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new Prev() prefix support using SeekForPrev()

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Summary:
1) The previous solution for Prev() prefix support is not clean.
Since I add api SeekForPrev(), now the Prev() can be symmetric to Next().
and we do not need SeekToLast() to be called in Prev() any more.

Also, Next() will Seek(prefix_seek_key_) to solve the problem of possible inconsistency between db_iter and merge_iter when
there is merge_operator. And prefix_seek_key is only refreshed when change direction to forward.

2) This diff also solves the bug of Iterator::SeekToLast() with iterate_upper_bound_ with prefix extractor.

add test cases for the above two cases.

There are some tests for the SeekToLast() in Prev(), I will clean them later.

Test Plan: make all check

Reviewers: IslamAbdelRahman, andrewkr, yiwu, sdong

Reviewed By: sdong

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D63933
This commit is contained in:
Aaron Gao 2016-10-11 13:54:26 -07:00
parent 991b585ee0
commit 447f17127c
7 changed files with 310 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
db/db_impl.cc
View File

@ -4345,7 +4345,8 @@ Iterator* DBImpl::NewIterator(const ReadOptions& read_options,
env_, *cfd->ioptions(), cfd->user_comparator(), snapshot,
sv->mutable_cf_options.max_sequential_skip_in_iterations,
sv->version_number, read_options.iterate_upper_bound,
read_options.prefix_same_as_start, read_options.pin_data);
read_options.prefix_same_as_start, read_options.pin_data,
read_options.total_order_seek);
InternalIterator* internal_iter =
NewInternalIterator(read_options, cfd, sv, db_iter->GetArena());

97
db/db_iter.cc
View File

@ -105,7 +105,8 @@ class DBIter: public Iterator {
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 prefix_same_as_start = false, bool pin_data = false,
bool total_order_seek = false)
: arena_mode_(arena_mode),
env_(env),
logger_(ioptions.info_log),
@ -120,7 +121,8 @@ class DBIter: public Iterator {
version_number_(version_number),
iterate_upper_bound_(iterate_upper_bound),
prefix_same_as_start_(prefix_same_as_start),
pin_thru_lifetime_(pin_data) {
pin_thru_lifetime_(pin_data),
total_order_seek_(total_order_seek) {
RecordTick(statistics_, NO_ITERATORS);
prefix_extractor_ = ioptions.prefix_extractor;
max_skip_ = max_sequential_skip_in_iterations;
@ -204,6 +206,7 @@ class DBIter: public Iterator {
virtual void SeekToLast() override;
private:
void ReverseToForward();
void ReverseToBackward();
void PrevInternal();
void FindParseableKey(ParsedInternalKey* ikey, Direction direction);
@ -256,6 +259,7 @@ class DBIter: public Iterator {
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_;
@ -266,6 +270,7 @@ class DBIter: public Iterator {
// 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_;
LocalStatistics local_stats_;
@ -294,11 +299,7 @@ void DBIter::Next() {
// Release temporarily pinned blocks from last operation
ReleaseTempPinnedData();
if (direction_ == kReverse) {
FindNextUserKey();
direction_ = kForward;
if (!iter_->Valid()) {
iter_->SeekToFirst();
}
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
@ -506,7 +507,29 @@ void DBIter::Prev() {
}
}
void DBIter::ReverseToForward() {
if (prefix_extractor_ != nullptr && !total_order_seek_) {
IterKey last_key;
last_key.SetInternalKey(ParsedInternalKey(
saved_key_.GetKey(), kMaxSequenceNumber, kValueTypeForSeek));
Slice db_iter_key = last_key.GetKey();
iter_->ResetPrefixSeekKey(&db_iter_key);
}
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));
Slice db_iter_key = last_key.GetKey();
iter_->ResetPrefixSeekKey(&db_iter_key);
}
if (current_entry_is_merged_) {
// Not placed in the same key. Need to call Prev() until finding the
// previous key.
@ -794,7 +817,6 @@ void DBIter::Seek(const Slice& target) {
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_) {
@ -815,6 +837,7 @@ void DBIter::Seek(const Slice& target) {
} 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();
@ -911,25 +934,15 @@ void DBIter::SeekToLast() {
// 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;
}
SeekForPrev(*iterate_upper_bound_);
if (!Valid()) {
return;
} else if (user_comparator_->Equal(*iterate_upper_bound_, key())) {
Prev();
}
} else {
PrevInternal();
}
PrevInternal();
if (statistics_ != nullptr) {
RecordTick(statistics_, NUMBER_DB_SEEK);
if (valid_) {
@ -943,18 +956,16 @@ void DBIter::SeekToLast() {
}
}
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);
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;
}
@ -993,15 +1004,15 @@ 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) {
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);
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);

6
db/db_iter.h
View File

@ -31,7 +31,8 @@ extern Iterator* NewDBIterator(
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 = nullptr,
bool prefix_same_as_start = false, bool pin_data = false);
bool prefix_same_as_start = false, bool pin_data = false,
bool total_order_seek = false);
// A wrapper iterator which wraps DB Iterator and the arena, with which the DB
// iterator is supposed be allocated. This class is used as an entry point of
@ -78,6 +79,7 @@ extern ArenaWrappedDBIter* NewArenaWrappedDbIterator(
const Comparator* user_key_comparator, const SequenceNumber& sequence,
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 prefix_same_as_start = false, bool pin_data = false,
bool total_order_seek = false);
} // namespace rocksdb

4
db/db_iter_test.cc
View File

@ -357,7 +357,7 @@ TEST_F(DBIteratorTest, DBIteratorPrevNext) {
db_iter->SeekToLast();
ASSERT_TRUE(db_iter->Valid());
ASSERT_EQ(static_cast<int>(perf_context.internal_key_skipped_count), 1);
ASSERT_EQ(static_cast<int>(perf_context.internal_key_skipped_count), 7);
ASSERT_EQ(db_iter->key().ToString(), "b");
SetPerfLevel(kDisable);
@ -480,7 +480,7 @@ TEST_F(DBIteratorTest, DBIteratorPrevNext) {
db_iter->SeekToLast();
ASSERT_TRUE(db_iter->Valid());
ASSERT_EQ(static_cast<int>(perf_context.internal_delete_skipped_count), 0);
ASSERT_EQ(static_cast<int>(perf_context.internal_delete_skipped_count), 1);
ASSERT_EQ(db_iter->key().ToString(), "b");
SetPerfLevel(kDisable);

223
db/prefix_test.cc
View File

@ -18,6 +18,7 @@ int main() {
#include <vector>
#include <gflags/gflags.h>
#include "db/db_impl.h"
#include "rocksdb/comparator.h"
#include "rocksdb/db.h"
#include "rocksdb/filter_policy.h"
@ -26,9 +27,11 @@ int main() {
#include "rocksdb/slice_transform.h"
#include "rocksdb/table.h"
#include "util/histogram.h"
#include "util/random.h"
#include "util/stop_watch.h"
#include "util/string_util.h"
#include "util/testharness.h"
#include "utilities/merge_operators.h"
using GFLAGS::ParseCommandLineFlags;
@ -46,6 +49,7 @@ DEFINE_int32(skiplist_height, 4, "");
DEFINE_double(memtable_prefix_bloom_size_ratio, 0.1, "");
DEFINE_int32(memtable_huge_page_size, 2 * 1024 * 1024, "");
DEFINE_int32(value_size, 40, "");
DEFINE_bool(enable_print, false, "Print options generated to console.");
// Path to the database on file system
const std::string kDbName = rocksdb::test::TmpDir() + "/prefix_test";
@ -106,6 +110,10 @@ class TestKeyComparator : public Comparator {
return 0;
}
bool operator()(const TestKey& a, const TestKey& b) const {
return Compare(TestKeyToSlice(a), TestKeyToSlice(b)) < 0;
}
virtual const char* Name() const override {
return "TestKeyComparator";
}
@ -124,6 +132,23 @@ void PutKey(DB* db, WriteOptions write_options, uint64_t prefix,
ASSERT_OK(db->Put(write_options, key, value));
}
void PutKey(DB* db, WriteOptions write_options, const TestKey& test_key,
const Slice& value) {
Slice key = TestKeyToSlice(test_key);
ASSERT_OK(db->Put(write_options, key, value));
}
void MergeKey(DB* db, WriteOptions write_options, const TestKey& test_key,
const Slice& value) {
Slice key = TestKeyToSlice(test_key);
ASSERT_OK(db->Merge(write_options, key, value));
}
void DeleteKey(DB* db, WriteOptions write_options, const TestKey& test_key) {
Slice key = TestKeyToSlice(test_key);
ASSERT_OK(db->Delete(write_options, key));
}
void SeekIterator(Iterator* iter, uint64_t prefix, uint64_t suffix) {
TestKey test_key(prefix, suffix);
Slice key = TestKeyToSlice(test_key);
@ -629,8 +654,206 @@ TEST_F(PrefixTest, DynamicPrefixIterator) {
}
}
TEST_F(PrefixTest, PrefixSeekModePrev) {
// Only for SkipListFactory
options.memtable_factory.reset(new SkipListFactory);
options.merge_operator = MergeOperators::CreatePutOperator();
options.write_buffer_size = 1024 * 1024;
Random rnd(1);
for (size_t m = 1; m < 100; m++) {
std::cout << "[" + std::to_string(m) + "]" + "*** Mem table: "
<< options.memtable_factory->Name() << std::endl;
DestroyDB(kDbName, Options());
auto db = OpenDb();
WriteOptions write_options;
ReadOptions read_options;
std::map<TestKey, std::string, TestKeyComparator> entry_maps[3], whole_map;
for (uint64_t i = 0; i < 10; i++) {
int div = i % 3 + 1;
for (uint64_t j = 0; j < 10; j++) {
whole_map[TestKey(i, j)] = entry_maps[rnd.Uniform(div)][TestKey(i, j)] =
'v' + std::to_string(i) + std::to_string(j);
}
}
std::map<TestKey, std::string, TestKeyComparator> type_map;
for (size_t i = 0; i < 3; i++) {
for (auto& kv : entry_maps[i]) {
if (rnd.OneIn(3)) {
PutKey(db.get(), write_options, kv.first, kv.second);
type_map[kv.first] = "value";
} else {
MergeKey(db.get(), write_options, kv.first, kv.second);
type_map[kv.first] = "merge";
}
}
if (i < 2) {
db->Flush(FlushOptions());
}
}
for (size_t i = 0; i < 2; i++) {
for (auto& kv : entry_maps[i]) {
if (rnd.OneIn(10)) {
whole_map.erase(kv.first);
DeleteKey(db.get(), write_options, kv.first);
entry_maps[2][kv.first] = "delete";
}
}
}
if (FLAGS_enable_print) {
for (size_t i = 0; i < 3; i++) {
for (auto& kv : entry_maps[i]) {
std::cout << "[" << i << "]" << kv.first.prefix << kv.first.sorted
<< " " << kv.second + " " + type_map[kv.first] << std::endl;
}
}
}
std::unique_ptr<Iterator> iter(db->NewIterator(read_options));
for (uint64_t prefix = 0; prefix < 10; prefix++) {
uint64_t start_suffix = rnd.Uniform(9);
SeekIterator(iter.get(), prefix, start_suffix);
auto it = whole_map.find(TestKey(prefix, start_suffix));
if (it == whole_map.end()) {
continue;
}
ASSERT_NE(it, whole_map.end());
ASSERT_TRUE(iter->Valid());
if (FLAGS_enable_print) {
std::cout << "round " << prefix
<< " iter: " << SliceToTestKey(iter->key())->prefix
<< SliceToTestKey(iter->key())->sorted
<< " | map: " << it->first.prefix << it->first.sorted << " | "
<< iter->value().ToString() << " " << it->second << std::endl;
}
ASSERT_EQ(iter->value(), it->second);
uint64_t stored_prefix = prefix;
for (size_t k = 0; k < 9; k++) {
if (rnd.OneIn(2) || it == whole_map.begin()) {
iter->Next();
it++;
if (FLAGS_enable_print) {
std::cout << "Next >> ";
}
} else {
iter->Prev();
it--;
if (FLAGS_enable_print) {
std::cout << "Prev >> ";
}
}
if (!iter->Valid() ||
SliceToTestKey(iter->key())->prefix != stored_prefix) {
break;
}
stored_prefix = SliceToTestKey(iter->key())->prefix;
ASSERT_TRUE(iter->Valid());
ASSERT_NE(it, whole_map.end());
ASSERT_EQ(iter->value(), it->second);
if (FLAGS_enable_print) {
std::cout << "iter: " << SliceToTestKey(iter->key())->prefix
<< SliceToTestKey(iter->key())->sorted
<< " | map: " << it->first.prefix << it->first.sorted
<< " | " << iter->value().ToString() << " " << it->second
<< std::endl;
}
}
}
}
}
TEST_F(PrefixTest, PrefixSeekModePrev2) {
// Only for SkipListFactory
// test the case
// iter1 iter2
// | prefix | suffix | | prefix | suffix |
// | 1 | 1 | | 1 | 2 |
// | 1 | 3 | | 1 | 4 |
// | 2 | 1 | | 3 | 3 |
// | 2 | 2 | | 3 | 4 |
// after seek(15), iter1 will be at 21 and iter2 will be 33.
// Then if call Prev() in prefix mode where SeekForPrev(21) gets called,
// iter2 should turn to invalid state because of bloom filter.
options.memtable_factory.reset(new SkipListFactory);
options.write_buffer_size = 1024 * 1024;
std::string v13("v13");
DestroyDB(kDbName, Options());
auto db = OpenDb();
WriteOptions write_options;
ReadOptions read_options;
PutKey(db.get(), write_options, TestKey(1, 2), "v12");
PutKey(db.get(), write_options, TestKey(1, 4), "v14");
PutKey(db.get(), write_options, TestKey(3, 3), "v33");
PutKey(db.get(), write_options, TestKey(3, 4), "v34");
db->Flush(FlushOptions());
reinterpret_cast<DBImpl*>(db.get())->TEST_WaitForFlushMemTable();
PutKey(db.get(), write_options, TestKey(1, 1), "v11");
PutKey(db.get(), write_options, TestKey(1, 3), "v13");
PutKey(db.get(), write_options, TestKey(2, 1), "v21");
PutKey(db.get(), write_options, TestKey(2, 2), "v22");
db->Flush(FlushOptions());
reinterpret_cast<DBImpl*>(db.get())->TEST_WaitForFlushMemTable();
std::unique_ptr<Iterator> iter(db->NewIterator(read_options));
SeekIterator(iter.get(), 1, 5);
iter->Prev();
ASSERT_EQ(iter->value(), v13);
}
TEST_F(PrefixTest, PrefixSeekModePrev3) {
// Only for SkipListFactory
// test SeekToLast() with iterate_upper_bound_ in prefix_seek_mode
options.memtable_factory.reset(new SkipListFactory);
options.write_buffer_size = 1024 * 1024;
std::string v14("v14");
TestKey upper_bound_key = TestKey(1, 5);
Slice upper_bound = TestKeyToSlice(upper_bound_key);
{
DestroyDB(kDbName, Options());
auto db = OpenDb();
WriteOptions write_options;
ReadOptions read_options;
read_options.iterate_upper_bound = &upper_bound;
PutKey(db.get(), write_options, TestKey(1, 2), "v12");
PutKey(db.get(), write_options, TestKey(1, 4), "v14");
db->Flush(FlushOptions());
reinterpret_cast<DBImpl*>(db.get())->TEST_WaitForFlushMemTable();
PutKey(db.get(), write_options, TestKey(1, 1), "v11");
PutKey(db.get(), write_options, TestKey(1, 3), "v13");
PutKey(db.get(), write_options, TestKey(2, 1), "v21");
PutKey(db.get(), write_options, TestKey(2, 2), "v22");
db->Flush(FlushOptions());
reinterpret_cast<DBImpl*>(db.get())->TEST_WaitForFlushMemTable();
std::unique_ptr<Iterator> iter(db->NewIterator(read_options));
iter->SeekToLast();
ASSERT_EQ(iter->value(), v14);
}
{
DestroyDB(kDbName, Options());
auto db = OpenDb();
WriteOptions write_options;
ReadOptions read_options;
read_options.iterate_upper_bound = &upper_bound;
PutKey(db.get(), write_options, TestKey(1, 2), "v12");
PutKey(db.get(), write_options, TestKey(1, 4), "v14");
PutKey(db.get(), write_options, TestKey(3, 3), "v33");
PutKey(db.get(), write_options, TestKey(3, 4), "v34");
db->Flush(FlushOptions());
reinterpret_cast<DBImpl*>(db.get())->TEST_WaitForFlushMemTable();
PutKey(db.get(), write_options, TestKey(1, 1), "v11");
PutKey(db.get(), write_options, TestKey(1, 3), "v13");
db->Flush(FlushOptions());
reinterpret_cast<DBImpl*>(db.get())->TEST_WaitForFlushMemTable();
std::unique_ptr<Iterator> iter(db->NewIterator(read_options));
iter->SeekToLast();
ASSERT_EQ(iter->value(), v14);
}
}
} // end namespace rocksdb
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
ParseCommandLineFlags(&argc, &argv, true);

6
table/internal_iterator.h
View File

@ -94,6 +94,12 @@ class InternalIterator : public Cleanable {
virtual Status GetProperty(std::string prop_name, std::string* prop) {
return Status::NotSupported("");
}
// Reset the key used for Seek() in merge iterator, especially for prefix
// seek mode
// When in prefix_seek_mode, there is inconsistency between db_iterator and
// merge iterator. This inconsistency can cause problem when do Seek() in
// merge iterator in prefix mode.
virtual void ResetPrefixSeekKey(const Slice* prefix_seek_key = nullptr) {}
protected:
void SeekForPrevImpl(const Slice& target, const Comparator* cmp) {

33
table/merger.cc
View File

@ -8,6 +8,7 @@
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "table/merger.h"
#include <string>
#include <vector>
#include "db/pinned_iterators_manager.h"
#include "rocksdb/comparator.h"
@ -157,7 +158,7 @@ class MergingIterator : public InternalIterator {
ClearHeaps();
for (auto& child : children_) {
if (&child != current_) {
child.Seek(key());
child.Seek(prefix_seek_key_ ? *prefix_seek_key_ : key());
if (child.Valid() && comparator_->Equal(key(), child.key())) {
child.Next();
}
@ -203,15 +204,9 @@ class MergingIterator : public InternalIterator {
InitMaxHeap();
for (auto& child : children_) {
if (&child != current_) {
child.Seek(key());
if (child.Valid()) {
// Child is at first entry >= key(). Step back one to be < key()
TEST_SYNC_POINT_CALLBACK("MergeIterator::Prev:BeforePrev", &child);
child.SeekForPrev(prefix_seek_key_ ? *prefix_seek_key_ : key());
if (child.Valid() && comparator_->Equal(key(), child.key())) {
child.Prev();
} else {
// Child has no entries >= key(). Position at last entry.
TEST_SYNC_POINT("MergeIterator::Prev:BeforeSeekToLast");
child.SeekToLast();
}
}
if (child.Valid()) {
@ -219,11 +214,9 @@ class MergingIterator : public InternalIterator {
}
}
direction_ = kReverse;
// Note that we don't do assert(current_ == CurrentReverse()) here
// because it is possible to have some keys larger than the seek-key
// inserted between Seek() and SeekToLast(), which makes current_ not
// equal to CurrentReverse().
current_ = CurrentReverse();
// The loop advanced all non-current children to be < key() so current_
// should still be strictly the smallest key.
assert(current_ == CurrentReverse());
}
// For the heap modifications below to be correct, current_ must be the
@ -284,6 +277,17 @@ class MergingIterator : public InternalIterator {
current_->IsValuePinned();
}
virtual void ResetPrefixSeekKey(const Slice* db_iter_key) override {
if (db_iter_key == nullptr) {
prefix_seek_key_.reset();
return;
}
if (!prefix_seek_key_) {
prefix_seek_key_.reset(new std::string);
}
*prefix_seek_key_ = db_iter_key->ToString();
}
private:
// Clears heaps for both directions, used when changing direction or seeking
void ClearHeaps();
@ -310,6 +314,7 @@ class MergingIterator : public InternalIterator {
// forward. Lazily initialize it to save memory.
std::unique_ptr<MergerMaxIterHeap> maxHeap_;
PinnedIteratorsManager* pinned_iters_mgr_;
std::unique_ptr<std::string> prefix_seek_key_;
IteratorWrapper* CurrentForward() const {
assert(direction_ == kForward);