mutable_cf_options.max_sequential_skip_in_iterations,
cur_sv_number, read_callback_, db_impl_, cfd_, allow_blob_,
allow_refresh_);
InternalIterator* internal_iter = db_impl_->NewInternalIterator(
read_options_, cfd_, sv, &arena_, db_iter_->GetRangeDelAggregator());
SetIterUnderDBIter(internal_iter);
} else {
db_iter_->set_sequence(latest_seq);
db_iter_->set_valid(false);
}
return Status::OK();
}
ArenaWrappedDBIter* NewArenaWrappedDbIterator(
Env* env, const ReadOptions& read_options,
const ImmutableCFOptions& cf_options,
const MutableCFOptions& mutable_cf_options, const SequenceNumber& sequence,
uint64_t max_sequential_skip_in_iterations, uint64_t version_number,
ReadCallback* read_callback, DBImpl* db_impl, ColumnFamilyData* cfd,
bool allow_blob, bool allow_refresh) {
ArenaWrappedDBIter* iter = new ArenaWrappedDBIter();
iter->Init(env, read_options, cf_options, mutable_cf_options, sequence,
max_sequential_skip_in_iterations, version_number, read_callback,
db_impl, cfd, allow_blob, allow_refresh);
if (db_impl != nullptr && cfd != nullptr && allow_refresh) {
iter->StoreRefreshInfo(read_options, db_impl, cfd, read_callback,
allow_blob);
}
return iter;
}
} // namespace rocksdb