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rocksdb/db/version_set.cc

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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 <climits>
#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"
#include "util/stop_watch.h"
namespace leveldb {
static uint64_t TotalFileSize(const std::vector<FileMetaData*>& files) {
uint64_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,
bool for_compaction) {
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),
nullptr /* don't need reference to table*/,
for_compaction);
}
}
Iterator* Version::NewConcatenatingIterator(const ReadOptions& options,
const EnvOptions& 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 EnvOptions& 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 // saver contains the current merge result (the operands)
};
struct Saver {
SaverState state;
const Comparator* ucmp;
Slice user_key;
bool* value_found; // Is value set correctly? Used by KeyMayExist
std::string* value;
const MergeOperator* merge_operator;
std::deque<std::string>* merge_operands; // the merge operations encountered
Logger* logger;
bool didIO; // did we do any disk io?
};
}
// Called from TableCache::Get and InternalGet when file/block in which key may
// exist are not there in TableCache/BlockCache respectively. In this case we
// can't guarantee that key does not exist and are not permitted to do IO to be
// certain.Set the status=kFound and value_found=false to let the caller know
// that key may exist but is not there in memory
static void MarkKeyMayExist(void* arg) {
Saver* s = reinterpret_cast<Saver*>(arg);
s->state = kFound;
if (s->value_found != nullptr) {
*(s->value_found) = false;
}
}
static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
Saver* s = reinterpret_cast<Saver*>(arg);
std::deque<std::string>* const ops = s->merge_operands; // shorter alias
std::string merge_result; // temporary area for merge results later
assert(s != nullptr && ops != nullptr);
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) {
// Key matches. Process it
switch (parsed_key.type) {
case kTypeValue:
if (kNotFound == s->state) {
s->state = kFound;
s->value->assign(v.data(), v.size());
} else if (kMerge == s->state) {
assert(s->merge_operator != nullptr);
s->state = kFound;
if (!s->merge_operator->Merge(s->user_key, &v, *ops,
s->value, s->logger)) {
s->state = kCorrupt;
}
} else {
assert(false);
}
return false;
case kTypeDeletion:
if (kNotFound == s->state) {
s->state = kDeleted;
} else if (kMerge == s->state) {
s->state = kFound;
if (!s->merge_operator->Merge(s->user_key, nullptr, *ops,
s->value, s->logger)) {
s->state = kCorrupt;
}
} else {
assert(false);
}
return false;
case kTypeMerge:
assert(s->state == kNotFound || s->state == kMerge);
s->state = kMerge;
ops->push_front(v.ToString());
while (ops->size() >= 2) {
// Attempt to merge operands together via user associateive merge
if (s->merge_operator->PartialMerge(s->user_key,
Slice((*ops)[0]),
Slice((*ops)[1]),
&merge_result,
s->logger)) {
ops->pop_front();
swap(ops->front(), merge_result);
} else {
// Associative merge returns false ==> stack the operands
break;
}
}
return true;
}
}
}
// s->state could be Corrupt, merge or notfound
return false;
}
static bool NewestFirst(FileMetaData* a, FileMetaData* b) {
return a->number > b->number;
}
static bool NewestFirstBySeqNo(FileMetaData* a, FileMetaData* b) {
if (a->smallest_seqno > b->smallest_seqno) {
assert(a->largest_seqno > b->largest_seqno);
return true;
}
assert(a->largest_seqno <= b->largest_seqno);
return false;
}
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,
std::deque<std::string>* operands,
GetStats* stats,
const Options& db_options,
const bool no_io,
bool* value_found) {
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());
if (no_io) {
assert(status->ok());
}
Saver saver;
saver.state = status->ok()? kNotFound : kMerge;
saver.ucmp = ucmp;
saver.user_key = user_key;
saver.value_found = value_found;
saver.value = value;
saver.merge_operator = merge_operator;
saver.merge_operands = operands;
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 (unless we
// are MergeInProgress).
std::vector<FileMetaData*> important_files;
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];
important_files.clear();
important_files.reserve(num_files);
// Some files may overlap each other. We find
// all files that overlap user_key and process them in order from
// newest to oldest. In the context of merge-operator,
// this can occur at any level. Otherwise, it only occurs
// at Level-0 (since Put/Deletes are always compacted into a single entry).
uint32_t start_index;
if (level == 0) {
// On Level-0, we read through all files to check for overlap.
start_index = 0;
} else {
// On Level-n (n>=1), files are sorted.
// Binary search to find earliest index whose largest key >= ikey.
// We will also stop when the file no longer overlaps ikey
start_index = FindFile(vset_->icmp_, files_[level], ikey);
}
// Traverse the list, finding all overlapping files.
for (uint32_t i = start_index; 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) {
important_files.push_back(f);
} else if (level > 0) {
// If on Level-n (n>=1) then the files are sorted.
// So we can stop looking when we are past the ikey.
break;
}
}
if (important_files.empty()) continue;
if (level == 0) {
if (vset_->options_->compaction_style == kCompactionStyleUniversal) {
std::sort(important_files.begin(), important_files.end(), NewestFirstBySeqNo);
} else {
std::sort(important_files.begin(), important_files.end(), NewestFirst);
}
} else {
// Sanity check to make sure that the files are correctly sorted
#ifndef NDEBUG
num_files = important_files.size();
for (uint32_t i = 1; i < num_files; ++i) {
FileMetaData* a = important_files[i-1];
FileMetaData* b = important_files[i];
int comp_sign = vset_->icmp_.Compare(a->largest, b->smallest);
assert(comp_sign < 0);
}
#endif
}
// Traverse each relevant file to find the desired key
num_files = important_files.size();
for (uint32_t i = 0; i < num_files; ++i) {
FileMetaData* f = important_files[i];
bool tableIO = false;
*status = vset_->table_cache_->Get(options, f->number, f->file_size,
ikey, &saver, SaveValue, &tableIO,
MarkKeyMayExist, no_io);
// 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_operands are in saver and we hit the beginning of the key history
// do a final merge of nullptr and operands;
if (merge_operator->Merge(user_key, nullptr, *saver.merge_operands,
value, logger.get())) {
*status = Status::OK();
} else {
*status = Status::Corruption("could not perform end-of-key merge for ",
user_key);
}
} else {
*status = Status::NotFound(Slice()); // Use an empty error message for speed
}
}
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 uint64_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);
}
}
// Returns true iff the first or last file in inputs contains
// an overlapping user key to the file "just outside" of it (i.e.
// just after the last file, or just before the first file)
// REQUIRES: "*inputs" is a sorted list of non-overlapping files
bool Version::HasOverlappingUserKey(
const std::vector<FileMetaData*>* inputs,
int level) {
// If inputs empty, there is no overlap.
// If level == 0, it is assumed that all needed files were already included.
if (inputs->empty() || level == 0){
return false;
}
const Comparator* user_cmp = vset_->icmp_.user_comparator();
const std::vector<FileMetaData*>& files = files_[level];
const size_t kNumFiles = files.size();
// Check the last file in inputs against the file after it
size_t last_file = FindFile(vset_->icmp_, files,
inputs->back()->largest.Encode());
assert(0 <= last_file && last_file < kNumFiles); // File should exist!
if (last_file < kNumFiles-1) { // If not the last file
const Slice last_key_in_input = files[last_file]->largest.user_key();
const Slice first_key_after = files[last_file+1]->smallest.user_key();
if (user_cmp->Compare(last_key_in_input, first_key_after) == 0) {
// The last user key in input overlaps with the next file's first key
return true;
}
}
// Check the first file in inputs against the file just before it
size_t first_file = FindFile(vset_->icmp_, files,
inputs->front()->smallest.Encode());
assert(0 <= first_file && first_file <= last_file); // File should exist!
if (first_file > 0) { // If not first file
const Slice& first_key_in_input = files[first_file]->smallest.user_key();
const Slice& last_key_before = files[first_file-1]->largest.user_key();
if (user_cmp->Compare(first_key_in_input, last_key_before) == 0) {
// The first user key in input overlaps with the previous file's last key
return true;
}
}
return false;
}
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 EnvOptions& 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 == 0 && options_->compaction_style == kCompactionStyleUniversal) {
max_file_size_[i] = ULLONG_MAX;
level_max_bytes_[i] = options_->max_bytes_for_level_base;
} else 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 *
options_->max_bytes_for_level_multiplier_additional[i-1];
} 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) {
StopWatch sw(env_, options_->statistics, MANIFEST_FILE_SYNC_MICROS);
s = descriptor_log_->file()->Fsync();
} else {
StopWatch sw(env_, options_->statistics, MANIFEST_FILE_SYNC_MICROS);
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(hex).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
// In normal mode: descending size
static bool compareSizeDescending(const VersionSet::Fsize& first,
const VersionSet::Fsize& second) {
return (first.file->file_size > second.file->file_size);
}
// A static compator used to sort files based on their seqno
// In universal style : descending seqno
static bool compareSeqnoDescending(const VersionSet::Fsize& first,
const VersionSet::Fsize& second) {
if (first.file->smallest_seqno > second.file->smallest_seqno) {
assert(first.file->largest_seqno > second.file->largest_seqno);
return true;
}
assert(first.file->largest_seqno <= second.file->largest_seqno);
return false;
}
// 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.
int max_level = (options_->compaction_style == kCompactionStyleUniversal) ?
NumberLevels() : NumberLevels() - 1;
for (int level = 0; level < max_level; 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
if (options_->compaction_style == kCompactionStyleUniversal) {
int num = temp.size();
std::partial_sort(temp.begin(), temp.begin() + num,
temp.end(), compareSeqnoDescending);
} else {
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(), compareSizeDescending);
}
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,
f->smallest_seqno, f->largest_seqno);
}
}
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;
}
const char* VersionSet::LevelFileSummary(
FileSummaryStorage* scratch, int level) const {
int len = snprintf(scratch->buffer, sizeof(scratch->buffer), "files_size[");
for (unsigned int i = 0; i < current_->files_[level].size(); i++) {
FileMetaData* f = current_->files_[level][i];
int sz = sizeof(scratch->buffer) - len;
int ret = snprintf(scratch->buffer + len, sz, "#%ld(seq=%ld,sz=%ld,%d) ",
f->number, f->smallest_seqno,
f->file_size, f->being_compacted);
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() {
uint64_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 uint64_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, nullptr,
true /* for compaction */);
}
} 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_,
true /* for compaction */);
}
}
}
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];
}
uint64_t VersionSet::ExpandedCompactionByteSizeLimit(int level) {
uint64_t result = MaxFileSizeForLevel(level);
result *= options_->expanded_compaction_factor;
return result;
}
uint64_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::PickCompactionUniversal(int level, double score) {
assert (level == 0);
// percentage flexibilty while comparing file sizes
uint64_t ratio = options_->compaction_options_universal.size_ratio;
unsigned int min_merge_width =
options_->compaction_options_universal.min_merge_width;
unsigned int max_merge_width =
options_->compaction_options_universal.max_merge_width;
if ((current_->files_[level].size() <=
(unsigned int)options_->level0_file_num_compaction_trigger)) {
Log(options_->info_log, "Universal: nothing to do\n");
return nullptr;
}
VersionSet::FileSummaryStorage tmp;
Log(options_->info_log, "Universal: candidate files(%lu): %s\n",
current_->files_[level].size(),
LevelFileSummary(&tmp, 0));
Compaction* c = nullptr;
c = new Compaction(level, level, MaxFileSizeForLevel(level),
LLONG_MAX, NumberLevels());
c->score_ = score;
// The files are sorted from newest first to oldest last.
std::vector<int>& file_by_time = current_->files_by_size_[level];
FileMetaData* f = nullptr;
bool done = false;
assert(file_by_time.size() == current_->files_[level].size());
unsigned int max_files_to_compact = std::min(max_merge_width, UINT_MAX);
// Make two pass. The first pass considers a candidate file
// only if it is smaller than the total size accumulated so far.
// The second pass does not look at the slope of the
// file-size curve to decide what to pick for compaction.
for (int iter = 0; !done && iter < 2; iter++) {
for (unsigned int loop = 0; loop < file_by_time.size(); ) {
// Skip files that are already being compacted
for (f = nullptr; loop < file_by_time.size(); loop++) {
int index = file_by_time[loop];
f = current_->files_[level][index];
if (!f->being_compacted) {
break;
}
Log(options_->info_log, "Universal: file %ld[%d] being compacted, skipping",
f->number, loop);
f = nullptr;
}
// This file is not being compacted. Consider it as the
// first candidate to be compacted.
unsigned int candidate_count = 1;
uint64_t candidate_size = f != nullptr? f->file_size : 0;
if (f != nullptr) {
Log(options_->info_log, "Universal: Possible candidate file %ld[%d] %s.",
f->number, loop, iter == 0? "" : "forced ");
}
// Check if the suceeding files need compaction.
for (unsigned int i = loop+1;
candidate_count < max_files_to_compact && i < file_by_time.size();
i++) {
int index = file_by_time[i];
FileMetaData* f = current_->files_[level][index];
if (f->being_compacted) {
break;
}
// If this is the first iteration, then we pick files if the
// total candidate file size (increased by the specified ratio)
// is still larger than the next candidate file.
if (iter == 0) {
uint64_t sz = (candidate_size * (100 + ratio)) /100;
if (sz < f->file_size) {
break;
}
}
candidate_count++;
candidate_size += f->file_size;
}
// Found a series of consecutive files that need compaction.
if (candidate_count >= (unsigned int)min_merge_width) {
for (unsigned int i = loop; i < loop + candidate_count; i++) {
int index = file_by_time[i];
FileMetaData* f = current_->files_[level][index];
c->inputs_[0].push_back(f);
Log(options_->info_log, "Universal: Picking file %ld[%d] with size %ld %s",
f->number, i, f->file_size,
(iter == 0 ? "" : "forced"));
}
done = true;
break;
} else {
for (unsigned int i = loop;
i < loop + candidate_count && i < file_by_time.size(); i++) {
int index = file_by_time[i];
FileMetaData* f = current_->files_[level][index];
Log(options_->info_log, "Universal: Skipping file %ld[%d] with size %ld %d %s",
f->number, i, f->file_size, f->being_compacted,
(iter == 0 ? "" : "forced"));
}
}
loop += candidate_count;
}
assert(done || c->inputs_[0].size() == 0);
// If we are unable to find a normal compaction run and we are still
// above the compaction threshold, iterate again to pick compaction
// candidates, this time without considering their size differences.
if (!done) {
int files_not_in_compaction = 0;
for (unsigned int i = 0; i < current_->files_[level].size(); i++) {
f = current_->files_[level][i];
if (!f->being_compacted) {
files_not_in_compaction++;
}
}
int expected_num_files = files_not_in_compaction +
compactions_in_progress_[level].size();
if (expected_num_files <=
options_->level0_file_num_compaction_trigger + 1) {
done = true; // nothing more to do
} else {
max_files_to_compact = std::min((int)max_merge_width,
expected_num_files - options_->level0_file_num_compaction_trigger);
Log(options_->info_log, "Universal: second loop with maxfiles %d",
max_files_to_compact);
}
}
}
if (c->inputs_[0].size() <= 1) {
Log(options_->info_log, "Universal: only %ld files, nothing to do.\n",
c->inputs_[0].size());
delete c;
return nullptr;
}
// validate that all the chosen files are non overlapping in time
FileMetaData* newerfile __attribute__((unused)) = nullptr;
for (unsigned int i = 0; i < c->inputs_[0].size(); i++) {
FileMetaData* f = c->inputs_[0][i];
assert (f->smallest_seqno <= f->largest_seqno);
assert(newerfile == nullptr ||
newerfile->smallest_seqno > f->largest_seqno);
newerfile = f;
}
// Is the earliest file part of this compaction?
int last_index = file_by_time[file_by_time.size()-1];
FileMetaData* last_file = current_->files_[level][last_index];
if (c->inputs_[0][c->inputs_[0].size()-1] == last_file) {
c->bottommost_level_ = true;
}
// update statistics
if (options_->statistics != nullptr) {
options_->statistics->measureTime(NUM_FILES_IN_SINGLE_COMPACTION,
c->inputs_[0].size());
}
c->input_version_ = current_;
c->input_version_->Ref();
// mark all the files that are being compacted
c->MarkFilesBeingCompacted(true);
// remember this currently undergoing compaction
compactions_in_progress_[level].insert(c);
return c;
}
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, level+1, MaxFileSizeForLevel(level+1),
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);
// In universal style of compaction, compact L0 files back into L0.
if (options_->compaction_style == kCompactionStyleUniversal) {
int level = 0;
c = PickCompactionUniversal(level, current_->compaction_score_[level]);
return c;
}
// 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]);
ExpandWhileOverlapping(c);
if (c != nullptr) {
break;
}
}
}
// Find compactions needed by seeks
FileMetaData* f = current_->file_to_compact_;
if (c == nullptr && f != nullptr && !f->being_compacted) {
level = current_->file_to_compact_level_;
int parent_index = -1;
// Only allow one level 0 compaction at a time.
// Do not pick this file if its parents at level+1 are being compacted.
if (level != 0 || compactions_in_progress_[0].empty()) {
if(!ParentRangeInCompaction(&f->smallest, &f->largest, level,
&parent_index)) {
c = new Compaction(level, level+1, MaxFileSizeForLevel(level+1),
MaxGrandParentOverlapBytes(level), NumberLevels(), true);
c->inputs_[0].push_back(f);
c->parent_index_ = parent_index;
current_->file_to_compact_ = nullptr;
ExpandWhileOverlapping(c);
}
}
}
if (c == nullptr) {
return nullptr;
}
c->input_version_ = current_;
c->input_version_->Ref();
// 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 we include more L0 files in the same compaction run it can
// cause the 'smallest' and 'largest' key to get extended to a
// larger range. So, re-invoke GetRange to get the new key range
GetRange(c->inputs_[0], &smallest, &largest);
if (ParentRangeInCompaction(&smallest, &largest,
level, &c->parent_index_)) {
delete c;
return nullptr;
}
assert(!c->inputs_[0].empty());
}
// Setup "level+1" files (inputs_[1])
SetupOtherInputs(c);
// mark all the files that are being compacted
c->MarkFilesBeingCompacted(true);
// Is this compaction creating a file at the bottommost level
c->SetupBottomMostLevel(false);
// 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;
}
// Add more files to the inputs on "level" to make sure that
// no newer version of a key is compacted to "level+1" while leaving an older
// version in a "level". Otherwise, any Get() will search "level" first,
// and will likely return an old/stale value for the key, since it always
// searches in increasing order of level to find the value. This could
// also scramble the order of merge operands. This function should be
// called any time a new Compaction is created, and its inputs_[0] are
// populated.
//
// Will set c to nullptr if it is impossible to apply this compaction.
void VersionSet::ExpandWhileOverlapping(Compaction* c) {
// If inputs are empty then there is nothing to expand.
if (!c || c->inputs_[0].empty()) {
return;
}
// GetOverlappingInputs will always do the right thing for level-0.
// So we don't need to do any expansion if level == 0.
if (c->level() == 0) {
return;
}
const int level = c->level();
InternalKey smallest, largest;
// Keep expanding c->inputs_[0] until we are sure that there is a
// "clean cut" boundary between the files in input and the surrounding files.
// This will ensure that no parts of a key are lost during compaction.
int hint_index = -1;
size_t old_size;
do {
old_size = c->inputs_[0].size();
GetRange(c->inputs_[0], &smallest, &largest);
c->inputs_[0].clear();
current_->GetOverlappingInputs(level, &smallest, &largest, &c->inputs_[0],
hint_index, &hint_index);
} while(c->inputs_[0].size() > old_size);
// Get the new range
GetRange(c->inputs_[0], &smallest, &largest);
// If, after the expansion, there are files that are already under
// compaction, then we must drop/cancel this compaction.
int parent_index = -1;
if (FilesInCompaction(c->inputs_[0]) ||
ParentRangeInCompaction(&smallest, &largest, level, &parent_index)) {
c->inputs_[0].clear();
c->inputs_[1].clear();
delete c;
c = nullptr;
}
}
// Populates the set of inputs from "level+1" that overlap with "level".
// Will also attempt to expand "level" if that doesn't expand "level+1"
// or cause "level" to include a file for compaction that has an overlapping
// user-key with another file.
void VersionSet::SetupOtherInputs(Compaction* c) {
// If inputs are empty, then there is nothing to expand.
if (c->inputs_[0].empty()) {
return;
}
const int level = c->level();
InternalKey smallest, largest;
// Get the range one last time.
GetRange(c->inputs_[0], &smallest, &largest);
// Populate the set of next-level files (inputs_[1]) to include in compaction
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 further grow the number of inputs in "level" without
// changing the number of "level+1" files we pick up. We also choose NOT
// to expand if this would cause "level" to include some entries for some
// user key, while excluding other entries for the same user key. This
// can happen when one user key spans multiple files.
if (!c->inputs_[1].empty()) {
std::vector<FileMetaData*> expanded0;
current_->GetOverlappingInputs(level, &all_start, &all_limit, &expanded0,
c->base_index_, nullptr);
const uint64_t inputs0_size = TotalFileSize(c->inputs_[0]);
const uint64_t inputs1_size = TotalFileSize(c->inputs_[1]);
const uint64_t expanded0_size = TotalFileSize(expanded0);
uint64_t limit = ExpandedCompactionByteSizeLimit(level);
if (expanded0.size() > c->inputs_[0].size() &&
inputs1_size + expanded0_size < limit &&
!FilesInCompaction(expanded0) &&
!current_->HasOverlappingUserKey(&expanded0, level)) {
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;
// All files are 'overlapping' in universal style compaction.
// We have to compact the entire range in one shot.
if (options_->compaction_style == kCompactionStyleUniversal) {
begin = nullptr;
end = nullptr;
}
current_->GetOverlappingInputs(level, begin, end, &inputs);
if (inputs.empty()) {
return nullptr;
}
// Avoid compacting too much in one shot in case the range is large.
// But we cannot do this for level-0 since level-0 files can overlap
// and we must not pick one file and drop another older file if the
// two files overlap.
if (level > 0) {
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;
}
}
}
int out_level = (options_->compaction_style == kCompactionStyleUniversal) ?
level : level+1;
Compaction* c = new Compaction(level, out_level, MaxFileSizeForLevel(out_level),
MaxGrandParentOverlapBytes(level), NumberLevels());
c->inputs_[0] = inputs;
ExpandWhileOverlapping(c);
if (c == nullptr) {
Log(options_->info_log, "Could not compact due to expansion failure.\n");
return nullptr;
}
c->input_version_ = current_;
c->input_version_->Ref();
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);
// Is this compaction creating a file at the bottommost level
c->SetupBottomMostLevel(true);
return c;
}
Compaction::Compaction(int level, int out_level, uint64_t target_file_size,
uint64_t max_grandparent_overlap_bytes, int number_levels,
bool seek_compaction)
: level_(level),
out_level_(out_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),
bottommost_level_(false),
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) {
if (input_version_->vset_->options_->compaction_style ==
kCompactionStyleUniversal) {
return bottommost_level_;
}
// 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;
}
}
}
// Is this compaction producing files at the bottommost level?
void Compaction::SetupBottomMostLevel(bool isManual) {
if (input_version_->vset_->options_->compaction_style ==
kCompactionStyleUniversal) {
// If universal compaction style is used and manual
// compaction is occuring, then we are guaranteed that
// all files will be picked in a single compaction
// run. We can safely set bottommost_level_ = true.
// If it is not manual compaction, then bottommost_level_
// is already set when the Compaction was created.
if (isManual) {
bottommost_level_ = true;
}
return;
}
bottommost_level_ = true;
int num_levels = input_version_->vset_->NumberLevels();
for (int i = level() + 2; i < num_levels; i++) {
if (input_version_->vset_->NumLevelFiles(i) > 0) {
bottommost_level_ = false;
break;
}
}
}
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