mirror of https://github.com/facebook/rocksdb.git
532 lines
18 KiB
C++
532 lines
18 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include "db/memtable.h"
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#include <memory>
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#include "db/dbformat.h"
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#include "db/merge_context.h"
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#include "rocksdb/comparator.h"
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#include "rocksdb/env.h"
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#include "rocksdb/iterator.h"
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#include "rocksdb/merge_operator.h"
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#include "rocksdb/slice_transform.h"
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#include "util/arena.h"
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#include "util/coding.h"
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#include "util/murmurhash.h"
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#include "util/mutexlock.h"
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#include "util/perf_context_imp.h"
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#include "util/statistics.h"
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#include "util/stop_watch.h"
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namespace std {
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template <>
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struct hash<rocksdb::Slice> {
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size_t operator()(const rocksdb::Slice& slice) const {
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return MurmurHash(slice.data(), slice.size(), 0);
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}
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};
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}
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namespace rocksdb {
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MemTable::MemTable(const InternalKeyComparator& cmp,
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const ColumnFamilyOptions& options)
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: comparator_(cmp),
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refs_(0),
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arena_(options.arena_block_size),
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table_(options.memtable_factory->CreateMemTableRep(comparator_, &arena_)),
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flush_in_progress_(false),
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flush_completed_(false),
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file_number_(0),
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first_seqno_(0),
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mem_next_logfile_number_(0),
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locks_(options.inplace_update_support ? options.inplace_update_num_locks
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: 0),
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prefix_extractor_(options.prefix_extractor) {
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if (prefix_extractor_ && options.memtable_prefix_bloom_bits > 0) {
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prefix_bloom_.reset(new DynamicBloom(options.memtable_prefix_bloom_bits,
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options.memtable_prefix_bloom_probes));
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}
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}
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MemTable::~MemTable() {
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assert(refs_ == 0);
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}
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size_t MemTable::ApproximateMemoryUsage() {
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return arena_.ApproximateMemoryUsage() + table_->ApproximateMemoryUsage();
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}
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int MemTable::KeyComparator::operator()(const char* prefix_len_key1,
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const char* prefix_len_key2) const {
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// Internal keys are encoded as length-prefixed strings.
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Slice k1 = GetLengthPrefixedSlice(prefix_len_key1);
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Slice k2 = GetLengthPrefixedSlice(prefix_len_key2);
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return comparator.Compare(k1, k2);
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}
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int MemTable::KeyComparator::operator()(const char* prefix_len_key,
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const Slice& key)
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const {
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// Internal keys are encoded as length-prefixed strings.
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Slice a = GetLengthPrefixedSlice(prefix_len_key);
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return comparator.Compare(a, key);
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}
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Slice MemTableRep::UserKey(const char* key) const {
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Slice slice = GetLengthPrefixedSlice(key);
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return Slice(slice.data(), slice.size() - 8);
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}
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// Encode a suitable internal key target for "target" and return it.
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// Uses *scratch as scratch space, and the returned pointer will point
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// into this scratch space.
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const char* EncodeKey(std::string* scratch, const Slice& target) {
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scratch->clear();
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PutVarint32(scratch, target.size());
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scratch->append(target.data(), target.size());
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return scratch->data();
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}
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class MemTableIterator: public Iterator {
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public:
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MemTableIterator(const MemTable& mem, const ReadOptions& options)
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: mem_(mem), iter_(), dynamic_prefix_seek_(false), valid_(false) {
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if (options.prefix) {
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iter_.reset(mem_.table_->GetPrefixIterator(*options.prefix));
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} else if (options.prefix_seek) {
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dynamic_prefix_seek_ = true;
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iter_.reset(mem_.table_->GetDynamicPrefixIterator());
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} else {
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iter_.reset(mem_.table_->GetIterator());
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}
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}
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virtual bool Valid() const { return valid_; }
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virtual void Seek(const Slice& k) {
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if (dynamic_prefix_seek_ && mem_.prefix_bloom_ &&
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!mem_.prefix_bloom_->MayContain(
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mem_.prefix_extractor_->Transform(ExtractUserKey(k)))) {
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valid_ = false;
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return;
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}
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iter_->Seek(k, nullptr);
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valid_ = iter_->Valid();
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}
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virtual void SeekToFirst() {
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iter_->SeekToFirst();
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valid_ = iter_->Valid();
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}
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virtual void SeekToLast() {
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iter_->SeekToLast();
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valid_ = iter_->Valid();
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}
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virtual void Next() {
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assert(Valid());
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iter_->Next();
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valid_ = iter_->Valid();
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}
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virtual void Prev() {
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assert(Valid());
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iter_->Prev();
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valid_ = iter_->Valid();
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}
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virtual Slice key() const {
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assert(Valid());
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return GetLengthPrefixedSlice(iter_->key());
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}
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virtual Slice value() const {
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assert(Valid());
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Slice key_slice = GetLengthPrefixedSlice(iter_->key());
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return GetLengthPrefixedSlice(key_slice.data() + key_slice.size());
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}
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virtual Status status() const { return Status::OK(); }
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private:
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const MemTable& mem_;
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std::shared_ptr<MemTableRep::Iterator> iter_;
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bool dynamic_prefix_seek_;
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bool valid_;
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// No copying allowed
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MemTableIterator(const MemTableIterator&);
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void operator=(const MemTableIterator&);
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};
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Iterator* MemTable::NewIterator(const ReadOptions& options) {
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return new MemTableIterator(*this, options);
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}
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port::RWMutex* MemTable::GetLock(const Slice& key) {
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return &locks_[std::hash<Slice>()(key) % locks_.size()];
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}
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void MemTable::Add(SequenceNumber s, ValueType type,
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const Slice& key, /* user key */
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const Slice& value) {
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// Format of an entry is concatenation of:
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// key_size : varint32 of internal_key.size()
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// key bytes : char[internal_key.size()]
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// value_size : varint32 of value.size()
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// value bytes : char[value.size()]
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size_t key_size = key.size();
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size_t val_size = value.size();
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size_t internal_key_size = key_size + 8;
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const size_t encoded_len =
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VarintLength(internal_key_size) + internal_key_size +
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VarintLength(val_size) + val_size;
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char* buf = arena_.Allocate(encoded_len);
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char* p = EncodeVarint32(buf, internal_key_size);
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memcpy(p, key.data(), key_size);
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p += key_size;
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EncodeFixed64(p, (s << 8) | type);
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p += 8;
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p = EncodeVarint32(p, val_size);
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memcpy(p, value.data(), val_size);
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assert((unsigned)(p + val_size - buf) == (unsigned)encoded_len);
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table_->Insert(buf);
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if (prefix_bloom_) {
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assert(prefix_extractor_);
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prefix_bloom_->Add(prefix_extractor_->Transform(key));
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}
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// The first sequence number inserted into the memtable
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assert(first_seqno_ == 0 || s > first_seqno_);
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if (first_seqno_ == 0) {
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first_seqno_ = s;
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}
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}
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// Callback from MemTable::Get()
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namespace {
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struct Saver {
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Status* status;
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const LookupKey* key;
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bool* found_final_value; // Is value set correctly? Used by KeyMayExist
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bool* merge_in_progress;
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std::string* value;
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const MergeOperator* merge_operator;
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// the merge operations encountered;
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MergeContext* merge_context;
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MemTable* mem;
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Logger* logger;
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Statistics* statistics;
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bool inplace_update_support;
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};
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} // namespace
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static bool SaveValue(void* arg, const char* entry) {
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Saver* s = reinterpret_cast<Saver*>(arg);
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MergeContext* merge_context = s->merge_context;
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const MergeOperator* merge_operator = s->merge_operator;
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assert(s != nullptr && merge_context != nullptr);
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// entry format is:
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// klength varint32
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// userkey char[klength-8]
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// tag uint64
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// vlength varint32
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// value char[vlength]
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// Check that it belongs to same user key. We do not check the
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// sequence number since the Seek() call above should have skipped
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// all entries with overly large sequence numbers.
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uint32_t key_length;
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const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
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if (s->mem->GetInternalKeyComparator().user_comparator()->Compare(
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Slice(key_ptr, key_length - 8), s->key->user_key()) == 0) {
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// Correct user key
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const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
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switch (static_cast<ValueType>(tag & 0xff)) {
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case kTypeValue: {
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if (s->inplace_update_support) {
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s->mem->GetLock(s->key->user_key())->ReadLock();
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}
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Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
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*(s->status) = Status::OK();
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if (*(s->merge_in_progress)) {
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assert(merge_operator);
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if (!merge_operator->FullMerge(s->key->user_key(), &v,
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merge_context->GetOperands(), s->value,
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s->logger)) {
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RecordTick(s->statistics, NUMBER_MERGE_FAILURES);
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*(s->status) =
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Status::Corruption("Error: Could not perform merge.");
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}
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} else {
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s->value->assign(v.data(), v.size());
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}
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if (s->inplace_update_support) {
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s->mem->GetLock(s->key->user_key())->Unlock();
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}
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*(s->found_final_value) = true;
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return false;
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}
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case kTypeDeletion: {
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if (*(s->merge_in_progress)) {
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assert(merge_operator);
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*(s->status) = Status::OK();
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if (!merge_operator->FullMerge(s->key->user_key(), nullptr,
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merge_context->GetOperands(), s->value,
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s->logger)) {
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RecordTick(s->statistics, NUMBER_MERGE_FAILURES);
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*(s->status) =
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Status::Corruption("Error: Could not perform merge.");
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}
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} else {
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*(s->status) = Status::NotFound();
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}
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*(s->found_final_value) = true;
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return false;
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}
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case kTypeMerge: {
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std::string merge_result; // temporary area for merge results later
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Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
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*(s->merge_in_progress) = true;
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merge_context->PushOperand(v);
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while (merge_context->GetNumOperands() >= 2) {
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// Attempt to associative merge. (Returns true if successful)
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if (merge_operator->PartialMerge(
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s->key->user_key(), merge_context->GetOperand(0),
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merge_context->GetOperand(1), &merge_result, s->logger)) {
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merge_context->PushPartialMergeResult(merge_result);
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} else {
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// Stack them because user can't associative merge
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break;
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}
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}
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return true;
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}
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default:
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assert(false);
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return true;
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}
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}
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// s->state could be Corrupt, merge or notfound
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return false;
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}
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bool MemTable::Get(const LookupKey& key, std::string* value, Status* s,
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MergeContext& merge_context, const Options& options) {
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StopWatchNano memtable_get_timer(options.env, false);
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StartPerfTimer(&memtable_get_timer);
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Slice user_key = key.user_key();
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bool found_final_value = false;
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bool merge_in_progress = s->IsMergeInProgress();
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if (prefix_bloom_ &&
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!prefix_bloom_->MayContain(prefix_extractor_->Transform(user_key))) {
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// iter is null if prefix bloom says the key does not exist
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} else {
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Saver saver;
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saver.status = s;
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saver.found_final_value = &found_final_value;
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saver.merge_in_progress = &merge_in_progress;
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saver.key = &key;
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saver.value = value;
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saver.status = s;
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saver.mem = this;
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saver.merge_context = &merge_context;
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saver.merge_operator = options.merge_operator.get();
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saver.logger = options.info_log.get();
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saver.inplace_update_support = options.inplace_update_support;
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saver.statistics = options.statistics.get();
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table_->Get(key, &saver, SaveValue);
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}
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// No change to value, since we have not yet found a Put/Delete
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if (!found_final_value && merge_in_progress) {
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*s = Status::MergeInProgress("");
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}
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BumpPerfTime(&perf_context.get_from_memtable_time, &memtable_get_timer);
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BumpPerfCount(&perf_context.get_from_memtable_count);
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return found_final_value;
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}
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void MemTable::Update(SequenceNumber seq,
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const Slice& key,
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const Slice& value) {
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LookupKey lkey(key, seq);
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Slice mem_key = lkey.memtable_key();
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std::unique_ptr<MemTableRep::Iterator> iter(
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table_->GetIterator(lkey.user_key()));
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iter->Seek(lkey.internal_key(), mem_key.data());
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if (iter->Valid()) {
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// entry format is:
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// key_length varint32
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// userkey char[klength-8]
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// tag uint64
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// vlength varint32
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// value char[vlength]
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// Check that it belongs to same user key. We do not check the
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// sequence number since the Seek() call above should have skipped
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// all entries with overly large sequence numbers.
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const char* entry = iter->key();
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uint32_t key_length = 0;
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const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
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if (comparator_.comparator.user_comparator()->Compare(
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Slice(key_ptr, key_length - 8), lkey.user_key()) == 0) {
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// Correct user key
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const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
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switch (static_cast<ValueType>(tag & 0xff)) {
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case kTypeValue: {
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Slice prev_value = GetLengthPrefixedSlice(key_ptr + key_length);
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uint32_t prev_size = prev_value.size();
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uint32_t new_size = value.size();
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// Update value, if new value size <= previous value size
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if (new_size <= prev_size ) {
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char* p = EncodeVarint32(const_cast<char*>(key_ptr) + key_length,
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new_size);
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WriteLock wl(GetLock(lkey.user_key()));
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memcpy(p, value.data(), value.size());
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assert((unsigned)((p + value.size()) - entry) ==
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(unsigned)(VarintLength(key_length) + key_length +
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VarintLength(value.size()) + value.size()));
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return;
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}
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}
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default:
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// If the latest value is kTypeDeletion, kTypeMerge or kTypeLogData
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// we don't have enough space for update inplace
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Add(seq, kTypeValue, key, value);
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return;
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}
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}
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}
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// key doesn't exist
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Add(seq, kTypeValue, key, value);
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}
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bool MemTable::UpdateCallback(SequenceNumber seq,
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const Slice& key,
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const Slice& delta,
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const Options& options) {
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LookupKey lkey(key, seq);
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Slice memkey = lkey.memtable_key();
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std::shared_ptr<MemTableRep::Iterator> iter(
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table_->GetIterator(lkey.user_key()));
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iter->Seek(lkey.internal_key(), memkey.data());
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if (iter->Valid()) {
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// entry format is:
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// key_length varint32
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// userkey char[klength-8]
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// tag uint64
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// vlength varint32
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// value char[vlength]
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// Check that it belongs to same user key. We do not check the
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// sequence number since the Seek() call above should have skipped
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// all entries with overly large sequence numbers.
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const char* entry = iter->key();
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uint32_t key_length = 0;
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const char* key_ptr = GetVarint32Ptr(entry, entry + 5, &key_length);
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if (comparator_.comparator.user_comparator()->Compare(
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Slice(key_ptr, key_length - 8), lkey.user_key()) == 0) {
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// Correct user key
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const uint64_t tag = DecodeFixed64(key_ptr + key_length - 8);
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switch (static_cast<ValueType>(tag & 0xff)) {
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case kTypeValue: {
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Slice prev_value = GetLengthPrefixedSlice(key_ptr + key_length);
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uint32_t prev_size = prev_value.size();
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char* prev_buffer = const_cast<char*>(prev_value.data());
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uint32_t new_prev_size = prev_size;
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std::string str_value;
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WriteLock wl(GetLock(lkey.user_key()));
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auto status = options.inplace_callback(prev_buffer, &new_prev_size,
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delta, &str_value);
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if (status == UpdateStatus::UPDATED_INPLACE) {
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// Value already updated by callback.
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assert(new_prev_size <= prev_size);
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if (new_prev_size < prev_size) {
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// overwrite the new prev_size
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char* p = EncodeVarint32(const_cast<char*>(key_ptr) + key_length,
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new_prev_size);
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if (VarintLength(new_prev_size) < VarintLength(prev_size)) {
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// shift the value buffer as well.
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memcpy(p, prev_buffer, new_prev_size);
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}
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}
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RecordTick(options.statistics.get(), NUMBER_KEYS_UPDATED);
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return true;
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} else if (status == UpdateStatus::UPDATED) {
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Add(seq, kTypeValue, key, Slice(str_value));
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RecordTick(options.statistics.get(), NUMBER_KEYS_WRITTEN);
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return true;
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} else if (status == UpdateStatus::UPDATE_FAILED) {
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// No action required. Return.
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return true;
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}
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}
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default:
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break;
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}
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}
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}
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// If the latest value is not kTypeValue
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// or key doesn't exist
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return false;
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}
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size_t MemTable::CountSuccessiveMergeEntries(const LookupKey& key) {
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|
Slice memkey = key.memtable_key();
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|
|
|
// 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.
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|
std::unique_ptr<MemTableRep::Iterator> iter(
|
|
table_->GetIterator(key.user_key()));
|
|
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()->Compare(
|
|
Slice(iter_key_ptr, key_length - 8), key.user_key()) == 0) {
|
|
break;
|
|
}
|
|
|
|
const uint64_t tag = DecodeFixed64(iter_key_ptr + key_length - 8);
|
|
if (static_cast<ValueType>(tag & 0xff) != 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 = GetIterator(k.user_key());
|
|
for (iter->Seek(k.internal_key(), k.memtable_key().data());
|
|
iter->Valid() && callback_func(callback_args, iter->key());
|
|
iter->Next()) {
|
|
}
|
|
}
|
|
|
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} // namespace rocksdb
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