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rocksdb/utilities/write_batch_with_index/write_batch_with_index.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.
#include "rocksdb/utilities/write_batch_with_index.h"
#include <memory>
#include "rocksdb/comparator.h"
#include "rocksdb/iterator.h"
#include "db/column_family.h"
#include "db/skiplist.h"
#include "util/arena.h"
namespace rocksdb {
// when direction == forward
// * current_at_base_ <=> base_iterator > delta_iterator
// when direction == backwards
// * current_at_base_ <=> base_iterator < delta_iterator
// always:
// * equal_keys_ <=> base_iterator == delta_iterator
class BaseDeltaIterator : public Iterator {
public:
BaseDeltaIterator(Iterator* base_iterator, WBWIIterator* delta_iterator,
const Comparator* comparator)
: forward_(true),
current_at_base_(true),
equal_keys_(false),
status_(Status::OK()),
base_iterator_(base_iterator),
delta_iterator_(delta_iterator),
comparator_(comparator) {}
virtual ~BaseDeltaIterator() {}
bool Valid() const override {
return current_at_base_ ? BaseValid() : DeltaValid();
}
void SeekToFirst() override {
forward_ = true;
base_iterator_->SeekToFirst();
delta_iterator_->SeekToFirst();
UpdateCurrent();
}
void SeekToLast() override {
forward_ = false;
base_iterator_->SeekToLast();
delta_iterator_->SeekToLast();
UpdateCurrent();
}
void Seek(const Slice& k) override {
forward_ = true;
base_iterator_->Seek(k);
delta_iterator_->Seek(k);
UpdateCurrent();
}
void Next() override {
if (!Valid()) {
status_ = Status::NotSupported("Next() on invalid iterator");
}
if (!forward_) {
// Need to change direction
// if our direction was backward and we're not equal, we have two states:
// * both iterators are valid: we're already in a good state (current
// shows to smaller)
// * only one iterator is valid: we need to advance that iterator
forward_ = true;
equal_keys_ = false;
if (!BaseValid()) {
assert(DeltaValid());
base_iterator_->SeekToFirst();
} else if (!DeltaValid()) {
delta_iterator_->SeekToFirst();
} else if (current_at_base_) {
// Change delta from larger than base to smaller
AdvanceDelta();
} else {
// Change base from larger than delta to smaller
AdvanceBase();
}
if (DeltaValid() && BaseValid()) {
if (Compare() == 0) {
equal_keys_ = true;
}
}
}
Advance();
}
void Prev() override {
if (!Valid()) {
status_ = Status::NotSupported("Prev() on invalid iterator");
}
if (forward_) {
// Need to change direction
// if our direction was backward and we're not equal, we have two states:
// * both iterators are valid: we're already in a good state (current
// shows to smaller)
// * only one iterator is valid: we need to advance that iterator
forward_ = false;
equal_keys_ = false;
if (!BaseValid()) {
assert(DeltaValid());
base_iterator_->SeekToLast();
} else if (!DeltaValid()) {
delta_iterator_->SeekToLast();
} else if (current_at_base_) {
// Change delta from less advanced than base to more advanced
AdvanceDelta();
} else {
// Change base from less advanced than delta to more advanced
AdvanceBase();
}
if (DeltaValid() && BaseValid()) {
if (Compare() == 0) {
equal_keys_ = true;
}
}
}
Advance();
}
Slice key() const override {
return current_at_base_ ? base_iterator_->key()
: delta_iterator_->Entry().key;
}
Slice value() const override {
return current_at_base_ ? base_iterator_->value()
: delta_iterator_->Entry().value;
}
Status status() const override {
if (!status_.ok()) {
return status_;
}
if (!base_iterator_->status().ok()) {
return base_iterator_->status();
}
return delta_iterator_->status();
}
private:
// -1 -- delta less advanced than base
// 0 -- delta == base
// 1 -- delta more advanced than base
int Compare() const {
assert(delta_iterator_->Valid() && base_iterator_->Valid());
int cmp = comparator_->Compare(delta_iterator_->Entry().key,
base_iterator_->key());
if (forward_) {
return cmp;
} else {
return -cmp;
}
}
bool IsDeltaDelete() {
assert(DeltaValid());
return delta_iterator_->Entry().type == kDeleteRecord;
}
void AssertInvariants() {
#ifndef NDEBUG
if (!Valid()) {
return;
}
if (!BaseValid()) {
assert(!current_at_base_ && delta_iterator_->Valid());
return;
}
if (!DeltaValid()) {
assert(current_at_base_ && base_iterator_->Valid());
return;
}
// we don't support those yet
assert(delta_iterator_->Entry().type != kMergeRecord &&
delta_iterator_->Entry().type != kLogDataRecord);
int compare = comparator_->Compare(delta_iterator_->Entry().key,
base_iterator_->key());
if (forward_) {
// current_at_base -> compare < 0
assert(!current_at_base_ || compare < 0);
// !current_at_base -> compare <= 0
assert(current_at_base_ && compare >= 0);
} else {
// current_at_base -> compare > 0
assert(!current_at_base_ || compare > 0);
// !current_at_base -> compare <= 0
assert(current_at_base_ && compare <= 0);
}
// equal_keys_ <=> compare == 0
assert((equal_keys_ || compare != 0) && (!equal_keys_ || compare == 0));
#endif
}
void Advance() {
if (equal_keys_) {
assert(BaseValid() && DeltaValid());
AdvanceBase();
AdvanceDelta();
} else {
if (current_at_base_) {
assert(BaseValid());
AdvanceBase();
} else {
assert(DeltaValid());
AdvanceDelta();
}
}
UpdateCurrent();
}
void AdvanceDelta() {
if (forward_) {
delta_iterator_->Next();
} else {
delta_iterator_->Prev();
}
}
void AdvanceBase() {
if (forward_) {
base_iterator_->Next();
} else {
base_iterator_->Prev();
}
}
bool BaseValid() const { return base_iterator_->Valid(); }
bool DeltaValid() const { return delta_iterator_->Valid(); }
void UpdateCurrent() {
while (true) {
equal_keys_ = false;
if (!BaseValid()) {
// Base has finished.
if (!DeltaValid()) {
// Finished
return;
}
if (IsDeltaDelete()) {
AdvanceDelta();
} else {
current_at_base_ = false;
return;
}
} else if (!DeltaValid()) {
// Delta has finished.
current_at_base_ = true;
return;
} else {
int compare = Compare();
if (compare <= 0) { // delta bigger or equal
if (compare == 0) {
equal_keys_ = true;
}
if (!IsDeltaDelete()) {
current_at_base_ = false;
return;
}
// Delta is less advanced and is delete.
AdvanceDelta();
if (equal_keys_) {
AdvanceBase();
}
} else {
current_at_base_ = true;
return;
}
}
}
AssertInvariants();
}
bool forward_;
bool current_at_base_;
bool equal_keys_;
Status status_;
std::unique_ptr<Iterator> base_iterator_;
std::unique_ptr<WBWIIterator> delta_iterator_;
const Comparator* comparator_; // not owned
};
class ReadableWriteBatch : public WriteBatch {
public:
explicit ReadableWriteBatch(size_t reserved_bytes = 0)
: WriteBatch(reserved_bytes) {}
// Retrieve some information from a write entry in the write batch, given
// the start offset of the write entry.
Status GetEntryFromDataOffset(size_t data_offset, WriteType* type, Slice* Key,
Slice* value, Slice* blob) const;
};
// Key used by skip list, as the binary searchable index of WriteBatchWithIndex.
struct WriteBatchIndexEntry {
WriteBatchIndexEntry(size_t o, uint32_t c)
: offset(o), column_family(c), search_key(nullptr) {}
WriteBatchIndexEntry(const Slice* sk, uint32_t c)
: offset(0), column_family(c), search_key(sk) {}
// If this flag appears in the offset, it indicates a key that is smaller
// than any other entry for the same column family
static const size_t kFlagMin = std::numeric_limits<size_t>::max();
size_t offset; // offset of an entry in write batch's string buffer.
uint32_t column_family; // column family of the entry
const Slice* search_key; // if not null, instead of reading keys from
// write batch, use it to compare. This is used
// for lookup key.
};
class WriteBatchEntryComparator {
public:
WriteBatchEntryComparator(const Comparator* _default_comparator,
const ReadableWriteBatch* write_batch)
: default_comparator_(_default_comparator), write_batch_(write_batch) {}
// Compare a and b. Return a negative value if a is less than b, 0 if they
// are equal, and a positive value if a is greater than b
int operator()(const WriteBatchIndexEntry* entry1,
const WriteBatchIndexEntry* entry2) const;
int CompareKey(uint32_t column_family, const Slice& key1,
const Slice& key2) const;
void SetComparatorForCF(uint32_t column_family_id,
const Comparator* comparator) {
cf_comparator_map_[column_family_id] = comparator;
}
const Comparator* default_comparator() { return default_comparator_; }
private:
const Comparator* default_comparator_;
std::unordered_map<uint32_t, const Comparator*> cf_comparator_map_;
const ReadableWriteBatch* write_batch_;
};
typedef SkipList<WriteBatchIndexEntry*, const WriteBatchEntryComparator&>
WriteBatchEntrySkipList;
class WBWIIteratorImpl : public WBWIIterator {
public:
WBWIIteratorImpl(uint32_t column_family_id,
WriteBatchEntrySkipList* skip_list,
const ReadableWriteBatch* write_batch)
: column_family_id_(column_family_id),
skip_list_iter_(skip_list),
write_batch_(write_batch),
valid_(false) {}
virtual ~WBWIIteratorImpl() {}
virtual bool Valid() const override { return valid_; }
virtual void SeekToFirst() override {
valid_ = true;
WriteBatchIndexEntry search_entry(WriteBatchIndexEntry::kFlagMin,
column_family_id_);
skip_list_iter_.Seek(&search_entry);
ReadEntry();
}
virtual void SeekToLast() override {
valid_ = true;
WriteBatchIndexEntry search_entry(WriteBatchIndexEntry::kFlagMin,
column_family_id_ + 1);
skip_list_iter_.Seek(&search_entry);
if (!skip_list_iter_.Valid()) {
skip_list_iter_.SeekToLast();
} else {
skip_list_iter_.Prev();
}
ReadEntry();
}
virtual void Seek(const Slice& key) override {
valid_ = true;
WriteBatchIndexEntry search_entry(&key, column_family_id_);
skip_list_iter_.Seek(&search_entry);
ReadEntry();
}
virtual void Next() override {
skip_list_iter_.Next();
ReadEntry();
}
virtual void Prev() override {
skip_list_iter_.Prev();
ReadEntry();
}
virtual const WriteEntry& Entry() const override { return current_; }
virtual Status status() const override { return status_; }
const WriteBatchIndexEntry* GetRawEntry() const {
return skip_list_iter_.key();
}
private:
uint32_t column_family_id_;
WriteBatchEntrySkipList::Iterator skip_list_iter_;
const ReadableWriteBatch* write_batch_;
Status status_;
bool valid_;
WriteEntry current_;
void ReadEntry() {
if (!status_.ok() || !skip_list_iter_.Valid()) {
valid_ = false;
return;
}
const WriteBatchIndexEntry* iter_entry = skip_list_iter_.key();
if (iter_entry == nullptr ||
iter_entry->column_family != column_family_id_) {
valid_ = false;
return;
}
Slice blob;
status_ = write_batch_->GetEntryFromDataOffset(
iter_entry->offset, &current_.type, &current_.key, &current_.value,
&blob);
if (!status_.ok()) {
valid_ = false;
} else if (current_.type != kPutRecord && current_.type != kDeleteRecord &&
current_.type != kMergeRecord) {
valid_ = false;
status_ = Status::Corruption("write batch index is corrupted");
}
}
};
struct WriteBatchWithIndex::Rep {
Rep(const Comparator* index_comparator, size_t reserved_bytes = 0,
bool _overwrite_key = false)
: write_batch(reserved_bytes),
comparator(index_comparator, &write_batch),
skip_list(comparator, &arena),
overwrite_key(_overwrite_key),
last_entry_offset(0) {}
ReadableWriteBatch write_batch;
WriteBatchEntryComparator comparator;
Arena arena;
WriteBatchEntrySkipList skip_list;
bool overwrite_key;
size_t last_entry_offset;
// Remember current offset of internal write batch, which is used as
// the starting offset of the next record.
void SetLastEntryOffset() { last_entry_offset = write_batch.GetDataSize(); }
// In overwrite mode, find the existing entry for the same key and update it
// to point to the current entry.
// Return true if the key is found and updated.
bool UpdateExistingEntry(ColumnFamilyHandle* column_family, const Slice& key);
bool UpdateExistingEntryWithCfId(uint32_t column_family_id, const Slice& key);
// Add the recent entry to the update.
// In overwrite mode, if key already exists in the index, update it.
void AddOrUpdateIndex(ColumnFamilyHandle* column_family, const Slice& key);
void AddOrUpdateIndex(const Slice& key);
// Allocate an index entry pointing to the last entry in the write batch and
// put it to skip list.
void AddNewEntry(uint32_t column_family_id);
// Clear all updates buffered in this batch.
void Clear();
};
bool WriteBatchWithIndex::Rep::UpdateExistingEntry(
ColumnFamilyHandle* column_family, const Slice& key) {
uint32_t cf_id = GetColumnFamilyID(column_family);
return UpdateExistingEntryWithCfId(cf_id, key);
}
bool WriteBatchWithIndex::Rep::UpdateExistingEntryWithCfId(
uint32_t column_family_id, const Slice& key) {
if (!overwrite_key) {
return false;
}
WBWIIteratorImpl iter(column_family_id, &skip_list, &write_batch);
iter.Seek(key);
if (!iter.Valid()) {
return false;
}
if (comparator.CompareKey(column_family_id, key, iter.Entry().key) != 0) {
return false;
}
WriteBatchIndexEntry* non_const_entry =
const_cast<WriteBatchIndexEntry*>(iter.GetRawEntry());
non_const_entry->offset = last_entry_offset;
return true;
}
void WriteBatchWithIndex::Rep::AddOrUpdateIndex(
ColumnFamilyHandle* column_family, const Slice& key) {
if (!UpdateExistingEntry(column_family, key)) {
uint32_t cf_id = GetColumnFamilyID(column_family);
const auto* cf_cmp = GetColumnFamilyUserComparator(column_family);
if (cf_cmp != nullptr) {
comparator.SetComparatorForCF(cf_id, cf_cmp);
}
AddNewEntry(cf_id);
}
}
void WriteBatchWithIndex::Rep::AddOrUpdateIndex(const Slice& key) {
if (!UpdateExistingEntryWithCfId(0, key)) {
AddNewEntry(0);
}
}
void WriteBatchWithIndex::Rep::AddNewEntry(uint32_t column_family_id) {
auto* mem = arena.Allocate(sizeof(WriteBatchIndexEntry));
auto* index_entry =
new (mem) WriteBatchIndexEntry(last_entry_offset, column_family_id);
skip_list.Insert(index_entry);
}
void WriteBatchWithIndex::Rep::Clear() {
write_batch.Clear();
arena.~Arena();
new (&arena) Arena();
skip_list.~WriteBatchEntrySkipList();
new (&skip_list) WriteBatchEntrySkipList(comparator, &arena);
last_entry_offset = 0;
}
Status ReadableWriteBatch::GetEntryFromDataOffset(size_t data_offset,
WriteType* type, Slice* Key,
Slice* value,
Slice* blob) const {
if (type == nullptr || Key == nullptr || value == nullptr ||
blob == nullptr) {
return Status::InvalidArgument("Output parameters cannot be null");
}
if (data_offset >= GetDataSize()) {
return Status::InvalidArgument("data offset exceed write batch size");
}
Slice input = Slice(rep_.data() + data_offset, rep_.size() - data_offset);
char tag;
uint32_t column_family;
Status s =
ReadRecordFromWriteBatch(&input, &tag, &column_family, Key, value, blob);
switch (tag) {
case kTypeColumnFamilyValue:
case kTypeValue:
*type = kPutRecord;
break;
case kTypeColumnFamilyDeletion:
case kTypeDeletion:
*type = kDeleteRecord;
break;
case kTypeColumnFamilyMerge:
case kTypeMerge:
*type = kMergeRecord;
break;
case kTypeLogData:
*type = kLogDataRecord;
break;
default:
return Status::Corruption("unknown WriteBatch tag");
}
return Status::OK();
}
WriteBatchWithIndex::WriteBatchWithIndex(
const Comparator* default_index_comparator, size_t reserved_bytes,
bool overwrite_key)
: rep(new Rep(default_index_comparator, reserved_bytes, overwrite_key)) {}
WriteBatchWithIndex::~WriteBatchWithIndex() { delete rep; }
WriteBatch* WriteBatchWithIndex::GetWriteBatch() { return &rep->write_batch; }
WBWIIterator* WriteBatchWithIndex::NewIterator() {
return new WBWIIteratorImpl(0, &(rep->skip_list), &rep->write_batch);
}
WBWIIterator* WriteBatchWithIndex::NewIterator(
ColumnFamilyHandle* column_family) {
return new WBWIIteratorImpl(GetColumnFamilyID(column_family),
&(rep->skip_list), &rep->write_batch);
}
Iterator* WriteBatchWithIndex::NewIteratorWithBase(
ColumnFamilyHandle* column_family, Iterator* base_iterator) {
if (rep->overwrite_key == false) {
assert(false);
return nullptr;
}
return new BaseDeltaIterator(base_iterator, NewIterator(column_family),
GetColumnFamilyUserComparator(column_family));
}
Iterator* WriteBatchWithIndex::NewIteratorWithBase(Iterator* base_iterator) {
if (rep->overwrite_key == false) {
assert(false);
return nullptr;
}
// default column family's comparator
return new BaseDeltaIterator(base_iterator, NewIterator(),
rep->comparator.default_comparator());
}
void WriteBatchWithIndex::Put(ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value) {
rep->SetLastEntryOffset();
rep->write_batch.Put(column_family, key, value);
rep->AddOrUpdateIndex(column_family, key);
}
void WriteBatchWithIndex::Put(const Slice& key, const Slice& value) {
rep->SetLastEntryOffset();
rep->write_batch.Put(key, value);
rep->AddOrUpdateIndex(key);
}
void WriteBatchWithIndex::Merge(ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value) {
rep->SetLastEntryOffset();
rep->write_batch.Merge(column_family, key, value);
rep->AddOrUpdateIndex(column_family, key);
}
void WriteBatchWithIndex::Merge(const Slice& key, const Slice& value) {
rep->SetLastEntryOffset();
rep->write_batch.Merge(key, value);
rep->AddOrUpdateIndex(key);
}
void WriteBatchWithIndex::PutLogData(const Slice& blob) {
rep->write_batch.PutLogData(blob);
}
void WriteBatchWithIndex::Delete(ColumnFamilyHandle* column_family,
const Slice& key) {
rep->SetLastEntryOffset();
rep->write_batch.Delete(column_family, key);
rep->AddOrUpdateIndex(column_family, key);
}
void WriteBatchWithIndex::Delete(const Slice& key) {
rep->SetLastEntryOffset();
rep->write_batch.Delete(key);
rep->AddOrUpdateIndex(key);
}
void WriteBatchWithIndex::Clear() { rep->Clear(); }
int WriteBatchEntryComparator::operator()(
const WriteBatchIndexEntry* entry1,
const WriteBatchIndexEntry* entry2) const {
if (entry1->column_family > entry2->column_family) {
return 1;
} else if (entry1->column_family < entry2->column_family) {
return -1;
}
if (entry1->offset == WriteBatchIndexEntry::kFlagMin) {
return -1;
} else if (entry2->offset == WriteBatchIndexEntry::kFlagMin) {
return 1;
}
Status s;
Slice key1, key2;
if (entry1->search_key == nullptr) {
Slice value, blob;
WriteType write_type;
s = write_batch_->GetEntryFromDataOffset(entry1->offset, &write_type, &key1,
&value, &blob);
if (!s.ok()) {
return 1;
}
} else {
key1 = *(entry1->search_key);
}
if (entry2->search_key == nullptr) {
Slice value, blob;
WriteType write_type;
s = write_batch_->GetEntryFromDataOffset(entry2->offset, &write_type, &key2,
&value, &blob);
if (!s.ok()) {
return -1;
}
} else {
key2 = *(entry2->search_key);
}
int cmp = CompareKey(entry1->column_family, key1, key2);
if (cmp != 0) {
return cmp;
} else if (entry1->offset > entry2->offset) {
return 1;
} else if (entry1->offset < entry2->offset) {
return -1;
}
return 0;
}
int WriteBatchEntryComparator::CompareKey(uint32_t column_family,
const Slice& key1,
const Slice& key2) const {
auto comparator_for_cf = cf_comparator_map_.find(column_family);
if (comparator_for_cf != cf_comparator_map_.end()) {
return comparator_for_cf->second->Compare(key1, key2);
} else {
return default_comparator_->Compare(key1, key2);
}
}
} // namespace rocksdb