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05e8854085
rocksdb/db/version_set.cc
Haobo Xu 05e8854085 [Rocksdb] Support Merge operation in rocksdb 
Summary:
This diff introduces a new Merge operation into rocksdb.
The purpose of this review is mostly getting feedback from the team (everyone please) on the design.

Please focus on the four files under include/leveldb/, as they spell the client visible interface change.
include/leveldb/db.h
include/leveldb/merge_operator.h
include/leveldb/options.h
include/leveldb/write_batch.h

Please go over local/my_test.cc carefully, as it is a concerete use case.

Please also review the impelmentation files to see if the straw man implementation makes sense.

Note that, the diff does pass all make check and truly supports forward iterator over db and a version
of Get that's based on iterator.

Future work:
- Integration with compaction
- A raw Get implementation

I am working on a wiki that explains the design and implementation choices, but coding comes
just naturally and I think it might be a good idea to share the code earlier. The code is
heavily commented.

Test Plan: run all local tests

Reviewers: dhruba, heyongqiang

Reviewed By: dhruba

CC: leveldb, zshao, sheki, emayanke, MarkCallaghan

Differential Revision: https://reviews.facebook.net/D9651
2013-05-03 16:59:02 -07:00

2386 lines
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// 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/version_set.h"
#include <algorithm>
#include <stdio.h>
#include "db/filename.h"
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
#include "db/table_cache.h"
#include "leveldb/env.h"
#include "leveldb/merge_operator.h"
#include "leveldb/table_builder.h"
#include "table/merger.h"
#include "table/two_level_iterator.h"
#include "util/coding.h"
#include "util/logging.h"
namespace leveldb {
static int64_t TotalFileSize(const std::vector<FileMetaData*>& files) {
int64_t sum = 0;
for (size_t i = 0; i < files.size() && files[i]; i++) {
sum += files[i]->file_size;
}
return sum;
}
Version::~Version() {
assert(refs_ == 0);
// Remove from linked list
prev_->next_ = next_;
next_->prev_ = prev_;
// Drop references to files
for (int level = 0; level < vset_->NumberLevels(); level++) {
for (size_t i = 0; i < files_[level].size(); i++) {
FileMetaData* f = files_[level][i];
assert(f->refs > 0);
f->refs--;
if (f->refs <= 0) {
delete f;
}
}
}
delete[] files_;
}
int FindFile(const InternalKeyComparator& icmp,
const std::vector<FileMetaData*>& files,
const Slice& key) {
uint32_t left = 0;
uint32_t right = files.size();
while (left < right) {
uint32_t mid = (left + right) / 2;
const FileMetaData* f = files[mid];
if (icmp.InternalKeyComparator::Compare(f->largest.Encode(), key) < 0) {
// Key at "mid.largest" is < "target". Therefore all
// files at or before "mid" are uninteresting.
left = mid + 1;
} else {
// Key at "mid.largest" is >= "target". Therefore all files
// after "mid" are uninteresting.
right = mid;
}
}
return right;
}
static bool AfterFile(const Comparator* ucmp,
const Slice* user_key, const FileMetaData* f) {
// nullptr user_key occurs before all keys and is therefore never after *f
return (user_key != nullptr &&
ucmp->Compare(*user_key, f->largest.user_key()) > 0);
}
static bool BeforeFile(const Comparator* ucmp,
const Slice* user_key, const FileMetaData* f) {
// nullptr user_key occurs after all keys and is therefore never before *f
return (user_key != nullptr &&
ucmp->Compare(*user_key, f->smallest.user_key()) < 0);
}
bool SomeFileOverlapsRange(
const InternalKeyComparator& icmp,
bool disjoint_sorted_files,
const std::vector<FileMetaData*>& files,
const Slice* smallest_user_key,
const Slice* largest_user_key) {
const Comparator* ucmp = icmp.user_comparator();
if (!disjoint_sorted_files) {
// Need to check against all files
for (size_t i = 0; i < files.size(); i++) {
const FileMetaData* f = files[i];
if (AfterFile(ucmp, smallest_user_key, f) ||
BeforeFile(ucmp, largest_user_key, f)) {
// No overlap
} else {
return true; // Overlap
}
}
return false;
}
// Binary search over file list
uint32_t index = 0;
if (smallest_user_key != nullptr) {
// Find the earliest possible internal key for smallest_user_key
InternalKey small(*smallest_user_key, kMaxSequenceNumber,kValueTypeForSeek);
index = FindFile(icmp, files, small.Encode());
}
if (index >= files.size()) {
// beginning of range is after all files, so no overlap.
return false;
}
return !BeforeFile(ucmp, largest_user_key, files[index]);
}
// An internal iterator. For a given version/level pair, yields
// information about the files in the level. For a given entry, key()
// is the largest key that occurs in the file, and value() is an
// 16-byte value containing the file number and file size, both
// encoded using EncodeFixed64.
class Version::LevelFileNumIterator : public Iterator {
public:
LevelFileNumIterator(const InternalKeyComparator& icmp,
const std::vector<FileMetaData*>* flist)
: icmp_(icmp),
flist_(flist),
index_(flist->size()) { // Marks as invalid
}
virtual bool Valid() const {
return index_ < flist_->size();
}
virtual void Seek(const Slice& target) {
index_ = FindFile(icmp_, *flist_, target);
}
virtual void SeekToFirst() { index_ = 0; }
virtual void SeekToLast() {
index_ = flist_->empty() ? 0 : flist_->size() - 1;
}
virtual void Next() {
assert(Valid());
index_++;
}
virtual void Prev() {
assert(Valid());
if (index_ == 0) {
index_ = flist_->size(); // Marks as invalid
} else {
index_--;
}
}
Slice key() const {
assert(Valid());
return (*flist_)[index_]->largest.Encode();
}
Slice value() const {
assert(Valid());
EncodeFixed64(value_buf_, (*flist_)[index_]->number);
EncodeFixed64(value_buf_+8, (*flist_)[index_]->file_size);
return Slice(value_buf_, sizeof(value_buf_));
}
virtual Status status() const { return Status::OK(); }
private:
const InternalKeyComparator icmp_;
const std::vector<FileMetaData*>* const flist_;
uint32_t index_;
// Backing store for value(). Holds the file number and size.
mutable char value_buf_[16];
};
static Iterator* GetFileIterator(void* arg,
const ReadOptions& options,
const EnvOptions& soptions,
const Slice& file_value) {
TableCache* cache = reinterpret_cast<TableCache*>(arg);
if (file_value.size() != 16) {
return NewErrorIterator(
Status::Corruption("FileReader invoked with unexpected value"));
} else {
return cache->NewIterator(options,
soptions,
DecodeFixed64(file_value.data()),
DecodeFixed64(file_value.data() + 8));
}
}
Iterator* Version::NewConcatenatingIterator(const ReadOptions& options,
const StorageOptions& soptions,
int level) const {
return NewTwoLevelIterator(
new LevelFileNumIterator(vset_->icmp_, &files_[level]),
&GetFileIterator, vset_->table_cache_, options, soptions);
}
void Version::AddIterators(const ReadOptions& options,
const StorageOptions& soptions,
std::vector<Iterator*>* iters) {
// Merge all level zero files together since they may overlap
for (size_t i = 0; i < files_[0].size(); i++) {
iters->push_back(
vset_->table_cache_->NewIterator(
options, soptions, files_[0][i]->number, files_[0][i]->file_size));
}
// For levels > 0, we can use a concatenating iterator that sequentially
// walks through the non-overlapping files in the level, opening them
// lazily.
for (int level = 1; level < vset_->NumberLevels(); level++) {
if (!files_[level].empty()) {
iters->push_back(NewConcatenatingIterator(options, soptions, level));
}
}
}
// Callback from TableCache::Get()
namespace {
enum SaverState {
kNotFound,
kFound,
kDeleted,
kCorrupt,
kMerge // value contains the current merge result (the operand)
};
struct Saver {
SaverState state;
const Comparator* ucmp;
Slice user_key;
std::string* value;
const MergeOperator* merge_operator;
Logger* logger;
bool didIO; // did we do any disk io?
};
}
static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
Saver* s = reinterpret_cast<Saver*>(arg);
ParsedInternalKey parsed_key;
// TODO: didIO and Merge?
s->didIO = didIO;
if (!ParseInternalKey(ikey, &parsed_key)) {
// TODO: what about corrupt during Merge?
s->state = kCorrupt;
} else {
if (s->ucmp->Compare(parsed_key.user_key, s->user_key) == 0) {
switch (parsed_key.type) {
case kTypeValue:
if (kNotFound == s->state) {
s->value->assign(v.data(), v.size());
} else if (kMerge == s->state) {
std::string operand;
swap(operand, *s->value);
s->merge_operator->Merge(s->user_key, &v, operand,
s->value, s->logger);
} else {
assert(false);
}
s->state = kFound;
return false;
case kTypeMerge:
if (kNotFound == s->state) {
s->state = kMerge;
s->value->assign(v.data(), v.size());
} else if (kMerge == s->state) {
std::string operand;
swap(operand, *s->value);
s->merge_operator->Merge(s->user_key, &v, operand,
s->value, s->logger);
} else {
assert(false);
}
return true;
case kTypeDeletion:
if (kNotFound == s->state) {
s->state = kDeleted;
} else if (kMerge == s->state) {
std::string operand;
swap(operand, *s->value);
s->merge_operator->Merge(s->user_key, nullptr, operand,
s->value, s->logger);
s->state = kFound;
} else {
assert(false);
}
return false;
}
}
}
// s->state could be Corrupt, merge or notfound
return false;
}
static bool NewestFirst(FileMetaData* a, FileMetaData* b) {
return a->number > b->number;
}
Version::Version(VersionSet* vset, uint64_t version_number)
: vset_(vset), next_(this), prev_(this), refs_(0),
files_by_size_(vset->NumberLevels()),
next_file_to_compact_by_size_(vset->NumberLevels()),
file_to_compact_(nullptr),
file_to_compact_level_(-1),
compaction_score_(vset->NumberLevels()),
compaction_level_(vset->NumberLevels()),
offset_manifest_file_(0),
version_number_(version_number) {
files_ = new std::vector<FileMetaData*>[vset->NumberLevels()];
}
void Version::Get(const ReadOptions& options,
const LookupKey& k,
std::string* value,
Status *status,
GetStats* stats,
const Options& db_options) {
Slice ikey = k.internal_key();
Slice user_key = k.user_key();
const Comparator* ucmp = vset_->icmp_.user_comparator();
auto merge_operator = db_options.merge_operator;
auto logger = db_options.info_log;
assert(status->ok() || status->IsMergeInProgress());
Saver saver;
saver.state = status->ok()? kNotFound : kMerge;
saver.ucmp = ucmp;
saver.user_key = user_key;
saver.value = value;
saver.merge_operator = merge_operator;
saver.logger = logger.get();
saver.didIO = false;
stats->seek_file = nullptr;
stats->seek_file_level = -1;
FileMetaData* last_file_read = nullptr;
int last_file_read_level = -1;
// We can search level-by-level since entries never hop across
// levels. Therefore we are guaranteed that if we find data
// in an smaller level, later levels are irrelevant.
std::vector<FileMetaData*> tmp;
FileMetaData* tmp2;
for (int level = 0; level < vset_->NumberLevels(); level++) {
size_t num_files = files_[level].size();
if (num_files == 0) continue;
// Get the list of files to search in this level
FileMetaData* const* files = &files_[level][0];
if (level == 0) {
// Level-0 files may overlap each other. Find all files that
// overlap user_key and process them in order from newest to oldest.
tmp.reserve(num_files);
for (uint32_t i = 0; i < num_files; i++) {
FileMetaData* f = files[i];
if (ucmp->Compare(user_key, f->smallest.user_key()) >= 0 &&
ucmp->Compare(user_key, f->largest.user_key()) <= 0) {
tmp.push_back(f);
}
}
if (tmp.empty()) continue;
std::sort(tmp.begin(), tmp.end(), NewestFirst);
files = &tmp[0];
num_files = tmp.size();
} else {
// Binary search to find earliest index whose largest key >= ikey.
uint32_t index = FindFile(vset_->icmp_, files_[level], ikey);
if (index >= num_files) {
files = nullptr;
num_files = 0;
} else {
tmp2 = files[index];
if (ucmp->Compare(user_key, tmp2->smallest.user_key()) < 0) {
// All of "tmp2" is past any data for user_key
files = nullptr;
num_files = 0;
} else {
files = &tmp2;
num_files = 1;
// TODO, is level 1-n files all disjoint in user key space?
}
}
}
for (uint32_t i = 0; i < num_files; ++i) {
FileMetaData* f = files[i];
bool tableIO = false;
*status = vset_->table_cache_->Get(options, f->number, f->file_size,
ikey, &saver, SaveValue, &tableIO);
// TODO: examine the behavior for corrupted key
if (!status->ok()) {
return;
}
if (last_file_read != nullptr && stats->seek_file == nullptr) {
// We have had more than one seek for this read. Charge the 1st file.
stats->seek_file = last_file_read;
stats->seek_file_level = last_file_read_level;
}
// If we did any IO as part of the read, then we remember it because
// it is a possible candidate for seek-based compaction. saver.didIO
// is true if the block had to be read in from storage and was not
// pre-exisiting in the block cache. Also, if this file was not pre-
// existing in the table cache and had to be freshly opened that needed
// the index blocks to be read-in, then tableIO is true. One thing
// to note is that the index blocks are not part of the block cache.
if (saver.didIO || tableIO) {
last_file_read = f;
last_file_read_level = level;
}
switch (saver.state) {
case kNotFound:
break; // Keep searching in other files
case kFound:
return;
case kDeleted:
*status = Status::NotFound(Slice()); // Use empty error message for speed
return;
case kCorrupt:
*status = Status::Corruption("corrupted key for ", user_key);
return;
case kMerge:
break;
}
}
}
if (kMerge == saver.state) {
// merge operand is in *value and we hit the beginning of the key history
// do a final merge of nullptr and operand;
std::string operand;
swap(operand, *value);
merge_operator->Merge(user_key, nullptr, operand,
value, logger.get());
*status = Status::OK();
return;
} else {
*status = Status::NotFound(Slice()); // Use an empty error message for speed
return;
}
}
bool Version::UpdateStats(const GetStats& stats) {
FileMetaData* f = stats.seek_file;
if (f != nullptr) {
f->allowed_seeks--;
if (f->allowed_seeks <= 0 && file_to_compact_ == nullptr) {
file_to_compact_ = f;
file_to_compact_level_ = stats.seek_file_level;
return true;
}
}
return false;
}
void Version::Ref() {
++refs_;
}
void Version::Unref() {
assert(this != &vset_->dummy_versions_);
assert(refs_ >= 1);
--refs_;
if (refs_ == 0) {
delete this;
}
}
bool Version::OverlapInLevel(int level,
const Slice* smallest_user_key,
const Slice* largest_user_key) {
return SomeFileOverlapsRange(vset_->icmp_, (level > 0), files_[level],
smallest_user_key, largest_user_key);
}
int Version::PickLevelForMemTableOutput(
const Slice& smallest_user_key,
const Slice& largest_user_key) {
int level = 0;
if (!OverlapInLevel(0, &smallest_user_key, &largest_user_key)) {
// Push to next level if there is no overlap in next level,
// and the #bytes overlapping in the level after that are limited.
InternalKey start(smallest_user_key, kMaxSequenceNumber, kValueTypeForSeek);
InternalKey limit(largest_user_key, 0, static_cast<ValueType>(0));
std::vector<FileMetaData*> overlaps;
int max_mem_compact_level = vset_->options_->max_mem_compaction_level;
while (max_mem_compact_level > 0 && level < max_mem_compact_level) {
if (OverlapInLevel(level + 1, &smallest_user_key, &largest_user_key)) {
break;
}
if (level + 2 >= vset_->NumberLevels()) {
level++;
break;
}
GetOverlappingInputs(level + 2, &start, &limit, &overlaps);
const int64_t sum = TotalFileSize(overlaps);
if (sum > vset_->MaxGrandParentOverlapBytes(level)) {
break;
}
level++;
}
}
return level;
}
// Store in "*inputs" all files in "level" that overlap [begin,end]
// If hint_index is specified, then it points to a file in the
// overlapping range.
// The file_index returns a pointer to any file in an overlapping range.
void Version::GetOverlappingInputs(
int level,
const InternalKey* begin,
const InternalKey* end,
std::vector<FileMetaData*>* inputs,
int hint_index,
int* file_index) {
inputs->clear();
Slice user_begin, user_end;
if (begin != nullptr) {
user_begin = begin->user_key();
}
if (end != nullptr) {
user_end = end->user_key();
}
if (file_index) {
*file_index = -1;
}
const Comparator* user_cmp = vset_->icmp_.user_comparator();
if (begin != nullptr && end != nullptr && level > 0) {
GetOverlappingInputsBinarySearch(level, user_begin, user_end, inputs,
hint_index, file_index);
return;
}
for (size_t i = 0; i < files_[level].size(); ) {
FileMetaData* f = files_[level][i++];
const Slice file_start = f->smallest.user_key();
const Slice file_limit = f->largest.user_key();
if (begin != nullptr && user_cmp->Compare(file_limit, user_begin) < 0) {
// "f" is completely before specified range; skip it
} else if (end != nullptr && user_cmp->Compare(file_start, user_end) > 0) {
// "f" is completely after specified range; skip it
} else {
inputs->push_back(f);
if (level == 0) {
// Level-0 files may overlap each other. So check if the newly
// added file has expanded the range. If so, restart search.
if (begin != nullptr && user_cmp->Compare(file_start, user_begin) < 0) {
user_begin = file_start;
inputs->clear();
i = 0;
} else if (end != nullptr
&& user_cmp->Compare(file_limit, user_end) > 0) {
user_end = file_limit;
inputs->clear();
i = 0;
}
} else if (file_index) {
*file_index = i-1;
}
}
}
}
// Store in "*inputs" all files in "level" that overlap [begin,end]
// Employ binary search to find at least one file that overlaps the
// specified range. From that file, iterate backwards and
// forwards to find all overlapping files.
void Version::GetOverlappingInputsBinarySearch(
int level,
const Slice& user_begin,
const Slice& user_end,
std::vector<FileMetaData*>* inputs,
int hint_index,
int* file_index) {
assert(level > 0);
int min = 0;
int mid = 0;
int max = files_[level].size() -1;
bool foundOverlap = false;
const Comparator* user_cmp = vset_->icmp_.user_comparator();
// if the caller already knows the index of a file that has overlap,
// then we can skip the binary search.
if (hint_index != -1) {
mid = hint_index;
foundOverlap = true;
}
while (!foundOverlap && min <= max) {
mid = (min + max)/2;
FileMetaData* f = files_[level][mid];
const Slice file_start = f->smallest.user_key();
const Slice file_limit = f->largest.user_key();
if (user_cmp->Compare(file_limit, user_begin) < 0) {
min = mid + 1;
} else if (user_cmp->Compare(user_end, file_start) < 0) {
max = mid - 1;
} else {
foundOverlap = true;
break;
}
}
// If there were no overlapping files, return immediately.
if (!foundOverlap) {
return;
}
// returns the index where an overlap is found
if (file_index) {
*file_index = mid;
}
ExtendOverlappingInputs(level, user_begin, user_end, inputs, mid);
}
// Store in "*inputs" all files in "level" that overlap [begin,end]
// The midIndex specifies the index of at least one file that
// overlaps the specified range. From that file, iterate backward
// and forward to find all overlapping files.
void Version::ExtendOverlappingInputs(
int level,
const Slice& user_begin,
const Slice& user_end,
std::vector<FileMetaData*>* inputs,
unsigned int midIndex) {
const Comparator* user_cmp = vset_->icmp_.user_comparator();
#ifndef NDEBUG
{
// assert that the file at midIndex overlaps with the range
assert(midIndex < files_[level].size());
FileMetaData* f = files_[level][midIndex];
const Slice fstart = f->smallest.user_key();
const Slice flimit = f->largest.user_key();
if (user_cmp->Compare(fstart, user_begin) >= 0) {
assert(user_cmp->Compare(fstart, user_end) <= 0);
} else {
assert(user_cmp->Compare(flimit, user_begin) >= 0);
}
}
#endif
int startIndex = midIndex + 1;
int endIndex = midIndex;
int count __attribute__((unused)) = 0;
// check backwards from 'mid' to lower indices
for (int i = midIndex; i >= 0 ; i--) {
FileMetaData* f = files_[level][i];
const Slice file_limit = f->largest.user_key();
if (user_cmp->Compare(file_limit, user_begin) >= 0) {
startIndex = i;
assert((count++, true));
} else {
break;
}
}
// check forward from 'mid+1' to higher indices
for (unsigned int i = midIndex+1; i < files_[level].size(); i++) {
FileMetaData* f = files_[level][i];
const Slice file_start = f->smallest.user_key();
if (user_cmp->Compare(file_start, user_end) <= 0) {
assert((count++, true));
endIndex = i;
} else {
break;
}
}
assert(count == endIndex - startIndex + 1);
// insert overlapping files into vector
for (int i = startIndex; i <= endIndex; i++) {
FileMetaData* f = files_[level][i];
inputs->push_back(f);
}
}
std::string Version::DebugString(bool hex) const {
std::string r;
for (int level = 0; level < vset_->NumberLevels(); level++) {
// E.g.,
// --- level 1 ---
// 17:123['a' .. 'd']
// 20:43['e' .. 'g']
r.append("--- level ");
AppendNumberTo(&r, level);
r.append(" --- version# ");
AppendNumberTo(&r, version_number_);
r.append(" ---\n");
const std::vector<FileMetaData*>& files = files_[level];
for (size_t i = 0; i < files.size(); i++) {
r.push_back(' ');
AppendNumberTo(&r, files[i]->number);
r.push_back(':');
AppendNumberTo(&r, files[i]->file_size);
r.append("[");
r.append(files[i]->smallest.DebugString(hex));
r.append(" .. ");
r.append(files[i]->largest.DebugString(hex));
r.append("]\n");
}
}
return r;
}
// this is used to batch writes to the manifest file
struct VersionSet::ManifestWriter {
Status status;
bool done;
port::CondVar cv;
VersionEdit* edit;
explicit ManifestWriter(port::Mutex* mu, VersionEdit* e) :
done(false), cv(mu), edit(e) {}
};
// A helper class so we can efficiently apply a whole sequence
// of edits to a particular state without creating intermediate
// Versions that contain full copies of the intermediate state.
class VersionSet::Builder {
private:
// Helper to sort by v->files_[file_number].smallest
struct BySmallestKey {
const InternalKeyComparator* internal_comparator;
bool operator()(FileMetaData* f1, FileMetaData* f2) const {
int r = internal_comparator->Compare(f1->smallest, f2->smallest);
if (r != 0) {
return (r < 0);
} else {
// Break ties by file number
return (f1->number < f2->number);
}
}
};
typedef std::set<FileMetaData*, BySmallestKey> FileSet;
struct LevelState {
std::set<uint64_t> deleted_files;
FileSet* added_files;
};
VersionSet* vset_;
Version* base_;
LevelState* levels_;
public:
// Initialize a builder with the files from *base and other info from *vset
Builder(VersionSet* vset, Version* base)
: vset_(vset),
base_(base) {
base_->Ref();
levels_ = new LevelState[vset_->NumberLevels()];
BySmallestKey cmp;
cmp.internal_comparator = &vset_->icmp_;
for (int level = 0; level < vset_->NumberLevels(); level++) {
levels_[level].added_files = new FileSet(cmp);
}
}
~Builder() {
for (int level = 0; level < vset_->NumberLevels(); level++) {
const FileSet* added = levels_[level].added_files;
std::vector<FileMetaData*> to_unref;
to_unref.reserve(added->size());
for (FileSet::const_iterator it = added->begin();
it != added->end(); ++it) {
to_unref.push_back(*it);
}
delete added;
for (uint32_t i = 0; i < to_unref.size(); i++) {
FileMetaData* f = to_unref[i];
f->refs--;
if (f->refs <= 0) {
delete f;
}
}
}
delete[] levels_;
base_->Unref();
}
void CheckConsistency(Version* v) {
#ifndef NDEBUG
for (int level = 0; level < vset_->NumberLevels(); level++) {
// Make sure there is no overlap in levels > 0
if (level > 0) {
for (uint32_t i = 1; i < v->files_[level].size(); i++) {
const InternalKey& prev_end = v->files_[level][i-1]->largest;
const InternalKey& this_begin = v->files_[level][i]->smallest;
if (vset_->icmp_.Compare(prev_end, this_begin) >= 0) {
fprintf(stderr, "overlapping ranges in same level %s vs. %s\n",
prev_end.DebugString().c_str(),
this_begin.DebugString().c_str());
abort();
}
}
}
}
#endif
}
void CheckConsistencyForDeletes(
VersionEdit* edit,
unsigned int number,
int level) {
#ifndef NDEBUG
// a file to be deleted better exist in the previous version
bool found = false;
for (int l = 0; !found && l < edit->number_levels_; l++) {
const std::vector<FileMetaData*>& base_files = base_->files_[l];
for (unsigned int i = 0; i < base_files.size(); i++) {
FileMetaData* f = base_files[i];
if (f->number == number) {
found = true;
break;
}
}
}
// if the file did not exist in the previous version, then it
// is possibly moved from lower level to higher level in current
// version
for (int l = level+1; !found && l < edit->number_levels_; l++) {
const FileSet* added = levels_[l].added_files;
for (FileSet::const_iterator added_iter = added->begin();
added_iter != added->end(); ++added_iter) {
FileMetaData* f = *added_iter;
if (f->number == number) {
found = true;
break;
}
}
}
// maybe this file was added in a previous edit that was Applied
if (!found) {
const FileSet* added = levels_[level].added_files;
for (FileSet::const_iterator added_iter = added->begin();
added_iter != added->end(); ++added_iter) {
FileMetaData* f = *added_iter;
if (f->number == number) {
found = true;
break;
}
}
}
assert(found);
#endif
}
// Apply all of the edits in *edit to the current state.
void Apply(VersionEdit* edit) {
CheckConsistency(base_);
// Update compaction pointers
for (size_t i = 0; i < edit->compact_pointers_.size(); i++) {
const int level = edit->compact_pointers_[i].first;
vset_->compact_pointer_[level] =
edit->compact_pointers_[i].second.Encode().ToString();
}
// Delete files
const VersionEdit::DeletedFileSet& del = edit->deleted_files_;
for (VersionEdit::DeletedFileSet::const_iterator iter = del.begin();
iter != del.end();
++iter) {
const int level = iter->first;
const uint64_t number = iter->second;
levels_[level].deleted_files.insert(number);
CheckConsistencyForDeletes(edit, number, level);
}
// Add new files
for (size_t i = 0; i < edit->new_files_.size(); i++) {
const int level = edit->new_files_[i].first;
FileMetaData* f = new FileMetaData(edit->new_files_[i].second);
f->refs = 1;
// We arrange to automatically compact this file after
// a certain number of seeks. Let's assume:
// (1) One seek costs 10ms
// (2) Writing or reading 1MB costs 10ms (100MB/s)
// (3) A compaction of 1MB does 25MB of IO:
// 1MB read from this level
// 10-12MB read from next level (boundaries may be misaligned)
// 10-12MB written to next level
// This implies that 25 seeks cost the same as the compaction
// of 1MB of data. I.e., one seek costs approximately the
// same as the compaction of 40KB of data. We are a little
// conservative and allow approximately one seek for every 16KB
// of data before triggering a compaction.
f->allowed_seeks = (f->file_size / 16384);
if (f->allowed_seeks < 100) f->allowed_seeks = 100;
levels_[level].deleted_files.erase(f->number);
levels_[level].added_files->insert(f);
}
}
// Save the current state in *v.
void SaveTo(Version* v) {
CheckConsistency(base_);
CheckConsistency(v);
BySmallestKey cmp;
cmp.internal_comparator = &vset_->icmp_;
for (int level = 0; level < vset_->NumberLevels(); level++) {
// Merge the set of added files with the set of pre-existing files.
// Drop any deleted files. Store the result in *v.
const std::vector<FileMetaData*>& base_files = base_->files_[level];
std::vector<FileMetaData*>::const_iterator base_iter = base_files.begin();
std::vector<FileMetaData*>::const_iterator base_end = base_files.end();
const FileSet* added = levels_[level].added_files;
v->files_[level].reserve(base_files.size() + added->size());
for (FileSet::const_iterator added_iter = added->begin();
added_iter != added->end();
++added_iter) {
// Add all smaller files listed in base_
for (std::vector<FileMetaData*>::const_iterator bpos
= std::upper_bound(base_iter, base_end, *added_iter, cmp);
base_iter != bpos;
++base_iter) {
MaybeAddFile(v, level, *base_iter);
}
MaybeAddFile(v, level, *added_iter);
}
// Add remaining base files
for (; base_iter != base_end; ++base_iter) {
MaybeAddFile(v, level, *base_iter);
}
}
CheckConsistency(v);
}
void MaybeAddFile(Version* v, int level, FileMetaData* f) {
if (levels_[level].deleted_files.count(f->number) > 0) {
// File is deleted: do nothing
} else {
std::vector<FileMetaData*>* files = &v->files_[level];
if (level > 0 && !files->empty()) {
// Must not overlap
assert(vset_->icmp_.Compare((*files)[files->size()-1]->largest,
f->smallest) < 0);
}
f->refs++;
files->push_back(f);
}
}
};
VersionSet::VersionSet(const std::string& dbname,
const Options* options,
const StorageOptions& storage_options,
TableCache* table_cache,
const InternalKeyComparator* cmp)
: env_(options->env),
dbname_(dbname),
options_(options),
table_cache_(table_cache),
icmp_(*cmp),
next_file_number_(2),
manifest_file_number_(0), // Filled by Recover()
last_sequence_(0),
log_number_(0),
prev_log_number_(0),
num_levels_(options_->num_levels),
dummy_versions_(this),
current_(nullptr),
compactions_in_progress_(options_->num_levels),
current_version_number_(0),
last_observed_manifest_size_(0),
storage_options_(storage_options),
storage_options_compactions_(storage_options_) {
compact_pointer_ = new std::string[options_->num_levels];
Init(options_->num_levels);
AppendVersion(new Version(this, current_version_number_++));
}
VersionSet::~VersionSet() {
current_->Unref();
assert(dummy_versions_.next_ == &dummy_versions_); // List must be empty
delete[] compact_pointer_;
delete[] max_file_size_;
delete[] level_max_bytes_;
}
void VersionSet::Init(int num_levels) {
max_file_size_ = new uint64_t[num_levels];
level_max_bytes_ = new uint64_t[num_levels];
int target_file_size_multiplier = options_->target_file_size_multiplier;
int max_bytes_multiplier = options_->max_bytes_for_level_multiplier;
for (int i = 0; i < num_levels; i++) {
if (i > 1) {
max_file_size_[i] = max_file_size_[i-1] * target_file_size_multiplier;
level_max_bytes_[i] = level_max_bytes_[i-1] * max_bytes_multiplier;
} else {
max_file_size_[i] = options_->target_file_size_base;
level_max_bytes_[i] = options_->max_bytes_for_level_base;
}
}
}
void VersionSet::AppendVersion(Version* v) {
// Make "v" current
assert(v->refs_ == 0);
assert(v != current_);
if (current_ != nullptr) {
assert(current_->refs_ > 0);
current_->Unref();
}
current_ = v;
v->Ref();
// Append to linked list
v->prev_ = dummy_versions_.prev_;
v->next_ = &dummy_versions_;
v->prev_->next_ = v;
v->next_->prev_ = v;
}
Status VersionSet::LogAndApply(VersionEdit* edit, port::Mutex* mu,
bool new_descriptor_log) {
mu->AssertHeld();
// queue our request
ManifestWriter w(mu, edit);
manifest_writers_.push_back(&w);
while (!w.done && &w != manifest_writers_.front()) {
w.cv.Wait();
}
if (w.done) {
return w.status;
}
std::vector<VersionEdit*> batch_edits;
Version* v = new Version(this, current_version_number_++);
Builder builder(this, current_);
// process all requests in the queue
ManifestWriter* last_writer = &w;
assert(!manifest_writers_.empty());
assert(manifest_writers_.front() == &w);
std::deque<ManifestWriter*>::iterator iter = manifest_writers_.begin();
for (; iter != manifest_writers_.end(); ++iter) {
last_writer = *iter;
LogAndApplyHelper(&builder, v, last_writer->edit, mu);
batch_edits.push_back(last_writer->edit);
}
builder.SaveTo(v);
// Initialize new descriptor log file if necessary by creating
// a temporary file that contains a snapshot of the current version.
std::string new_manifest_file;
uint64_t new_manifest_file_size = 0;
Status s;
// No need to perform this check if a new Manifest is being created anyways.
if (!descriptor_log_ ||
last_observed_manifest_size_ > options_->max_manifest_file_size) {
new_descriptor_log = true;
manifest_file_number_ = NewFileNumber(); // Change manifest file no.
}
if (!descriptor_log_ || new_descriptor_log) {
// No reason to unlock *mu here since we only hit this path in the
// first call to LogAndApply (when opening the database).
assert(!descriptor_log_ || new_descriptor_log);
new_manifest_file = DescriptorFileName(dbname_, manifest_file_number_);
edit->SetNextFile(next_file_number_);
unique_ptr<WritableFile> descriptor_file;
s = env_->NewWritableFile(new_manifest_file, &descriptor_file,
storage_options_);
if (s.ok()) {
descriptor_log_.reset(new log::Writer(std::move(descriptor_file)));
s = WriteSnapshot(descriptor_log_.get());
}
}
// Unlock during expensive MANIFEST log write. New writes cannot get here
// because &w is ensuring that all new writes get queued.
{
// calculate the amount of data being compacted at every level
std::vector<uint64_t> size_being_compacted(NumberLevels()-1);
SizeBeingCompacted(size_being_compacted);
mu->Unlock();
// The calls to Finalize and UpdateFilesBySize are cpu-heavy
// and is best called outside the mutex.
Finalize(v, size_being_compacted);
UpdateFilesBySize(v);
// Write new record to MANIFEST log
if (s.ok()) {
std::string record;
for (unsigned int i = 0; i < batch_edits.size(); i++) {
batch_edits[i]->EncodeTo(&record);
s = descriptor_log_->AddRecord(record);
if (!s.ok()) {
break;
}
}
if (s.ok()) {
if (options_->use_fsync) {
s = descriptor_log_->file()->Fsync();
} else {
s = descriptor_log_->file()->Sync();
}
}
if (!s.ok()) {
Log(options_->info_log, "MANIFEST write: %s\n", s.ToString().c_str());
if (ManifestContains(record)) {
Log(options_->info_log,
"MANIFEST contains log record despite error; advancing to new "
"version to prevent mismatch between in-memory and logged state"
" If paranoid is set, then the db is now in readonly mode.");
s = Status::OK();
}
}
}
// If we just created a new descriptor file, install it by writing a
// new CURRENT file that points to it.
if (s.ok() && !new_manifest_file.empty()) {
s = SetCurrentFile(env_, dbname_, manifest_file_number_);
}
// find offset in manifest file where this version is stored.
new_manifest_file_size = descriptor_log_->file()->GetFileSize();
mu->Lock();
// cache the manifest_file_size so that it can be used to rollover in the
// next call to LogAndApply
last_observed_manifest_size_ = new_manifest_file_size;
}
// Install the new version
if (s.ok()) {
v->offset_manifest_file_ = new_manifest_file_size;
AppendVersion(v);
log_number_ = edit->log_number_;
prev_log_number_ = edit->prev_log_number_;
} else {
Log(options_->info_log, "Error in committing version %ld",
v->GetVersionNumber());
delete v;
if (!new_manifest_file.empty()) {
descriptor_log_.reset();
env_->DeleteFile(new_manifest_file);
}
}
// wake up all the waiting writers
while (true) {
ManifestWriter* ready = manifest_writers_.front();
manifest_writers_.pop_front();
if (ready != &w) {
ready->status = s;
ready->done = true;
ready->cv.Signal();
}
if (ready == last_writer) break;
}
// Notify new head of write queue
if (!manifest_writers_.empty()) {
manifest_writers_.front()->cv.Signal();
}
return s;
}
void VersionSet::LogAndApplyHelper(Builder* builder, Version* v,
VersionEdit* edit, port::Mutex* mu) {
mu->AssertHeld();
if (edit->has_log_number_) {
assert(edit->log_number_ >= log_number_);
assert(edit->log_number_ < next_file_number_);
} else {
edit->SetLogNumber(log_number_);
}
if (!edit->has_prev_log_number_) {
edit->SetPrevLogNumber(prev_log_number_);
}
edit->SetNextFile(next_file_number_);
edit->SetLastSequence(last_sequence_);
builder->Apply(edit);
}
Status VersionSet::Recover() {
struct LogReporter : public log::Reader::Reporter {
Status* status;
virtual void Corruption(size_t bytes, const Status& s) {
if (this->status->ok()) *this->status = s;
}
};
// Read "CURRENT" file, which contains a pointer to the current manifest file
std::string current;
Status s = ReadFileToString(env_, CurrentFileName(dbname_), &current);
if (!s.ok()) {
return s;
}
if (current.empty() || current[current.size()-1] != '\n') {
return Status::Corruption("CURRENT file does not end with newline");
}
current.resize(current.size() - 1);
Log(options_->info_log, "Recovering from manifest file:%s\n",
current.c_str());
std::string dscname = dbname_ + "/" + current;
unique_ptr<SequentialFile> file;
s = env_->NewSequentialFile(dscname, &file, storage_options_);
if (!s.ok()) {
return s;
}
uint64_t manifest_file_size;
s = env_->GetFileSize(dscname, &manifest_file_size);
if (!s.ok()) {
return s;
}
bool have_log_number = false;
bool have_prev_log_number = false;
bool have_next_file = false;
bool have_last_sequence = false;
uint64_t next_file = 0;
uint64_t last_sequence = 0;
uint64_t log_number = 0;
uint64_t prev_log_number = 0;
Builder builder(this, current_);
{
LogReporter reporter;
reporter.status = &s;
log::Reader reader(std::move(file), &reporter, true/*checksum*/,
0/*initial_offset*/);
Slice record;
std::string scratch;
while (reader.ReadRecord(&record, &scratch) && s.ok()) {
VersionEdit edit(NumberLevels());
s = edit.DecodeFrom(record);
if (s.ok()) {
if (edit.has_comparator_ &&
edit.comparator_ != icmp_.user_comparator()->Name()) {
s = Status::InvalidArgument(
edit.comparator_ + "does not match existing comparator ",
icmp_.user_comparator()->Name());
}
}
if (s.ok()) {
builder.Apply(&edit);
}
if (edit.has_log_number_) {
log_number = edit.log_number_;
have_log_number = true;
}
if (edit.has_prev_log_number_) {
prev_log_number = edit.prev_log_number_;
have_prev_log_number = true;
}
if (edit.has_next_file_number_) {
next_file = edit.next_file_number_;
have_next_file = true;
}
if (edit.has_last_sequence_) {
last_sequence = edit.last_sequence_;
have_last_sequence = true;
}
}
}
file.reset();
if (s.ok()) {
if (!have_next_file) {
s = Status::Corruption("no meta-nextfile entry in descriptor");
} else if (!have_log_number) {
s = Status::Corruption("no meta-lognumber entry in descriptor");
} else if (!have_last_sequence) {
s = Status::Corruption("no last-sequence-number entry in descriptor");
}
if (!have_prev_log_number) {
prev_log_number = 0;
}
MarkFileNumberUsed(prev_log_number);
MarkFileNumberUsed(log_number);
}
if (s.ok()) {
Version* v = new Version(this, current_version_number_++);
builder.SaveTo(v);
// Install recovered version
std::vector<uint64_t> size_being_compacted(NumberLevels()-1);
SizeBeingCompacted(size_being_compacted);
Finalize(v, size_being_compacted);
v->offset_manifest_file_ = manifest_file_size;
AppendVersion(v);
manifest_file_number_ = next_file;
next_file_number_ = next_file + 1;
last_sequence_ = last_sequence;
log_number_ = log_number;
prev_log_number_ = prev_log_number;
Log(options_->info_log, "Recovered from manifest file:%s succeeded,"
"manifest_file_number is %ld, next_file_number is %ld, "
"last_sequence is %ld, log_number is %ld,"
"prev_log_number is %ld\n",
current.c_str(), manifest_file_number_, next_file_number_,
last_sequence_, log_number_, prev_log_number_);
}
return s;
}
Status VersionSet::DumpManifest(Options& options, std::string& dscname,
bool verbose, bool hex) {
struct LogReporter : public log::Reader::Reporter {
Status* status;
virtual void Corruption(size_t bytes, const Status& s) {
if (this->status->ok()) *this->status = s;
}
};
// Open the specified manifest file.
unique_ptr<SequentialFile> file;
Status s = options.env->NewSequentialFile(dscname, &file, storage_options_);
if (!s.ok()) {
return s;
}
bool have_log_number = false;
bool have_prev_log_number = false;
bool have_next_file = false;
bool have_last_sequence = false;
uint64_t next_file = 0;
uint64_t last_sequence = 0;
uint64_t log_number = 0;
uint64_t prev_log_number = 0;
int count = 0;
VersionSet::Builder builder(this, current_);
{
LogReporter reporter;
reporter.status = &s;
log::Reader reader(std::move(file), &reporter, true/*checksum*/,
0/*initial_offset*/);
Slice record;
std::string scratch;
while (reader.ReadRecord(&record, &scratch) && s.ok()) {
VersionEdit edit(NumberLevels());
s = edit.DecodeFrom(record);
if (s.ok()) {
if (edit.has_comparator_ &&
edit.comparator_ != icmp_.user_comparator()->Name()) {
s = Status::InvalidArgument(
edit.comparator_ + "does not match existing comparator ",
icmp_.user_comparator()->Name());
}
}
// Write out each individual edit
if (verbose) {
printf("*************************Edit[%d] = %s\n",
count, edit.DebugString().c_str());
}
count++;
if (s.ok()) {
builder.Apply(&edit);
}
if (edit.has_log_number_) {
log_number = edit.log_number_;
have_log_number = true;
}
if (edit.has_prev_log_number_) {
prev_log_number = edit.prev_log_number_;
have_prev_log_number = true;
}
if (edit.has_next_file_number_) {
next_file = edit.next_file_number_;
have_next_file = true;
}
if (edit.has_last_sequence_) {
last_sequence = edit.last_sequence_;
have_last_sequence = true;
}
}
}
file.reset();
if (s.ok()) {
if (!have_next_file) {
s = Status::Corruption("no meta-nextfile entry in descriptor");
printf("no meta-nextfile entry in descriptor");
} else if (!have_log_number) {
s = Status::Corruption("no meta-lognumber entry in descriptor");
printf("no meta-lognumber entry in descriptor");
} else if (!have_last_sequence) {
printf("no last-sequence-number entry in descriptor");
s = Status::Corruption("no last-sequence-number entry in descriptor");
}
if (!have_prev_log_number) {
prev_log_number = 0;
}
MarkFileNumberUsed(prev_log_number);
MarkFileNumberUsed(log_number);
}
if (s.ok()) {
Version* v = new Version(this, 0);
builder.SaveTo(v);
// Install recovered version
std::vector<uint64_t> size_being_compacted(NumberLevels()-1);
SizeBeingCompacted(size_being_compacted);
Finalize(v, size_being_compacted);
AppendVersion(v);
manifest_file_number_ = next_file;
next_file_number_ = next_file + 1;
last_sequence_ = last_sequence;
log_number_ = log_number;
prev_log_number_ = prev_log_number;
printf("manifest_file_number %ld next_file_number %ld last_sequence %ld log_number %ld prev_log_number %ld\n",
manifest_file_number_, next_file_number_,
last_sequence, log_number, prev_log_number);
printf("%s \n", v->DebugString(hex).c_str());
}
return s;
}
void VersionSet::MarkFileNumberUsed(uint64_t number) {
if (next_file_number_ <= number) {
next_file_number_ = number + 1;
}
}
void VersionSet::Finalize(Version* v,
std::vector<uint64_t>& size_being_compacted) {
double max_score = 0;
int max_score_level = 0;
for (int level = 0; level < NumberLevels()-1; level++) {
double score;
if (level == 0) {
// We treat level-0 specially by bounding the number of files
// instead of number of bytes for two reasons:
//
// (1) With larger write-buffer sizes, it is nice not to do too
// many level-0 compactions.
//
// (2) The files in level-0 are merged on every read and
// therefore we wish to avoid too many files when the individual
// file size is small (perhaps because of a small write-buffer
// setting, or very high compression ratios, or lots of
// overwrites/deletions).
int numfiles = 0;
for (unsigned int i = 0; i < v->files_[level].size(); i++) {
if (!v->files_[level][i]->being_compacted) {
numfiles++;
}
}
// If we are slowing down writes, then we better compact that first
if (numfiles >= options_->level0_stop_writes_trigger) {
score = 1000000;
// Log(options_->info_log, "XXX score l0 = 1000000000 max");
} else if (numfiles >= options_->level0_slowdown_writes_trigger) {
score = 10000;
// Log(options_->info_log, "XXX score l0 = 1000000 medium");
} else {
score = numfiles /
static_cast<double>(options_->level0_file_num_compaction_trigger);
if (score >= 1) {
// Log(options_->info_log, "XXX score l0 = %d least", (int)score);
}
}
} else {
// Compute the ratio of current size to size limit.
const uint64_t level_bytes = TotalFileSize(v->files_[level]) -
size_being_compacted[level];
score = static_cast<double>(level_bytes) / MaxBytesForLevel(level);
if (score > 1) {
// Log(options_->info_log, "XXX score l%d = %d ", level, (int)score);
}
if (max_score < score) {
max_score = score;
max_score_level = level;
}
}
v->compaction_level_[level] = level;
v->compaction_score_[level] = score;
}
// update the max compaction score in levels 1 to n-1
v->max_compaction_score_ = max_score;
v->max_compaction_score_level_ = max_score_level;
// sort all the levels based on their score. Higher scores get listed
// first. Use bubble sort because the number of entries are small.
for(int i = 0; i < NumberLevels()-2; i++) {
for (int j = i+1; j < NumberLevels()-1; j++) {
if (v->compaction_score_[i] < v->compaction_score_[j]) {
double score = v->compaction_score_[i];
int level = v->compaction_level_[i];
v->compaction_score_[i] = v->compaction_score_[j];
v->compaction_level_[i] = v->compaction_level_[j];
v->compaction_score_[j] = score;
v->compaction_level_[j] = level;
}
}
}
}
// a static compator used to sort files based on their size
static bool compareSize(const VersionSet::Fsize& first,
const VersionSet::Fsize& second) {
return (first.file->file_size > second.file->file_size);
}
// sort all files in level1 to level(n-1) based on file size
void VersionSet::UpdateFilesBySize(Version* v) {
// No need to sort the highest level because it is never compacted.
for (int level = 0; level < NumberLevels()-1; level++) {
const std::vector<FileMetaData*>& files = v->files_[level];
std::vector<int>& files_by_size = v->files_by_size_[level];
assert(files_by_size.size() == 0);
// populate a temp vector for sorting based on size
std::vector<Fsize> temp(files.size());
for (unsigned int i = 0; i < files.size(); i++) {
temp[i].index = i;
temp[i].file = files[i];
}
// sort the top number_of_files_to_sort_ based on file size
int num = Version::number_of_files_to_sort_;
if (num > (int)temp.size()) {
num = temp.size();
}
std::partial_sort(temp.begin(), temp.begin() + num,
temp.end(), compareSize);
assert(temp.size() == files.size());
// initialize files_by_size_
for (unsigned int i = 0; i < temp.size(); i++) {
files_by_size.push_back(temp[i].index);
}
v->next_file_to_compact_by_size_[level] = 0;
assert(v->files_[level].size() == v->files_by_size_[level].size());
}
}
Status VersionSet::WriteSnapshot(log::Writer* log) {
// TODO: Break up into multiple records to reduce memory usage on recovery?
// Save metadata
VersionEdit edit(NumberLevels());
edit.SetComparatorName(icmp_.user_comparator()->Name());
// Save compaction pointers
for (int level = 0; level < NumberLevels(); level++) {
if (!compact_pointer_[level].empty()) {
InternalKey key;
key.DecodeFrom(compact_pointer_[level]);
edit.SetCompactPointer(level, key);
}
}
// Save files
for (int level = 0; level < NumberLevels(); level++) {
const std::vector<FileMetaData*>& files = current_->files_[level];
for (size_t i = 0; i < files.size(); i++) {
const FileMetaData* f = files[i];
edit.AddFile(level, f->number, f->file_size, f->smallest, f->largest);
}
}
std::string record;
edit.EncodeTo(&record);
return log->AddRecord(record);
}
int VersionSet::NumLevelFiles(int level) const {
assert(level >= 0);
assert(level < NumberLevels());
return current_->files_[level].size();
}
const char* VersionSet::LevelSummary(LevelSummaryStorage* scratch) const {
int len = snprintf(scratch->buffer, sizeof(scratch->buffer), "files[");
for (int i = 0; i < NumberLevels(); i++) {
int sz = sizeof(scratch->buffer) - len;
int ret = snprintf(scratch->buffer + len, sz, "%d ",
int(current_->files_[i].size()));
if (ret < 0 || ret >= sz)
break;
len += ret;
}
snprintf(scratch->buffer + len, sizeof(scratch->buffer) - len, "]");
return scratch->buffer;
}
const char* VersionSet::LevelDataSizeSummary(
LevelSummaryStorage* scratch) const {
int len = snprintf(scratch->buffer, sizeof(scratch->buffer), "files_size[");
for (int i = 0; i < NumberLevels(); i++) {
int sz = sizeof(scratch->buffer) - len;
int ret = snprintf(scratch->buffer + len, sz, "%ld ",
NumLevelBytes(i));
if (ret < 0 || ret >= sz)
break;
len += ret;
}
snprintf(scratch->buffer + len, sizeof(scratch->buffer) - len, "]");
return scratch->buffer;
}
// Opens the mainfest file and reads all records
// till it finds the record we are looking for.
bool VersionSet::ManifestContains(const std::string& record) const {
std::string fname = DescriptorFileName(dbname_, manifest_file_number_);
Log(options_->info_log, "ManifestContains: checking %s\n", fname.c_str());
unique_ptr<SequentialFile> file;
Status s = env_->NewSequentialFile(fname, &file, storage_options_);
if (!s.ok()) {
Log(options_->info_log, "ManifestContains: %s\n", s.ToString().c_str());
Log(options_->info_log,
"ManifestContains: is unable to reopen the manifest file %s",
fname.c_str());
return false;
}
log::Reader reader(std::move(file), nullptr, true/*checksum*/, 0);
Slice r;
std::string scratch;
bool result = false;
while (reader.ReadRecord(&r, &scratch)) {
if (r == Slice(record)) {
result = true;
break;
}
}
Log(options_->info_log, "ManifestContains: result = %d\n", result ? 1 : 0);
return result;
}
uint64_t VersionSet::ApproximateOffsetOf(Version* v, const InternalKey& ikey) {
uint64_t result = 0;
for (int level = 0; level < NumberLevels(); level++) {
const std::vector<FileMetaData*>& files = v->files_[level];
for (size_t i = 0; i < files.size(); i++) {
if (icmp_.Compare(files[i]->largest, ikey) <= 0) {
// Entire file is before "ikey", so just add the file size
result += files[i]->file_size;
} else if (icmp_.Compare(files[i]->smallest, ikey) > 0) {
// Entire file is after "ikey", so ignore
if (level > 0) {
// Files other than level 0 are sorted by meta->smallest, so
// no further files in this level will contain data for
// "ikey".
break;
}
} else {
// "ikey" falls in the range for this table. Add the
// approximate offset of "ikey" within the table.
Table* tableptr;
Iterator* iter = table_cache_->NewIterator(
ReadOptions(), storage_options_, files[i]->number,
files[i]->file_size, &tableptr);
if (tableptr != nullptr) {
result += tableptr->ApproximateOffsetOf(ikey.Encode());
}
delete iter;
}
}
}
return result;
}
void VersionSet::AddLiveFiles(std::vector<uint64_t>* live_list) {
// pre-calculate space requirement
int64_t total_files = 0;
for (Version* v = dummy_versions_.next_;
v != &dummy_versions_;
v = v->next_) {
for (int level = 0; level < NumberLevels(); level++) {
total_files += v->files_[level].size();
}
}
// just one time extension to the right size
live_list->reserve(live_list->size() + total_files);
for (Version* v = dummy_versions_.next_;
v != &dummy_versions_;
v = v->next_) {
for (int level = 0; level < NumberLevels(); level++) {
for (const auto& f : v->files_[level]) {
live_list->push_back(f->number);
}
}
}
}
void VersionSet::AddLiveFilesCurrentVersion(std::set<uint64_t>* live) {
Version* v = current_;
for (int level = 0; level < NumberLevels(); level++) {
const std::vector<FileMetaData*>& files = v->files_[level];
for (size_t i = 0; i < files.size(); i++) {
live->insert(files[i]->number);
}
}
}
int64_t VersionSet::NumLevelBytes(int level) const {
assert(level >= 0);
assert(level < NumberLevels());
assert(current_);
return TotalFileSize(current_->files_[level]);
}
int64_t VersionSet::MaxNextLevelOverlappingBytes() {
int64_t result = 0;
std::vector<FileMetaData*> overlaps;
for (int level = 1; level < NumberLevels() - 1; level++) {
for (size_t i = 0; i < current_->files_[level].size(); i++) {
const FileMetaData* f = current_->files_[level][i];
current_->GetOverlappingInputs(level+1, &f->smallest, &f->largest,
&overlaps);
const int64_t sum = TotalFileSize(overlaps);
if (sum > result) {
result = sum;
}
}
}
return result;
}
// Stores the minimal range that covers all entries in inputs in
// *smallest, *largest.
// REQUIRES: inputs is not empty
void VersionSet::GetRange(const std::vector<FileMetaData*>& inputs,
InternalKey* smallest,
InternalKey* largest) {
assert(!inputs.empty());
smallest->Clear();
largest->Clear();
for (size_t i = 0; i < inputs.size(); i++) {
FileMetaData* f = inputs[i];
if (i == 0) {
*smallest = f->smallest;
*largest = f->largest;
} else {
if (icmp_.Compare(f->smallest, *smallest) < 0) {
*smallest = f->smallest;
}
if (icmp_.Compare(f->largest, *largest) > 0) {
*largest = f->largest;
}
}
}
}
// Stores the minimal range that covers all entries in inputs1 and inputs2
// in *smallest, *largest.
// REQUIRES: inputs is not empty
void VersionSet::GetRange2(const std::vector<FileMetaData*>& inputs1,
const std::vector<FileMetaData*>& inputs2,
InternalKey* smallest,
InternalKey* largest) {
std::vector<FileMetaData*> all = inputs1;
all.insert(all.end(), inputs2.begin(), inputs2.end());
GetRange(all, smallest, largest);
}
Iterator* VersionSet::MakeInputIterator(Compaction* c) {
ReadOptions options;
options.verify_checksums = options_->paranoid_checks;
options.fill_cache = false;
// Level-0 files have to be merged together. For other levels,
// we will make a concatenating iterator per level.
// TODO(opt): use concatenating iterator for level-0 if there is no overlap
const int space = (c->level() == 0 ? c->inputs_[0].size() + 1 : 2);
Iterator** list = new Iterator*[space];
int num = 0;
for (int which = 0; which < 2; which++) {
if (!c->inputs_[which].empty()) {
if (c->level() + which == 0) {
const std::vector<FileMetaData*>& files = c->inputs_[which];
for (size_t i = 0; i < files.size(); i++) {
list[num++] = table_cache_->NewIterator(
options, storage_options_compactions_,
files[i]->number, files[i]->file_size);
}
} else {
// Create concatenating iterator for the files from this level
list[num++] = NewTwoLevelIterator(
new Version::LevelFileNumIterator(icmp_, &c->inputs_[which]),
&GetFileIterator, table_cache_, options, storage_options_);
}
}
}
assert(num <= space);
Iterator* result = NewMergingIterator(&icmp_, list, num);
delete[] list;
return result;
}
double VersionSet::MaxBytesForLevel(int level) {
// Note: the result for level zero is not really used since we set
// the level-0 compaction threshold based on number of files.
assert(level >= 0);
assert(level < NumberLevels());
return level_max_bytes_[level];
}
uint64_t VersionSet::MaxFileSizeForLevel(int level) {
assert(level >= 0);
assert(level < NumberLevels());
return max_file_size_[level];
}
int64_t VersionSet::ExpandedCompactionByteSizeLimit(int level) {
uint64_t result = MaxFileSizeForLevel(level);
result *= options_->expanded_compaction_factor;
return result;
}
int64_t VersionSet::MaxGrandParentOverlapBytes(int level) {
uint64_t result = MaxFileSizeForLevel(level);
result *= options_->max_grandparent_overlap_factor;
return result;
}
// verify that the files listed in this compaction are present
// in the current version
bool VersionSet::VerifyCompactionFileConsistency(Compaction* c) {
#ifndef NDEBUG
if (c->input_version_ != current_) {
Log(options_->info_log, "VerifyCompactionFileConsistency version mismatch");
}
// verify files in level
int level = c->level();
for (int i = 0; i < c->num_input_files(0); i++) {
uint64_t number = c->input(0,i)->number;
// look for this file in the current version
bool found = false;
for (unsigned int j = 0; j < current_->files_[level].size(); j++) {
FileMetaData* f = current_->files_[level][j];
if (f->number == number) {
found = true;
break;
}
}
if (!found) {
return false; // input files non existant in current version
}
}
// verify level+1 files
level++;
for (int i = 0; i < c->num_input_files(1); i++) {
uint64_t number = c->input(1,i)->number;
// look for this file in the current version
bool found = false;
for (unsigned int j = 0; j < current_->files_[level].size(); j++) {
FileMetaData* f = current_->files_[level][j];
if (f->number == number) {
found = true;
break;
}
}
if (!found) {
return false; // input files non existant in current version
}
}
#endif
return true; // everything good
}
// Clear all files to indicate that they are not being compacted
// Delete this compaction from the list of running compactions.
void VersionSet::ReleaseCompactionFiles(Compaction* c, Status status) {
c->MarkFilesBeingCompacted(false);
compactions_in_progress_[c->level()].erase(c);
if (!status.ok()) {
c->ResetNextCompactionIndex();
}
}
// The total size of files that are currently being compacted
// at at every level upto the penultimate level.
void VersionSet::SizeBeingCompacted(std::vector<uint64_t>& sizes) {
for (int level = 0; level < NumberLevels()-1; level++) {
uint64_t total = 0;
for (std::set<Compaction*>::iterator it =
compactions_in_progress_[level].begin();
it != compactions_in_progress_[level].end();
++it) {
Compaction* c = (*it);
assert(c->level() == level);
for (int i = 0; i < c->num_input_files(0); i++) {
total += c->input(0,i)->file_size;
}
}
sizes[level] = total;
}
}
Compaction* VersionSet::PickCompactionBySize(int level, double score) {
Compaction* c = nullptr;
// level 0 files are overlapping. So we cannot pick more
// than one concurrent compactions at this level. This
// could be made better by looking at key-ranges that are
// being compacted at level 0.
if (level == 0 && compactions_in_progress_[level].size() == 1) {
return nullptr;
}
assert(level >= 0);
assert(level+1 < NumberLevels());
c = new Compaction(level, MaxFileSizeForLevel(level),
MaxGrandParentOverlapBytes(level), NumberLevels());
c->score_ = score;
// Pick the largest file in this level that is not already
// being compacted
std::vector<int>& file_size = current_->files_by_size_[level];
// record the first file that is not yet compacted
int nextIndex = -1;
for (unsigned int i = current_->next_file_to_compact_by_size_[level];
i < file_size.size(); i++) {
int index = file_size[i];
FileMetaData* f = current_->files_[level][index];
// check to verify files are arranged in descending size
assert((i == file_size.size() - 1) ||
(i >= Version::number_of_files_to_sort_-1) ||
(f->file_size >= current_->files_[level][file_size[i+1]]->file_size));
// do not pick a file to compact if it is being compacted
// from n-1 level.
if (f->being_compacted) {
continue;
}
// remember the startIndex for the next call to PickCompaction
if (nextIndex == -1) {
nextIndex = i;
}
//if (i > Version::number_of_files_to_sort_) {
// Log(options_->info_log, "XXX Looking at index %d", i);
//}
// Do not pick this file if its parents at level+1 are being compacted.
// Maybe we can avoid redoing this work in SetupOtherInputs
int parent_index = -1;
if (ParentRangeInCompaction(&f->smallest, &f->largest, level,
&parent_index)) {
continue;
}
c->inputs_[0].push_back(f);
c->base_index_ = index;
c->parent_index_ = parent_index;
break;
}
if (c->inputs_[0].empty()) {
delete c;
c = nullptr;
}
// store where to start the iteration in the next call to PickCompaction
current_->next_file_to_compact_by_size_[level] = nextIndex;
return c;
}
Compaction* VersionSet::PickCompaction() {
Compaction* c = nullptr;
int level = -1;
// compute the compactions needed. It is better to do it here
// and also in LogAndApply(), otherwise the values could be stale.
std::vector<uint64_t> size_being_compacted(NumberLevels()-1);
current_->vset_->SizeBeingCompacted(size_being_compacted);
Finalize(current_, size_being_compacted);
// We prefer compactions triggered by too much data in a level over
// the compactions triggered by seeks.
//
// Find the compactions by size on all levels.
for (int i = 0; i < NumberLevels()-1; i++) {
assert(i == 0 || current_->compaction_score_[i] <=
current_->compaction_score_[i-1]);
level = current_->compaction_level_[i];
if ((current_->compaction_score_[i] >= 1)) {
c = PickCompactionBySize(level, current_->compaction_score_[i]);
if (c != nullptr) {
break;
}
}
}
// Find compactions needed by seeks
if (c == nullptr && (current_->file_to_compact_ != nullptr)) {
level = current_->file_to_compact_level_;
// Only allow one level 0 compaction at a time.
if (level != 0 || compactions_in_progress_[0].empty()) {
c = new Compaction(level, MaxFileSizeForLevel(level),
MaxGrandParentOverlapBytes(level), NumberLevels(), true);
c->inputs_[0].push_back(current_->file_to_compact_);
}
}
if (c == nullptr) {
return nullptr;
}
c->input_version_ = current_;
c->input_version_->Ref();
// Files in level 0 may overlap each other, so pick up all overlapping ones
// Two level 0 compaction won't run at the same time, so don't need to worry
// about files on level 0 being compacted.
if (level == 0) {
assert(compactions_in_progress_[0].empty());
InternalKey smallest, largest;
GetRange(c->inputs_[0], &smallest, &largest);
// Note that the next call will discard the file we placed in
// c->inputs_[0] earlier and replace it with an overlapping set
// which will include the picked file.
c->inputs_[0].clear();
current_->GetOverlappingInputs(0, &smallest, &largest, &c->inputs_[0]);
if (ParentRangeInCompaction(&smallest, &largest,
level, &c->parent_index_)) {
delete c;
return nullptr;
}
assert(!c->inputs_[0].empty());
}
SetupOtherInputs(c);
// mark all the files that are being compacted
c->MarkFilesBeingCompacted(true);
// remember this currently undergoing compaction
compactions_in_progress_[level].insert(c);
return c;
}
// Returns true if any one of the parent files are being compacted
bool VersionSet::ParentRangeInCompaction(const InternalKey* smallest,
const InternalKey* largest, int level, int* parent_index) {
std::vector<FileMetaData*> inputs;
current_->GetOverlappingInputs(level+1, smallest, largest,
&inputs, *parent_index, parent_index);
return FilesInCompaction(inputs);
}
// Returns true if any one of specified files are being compacted
bool VersionSet::FilesInCompaction(std::vector<FileMetaData*>& files) {
for (unsigned int i = 0; i < files.size(); i++) {
if (files[i]->being_compacted) {
return true;
}
}
return false;
}
void VersionSet::SetupOtherInputs(Compaction* c) {
const int level = c->level();
InternalKey smallest, largest;
GetRange(c->inputs_[0], &smallest, &largest);
current_->GetOverlappingInputs(level+1, &smallest, &largest, &c->inputs_[1],
c->parent_index_, &c->parent_index_);
// Get entire range covered by compaction
InternalKey all_start, all_limit;
GetRange2(c->inputs_[0], c->inputs_[1], &all_start, &all_limit);
// See if we can grow the number of inputs in "level" without
// changing the number of "level+1" files we pick up.
if (!c->inputs_[1].empty()) {
std::vector<FileMetaData*> expanded0;
current_->GetOverlappingInputs(level, &all_start, &all_limit, &expanded0,
c->base_index_, nullptr);
const int64_t inputs0_size = TotalFileSize(c->inputs_[0]);
const int64_t inputs1_size = TotalFileSize(c->inputs_[1]);
const int64_t expanded0_size = TotalFileSize(expanded0);
int64_t limit = ExpandedCompactionByteSizeLimit(level);
if (expanded0.size() > c->inputs_[0].size() &&
inputs1_size + expanded0_size < limit &&
!FilesInCompaction(expanded0)) {
InternalKey new_start, new_limit;
GetRange(expanded0, &new_start, &new_limit);
std::vector<FileMetaData*> expanded1;
current_->GetOverlappingInputs(level+1, &new_start, &new_limit,
&expanded1, c->parent_index_,
&c->parent_index_);
if (expanded1.size() == c->inputs_[1].size() &&
!FilesInCompaction(expanded1)) {
Log(options_->info_log,
"Expanding@%d %d+%d (%ld+%ld bytes) to %d+%d (%ld+%ld bytes)\n",
level,
int(c->inputs_[0].size()),
int(c->inputs_[1].size()),
long(inputs0_size), long(inputs1_size),
int(expanded0.size()),
int(expanded1.size()),
long(expanded0_size), long(inputs1_size));
smallest = new_start;
largest = new_limit;
c->inputs_[0] = expanded0;
c->inputs_[1] = expanded1;
GetRange2(c->inputs_[0], c->inputs_[1], &all_start, &all_limit);
}
}
}
// Compute the set of grandparent files that overlap this compaction
// (parent == level+1; grandparent == level+2)
if (level + 2 < NumberLevels()) {
current_->GetOverlappingInputs(level + 2, &all_start, &all_limit,
&c->grandparents_);
}
if (false) {
Log(options_->info_log, "Compacting %d '%s' .. '%s'",
level,
smallest.DebugString().c_str(),
largest.DebugString().c_str());
}
// Update the place where we will do the next compaction for this level.
// We update this immediately instead of waiting for the VersionEdit
// to be applied so that if the compaction fails, we will try a different
// key range next time.
compact_pointer_[level] = largest.Encode().ToString();
c->edit_->SetCompactPointer(level, largest);
}
Compaction* VersionSet::CompactRange(
int level,
const InternalKey* begin,
const InternalKey* end) {
std::vector<FileMetaData*> inputs;
current_->GetOverlappingInputs(level, begin, end, &inputs);
if (inputs.empty()) {
return nullptr;
}
// Avoid compacting too much in one shot in case the range is large.
const uint64_t limit = MaxFileSizeForLevel(level) *
options_->source_compaction_factor;
uint64_t total = 0;
for (size_t i = 0; i < inputs.size(); i++) {
uint64_t s = inputs[i]->file_size;
total += s;
if (total >= limit) {
inputs.resize(i + 1);
break;
}
}
Compaction* c = new Compaction(level, MaxFileSizeForLevel(level),
MaxGrandParentOverlapBytes(level), NumberLevels());
c->input_version_ = current_;
c->input_version_->Ref();
c->inputs_[0] = inputs;
SetupOtherInputs(c);
// These files that are to be manaully compacted do not trample
// upon other files because manual compactions are processed when
// the system has a max of 1 background compaction thread.
c->MarkFilesBeingCompacted(true);
return c;
}
Compaction::Compaction(int level, uint64_t target_file_size,
uint64_t max_grandparent_overlap_bytes, int number_levels,
bool seek_compaction)
: level_(level),
max_output_file_size_(target_file_size),
maxGrandParentOverlapBytes_(max_grandparent_overlap_bytes),
input_version_(nullptr),
number_levels_(number_levels),
seek_compaction_(seek_compaction),
grandparent_index_(0),
seen_key_(false),
overlapped_bytes_(0),
base_index_(-1),
parent_index_(-1),
score_(0),
level_ptrs_(std::vector<size_t>(number_levels)) {
edit_ = new VersionEdit(number_levels_);
for (int i = 0; i < number_levels_; i++) {
level_ptrs_[i] = 0;
}
}
Compaction::~Compaction() {
delete edit_;
if (input_version_ != nullptr) {
input_version_->Unref();
}
}
bool Compaction::IsTrivialMove() const {
// Avoid a move if there is lots of overlapping grandparent data.
// Otherwise, the move could create a parent file that will require
// a very expensive merge later on.
return (num_input_files(0) == 1 &&
num_input_files(1) == 0 &&
TotalFileSize(grandparents_) <= maxGrandParentOverlapBytes_);
}
void Compaction::AddInputDeletions(VersionEdit* edit) {
for (int which = 0; which < 2; which++) {
for (size_t i = 0; i < inputs_[which].size(); i++) {
edit->DeleteFile(level_ + which, inputs_[which][i]->number);
}
}
}
bool Compaction::IsBaseLevelForKey(const Slice& user_key) {
// Maybe use binary search to find right entry instead of linear search?
const Comparator* user_cmp = input_version_->vset_->icmp_.user_comparator();
for (int lvl = level_ + 2; lvl < number_levels_; lvl++) {
const std::vector<FileMetaData*>& files = input_version_->files_[lvl];
for (; level_ptrs_[lvl] < files.size(); ) {
FileMetaData* f = files[level_ptrs_[lvl]];
if (user_cmp->Compare(user_key, f->largest.user_key()) <= 0) {
// We've advanced far enough
if (user_cmp->Compare(user_key, f->smallest.user_key()) >= 0) {
// Key falls in this file's range, so definitely not base level
return false;
}
break;
}
level_ptrs_[lvl]++;
}
}
return true;
}
bool Compaction::ShouldStopBefore(const Slice& internal_key) {
// Scan to find earliest grandparent file that contains key.
const InternalKeyComparator* icmp = &input_version_->vset_->icmp_;
while (grandparent_index_ < grandparents_.size() &&
icmp->Compare(internal_key,
grandparents_[grandparent_index_]->largest.Encode()) > 0) {
if (seen_key_) {
overlapped_bytes_ += grandparents_[grandparent_index_]->file_size;
}
assert(grandparent_index_ + 1 >= grandparents_.size() ||
icmp->Compare(grandparents_[grandparent_index_]->largest.Encode(),
grandparents_[grandparent_index_+1]->smallest.Encode())
< 0);
grandparent_index_++;
}
seen_key_ = true;
if (overlapped_bytes_ > maxGrandParentOverlapBytes_) {
// Too much overlap for current output; start new output
overlapped_bytes_ = 0;
return true;
} else {
return false;
}
}
// Mark (or clear) each file that is being compacted
void Compaction::MarkFilesBeingCompacted(bool value) {
for (int i = 0; i < 2; i++) {
std::vector<FileMetaData*> v = inputs_[i];
for (unsigned int j = 0; j < inputs_[i].size(); j++) {
assert(value ? !inputs_[i][j]->being_compacted :
inputs_[i][j]->being_compacted);
inputs_[i][j]->being_compacted = value;
}
}
}
void Compaction::ReleaseInputs() {
if (input_version_ != nullptr) {
input_version_->Unref();
input_version_ = nullptr;
}
}
void Compaction::ResetNextCompactionIndex() {
input_version_->ResetNextCompactionIndex(level_);
}
static void InputSummary(std::vector<FileMetaData*>& files,
char* output,
int len) {
int write = 0;
for (unsigned int i = 0; i < files.size(); i++) {
int sz = len - write;
int ret = snprintf(output + write, sz, "%lu(%lu) ",
files.at(i)->number,
files.at(i)->file_size);
if (ret < 0 || ret >= sz)
break;
write += ret;
}
}
void Compaction::Summary(char* output, int len) {
int write = snprintf(output, len,
"Base version %ld Base level %d, seek compaction:%d, inputs:",
input_version_->GetVersionNumber(), level_, seek_compaction_);
if(write < 0 || write > len)
return;
char level_low_summary[100];
InputSummary(inputs_[0], level_low_summary, sizeof(level_low_summary));
char level_up_summary[100];
if (inputs_[1].size()) {
InputSummary(inputs_[1], level_up_summary, sizeof(level_up_summary));
} else {
level_up_summary[0] = '\0';
}
snprintf(output + write, len - write, "[%s],[%s]",
level_low_summary, level_up_summary);
}
} // namespace leveldb
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