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LevelDB-course-Lab/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 <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 "include/env.h"
#include "include/table_builder.h"
#include "table/merger.h"
#include "table/two_level_iterator.h"
#include "util/coding.h"
#include "util/logging.h"
namespace leveldb {
// Maximum number of overlaps in grandparent (i.e., level+2) before we
// stop building a single file in a level->level+1 compaction.
static const int kMaxGrandParentFiles = 10;
static double MaxBytesForLevel(int level) {
if (level == 0) {
return 4 * 1048576.0;
} else {
double result = 10 * 1048576.0;
while (level > 1) {
result *= 10;
level--;
}
return result;
}
}
static uint64_t MaxFileSizeForLevel(int level) {
return 2 << 20; // We could vary per level to reduce number of files?
}
namespace {
std::string IntSetToString(const std::set<uint64_t>& s) {
std::string result = "{";
for (std::set<uint64_t>::const_iterator it = s.begin();
it != s.end();
++it) {
result += (result.size() > 1) ? "," : "";
result += NumberToString(*it);
}
result += "}";
return result;
}
}
Version::~Version() {
assert(refs_ == 0);
for (int level = 0; level < config::kNumLevels; level++) {
for (int 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 cleanup_mem_;
}
// 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
// 8-byte value containing the file number of the file, encoding using
// EncodeFixed64.
class Version::LevelFileNumIterator : public Iterator {
public:
LevelFileNumIterator(const Version* version,
const std::vector<FileMetaData*>* flist)
: icmp_(version->vset_->icmp_.user_comparator()),
flist_(flist),
index_(flist->size()) { // Marks as invalid
}
virtual bool Valid() const {
return index_ < flist_->size();
}
virtual void Seek(const Slice& target) {
uint32_t left = 0;
uint32_t right = flist_->size() - 1;
while (left < right) {
uint32_t mid = (left + right) / 2;
int cmp = icmp_.Compare((*flist_)[mid]->largest.Encode(), target);
if (cmp < 0) {
// Key at "mid.largest" is < than "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;
}
}
index_ = left;
}
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);
return Slice(value_buf_, sizeof(value_buf_));
}
virtual Status status() const { return Status::OK(); }
private:
const InternalKeyComparator icmp_;
const std::vector<FileMetaData*>* const flist_;
int index_;
mutable char value_buf_[8]; // Used for encoding the file number for value()
};
static Iterator* GetFileIterator(void* arg,
const ReadOptions& options,
const Slice& file_value) {
TableCache* cache = reinterpret_cast<TableCache*>(arg);
if (file_value.size() != 8) {
return NewErrorIterator(
Status::Corruption("FileReader invoked with unexpected value"));
} else {
return cache->NewIterator(options, DecodeFixed64(file_value.data()));
}
}
Iterator* Version::NewConcatenatingIterator(const ReadOptions& options,
int level) const {
return NewTwoLevelIterator(
new LevelFileNumIterator(this, &files_[level]),
&GetFileIterator, vset_->table_cache_, options);
}
void Version::AddIterators(const ReadOptions& options,
std::vector<Iterator*>* iters) {
// Merge all level zero files together since they may overlap
for (int i = 0; i < files_[0].size(); i++) {
iters->push_back(
vset_->table_cache_->NewIterator(options, files_[0][i]->number));
}
// 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 < config::kNumLevels; level++) {
if (!files_[level].empty()) {
iters->push_back(NewConcatenatingIterator(options, level));
}
}
}
void Version::Ref() {
++refs_;
}
void Version::Unref() {
assert(refs_ >= 1);
--refs_;
if (refs_ == 0) {
vset_->MaybeDeleteOldVersions();
// TODO: try to delete obsolete files
}
}
std::string Version::DebugString() const {
std::string r;
for (int level = 0; level < config::kNumLevels; level++) {
// E.g., level 1: 17:123['a' .. 'd'] 20:43['e' .. 'g']
r.append("level ");
AppendNumberTo(&r, level);
r.push_back(':');
const std::vector<FileMetaData*>& files = files_[level];
for (int 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("['");
AppendEscapedStringTo(&r, files[i]->smallest.Encode());
r.append("' .. '");
AppendEscapedStringTo(&r, files[i]->largest.Encode());
r.append("']");
}
r.push_back('\n');
}
return r;
}
// 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:
typedef std::map<uint64_t, FileMetaData*> FileMap;
VersionSet* vset_;
FileMap files_[config::kNumLevels];
public:
// Initialize a builder with the files from *base and other info from *vset
Builder(VersionSet* vset, Version* base)
: vset_(vset) {
for (int level = 0; level < config::kNumLevels; level++) {
const std::vector<FileMetaData*>& files = base->files_[level];
for (int i = 0; i < files.size(); i++) {
FileMetaData* f = files[i];
f->refs++;
files_[level].insert(std::make_pair(f->number, f));
}
}
}
~Builder() {
for (int level = 0; level < config::kNumLevels; level++) {
const FileMap& fmap = files_[level];
for (FileMap::const_iterator iter = fmap.begin();
iter != fmap.end();
++iter) {
FileMetaData* f = iter->second;
f->refs--;
if (f->refs <= 0) {
delete f;
}
}
}
}
// Apply all of the edits in *edit to the current state.
void Apply(VersionEdit* edit) {
// Update compaction pointers
for (int 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;
FileMap::iterator fiter = files_[level].find(number);
assert(fiter != files_[level].end()); // Sanity check for debug mode
if (fiter != files_[level].end()) {
FileMetaData* f = fiter->second;
f->refs--;
if (f->refs <= 0) {
delete f;
}
files_[level].erase(fiter);
}
}
// Add new files
for (int 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;
assert(files_[level].count(f->number) == 0);
files_[level].insert(std::make_pair(f->number, f));
}
// Add large value refs
for (int i = 0; i < edit->large_refs_added_.size(); i++) {
const VersionEdit::Large& l = edit->large_refs_added_[i];
vset_->RegisterLargeValueRef(l.large_ref, l.fnum, l.internal_key);
}
}
// Save the current state in *v.
void SaveTo(Version* v) {
for (int level = 0; level < config::kNumLevels; level++) {
const FileMap& fmap = files_[level];
for (FileMap::const_iterator iter = fmap.begin();
iter != fmap.end();
++iter) {
FileMetaData* f = iter->second;
f->refs++;
v->files_[level].push_back(f);
}
}
}
};
VersionSet::VersionSet(const std::string& dbname,
const Options* 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()
descriptor_file_(NULL),
descriptor_log_(NULL),
current_(new Version(this)),
oldest_(current_) {
}
VersionSet::~VersionSet() {
for (Version* v = oldest_; v != NULL; ) {
Version* next = v->next_;
assert(v->refs_ == 0);
delete v;
v = next;
}
delete descriptor_log_;
delete descriptor_file_;
}
Status VersionSet::LogAndApply(VersionEdit* edit, MemTable* cleanup_mem) {
edit->SetNextFile(next_file_number_);
Version* v = new Version(this);
{
Builder builder(this, current_);
builder.Apply(edit);
builder.SaveTo(v);
}
std::string new_manifest_file;
Status s = Finalize(v);
// Initialize new descriptor log file if necessary by creating
// a temporary file that contains a snapshot of the current version.
if (s.ok()) {
if (descriptor_log_ == NULL) {
assert(descriptor_file_ == NULL);
new_manifest_file = DescriptorFileName(dbname_, manifest_file_number_);
edit->SetNextFile(next_file_number_);
s = env_->NewWritableFile(new_manifest_file, &descriptor_file_);
if (s.ok()) {
descriptor_log_ = new log::Writer(descriptor_file_);
s = WriteSnapshot(descriptor_log_);
}
}
}
// Write new record to log file
if (s.ok()) {
std::string record;
edit->EncodeTo(&record);
s = descriptor_log_->AddRecord(record);
if (s.ok()) {
s = descriptor_file_->Sync();
}
}
// 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_);
}
// Install the new version
if (s.ok()) {
assert(current_->next_ == NULL);
assert(current_->cleanup_mem_ == NULL);
current_->cleanup_mem_ = cleanup_mem;
v->next_ = NULL;
current_->next_ = v;
current_ = v;
} else {
delete v;
if (!new_manifest_file.empty()) {
delete descriptor_log_;
delete descriptor_file_;
descriptor_log_ = NULL;
descriptor_file_ = NULL;
env_->DeleteFile(new_manifest_file);
}
}
//Log(env_, options_->info_log, "State\n%s", current_->DebugString().c_str());
return s;
}
Status VersionSet::Recover(uint64_t* log_number,
SequenceNumber* last_sequence) {
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);
std::string dscname = dbname_ + "/" + current;
SequentialFile* file;
s = env_->NewSequentialFile(dscname, &file);
if (!s.ok()) {
return s;
}
bool have_log_number = false;
bool have_next_file = false;
bool have_last_sequence = false;
uint64_t next_file = 0;
Builder builder(this, current_);
{
LogReporter reporter;
reporter.status = &s;
log::Reader reader(file, &reporter, true/*checksum*/);
Slice record;
std::string scratch;
while (reader.ReadRecord(&record, &scratch) && s.ok()) {
VersionEdit edit;
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_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;
}
}
}
delete file;
file = NULL;
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 (s.ok()) {
Version* v = new Version(this);
builder.SaveTo(v);
s = Finalize(v);
if (!s.ok()) {
delete v;
} else {
// Install recovered version
v->next_ = NULL;
current_->next_ = v;
current_ = v;
manifest_file_number_ = next_file;
next_file_number_ = next_file + 1;
}
}
return s;
}
Status VersionSet::Finalize(Version* v) {
// Precomputed best level for next compaction
int best_level = -1;
double best_score = -1;
Status s;
for (int level = 0; s.ok() && level < config::kNumLevels-1; level++) {
s = SortLevel(v, level);
// Compute the ratio of current size to size limit.
uint64_t level_bytes = 0;
for (int i = 0; i < v->files_[level].size(); i++) {
level_bytes += v->files_[level][i]->file_size;
}
double score = static_cast<double>(level_bytes) / MaxBytesForLevel(level);
if (level == 0) {
// Level-0 file sizes are going to be often much smaller than
// MaxBytesForLevel(0) since we do not account for compression
// when producing a level-0 file; and too many level-0 files
// increase merging costs. So use a file-count limit for
// level-0 in addition to the byte-count limit.
double count_score = v->files_[level].size() / 4.0;
if (count_score > score) {
score = count_score;
}
}
if (score > best_score) {
best_level = level;
best_score = score;
}
}
v->compaction_level_ = best_level;
v->compaction_score_ = best_score;
return s;
}
Status VersionSet::WriteSnapshot(log::Writer* log) {
// TODO: Break up into multiple records to reduce memory usage on recovery?
// Save metadata
VersionEdit edit;
edit.SetComparatorName(icmp_.user_comparator()->Name());
// Save compaction pointers
for (int level = 0; level < config::kNumLevels; level++) {
if (!compact_pointer_[level].empty()) {
InternalKey key;
key.DecodeFrom(compact_pointer_[level]);
edit.SetCompactPointer(level, key);
}
}
// Save files
for (int level = 0; level < config::kNumLevels; level++) {
const std::vector<FileMetaData*>& files = current_->files_[level];
for (int i = 0; i < files.size(); i++) {
const FileMetaData* f = files[i];
edit.AddFile(level, f->number, f->file_size, f->smallest, f->largest);
}
}
// Save large value refs
for (LargeValueMap::const_iterator it = large_value_refs_.begin();
it != large_value_refs_.end();
++it) {
const LargeValueRef& ref = it->first;
const LargeReferencesSet& pointers = it->second;
for (LargeReferencesSet::const_iterator j = pointers.begin();
j != pointers.end();
++j) {
edit.AddLargeValueRef(ref, j->first, j->second);
}
}
std::string record;
edit.EncodeTo(&record);
return log->AddRecord(record);
}
// Helper to sort by tables_[file_number].smallest
struct VersionSet::BySmallestKey {
const InternalKeyComparator* internal_comparator;
bool operator()(FileMetaData* f1, FileMetaData* f2) const {
return internal_comparator->Compare(f1->smallest, f2->smallest) < 0;
}
};
Status VersionSet::SortLevel(Version* v, uint64_t level) {
Status result;
BySmallestKey cmp;
cmp.internal_comparator = &icmp_;
std::sort(v->files_[level].begin(), v->files_[level].end(), cmp);
if (result.ok() && level > 0) {
// There should be no overlap
for (int 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 (icmp_.Compare(prev_end, this_begin) >= 0) {
result = Status::Corruption(
"overlapping ranges in same level",
(EscapeString(prev_end.Encode()) + " vs. " +
EscapeString(this_begin.Encode())));
break;
}
}
}
return result;
}
int VersionSet::NumLevelFiles(int level) const {
assert(level >= 0);
assert(level < config::kNumLevels);
return current_->files_[level].size();
}
uint64_t VersionSet::ApproximateOffsetOf(Version* v, const InternalKey& ikey) {
uint64_t result = 0;
for (int level = 0; level < config::kNumLevels; level++) {
const std::vector<FileMetaData*>& files = v->files_[level];
for (int 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(), files[i]->number, &tableptr);
if (tableptr != NULL) {
result += tableptr->ApproximateOffsetOf(ikey.Encode());
}
delete iter;
}
}
}
// Add in large value files which are references from internal keys
// stored in the table files
//
// TODO(opt): this is O(# large values in db). If this becomes too slow,
// we could store an auxiliary data structure indexed by internal key
for (LargeValueMap::const_iterator it = large_value_refs_.begin();
it != large_value_refs_.end();
++it) {
const LargeValueRef& lref = it->first;
for (LargeReferencesSet::const_iterator it2 = it->second.begin();
it2 != it->second.end();
++it2) {
if (icmp_.Compare(it2->second, ikey.Encode()) <= 0) {
// Internal key for large value is before our key of interest
result += lref.ValueSize();
}
}
}
return result;
}
bool VersionSet::RegisterLargeValueRef(const LargeValueRef& large_ref,
uint64_t fnum,
const InternalKey& internal_key) {
LargeReferencesSet* refs = &large_value_refs_[large_ref];
bool is_first = refs->empty();
refs->insert(make_pair(fnum, internal_key.Encode().ToString()));
return is_first;
}
void VersionSet::CleanupLargeValueRefs(const std::set<uint64_t>& live_tables,
uint64_t log_file_num) {
for (LargeValueMap::iterator it = large_value_refs_.begin();
it != large_value_refs_.end();
) {
LargeReferencesSet* refs = &it->second;
for (LargeReferencesSet::iterator ref_it = refs->begin();
ref_it != refs->end();
) {
if (ref_it->first != log_file_num && // Not in log file
live_tables.count(ref_it->first) == 0) { // Not in a live table
// No longer live: erase
LargeReferencesSet::iterator to_erase = ref_it;
++ref_it;
refs->erase(to_erase);
} else {
// Still live: leave this reference alone
++ref_it;
}
}
if (refs->empty()) {
// No longer any live references to this large value: remove from
// large_value_refs
Log(env_, options_->info_log, "large value is dead: '%s'",
LargeValueRefToFilenameString(it->first).c_str());
LargeValueMap::iterator to_erase = it;
++it;
large_value_refs_.erase(to_erase);
} else {
++it;
}
}
}
bool VersionSet::LargeValueIsLive(const LargeValueRef& large_ref) {
LargeValueMap::iterator it = large_value_refs_.find(large_ref);
if (it == large_value_refs_.end()) {
return false;
} else {
assert(!it->second.empty());
return true;
}
}
void VersionSet::MaybeDeleteOldVersions() {
// Note: it is important to delete versions in order since a newer
// version with zero refs may be holding a pointer to a memtable
// that is used by somebody who has a ref on an older version.
while (oldest_ != current_ && oldest_->refs_ == 0) {
Version* next = oldest_->next_;
delete oldest_;
oldest_ = next;
}
}
void VersionSet::AddLiveFiles(std::set<uint64_t>* live) {
for (Version* v = oldest_; v != NULL; v = v->next_) {
for (int level = 0; level < config::kNumLevels; level++) {
const std::vector<FileMetaData*>& files = v->files_[level];
for (int i = 0; i < files.size(); i++) {
live->insert(files[i]->number);
}
}
}
}
int64 VersionSet::MaxNextLevelOverlappingBytes() {
int64 result = 0;
std::vector<FileMetaData*> overlaps;
for (int level = 0; level < config::kNumLevels - 1; level++) {
for (int i = 0; i < current_->files_[level].size(); i++) {
const FileMetaData* f = current_->files_[level][i];
GetOverlappingInputs(level+1, f->smallest, f->largest, &overlaps);
int64 sum = 0;
for (int j = 0; j < overlaps.size(); j++) {
sum += overlaps[j]->file_size;
}
if (sum > result) {
result = sum;
}
}
}
return result;
}
// Store in "*inputs" all files in "level" that overlap [begin,end]
void VersionSet::GetOverlappingInputs(
int level,
const InternalKey& begin,
const InternalKey& end,
std::vector<FileMetaData*>* inputs) {
inputs->clear();
Slice user_begin = begin.user_key();
Slice user_end = end.user_key();
const Comparator* user_cmp = icmp_.user_comparator();
for (int i = 0; i < current_->files_[level].size(); i++) {
FileMetaData* f = current_->files_[level][i];
if (user_cmp->Compare(f->largest.user_key(), user_begin) < 0 ||
user_cmp->Compare(f->smallest.user_key(), user_end) > 0) {
// Either completely before or after range; skip it
} else {
inputs->push_back(f);
}
}
}
// 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 (int 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 (int i = 0; i < files.size(); i++) {
list[num++] = table_cache_->NewIterator(options, files[i]->number);
}
} else {
// Create concatenating iterator for the files from this level
list[num++] = NewTwoLevelIterator(
new Version::LevelFileNumIterator(
c->input_version_, &c->inputs_[which]),
&GetFileIterator, table_cache_, options);
}
}
}
assert(num <= space);
Iterator* result = NewMergingIterator(&icmp_, list, num);
delete[] list;
return result;
}
Compaction* VersionSet::PickCompaction() {
if (!NeedsCompaction()) {
return NULL;
}
const int level = current_->compaction_level_;
assert(level >= 0);
assert(level+1 < config::kNumLevels);
Compaction* c = new Compaction(level);
c->input_version_ = current_;
c->input_version_->Ref();
// Pick the first file that comes after compact_pointer_[level]
for (int i = 0; i < current_->files_[level].size(); i++) {
FileMetaData* f = current_->files_[level][i];
if (compact_pointer_[level].empty() ||
icmp_.Compare(f->largest.Encode(), compact_pointer_[level]) > 0) {
c->inputs_[0].push_back(f);
break;
}
}
if (c->inputs_[0].empty()) {
// Wrap-around to the beginning of the key space
c->inputs_[0].push_back(current_->files_[level][0]);
}
// Files in level 0 may overlap each other, so pick up all overlapping ones
if (level == 0) {
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.
GetOverlappingInputs(0, smallest, largest, &c->inputs_[0]);
assert(!c->inputs_[0].empty());
}
SetupOtherInputs(c);
return c;
}
void VersionSet::SetupOtherInputs(Compaction* c) {
const int level = c->level();
InternalKey smallest, largest;
GetRange(c->inputs_[0], &smallest, &largest);
GetOverlappingInputs(level+1, smallest, largest, &c->inputs_[1]);
// 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;
GetOverlappingInputs(level, all_start, all_limit, &expanded0);
if (expanded0.size() > c->inputs_[0].size()) {
InternalKey new_start, new_limit;
GetRange(expanded0, &new_start, &new_limit);
std::vector<FileMetaData*> expanded1;
GetOverlappingInputs(level+1, new_start, new_limit, &expanded1);
if (expanded1.size() == c->inputs_[1].size()) {
Log(env_, options_->info_log,
"Expanding@%d %d+%d to %d+%d\n",
level,
int(c->inputs_[0].size()),
int(c->inputs_[1].size()),
int(expanded0.size()),
int(expanded1.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 < config::kNumLevels) {
GetOverlappingInputs(level + 2, all_start, all_limit, &c->grandparents_);
}
if (false) {
Log(env_, options_->info_log, "Compacting %d '%s' .. '%s'",
level,
EscapeString(smallest.Encode()).c_str(),
EscapeString(largest.Encode()).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;
GetOverlappingInputs(level, begin, end, &inputs);
if (inputs.empty()) {
return NULL;
}
Compaction* c = new Compaction(level);
c->input_version_ = current_;
c->input_version_->Ref();
c->inputs_[0] = inputs;
SetupOtherInputs(c);
return c;
}
Compaction::Compaction(int level)
: level_(level),
max_output_file_size_(MaxFileSizeForLevel(level)),
input_version_(NULL),
grandparent_index_(0),
output_start_(-1) {
for (int i = 0; i < config::kNumLevels; i++) {
level_ptrs_[i] = 0;
}
}
Compaction::~Compaction() {
if (input_version_ != NULL) {
input_version_->Unref();
}
}
bool Compaction::IsTrivialMove() const {
// Avoid a move if there are lots of overlapping grandparent files.
// 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
&& grandparents_.size() <= kMaxGrandParentFiles);
}
void Compaction::AddInputDeletions(VersionEdit* edit) {
for (int which = 0; which < 2; which++) {
for (int 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 < config::kNumLevels; 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 InternalKey& key) {
// Scan to find earliest grandparent file that contains key.
const InternalKeyComparator* icmp = &input_version_->vset_->icmp_;
while (grandparent_index_ < grandparents_.size() &&
icmp->Compare(key, grandparents_[grandparent_index_]->largest) > 0) {
grandparent_index_++;
}
// First call?
if (output_start_ < 0) {
output_start_ = grandparent_index_;
}
if (grandparent_index_ - output_start_ + 1 > kMaxGrandParentFiles) {
// Too many overlaps for current output; start new output
output_start_ = grandparent_index_;
return true;
} else {
return false;
}
}
void Compaction::ReleaseInputs() {
if (input_version_ != NULL) {
input_version_->Unref();
input_version_ = NULL;
}
}
}