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rocksdb/db/write_batch.cc

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// Copyright (c) 2013, 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.
//
// WriteBatch::rep_ :=
// sequence: fixed64
// count: fixed32
// data: record[count]
// record :=
// kTypeValue varstring varstring
// kTypeMerge varstring varstring
// kTypeDeletion varstring
// varstring :=
// len: varint32
// data: uint8[len]
#include "rocksdb/write_batch.h"
#include "rocksdb/options.h"
#include "rocksdb/merge_operator.h"
#include "db/dbformat.h"
#include "db/db_impl.h"
#include "db/memtable.h"
#include "db/snapshot.h"
#include "db/write_batch_internal.h"
#include "util/coding.h"
#include "util/statistics_imp.h"
#include <stdexcept>
namespace rocksdb {
// WriteBatch header has an 8-byte sequence number followed by a 4-byte count.
static const size_t kHeader = 12;
WriteBatch::WriteBatch(size_t reserved_bytes) {
rep_.reserve((reserved_bytes > kHeader) ? reserved_bytes : kHeader);
Clear();
}
WriteBatch::~WriteBatch() { }
WriteBatch::Handler::~Handler() { }
void WriteBatch::Handler::Merge(const Slice& key, const Slice& value) {
throw std::runtime_error("Handler::Merge not implemented!");
}
void WriteBatch::Handler::LogData(const Slice& blob) {
// If the user has not specified something to do with blobs, then we ignore
// them.
}
bool WriteBatch::Handler::Continue() {
return true;
}
void WriteBatch::Clear() {
rep_.clear();
rep_.resize(kHeader);
}
int WriteBatch::Count() const {
return WriteBatchInternal::Count(this);
}
Status WriteBatch::Iterate(Handler* handler) const {
Slice input(rep_);
if (input.size() < kHeader) {
return Status::Corruption("malformed WriteBatch (too small)");
}
input.remove_prefix(kHeader);
Slice key, value, blob;
int found = 0;
while (!input.empty() && handler->Continue()) {
char tag = input[0];
input.remove_prefix(1);
switch (tag) {
case kTypeValue:
if (GetLengthPrefixedSlice(&input, &key) &&
GetLengthPrefixedSlice(&input, &value)) {
handler->Put(key, value);
found++;
} else {
return Status::Corruption("bad WriteBatch Put");
}
break;
case kTypeDeletion:
if (GetLengthPrefixedSlice(&input, &key)) {
handler->Delete(key);
found++;
} else {
return Status::Corruption("bad WriteBatch Delete");
}
break;
case kTypeMerge:
if (GetLengthPrefixedSlice(&input, &key) &&
GetLengthPrefixedSlice(&input, &value)) {
handler->Merge(key, value);
found++;
} else {
return Status::Corruption("bad WriteBatch Merge");
}
break;
case kTypeLogData:
if (GetLengthPrefixedSlice(&input, &blob)) {
handler->LogData(blob);
} else {
return Status::Corruption("bad WriteBatch Blob");
}
break;
default:
return Status::Corruption("unknown WriteBatch tag");
}
}
if (found != WriteBatchInternal::Count(this)) {
return Status::Corruption("WriteBatch has wrong count");
} else {
return Status::OK();
}
}
int WriteBatchInternal::Count(const WriteBatch* b) {
return DecodeFixed32(b->rep_.data() + 8);
}
void WriteBatchInternal::SetCount(WriteBatch* b, int n) {
EncodeFixed32(&b->rep_[8], n);
}
SequenceNumber WriteBatchInternal::Sequence(const WriteBatch* b) {
return SequenceNumber(DecodeFixed64(b->rep_.data()));
}
void WriteBatchInternal::SetSequence(WriteBatch* b, SequenceNumber seq) {
EncodeFixed64(&b->rep_[0], seq);
}
void WriteBatch::Put(const Slice& key, const Slice& value) {
WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
rep_.push_back(static_cast<char>(kTypeValue));
PutLengthPrefixedSlice(&rep_, key);
PutLengthPrefixedSlice(&rep_, value);
}
void WriteBatch::Put(const SliceParts& key, const SliceParts& value) {
WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
rep_.push_back(static_cast<char>(kTypeValue));
PutLengthPrefixedSliceParts(&rep_, key);
PutLengthPrefixedSliceParts(&rep_, value);
}
void WriteBatch::Delete(const Slice& key) {
WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
rep_.push_back(static_cast<char>(kTypeDeletion));
PutLengthPrefixedSlice(&rep_, key);
}
void WriteBatch::Merge(const Slice& key, const Slice& value) {
WriteBatchInternal::SetCount(this, WriteBatchInternal::Count(this) + 1);
rep_.push_back(static_cast<char>(kTypeMerge));
PutLengthPrefixedSlice(&rep_, key);
PutLengthPrefixedSlice(&rep_, value);
}
void WriteBatch::PutLogData(const Slice& blob) {
rep_.push_back(static_cast<char>(kTypeLogData));
PutLengthPrefixedSlice(&rep_, blob);
}
namespace {
class MemTableInserter : public WriteBatch::Handler {
public:
SequenceNumber sequence_;
MemTable* mem_;
const Options* options_;
DBImpl* db_;
const bool filter_deletes_;
MemTableInserter(SequenceNumber sequence, MemTable* mem, const Options* opts,
DB* db, const bool filter_deletes)
: sequence_(sequence),
mem_(mem),
options_(opts),
db_(reinterpret_cast<DBImpl*>(db)),
filter_deletes_(filter_deletes) {
assert(mem_);
if (filter_deletes_) {
assert(options_);
assert(db_);
}
}
virtual void Put(const Slice& key, const Slice& value) {
if (options_->inplace_update_support
&& mem_->Update(sequence_, kTypeValue, key, value)) {
RecordTick(options_->statistics.get(), NUMBER_KEYS_UPDATED);
} else {
mem_->Add(sequence_, kTypeValue, key, value);
}
sequence_++;
}
virtual void Merge(const Slice& key, const Slice& value) {
bool perform_merge = false;
if (options_->max_successive_merges > 0 && db_ != nullptr) {
LookupKey lkey(key, sequence_);
// Count the number of successive merges at the head
// of the key in the memtable
size_t num_merges = mem_->CountSuccessiveMergeEntries(lkey);
if (num_merges >= options_->max_successive_merges) {
perform_merge = true;
}
}
if (perform_merge) {
// 1) Get the existing value
std::string get_value;
// Pass in the sequence number so that we also include previous merge
// operations in the same batch.
SnapshotImpl read_from_snapshot;
read_from_snapshot.number_ = sequence_;
ReadOptions read_options;
read_options.snapshot = &read_from_snapshot;
db_->Get(read_options, key, &get_value);
Slice get_value_slice = Slice(get_value);
// 2) Apply this merge
auto merge_operator = options_->merge_operator.get();
assert(merge_operator);
std::deque<std::string> operands;
operands.push_front(value.ToString());
std::string new_value;
if (!merge_operator->FullMerge(key,
&get_value_slice,
operands,
&new_value,
options_->info_log.get())) {
// Failed to merge!
RecordTick(options_->statistics.get(), NUMBER_MERGE_FAILURES);
// Store the delta in memtable
perform_merge = false;
} else {
// 3) Add value to memtable
mem_->Add(sequence_, kTypeValue, key, new_value);
}
}
if (!perform_merge) {
// Add merge operator to memtable
mem_->Add(sequence_, kTypeMerge, key, value);
}
sequence_++;
}
virtual void Delete(const Slice& key) {
if (filter_deletes_) {
SnapshotImpl read_from_snapshot;
read_from_snapshot.number_ = sequence_;
ReadOptions ropts;
ropts.snapshot = &read_from_snapshot;
std::string value;
if (!db_->KeyMayExist(ropts, key, &value)) {
RecordTick(options_->statistics.get(), NUMBER_FILTERED_DELETES);
return;
}
}
mem_->Add(sequence_, kTypeDeletion, key, Slice());
sequence_++;
}
};
} // namespace
Status WriteBatchInternal::InsertInto(const WriteBatch* b, MemTable* mem,
const Options* opts, DB* db,
const bool filter_deletes) {
MemTableInserter inserter(WriteBatchInternal::Sequence(b), mem, opts, db,
filter_deletes);
return b->Iterate(&inserter);
}
void WriteBatchInternal::SetContents(WriteBatch* b, const Slice& contents) {
assert(contents.size() >= kHeader);
b->rep_.assign(contents.data(), contents.size());
}
void WriteBatchInternal::Append(WriteBatch* dst, const WriteBatch* src) {
SetCount(dst, Count(dst) + Count(src));
assert(src->rep_.size() >= kHeader);
dst->rep_.append(src->rep_.data() + kHeader, src->rep_.size() - kHeader);
}
} // namespace rocksdb