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4c49e38f15
rocksdb/db/memtable.cc
Vijay Nadimpalli 4c49e38f15 MultiGet batching in memtable (#5818) 
Summary:
RocksDB has a MultiGet() API that implements batched key lookup for higher performance (https://github.com/facebook/rocksdb/blob/master/include/rocksdb/db.h#L468). Currently, batching is implemented in BlockBasedTableReader::MultiGet() for SST file lookups. One of the ways it improves performance is by pipelining bloom filter lookups (by prefetching required cachelines for all the keys in the batch, and then doing the probe) and thus hiding the cache miss latency. The same concept can be extended to the memtable as well. This PR involves implementing a pipelined bloom filter lookup in DynamicBloom, and implementing MemTable::MultiGet() that can leverage it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5818

Test Plan:
Existing tests

Performance Test:
Ran the below command which fills up the memtable and makes sure there are no flushes and then call multiget. Ran it on master and on the new change and see atleast 1% performance improvement across all the test runs I did. Sometimes the improvement was upto 5%.

TEST_TMPDIR=/data/users/$USER/benchmarks/feature/ numactl -C 10 ./db_bench -benchmarks="fillseq,multireadrandom" -num=600000 -compression_type="none" -level_compaction_dynamic_level_bytes -write_buffer_size=200000000 -target_file_size_base=200000000 -max_bytes_for_level_base=16777216 -reads=90000 -threads=1 -compression_type=none -cache_size=4194304000 -batch_size=32 -disable_auto_compactions=true -bloom_bits=10 -cache_index_and_filter_blocks=true -pin_l0_filter_and_index_blocks_in_cache=true -multiread_batched=true -multiread_stride=4 -statistics -memtable_whole_key_filtering=true -memtable_bloom_size_ratio=10

Differential Revision: D17578869

Pulled By: vjnadimpalli

fbshipit-source-id: 23dc651d9bf49db11d22375bf435708875a1f192
2019-10-10 09:39:39 -07:00

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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/memtable.h"
#include <algorithm>
#include <array>
#include <limits>
#include <memory>
#include "db/dbformat.h"
#include "db/merge_context.h"
#include "db/merge_helper.h"
#include "db/pinned_iterators_manager.h"
#include "db/range_tombstone_fragmenter.h"
#include "db/read_callback.h"
#include "memory/arena.h"
#include "memory/memory_usage.h"
#include "monitoring/perf_context_imp.h"
#include "monitoring/statistics.h"
#include "port/port.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/iterator_wrapper.h"
#include "table/merging_iterator.h"
#include "util/autovector.h"
#include "util/coding.h"
#include "util/mutexlock.h"
#include "util/util.h"
namespace rocksdb {
ImmutableMemTableOptions::ImmutableMemTableOptions(
const ImmutableCFOptions& ioptions,
const MutableCFOptions& mutable_cf_options)
: 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_huge_page_size(mutable_cf_options.memtable_huge_page_size),
memtable_whole_key_filtering(
mutable_cf_options.memtable_whole_key_filtering),
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 latest_seq, uint32_t column_family_id)
: comparator_(cmp),
moptions_(ioptions, mutable_cf_options),
refs_(0),
kArenaBlockSize(OptimizeBlockSize(moptions_.arena_block_size)),
mem_tracker_(write_buffer_manager),
arena_(moptions_.arena_block_size,
(write_buffer_manager != nullptr &&
(write_buffer_manager->enabled() ||
write_buffer_manager->cost_to_cache()))
? &mem_tracker_
: nullptr,
mutable_cf_options.memtable_huge_page_size),
table_(ioptions.memtable_factory->CreateMemTableRep(
comparator_, &arena_, mutable_cf_options.prefix_extractor.get(),
ioptions.info_log, column_family_id)),
range_del_table_(SkipListFactory().CreateMemTableRep(
comparator_, &arena_, nullptr /* transform */, ioptions.info_log,
column_family_id)),
is_range_del_table_empty_(true),
data_size_(0),
num_entries_(0),
num_deletes_(0),
write_buffer_size_(mutable_cf_options.write_buffer_size),
flush_in_progress_(false),
flush_completed_(false),
file_number_(0),
first_seqno_(0),
earliest_seqno_(latest_seq),
creation_seq_(latest_seq),
mem_next_logfile_number_(0),
min_prep_log_referenced_(0),
locks_(moptions_.inplace_update_support
? moptions_.inplace_update_num_locks
: 0),
prefix_extractor_(mutable_cf_options.prefix_extractor.get()),
flush_state_(FLUSH_NOT_REQUESTED),
env_(ioptions.env),
insert_with_hint_prefix_extractor_(
ioptions.memtable_insert_with_hint_prefix_extractor),
oldest_key_time_(std::numeric_limits<uint64_t>::max()),
atomic_flush_seqno_(kMaxSequenceNumber),
approximate_memory_usage_(0) {
UpdateFlushState();
// something went wrong if we need to flush before inserting anything
assert(!ShouldScheduleFlush());
// use bloom_filter_ for both whole key and prefix bloom filter
if ((prefix_extractor_ || moptions_.memtable_whole_key_filtering) &&
moptions_.memtable_prefix_bloom_bits > 0) {
bloom_filter_.reset(
new DynamicBloom(&arena_, moptions_.memtable_prefix_bloom_bits,
6 /* hard coded 6 probes */,
moptions_.memtable_huge_page_size, ioptions.info_log));
}
}
MemTable::~MemTable() {
mem_tracker_.FreeMem();
assert(refs_ == 0);
}
size_t MemTable::ApproximateMemoryUsage() {
autovector<size_t> usages = {arena_.ApproximateMemoryUsage(),
table_->ApproximateMemoryUsage(),
range_del_table_->ApproximateMemoryUsage(),
rocksdb::ApproximateMemoryUsage(insert_hints_)};
size_t total_usage = 0;
for (size_t usage : usages) {
// If usage + total_usage >= kMaxSizet, return kMaxSizet.
// the following variation is to avoid numeric overflow.
if (usage >= port::kMaxSizet - total_usage) {
return port::kMaxSizet;
}
total_usage += usage;
}
approximate_memory_usage_.store(total_usage, std::memory_order_relaxed);
// otherwise, return the actual usage
return total_usage;
}
bool MemTable::ShouldFlushNow() {
size_t write_buffer_size = write_buffer_size_.load(std::memory_order_relaxed);
// 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() +
range_del_table_->ApproximateMemoryUsage() +
arena_.MemoryAllocatedBytes();
approximate_memory_usage_.store(allocated_memory, std::memory_order_relaxed);
// if we can still allocate one more block without exceeding the
// over-allocation ratio, then we should not flush.
if (allocated_memory + kArenaBlockSize <
write_buffer_size + kArenaBlockSize * kAllowOverAllocationRatio) {
return false;
}
// if user keeps adding entries that exceeds write_buffer_size, we need to
// flush earlier even though we still have much available memory left.
if (allocated_memory >
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);
}
}
void MemTable::UpdateOldestKeyTime() {
uint64_t oldest_key_time = oldest_key_time_.load(std::memory_order_relaxed);
if (oldest_key_time == std::numeric_limits<uint64_t>::max()) {
int64_t current_time = 0;
auto s = env_->GetCurrentTime(&current_time);
if (s.ok()) {
assert(current_time >= 0);
// If fail, the timestamp is already set.
oldest_key_time_.compare_exchange_strong(
oldest_key_time, static_cast<uint64_t>(current_time),
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.CompareKeySeq(k1, k2);
}
int MemTable::KeyComparator::operator()(const char* prefix_len_key,
const KeyComparator::DecodedType& key)
const {
// Internal keys are encoded as length-prefixed strings.
Slice a = GetLengthPrefixedSlice(prefix_len_key);
return comparator.CompareKeySeq(a, key);
}
void MemTableRep::InsertConcurrently(KeyHandle /*handle*/) {
#ifndef ROCKSDB_LITE
throw std::runtime_error("concurrent insert not supported");
#else
abort();
#endif
}
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, bool use_range_del_table = false)
: bloom_(nullptr),
prefix_extractor_(mem.prefix_extractor_),
comparator_(mem.comparator_),
valid_(false),
arena_mode_(arena != nullptr),
value_pinned_(
!mem.GetImmutableMemTableOptions()->inplace_update_support) {
if (use_range_del_table) {
iter_ = mem.range_del_table_->GetIterator(arena);
} else if (prefix_extractor_ != nullptr && !read_options.total_order_seek) {
bloom_ = mem.bloom_filter_.get();
iter_ = mem.table_->GetDynamicPrefixIterator(arena);
} else {
iter_ = mem.table_->GetIterator(arena);
}
}
// No copying allowed
MemTableIterator(const MemTableIterator&) = delete;
void operator=(const MemTableIterator&) = delete;
~MemTableIterator() override {
#ifndef NDEBUG
// Assert that the MemTableIterator is never deleted while
// Pinning is Enabled.
assert(!pinned_iters_mgr_ || !pinned_iters_mgr_->PinningEnabled());
#endif
if (arena_mode_) {
iter_->~Iterator();
} else {
delete iter_;
}
}
#ifndef NDEBUG
void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) override {
pinned_iters_mgr_ = pinned_iters_mgr;
}
PinnedIteratorsManager* pinned_iters_mgr_ = nullptr;
#endif
bool Valid() const override { return valid_; }
void Seek(const Slice& k) override {
PERF_TIMER_GUARD(seek_on_memtable_time);
PERF_COUNTER_ADD(seek_on_memtable_count, 1);
if (bloom_) {
// iterator should only use prefix bloom filter
Slice user_k(ExtractUserKey(k));
if (prefix_extractor_->InDomain(user_k) &&
!bloom_->MayContain(prefix_extractor_->Transform(user_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();
}
void SeekForPrev(const Slice& k) override {
PERF_TIMER_GUARD(seek_on_memtable_time);
PERF_COUNTER_ADD(seek_on_memtable_count, 1);
if (bloom_) {
Slice user_k(ExtractUserKey(k));
if (prefix_extractor_->InDomain(user_k) &&
!bloom_->MayContain(prefix_extractor_->Transform(user_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();
if (!Valid()) {
SeekToLast();
}
while (Valid() && comparator_.comparator.Compare(k, key()) < 0) {
Prev();
}
}
void SeekToFirst() override {
iter_->SeekToFirst();
valid_ = iter_->Valid();
}
void SeekToLast() override {
iter_->SeekToLast();
valid_ = iter_->Valid();
}
void Next() override {
PERF_COUNTER_ADD(next_on_memtable_count, 1);
assert(Valid());
iter_->Next();
valid_ = iter_->Valid();
}
void Prev() override {
PERF_COUNTER_ADD(prev_on_memtable_count, 1);
assert(Valid());
iter_->Prev();
valid_ = iter_->Valid();
}
Slice key() const override {
assert(Valid());
return GetLengthPrefixedSlice(iter_->key());
}
Slice value() const override {
assert(Valid());
Slice key_slice = GetLengthPrefixedSlice(iter_->key());
return GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
}
Status status() const override { return Status::OK(); }
bool IsKeyPinned() const override {
// memtable data is always pinned
return true;
}
bool IsValuePinned() const override {
// memtable value is always pinned, except if we allow inplace update.
return value_pinned_;
}
private:
DynamicBloom* bloom_;
const SliceTransform* const prefix_extractor_;
const MemTable::KeyComparator comparator_;
MemTableRep::Iterator* iter_;
bool valid_;
bool arena_mode_;
bool value_pinned_;
};
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);
}
FragmentedRangeTombstoneIterator* MemTable::NewRangeTombstoneIterator(
const ReadOptions& read_options, SequenceNumber read_seq) {
if (read_options.ignore_range_deletions ||
is_range_del_table_empty_.load(std::memory_order_relaxed)) {
return nullptr;
}
auto* unfragmented_iter = new MemTableIterator(
*this, read_options, nullptr /* arena */, true /* use_range_del_table */);
if (unfragmented_iter == nullptr) {
return nullptr;
}
auto fragmented_tombstone_list =
std::make_shared<FragmentedRangeTombstoneList>(
std::unique_ptr<InternalIterator>(unfragmented_iter),
comparator_.comparator);
auto* fragmented_iter = new FragmentedRangeTombstoneIterator(
fragmented_tombstone_list, comparator_.comparator, read_seq);
return fragmented_iter;
}
port::RWMutex* MemTable::GetLock(const Slice& key) {
return &locks_[static_cast<size_t>(GetSliceNPHash64(key)) % locks_.size()];
}
MemTable::MemTableStats MemTable::ApproximateStats(const Slice& start_ikey,
const Slice& end_ikey) {
uint64_t entry_count = table_->ApproximateNumEntries(start_ikey, end_ikey);
entry_count += range_del_table_->ApproximateNumEntries(start_ikey, end_ikey);
if (entry_count == 0) {
return {0, 0};
}
uint64_t n = num_entries_.load(std::memory_order_relaxed);
if (n == 0) {
return {0, 0};
}
if (entry_count > n) {
// (range_del_)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), entry_count};
}
bool MemTable::Add(SequenceNumber s, ValueType type,
const Slice& key, /* user key */
const Slice& value, bool allow_concurrent,
MemTablePostProcessInfo* post_process_info, void** hint) {
// 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;
std::unique_ptr<MemTableRep>& table =
type == kTypeRangeDeletion ? range_del_table_ : table_;
KeyHandle handle = table->Allocate(encoded_len, &buf);
char* p = EncodeVarint32(buf, internal_key_size);
memcpy(p, key.data(), key_size);
Slice key_slice(p, 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);
size_t ts_sz = GetInternalKeyComparator().user_comparator()->timestamp_size();
if (!allow_concurrent) {
// Extract prefix for insert with hint.
if (insert_with_hint_prefix_extractor_ != nullptr &&
insert_with_hint_prefix_extractor_->InDomain(key_slice)) {
Slice prefix = insert_with_hint_prefix_extractor_->Transform(key_slice);
bool res = table->InsertKeyWithHint(handle, &insert_hints_[prefix]);
if (UNLIKELY(!res)) {
return res;
}
} else {
bool res = table->InsertKey(handle);
if (UNLIKELY(!res)) {
return res;
}
}
// 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 (bloom_filter_ && prefix_extractor_ &&
prefix_extractor_->InDomain(key)) {
bloom_filter_->Add(prefix_extractor_->Transform(key));
}
if (bloom_filter_ && moptions_.memtable_whole_key_filtering) {
bloom_filter_->Add(StripTimestampFromUserKey(key, ts_sz));
}
// 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 {
bool res = (hint == nullptr)
? table->InsertKeyConcurrently(handle)
: table->InsertKeyWithHintConcurrently(handle, hint);
if (UNLIKELY(!res)) {
return res;
}
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 (bloom_filter_ && prefix_extractor_ &&
prefix_extractor_->InDomain(key)) {
bloom_filter_->AddConcurrently(prefix_extractor_->Transform(key));
}
if (bloom_filter_ && moptions_.memtable_whole_key_filtering) {
bloom_filter_->AddConcurrently(StripTimestampFromUserKey(key, ts_sz));
}
// 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)) {
}
}
if (type == kTypeRangeDeletion) {
is_range_del_table_empty_.store(false, std::memory_order_relaxed);
}
UpdateOldestKeyTime();
return true;
}
// 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;
SequenceNumber max_covering_tombstone_seq;
MemTable* mem;
Logger* logger;
Statistics* statistics;
bool inplace_update_support;
bool do_merge;
Env* env_;
ReadCallback* callback_;
bool* is_blob_index;
bool CheckCallback(SequenceNumber _seq) {
if (callback_) {
return callback_->IsVisible(_seq);
}
return true;
}
};
} // namespace
static bool SaveValue(void* arg, const char* entry) {
Saver* s = reinterpret_cast<Saver*>(arg);
assert(s != nullptr);
MergeContext* merge_context = s->merge_context;
SequenceNumber max_covering_tombstone_seq = s->max_covering_tombstone_seq;
const MergeOperator* merge_operator = s->merge_operator;
assert(merge_context != nullptr);
// entry format is:
// klength varint32
// userkey char[klength-8]
// tag uint64
// vlength varint32f
// 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);
Slice user_key_slice = Slice(key_ptr, key_length - 8);
if (s->mem->GetInternalKeyComparator()
.user_comparator()
->CompareWithoutTimestamp(user_key_slice, s->key->user_key()) == 0) {
// Correct user key
const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
ValueType type;
SequenceNumber seq;
UnPackSequenceAndType(tag, &seq, &type);
// If the value is not in the snapshot, skip it
if (!s->CheckCallback(seq)) {
return true; // to continue to the next seq
}
s->seq = seq;
if ((type == kTypeValue || type == kTypeMerge || type == kTypeBlobIndex) &&
max_covering_tombstone_seq > seq) {
type = kTypeRangeDeletion;
}
switch (type) {
case kTypeBlobIndex:
if (s->is_blob_index == nullptr) {
ROCKS_LOG_ERROR(s->logger, "Encounter unexpected blob index.");
*(s->status) = Status::NotSupported(
"Encounter unsupported blob value. Please open DB with "
"rocksdb::blob_db::BlobDB instead.");
} else if (*(s->merge_in_progress)) {
*(s->status) =
Status::NotSupported("Blob DB does not support merge operator.");
}
if (!s->status->ok()) {
*(s->found_final_value) = true;
return false;
}
FALLTHROUGH_INTENDED;
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)) {
if (s->do_merge) {
if (s->value != nullptr) {
*(s->status) = MergeHelper::TimedFullMerge(
merge_operator, s->key->user_key(), &v,
merge_context->GetOperands(), s->value, s->logger,
s->statistics, s->env_, nullptr /* result_operand */, true);
}
} else {
// Preserve the value with the goal of returning it as part of
// raw merge operands to the user
merge_context->PushOperand(
v, s->inplace_update_support == false /* operand_pinned */);
}
} else if (!s->do_merge) {
// Preserve the value with the goal of returning it as part of
// raw merge operands to the user
merge_context->PushOperand(
v, s->inplace_update_support == false /* operand_pinned */);
} 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;
if (s->is_blob_index != nullptr) {
*(s->is_blob_index) = (type == kTypeBlobIndex);
}
return false;
}
case kTypeDeletion:
case kTypeSingleDeletion:
case kTypeRangeDeletion: {
if (*(s->merge_in_progress)) {
if (s->value != nullptr) {
*(s->status) = MergeHelper::TimedFullMerge(
merge_operator, s->key->user_key(), nullptr,
merge_context->GetOperands(), s->value, s->logger,
s->statistics, s->env_, nullptr /* result_operand */, true);
}
} 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, s->inplace_update_support == false /* operand_pinned */);
if (s->do_merge && merge_operator->ShouldMerge(
merge_context->GetOperandsDirectionBackward())) {
*(s->status) = MergeHelper::TimedFullMerge(
merge_operator, s->key->user_key(), nullptr,
merge_context->GetOperands(), s->value, s->logger, s->statistics,
s->env_, nullptr /* result_operand */, true);
*(s->found_final_value) = true;
return false;
}
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* max_covering_tombstone_seq,
SequenceNumber* seq, const ReadOptions& read_opts,
ReadCallback* callback, bool* is_blob_index, bool do_merge) {
// 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);
std::unique_ptr<FragmentedRangeTombstoneIterator> range_del_iter(
NewRangeTombstoneIterator(read_opts,
GetInternalKeySeqno(key.internal_key())));
if (range_del_iter != nullptr) {
*max_covering_tombstone_seq =
std::max(*max_covering_tombstone_seq,
range_del_iter->MaxCoveringTombstoneSeqnum(key.user_key()));
}
Slice user_key = key.user_key();
bool found_final_value = false;
bool merge_in_progress = s->IsMergeInProgress();
bool may_contain = true;
size_t ts_sz = GetInternalKeyComparator().user_comparator()->timestamp_size();
if (bloom_filter_) {
// when both memtable_whole_key_filtering and prefix_extractor_ are set,
// only do whole key filtering for Get() to save CPU
if (moptions_.memtable_whole_key_filtering) {
may_contain =
bloom_filter_->MayContain(StripTimestampFromUserKey(user_key, ts_sz));
} else {
assert(prefix_extractor_);
may_contain =
!prefix_extractor_->InDomain(user_key) ||
bloom_filter_->MayContain(prefix_extractor_->Transform(user_key));
}
}
if (bloom_filter_ && !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 (bloom_filter_) {
PERF_COUNTER_ADD(bloom_memtable_hit_count, 1);
}
GetFromTable(key, *max_covering_tombstone_seq, do_merge, callback,
is_blob_index, value, s, merge_context, seq,
&found_final_value, &merge_in_progress);
}
// 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::GetFromTable(const LookupKey& key,
SequenceNumber max_covering_tombstone_seq,
bool do_merge, ReadCallback* callback,
bool* is_blob_index, std::string* value, Status* s,
MergeContext* merge_context, SequenceNumber* seq,
bool* found_final_value, bool* merge_in_progress) {
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.max_covering_tombstone_seq = max_covering_tombstone_seq;
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_;
saver.callback_ = callback;
saver.is_blob_index = is_blob_index;
saver.do_merge = do_merge;
table_->Get(key, &saver, SaveValue);
*seq = saver.seq;
}
void MemTable::MultiGet(const ReadOptions& read_options, MultiGetRange* range,
ReadCallback* callback, bool* is_blob) {
// The sequence number is updated synchronously in version_set.h
if (IsEmpty()) {
// Avoiding recording stats for speed.
return;
}
PERF_TIMER_GUARD(get_from_memtable_time);
MultiGetRange temp_range(*range, range->begin(), range->end());
if (bloom_filter_) {
std::array<Slice*, MultiGetContext::MAX_BATCH_SIZE> keys;
std::array<bool, MultiGetContext::MAX_BATCH_SIZE> may_match = {{true}};
autovector<Slice, MultiGetContext::MAX_BATCH_SIZE> prefixes;
int num_keys = 0;
for (auto iter = temp_range.begin(); iter != temp_range.end(); ++iter) {
if (!prefix_extractor_) {
keys[num_keys++] = &iter->ukey;
} else if (prefix_extractor_->InDomain(iter->ukey)) {
prefixes.emplace_back(prefix_extractor_->Transform(iter->ukey));
keys[num_keys++] = &prefixes.back();
}
}
bloom_filter_->MayContain(num_keys, &keys[0], &may_match[0]);
int idx = 0;
for (auto iter = temp_range.begin(); iter != temp_range.end(); ++iter) {
if (prefix_extractor_ && !prefix_extractor_->InDomain(iter->ukey)) {
PERF_COUNTER_ADD(bloom_memtable_hit_count, 1);
continue;
}
if (!may_match[idx]) {
temp_range.SkipKey(iter);
PERF_COUNTER_ADD(bloom_memtable_miss_count, 1);
} else {
PERF_COUNTER_ADD(bloom_memtable_hit_count, 1);
}
idx++;
}
}
for (auto iter = temp_range.begin(); iter != temp_range.end(); ++iter) {
SequenceNumber seq = kMaxSequenceNumber;
bool found_final_value{false};
bool merge_in_progress = iter->s->IsMergeInProgress();
std::unique_ptr<FragmentedRangeTombstoneIterator> range_del_iter(
NewRangeTombstoneIterator(
read_options, GetInternalKeySeqno(iter->lkey->internal_key())));
if (range_del_iter != nullptr) {
iter->max_covering_tombstone_seq = std::max(
iter->max_covering_tombstone_seq,
range_del_iter->MaxCoveringTombstoneSeqnum(iter->lkey->user_key()));
}
GetFromTable(*(iter->lkey), iter->max_covering_tombstone_seq, true,
callback, is_blob, iter->value->GetSelf(), iter->s,
&(iter->merge_context), &seq, &found_final_value,
&merge_in_progress);
if (!found_final_value && merge_in_progress) {
*(iter->s) = Status::MergeInProgress();
}
if (found_final_value) {
iter->value->PinSelf();
range->MarkKeyDone(iter);
RecordTick(moptions_.statistics, MEMTABLE_HIT);
}
}
PERF_COUNTER_ADD(get_from_memtable_count, 1);
}
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 existing_seq;
UnPackSequenceAndType(tag, &existing_seq, &type);
assert(existing_seq != seq);
if (type == 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()));
RecordTick(moptions_.statistics, NUMBER_KEYS_UPDATED);
return;
}
}
}
}
// key doesn't exist
bool add_res __attribute__((__unused__));
add_res = Add(seq, kTypeValue, key, value);
// We already checked unused != seq above. In that case, Add should not fail.
assert(add_res);
}
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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