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21c55bdb6e
rocksdb/db/memtable.cc
sdong 907f24d0e1 Concurrent memtable inserter to update counters and flush state after all inserts 
Summary: In concurrent memtable insert case, updating counters in MemTable::Add() can count for 5% CPU usage. By batch all the counters and update in the end of the write batch, the CPU overheads are overhead in the use cases where more than one key is updated in one write batch.

Test Plan:
Write throughput increases 12% with this benchmark setting:

TEST_TMPDIR=/dev/shm/ ./db_bench --benchmarks=fillrandom -disable_auto_compactions -level0_slowdown_writes_trigger=9999 -level0_stop_writes_trigger=9999 -num=10000000 --writes=1000000 -max_background_flushes=16 -max_write_buffer_number=16 --threads=64 --batch_size=128   -allow_concurrent_memtable_write -enable_write_thread_adaptive_yield

Reviewers: andrewkr, IslamAbdelRahman, ngbronson, igor

Reviewed By: ngbronson

Subscribers: ngbronson, leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D60495
2016-07-08 10:19:55 -07:00

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#include "db/memtable.h"
#include <memory>
#include <algorithm>
#include <limits>
#include "db/dbformat.h"
#include "db/merge_context.h"
#include "db/merge_helper.h"
#include "db/pinned_iterators_manager.h"
#include "rocksdb/comparator.h"
#include "rocksdb/env.h"
#include "rocksdb/iterator.h"
#include "rocksdb/merge_operator.h"
#include "rocksdb/slice_transform.h"
#include "rocksdb/write_buffer_manager.h"
#include "table/internal_iterator.h"
#include "table/merger.h"
#include "util/arena.h"
#include "util/coding.h"
#include "util/murmurhash.h"
#include "util/mutexlock.h"
#include "util/perf_context_imp.h"
#include "util/statistics.h"
#include "util/stop_watch.h"
namespace rocksdb {
MemTableOptions::MemTableOptions(const ImmutableCFOptions& ioptions,
const MutableCFOptions& mutable_cf_options)
: write_buffer_size(mutable_cf_options.write_buffer_size),
arena_block_size(mutable_cf_options.arena_block_size),
memtable_prefix_bloom_bits(
static_cast<uint32_t>(
static_cast<double>(mutable_cf_options.write_buffer_size) *
mutable_cf_options.memtable_prefix_bloom_size_ratio) *
8u),
memtable_prefix_bloom_huge_page_tlb_size(
mutable_cf_options.memtable_prefix_bloom_huge_page_tlb_size),
inplace_update_support(ioptions.inplace_update_support),
inplace_update_num_locks(mutable_cf_options.inplace_update_num_locks),
inplace_callback(ioptions.inplace_callback),
max_successive_merges(mutable_cf_options.max_successive_merges),
statistics(ioptions.statistics),
merge_operator(ioptions.merge_operator),
info_log(ioptions.info_log) {}
MemTable::MemTable(const InternalKeyComparator& cmp,
const ImmutableCFOptions& ioptions,
const MutableCFOptions& mutable_cf_options,
WriteBufferManager* write_buffer_manager,
SequenceNumber earliest_seq)
: comparator_(cmp),
moptions_(ioptions, mutable_cf_options),
refs_(0),
kArenaBlockSize(OptimizeBlockSize(moptions_.arena_block_size)),
arena_(moptions_.arena_block_size, 0),
allocator_(&arena_, write_buffer_manager),
table_(ioptions.memtable_factory->CreateMemTableRep(
comparator_, &allocator_, ioptions.prefix_extractor,
ioptions.info_log)),
data_size_(0),
num_entries_(0),
num_deletes_(0),
flush_in_progress_(false),
flush_completed_(false),
file_number_(0),
first_seqno_(0),
earliest_seqno_(earliest_seq),
mem_next_logfile_number_(0),
min_prep_log_referenced_(0),
locks_(moptions_.inplace_update_support
? moptions_.inplace_update_num_locks
: 0),
prefix_extractor_(ioptions.prefix_extractor),
flush_state_(FLUSH_NOT_REQUESTED),
env_(ioptions.env) {
UpdateFlushState();
// something went wrong if we need to flush before inserting anything
assert(!ShouldScheduleFlush());
if (prefix_extractor_ && moptions_.memtable_prefix_bloom_bits > 0) {
prefix_bloom_.reset(new DynamicBloom(
&allocator_, moptions_.memtable_prefix_bloom_bits,
ioptions.bloom_locality, 6 /* hard coded 6 probes */, nullptr,
moptions_.memtable_prefix_bloom_huge_page_tlb_size, ioptions.info_log));
}
}
MemTable::~MemTable() { assert(refs_ == 0); }
size_t MemTable::ApproximateMemoryUsage() {
size_t arena_usage = arena_.ApproximateMemoryUsage();
size_t table_usage = table_->ApproximateMemoryUsage();
// let MAX_USAGE = std::numeric_limits<size_t>::max()
// then if arena_usage + total_usage >= MAX_USAGE, return MAX_USAGE.
// the following variation is to avoid numeric overflow.
if (arena_usage >= std::numeric_limits<size_t>::max() - table_usage) {
return std::numeric_limits<size_t>::max();
}
// otherwise, return the actual usage
return arena_usage + table_usage;
}
bool MemTable::ShouldFlushNow() const {
// In a lot of times, we cannot allocate arena blocks that exactly matches the
// buffer size. Thus we have to decide if we should over-allocate or
// under-allocate.
// This constant variable can be interpreted as: if we still have more than
// "kAllowOverAllocationRatio * kArenaBlockSize" space left, we'd try to over
// allocate one more block.
const double kAllowOverAllocationRatio = 0.6;
// If arena still have room for new block allocation, we can safely say it
// shouldn't flush.
auto allocated_memory =
table_->ApproximateMemoryUsage() + arena_.MemoryAllocatedBytes();
// if we can still allocate one more block without exceeding the
// over-allocation ratio, then we should not flush.
if (allocated_memory + kArenaBlockSize <
moptions_.write_buffer_size +
kArenaBlockSize * kAllowOverAllocationRatio) {
return false;
}
// if user keeps adding entries that exceeds moptions.write_buffer_size,
// we need to flush earlier even though we still have much available
// memory left.
if (allocated_memory > moptions_.write_buffer_size +
kArenaBlockSize * kAllowOverAllocationRatio) {
return true;
}
// In this code path, Arena has already allocated its "last block", which
// means the total allocatedmemory size is either:
// (1) "moderately" over allocated the memory (no more than `0.6 * arena
// block size`. Or,
// (2) the allocated memory is less than write buffer size, but we'll stop
// here since if we allocate a new arena block, we'll over allocate too much
// more (half of the arena block size) memory.
//
// In either case, to avoid over-allocate, the last block will stop allocation
// when its usage reaches a certain ratio, which we carefully choose "0.75
// full" as the stop condition because it addresses the following issue with
// great simplicity: What if the next inserted entry's size is
// bigger than AllocatedAndUnused()?
//
// The answer is: if the entry size is also bigger than 0.25 *
// kArenaBlockSize, a dedicated block will be allocated for it; otherwise
// arena will anyway skip the AllocatedAndUnused() and allocate a new, empty
// and regular block. In either case, we *overly* over-allocated.
//
// Therefore, setting the last block to be at most "0.75 full" avoids both
// cases.
//
// NOTE: the average percentage of waste space of this approach can be counted
// as: "arena block size * 0.25 / write buffer size". User who specify a small
// write buffer size and/or big arena block size may suffer.
return arena_.AllocatedAndUnused() < kArenaBlockSize / 4;
}
void MemTable::UpdateFlushState() {
auto state = flush_state_.load(std::memory_order_relaxed);
if (state == FLUSH_NOT_REQUESTED && ShouldFlushNow()) {
// ignore CAS failure, because that means somebody else requested
// a flush
flush_state_.compare_exchange_strong(state, FLUSH_REQUESTED,
std::memory_order_relaxed,
std::memory_order_relaxed);
}
}
int MemTable::KeyComparator::operator()(const char* prefix_len_key1,
const char* prefix_len_key2) const {
// Internal keys are encoded as length-prefixed strings.
Slice k1 = GetLengthPrefixedSlice(prefix_len_key1);
Slice k2 = GetLengthPrefixedSlice(prefix_len_key2);
return comparator.Compare(k1, k2);
}
int MemTable::KeyComparator::operator()(const char* prefix_len_key,
const Slice& key)
const {
// Internal keys are encoded as length-prefixed strings.
Slice a = GetLengthPrefixedSlice(prefix_len_key);
return comparator.Compare(a, key);
}
Slice MemTableRep::UserKey(const char* key) const {
Slice slice = GetLengthPrefixedSlice(key);
return Slice(slice.data(), slice.size() - 8);
}
KeyHandle MemTableRep::Allocate(const size_t len, char** buf) {
*buf = allocator_->Allocate(len);
return static_cast<KeyHandle>(*buf);
}
// Encode a suitable internal key target for "target" and return it.
// Uses *scratch as scratch space, and the returned pointer will point
// into this scratch space.
const char* EncodeKey(std::string* scratch, const Slice& target) {
scratch->clear();
PutVarint32(scratch, static_cast<uint32_t>(target.size()));
scratch->append(target.data(), target.size());
return scratch->data();
}
class MemTableIterator : public InternalIterator {
public:
MemTableIterator(
const MemTable& mem, const ReadOptions& read_options, Arena* arena)
: bloom_(nullptr),
prefix_extractor_(mem.prefix_extractor_),
valid_(false),
arena_mode_(arena != nullptr) {
if (prefix_extractor_ != nullptr && !read_options.total_order_seek) {
bloom_ = mem.prefix_bloom_.get();
iter_ = mem.table_->GetDynamicPrefixIterator(arena);
} else {
iter_ = mem.table_->GetIterator(arena);
}
}
~MemTableIterator() {
#ifndef NDEBUG
// Assert that the MemTableIterator is never deleted while
// Pinning is Enabled.
assert(!pinned_iters_mgr_ ||
(pinned_iters_mgr_ && !pinned_iters_mgr_->PinningEnabled()));
#endif
if (arena_mode_) {
iter_->~Iterator();
} else {
delete iter_;
}
}
#ifndef NDEBUG
virtual void SetPinnedItersMgr(
PinnedIteratorsManager* pinned_iters_mgr) override {
pinned_iters_mgr_ = pinned_iters_mgr;
}
PinnedIteratorsManager* pinned_iters_mgr_ = nullptr;
#endif
virtual bool Valid() const override { return valid_; }
virtual void Seek(const Slice& k) override {
PERF_TIMER_GUARD(seek_on_memtable_time);
PERF_COUNTER_ADD(seek_on_memtable_count, 1);
if (bloom_ != nullptr) {
if (!bloom_->MayContain(
prefix_extractor_->Transform(ExtractUserKey(k)))) {
PERF_COUNTER_ADD(bloom_memtable_miss_count, 1);
valid_ = false;
return;
} else {
PERF_COUNTER_ADD(bloom_memtable_hit_count, 1);
}
}
iter_->Seek(k, nullptr);
valid_ = iter_->Valid();
}
virtual void SeekToFirst() override {
iter_->SeekToFirst();
valid_ = iter_->Valid();
}
virtual void SeekToLast() override {
iter_->SeekToLast();
valid_ = iter_->Valid();
}
virtual void Next() override {
assert(Valid());
iter_->Next();
valid_ = iter_->Valid();
}
virtual void Prev() override {
assert(Valid());
iter_->Prev();
valid_ = iter_->Valid();
}
virtual Slice key() const override {
assert(Valid());
return GetLengthPrefixedSlice(iter_->key());
}
virtual Slice value() const override {
assert(Valid());
Slice key_slice = GetLengthPrefixedSlice(iter_->key());
return GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
}
virtual Status status() const override { return Status::OK(); }
virtual bool IsKeyPinned() const override {
// memtable data is always pinned
return true;
}
private:
DynamicBloom* bloom_;
const SliceTransform* const prefix_extractor_;
MemTableRep::Iterator* iter_;
bool valid_;
bool arena_mode_;
// No copying allowed
MemTableIterator(const MemTableIterator&);
void operator=(const MemTableIterator&);
};
InternalIterator* MemTable::NewIterator(const ReadOptions& read_options,
Arena* arena) {
assert(arena != nullptr);
auto mem = arena->AllocateAligned(sizeof(MemTableIterator));
return new (mem) MemTableIterator(*this, read_options, arena);
}
port::RWMutex* MemTable::GetLock(const Slice& key) {
static murmur_hash hash;
return &locks_[hash(key) % locks_.size()];
}
uint64_t MemTable::ApproximateSize(const Slice& start_ikey,
const Slice& end_ikey) {
uint64_t entry_count = table_->ApproximateNumEntries(start_ikey, end_ikey);
if (entry_count == 0) {
return 0;
}
uint64_t n = num_entries_.load(std::memory_order_relaxed);
if (n == 0) {
return 0;
}
if (entry_count > n) {
// table_->ApproximateNumEntries() is just an estimate so it can be larger
// than actual entries we have. Cap it to entries we have to limit the
// inaccuracy.
entry_count = n;
}
uint64_t data_size = data_size_.load(std::memory_order_relaxed);
return entry_count * (data_size / n);
}
void MemTable::Add(SequenceNumber s, ValueType type,
const Slice& key, /* user key */
const Slice& value, bool allow_concurrent,
MemTablePostProcessInfo* post_process_info) {
// Format of an entry is concatenation of:
// key_size : varint32 of internal_key.size()
// key bytes : char[internal_key.size()]
// value_size : varint32 of value.size()
// value bytes : char[value.size()]
uint32_t key_size = static_cast<uint32_t>(key.size());
uint32_t val_size = static_cast<uint32_t>(value.size());
uint32_t internal_key_size = key_size + 8;
const uint32_t encoded_len = VarintLength(internal_key_size) +
internal_key_size + VarintLength(val_size) +
val_size;
char* buf = nullptr;
KeyHandle handle = table_->Allocate(encoded_len, &buf);
char* p = EncodeVarint32(buf, internal_key_size);
memcpy(p, key.data(), key_size);
p += key_size;
uint64_t packed = PackSequenceAndType(s, type);
EncodeFixed64(p, packed);
p += 8;
p = EncodeVarint32(p, val_size);
memcpy(p, value.data(), val_size);
assert((unsigned)(p + val_size - buf) == (unsigned)encoded_len);
if (!allow_concurrent) {
table_->Insert(handle);
// this is a bit ugly, but is the way to avoid locked instructions
// when incrementing an atomic
num_entries_.store(num_entries_.load(std::memory_order_relaxed) + 1,
std::memory_order_relaxed);
data_size_.store(data_size_.load(std::memory_order_relaxed) + encoded_len,
std::memory_order_relaxed);
if (type == kTypeDeletion) {
num_deletes_.store(num_deletes_.load(std::memory_order_relaxed) + 1,
std::memory_order_relaxed);
}
if (prefix_bloom_) {
assert(prefix_extractor_);
prefix_bloom_->Add(prefix_extractor_->Transform(key));
}
// The first sequence number inserted into the memtable
assert(first_seqno_ == 0 || s > first_seqno_);
if (first_seqno_ == 0) {
first_seqno_.store(s, std::memory_order_relaxed);
if (earliest_seqno_ == kMaxSequenceNumber) {
earliest_seqno_.store(GetFirstSequenceNumber(),
std::memory_order_relaxed);
}
assert(first_seqno_.load() >= earliest_seqno_.load());
}
assert(post_process_info == nullptr);
UpdateFlushState();
} else {
table_->InsertConcurrently(handle);
assert(post_process_info != nullptr);
post_process_info->num_entries++;
post_process_info->data_size += encoded_len;
if (type == kTypeDeletion) {
post_process_info->num_deletes++;
}
if (prefix_bloom_) {
assert(prefix_extractor_);
prefix_bloom_->AddConcurrently(prefix_extractor_->Transform(key));
}
// atomically update first_seqno_ and earliest_seqno_.
uint64_t cur_seq_num = first_seqno_.load(std::memory_order_relaxed);
while ((cur_seq_num == 0 || s < cur_seq_num) &&
!first_seqno_.compare_exchange_weak(cur_seq_num, s)) {
}
uint64_t cur_earliest_seqno =
earliest_seqno_.load(std::memory_order_relaxed);
while (
(cur_earliest_seqno == kMaxSequenceNumber || s < cur_earliest_seqno) &&
!first_seqno_.compare_exchange_weak(cur_earliest_seqno, s)) {
}
}
}
// Callback from MemTable::Get()
namespace {
struct Saver {
Status* status;
const LookupKey* key;
bool* found_final_value; // Is value set correctly? Used by KeyMayExist
bool* merge_in_progress;
std::string* value;
SequenceNumber seq;
const MergeOperator* merge_operator;
// the merge operations encountered;
MergeContext* merge_context;
MemTable* mem;
Logger* logger;
Statistics* statistics;
bool inplace_update_support;
Env* env_;
};
} // namespace
static bool SaveValue(void* arg, const char* entry) {
Saver* s = reinterpret_cast<Saver*>(arg);
MergeContext* merge_context = s->merge_context;
const MergeOperator* merge_operator = s->merge_operator;
assert(s != nullptr && merge_context != nullptr);
// entry format is:
// klength varint32
// userkey char[klength-8]
// tag uint64
// vlength varint32
// value char[vlength]
// Check that it belongs to same user key. We do not check the
// sequence number since the Seek() call above should have skipped
// all entries with overly large sequence numbers.
uint32_t key_length;
const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
if (s->mem->GetInternalKeyComparator().user_comparator()->Equal(
Slice(key_ptr, key_length - 8), s->key->user_key())) {
// Correct user key
const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
ValueType type;
UnPackSequenceAndType(tag, &s->seq, &type);
switch (type) {
case kTypeValue: {
if (s->inplace_update_support) {
s->mem->GetLock(s->key->user_key())->ReadLock();
}
Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
*(s->status) = Status::OK();
if (*(s->merge_in_progress)) {
*(s->status) = MergeHelper::TimedFullMerge(
merge_operator, s->key->user_key(), &v,
merge_context->GetOperands(), s->value, s->logger, s->statistics,
s->env_);
} else if (s->value != nullptr) {
s->value->assign(v.data(), v.size());
}
if (s->inplace_update_support) {
s->mem->GetLock(s->key->user_key())->ReadUnlock();
}
*(s->found_final_value) = true;
return false;
}
case kTypeDeletion:
case kTypeSingleDeletion: {
if (*(s->merge_in_progress)) {
*(s->status) = Status::OK();
*(s->status) = MergeHelper::TimedFullMerge(
merge_operator, s->key->user_key(), nullptr,
merge_context->GetOperands(), s->value, s->logger, s->statistics,
s->env_);
} else {
*(s->status) = Status::NotFound();
}
*(s->found_final_value) = true;
return false;
}
case kTypeMerge: {
if (!merge_operator) {
*(s->status) = Status::InvalidArgument(
"merge_operator is not properly initialized.");
// Normally we continue the loop (return true) when we see a merge
// operand. But in case of an error, we should stop the loop
// immediately and pretend we have found the value to stop further
// seek. Otherwise, the later call will override this error status.
*(s->found_final_value) = true;
return false;
}
Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
*(s->merge_in_progress) = true;
merge_context->PushOperand(v);
return true;
}
default:
assert(false);
return true;
}
}
// s->state could be Corrupt, merge or notfound
return false;
}
bool MemTable::Get(const LookupKey& key, std::string* value, Status* s,
MergeContext* merge_context, SequenceNumber* seq) {
// The sequence number is updated synchronously in version_set.h
if (IsEmpty()) {
// Avoiding recording stats for speed.
return false;
}
PERF_TIMER_GUARD(get_from_memtable_time);
Slice user_key = key.user_key();
bool found_final_value = false;
bool merge_in_progress = s->IsMergeInProgress();
bool const may_contain =
nullptr == prefix_bloom_
? false
: prefix_bloom_->MayContain(prefix_extractor_->Transform(user_key));
if (prefix_bloom_ && !may_contain) {
// iter is null if prefix bloom says the key does not exist
PERF_COUNTER_ADD(bloom_memtable_miss_count, 1);
*seq = kMaxSequenceNumber;
} else {
if (prefix_bloom_) {
PERF_COUNTER_ADD(bloom_memtable_hit_count, 1);
}
Saver saver;
saver.status = s;
saver.found_final_value = &found_final_value;
saver.merge_in_progress = &merge_in_progress;
saver.key = &key;
saver.value = value;
saver.seq = kMaxSequenceNumber;
saver.mem = this;
saver.merge_context = merge_context;
saver.merge_operator = moptions_.merge_operator;
saver.logger = moptions_.info_log;
saver.inplace_update_support = moptions_.inplace_update_support;
saver.statistics = moptions_.statistics;
saver.env_ = env_;
table_->Get(key, &saver, SaveValue);
*seq = saver.seq;
}
// No change to value, since we have not yet found a Put/Delete
if (!found_final_value && merge_in_progress) {
*s = Status::MergeInProgress();
}
PERF_COUNTER_ADD(get_from_memtable_count, 1);
return found_final_value;
}
void MemTable::Update(SequenceNumber seq,
const Slice& key,
const Slice& value) {
LookupKey lkey(key, seq);
Slice mem_key = lkey.memtable_key();
std::unique_ptr<MemTableRep::Iterator> iter(
table_->GetDynamicPrefixIterator());
iter->Seek(lkey.internal_key(), mem_key.data());
if (iter->Valid()) {
// entry format is:
// key_length varint32
// userkey char[klength-8]
// tag uint64
// vlength varint32
// value char[vlength]
// Check that it belongs to same user key. We do not check the
// sequence number since the Seek() call above should have skipped
// all entries with overly large sequence numbers.
const char* entry = iter->key();
uint32_t key_length = 0;
const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
if (comparator_.comparator.user_comparator()->Equal(
Slice(key_ptr, key_length - 8), lkey.user_key())) {
// Correct user key
const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
ValueType type;
SequenceNumber unused;
UnPackSequenceAndType(tag, &unused, &type);
switch (type) {
case kTypeValue: {
Slice prev_value = GetLengthPrefixedSlice(key_ptr + key_length);
uint32_t prev_size = static_cast<uint32_t>(prev_value.size());
uint32_t new_size = static_cast<uint32_t>(value.size());
// Update value, if new value size <= previous value size
if (new_size <= prev_size ) {
char* p = EncodeVarint32(const_cast<char*>(key_ptr) + key_length,
new_size);
WriteLock wl(GetLock(lkey.user_key()));
memcpy(p, value.data(), value.size());
assert((unsigned)((p + value.size()) - entry) ==
(unsigned)(VarintLength(key_length) + key_length +
VarintLength(value.size()) + value.size()));
return;
}
}
default:
// If the latest value is kTypeDeletion, kTypeMerge or kTypeLogData
// we don't have enough space for update inplace
Add(seq, kTypeValue, key, value);
return;
}
}
}
// key doesn't exist
Add(seq, kTypeValue, key, value);
}
bool MemTable::UpdateCallback(SequenceNumber seq,
const Slice& key,
const Slice& delta) {
LookupKey lkey(key, seq);
Slice memkey = lkey.memtable_key();
std::unique_ptr<MemTableRep::Iterator> iter(
table_->GetDynamicPrefixIterator());
iter->Seek(lkey.internal_key(), memkey.data());
if (iter->Valid()) {
// entry format is:
// key_length varint32
// userkey char[klength-8]
// tag uint64
// vlength varint32
// value char[vlength]
// Check that it belongs to same user key. We do not check the
// sequence number since the Seek() call above should have skipped
// all entries with overly large sequence numbers.
const char* entry = iter->key();
uint32_t key_length = 0;
const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
if (comparator_.comparator.user_comparator()->Equal(
Slice(key_ptr, key_length - 8), lkey.user_key())) {
// Correct user key
const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
ValueType type;
uint64_t unused;
UnPackSequenceAndType(tag, &unused, &type);
switch (type) {
case kTypeValue: {
Slice prev_value = GetLengthPrefixedSlice(key_ptr + key_length);
uint32_t prev_size = static_cast<uint32_t>(prev_value.size());
char* prev_buffer = const_cast<char*>(prev_value.data());
uint32_t new_prev_size = prev_size;
std::string str_value;
WriteLock wl(GetLock(lkey.user_key()));
auto status = moptions_.inplace_callback(prev_buffer, &new_prev_size,
delta, &str_value);
if (status == UpdateStatus::UPDATED_INPLACE) {
// Value already updated by callback.
assert(new_prev_size <= prev_size);
if (new_prev_size < prev_size) {
// overwrite the new prev_size
char* p = EncodeVarint32(const_cast<char*>(key_ptr) + key_length,
new_prev_size);
if (VarintLength(new_prev_size) < VarintLength(prev_size)) {
// shift the value buffer as well.
memcpy(p, prev_buffer, new_prev_size);
}
}
RecordTick(moptions_.statistics, NUMBER_KEYS_UPDATED);
UpdateFlushState();
return true;
} else if (status == UpdateStatus::UPDATED) {
Add(seq, kTypeValue, key, Slice(str_value));
RecordTick(moptions_.statistics, NUMBER_KEYS_WRITTEN);
UpdateFlushState();
return true;
} else if (status == UpdateStatus::UPDATE_FAILED) {
// No action required. Return.
UpdateFlushState();
return true;
}
}
default:
break;
}
}
}
// If the latest value is not kTypeValue
// or key doesn't exist
return false;
}
size_t MemTable::CountSuccessiveMergeEntries(const LookupKey& key) {
Slice memkey = key.memtable_key();
// A total ordered iterator is costly for some memtablerep (prefix aware
// reps). By passing in the user key, we allow efficient iterator creation.
// The iterator only needs to be ordered within the same user key.
std::unique_ptr<MemTableRep::Iterator> iter(
table_->GetDynamicPrefixIterator());
iter->Seek(key.internal_key(), memkey.data());
size_t num_successive_merges = 0;
for (; iter->Valid(); iter->Next()) {
const char* entry = iter->key();
uint32_t key_length = 0;
const char* iter_key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
if (!comparator_.comparator.user_comparator()->Equal(
Slice(iter_key_ptr, key_length - 8), key.user_key())) {
break;
}
const uint64_t tag = DecodeFixed64(iter_key_ptr + key_length - 8);
ValueType type;
uint64_t unused;
UnPackSequenceAndType(tag, &unused, &type);
if (type != kTypeMerge) {
break;
}
++num_successive_merges;
}
return num_successive_merges;
}
void MemTableRep::Get(const LookupKey& k, void* callback_args,
bool (*callback_func)(void* arg, const char* entry)) {
auto iter = GetDynamicPrefixIterator();
for (iter->Seek(k.internal_key(), k.memtable_key().data());
iter->Valid() && callback_func(callback_args, iter->key());
iter->Next()) {
}
}
void MemTable::RefLogContainingPrepSection(uint64_t log) {
assert(log > 0);
auto cur = min_prep_log_referenced_.load();
while ((log < cur || cur == 0) &&
!min_prep_log_referenced_.compare_exchange_strong(cur, log)) {
cur = min_prep_log_referenced_.load();
}
}
uint64_t MemTable::GetMinLogContainingPrepSection() {
return min_prep_log_referenced_.load();
}
} // namespace rocksdb
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