db_impl.cc raw
1 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file. See the AUTHORS file for names of contributors.
4
5 #include "db/db_impl.h"
6
7 #include <stdint.h>
8 #include <stdio.h>
9
10 #include <algorithm>
11 #include <atomic>
12 #include <set>
13 #include <string>
14 #include <vector>
15
16 #include "db/builder.h"
17 #include "db/db_iter.h"
18 #include "db/dbformat.h"
19 #include "db/filename.h"
20 #include "db/log_reader.h"
21 #include "db/log_writer.h"
22 #include "db/memtable.h"
23 #include "db/table_cache.h"
24 #include "db/version_set.h"
25 #include "db/write_batch_internal.h"
26 #include "leveldb/db.h"
27 #include "leveldb/env.h"
28 #include "leveldb/status.h"
29 #include "leveldb/table.h"
30 #include "leveldb/table_builder.h"
31 #include "port/port.h"
32 #include "table/block.h"
33 #include "table/merger.h"
34 #include "table/two_level_iterator.h"
35 #include "util/coding.h"
36 #include "util/logging.h"
37 #include "util/mutexlock.h"
38
39 namespace leveldb {
40
41 const int kNumNonTableCacheFiles = 10;
42
43 // Information kept for every waiting writer
44 struct DBImpl::Writer {
45 explicit Writer(port::Mutex* mu)
46 : batch(nullptr), sync(false), done(false), cv(mu) {}
47
48 Status status;
49 WriteBatch* batch;
50 bool sync;
51 bool done;
52 port::CondVar cv;
53 };
54
55 struct DBImpl::CompactionState {
56 // Files produced by compaction
57 struct Output {
58 uint64_t number;
59 uint64_t file_size;
60 InternalKey smallest, largest;
61 };
62
63 Output* current_output() { return &outputs[outputs.size() - 1]; }
64
65 explicit CompactionState(Compaction* c)
66 : compaction(c),
67 smallest_snapshot(0),
68 outfile(nullptr),
69 builder(nullptr),
70 total_bytes(0) {}
71
72 Compaction* const compaction;
73
74 // Sequence numbers < smallest_snapshot are not significant since we
75 // will never have to service a snapshot below smallest_snapshot.
76 // Therefore if we have seen a sequence number S <= smallest_snapshot,
77 // we can drop all entries for the same key with sequence numbers < S.
78 SequenceNumber smallest_snapshot;
79
80 std::vector<Output> outputs;
81
82 // State kept for output being generated
83 WritableFile* outfile;
84 TableBuilder* builder;
85
86 uint64_t total_bytes;
87 };
88
89 // Fix user-supplied options to be reasonable
90 template <class T, class V>
91 static void ClipToRange(T* ptr, V minvalue, V maxvalue) {
92 if (static_cast<V>(*ptr) > maxvalue) *ptr = maxvalue;
93 if (static_cast<V>(*ptr) < minvalue) *ptr = minvalue;
94 }
95 Options SanitizeOptions(const std::string& dbname,
96 const InternalKeyComparator* icmp,
97 const InternalFilterPolicy* ipolicy,
98 const Options& src) {
99 Options result = src;
100 result.comparator = icmp;
101 result.filter_policy = (src.filter_policy != nullptr) ? ipolicy : nullptr;
102 ClipToRange(&result.max_open_files, 64 + kNumNonTableCacheFiles, 50000);
103 ClipToRange(&result.write_buffer_size, 64 << 10, 1 << 30);
104 ClipToRange(&result.max_file_size, 1 << 20, 1 << 30);
105 ClipToRange(&result.block_size, 1 << 10, 4 << 20);
106 if (result.info_log == nullptr) {
107 // Open a log file in the same directory as the db
108 src.env->CreateDir(dbname); // In case it does not exist
109 src.env->RenameFile(InfoLogFileName(dbname), OldInfoLogFileName(dbname));
110 Status s = src.env->NewLogger(InfoLogFileName(dbname), &result.info_log);
111 if (!s.ok()) {
112 // No place suitable for logging
113 result.info_log = nullptr;
114 }
115 }
116 if (result.block_cache == nullptr) {
117 result.block_cache = NewLRUCache(8 << 20);
118 }
119 return result;
120 }
121
122 static int TableCacheSize(const Options& sanitized_options) {
123 // Reserve ten files or so for other uses and give the rest to TableCache.
124 return sanitized_options.max_open_files - kNumNonTableCacheFiles;
125 }
126
127 DBImpl::DBImpl(const Options& raw_options, const std::string& dbname)
128 : env_(raw_options.env),
129 internal_comparator_(raw_options.comparator),
130 internal_filter_policy_(raw_options.filter_policy),
131 options_(SanitizeOptions(dbname, &internal_comparator_,
132 &internal_filter_policy_, raw_options)),
133 owns_info_log_(options_.info_log != raw_options.info_log),
134 owns_cache_(options_.block_cache != raw_options.block_cache),
135 dbname_(dbname),
136 table_cache_(new TableCache(dbname_, options_, TableCacheSize(options_))),
137 db_lock_(nullptr),
138 shutting_down_(false),
139 background_work_finished_signal_(&mutex_),
140 mem_(nullptr),
141 imm_(nullptr),
142 has_imm_(false),
143 logfile_(nullptr),
144 logfile_number_(0),
145 log_(nullptr),
146 seed_(0),
147 tmp_batch_(new WriteBatch),
148 background_compaction_scheduled_(false),
149 manual_compaction_(nullptr),
150 versions_(new VersionSet(dbname_, &options_, table_cache_,
151 &internal_comparator_)) {}
152
153 DBImpl::~DBImpl() {
154 // Wait for background work to finish.
155 mutex_.Lock();
156 shutting_down_.store(true, std::memory_order_release);
157 while (background_compaction_scheduled_) {
158 background_work_finished_signal_.Wait();
159 }
160 mutex_.Unlock();
161
162 if (db_lock_ != nullptr) {
163 env_->UnlockFile(db_lock_);
164 }
165
166 delete versions_;
167 if (mem_ != nullptr) mem_->Unref();
168 if (imm_ != nullptr) imm_->Unref();
169 delete tmp_batch_;
170 delete log_;
171 delete logfile_;
172 delete table_cache_;
173
174 if (owns_info_log_) {
175 delete options_.info_log;
176 }
177 if (owns_cache_) {
178 delete options_.block_cache;
179 }
180 }
181
182 Status DBImpl::NewDB() {
183 VersionEdit new_db;
184 new_db.SetComparatorName(user_comparator()->Name());
185 new_db.SetLogNumber(0);
186 new_db.SetNextFile(2);
187 new_db.SetLastSequence(0);
188
189 const std::string manifest = DescriptorFileName(dbname_, 1);
190 WritableFile* file;
191 Status s = env_->NewWritableFile(manifest, &file);
192 if (!s.ok()) {
193 return s;
194 }
195 {
196 log::Writer log(file);
197 std::string record;
198 new_db.EncodeTo(&record);
199 s = log.AddRecord(record);
200 if (s.ok()) {
201 s = file->Close();
202 }
203 }
204 delete file;
205 if (s.ok()) {
206 // Make "CURRENT" file that points to the new manifest file.
207 s = SetCurrentFile(env_, dbname_, 1);
208 } else {
209 env_->DeleteFile(manifest);
210 }
211 return s;
212 }
213
214 void DBImpl::MaybeIgnoreError(Status* s) const {
215 if (s->ok() || options_.paranoid_checks) {
216 // No change needed
217 } else {
218 Log(options_.info_log, "Ignoring error %s", s->ToString().c_str());
219 *s = Status::OK();
220 }
221 }
222
223 void DBImpl::DeleteObsoleteFiles() {
224 mutex_.AssertHeld();
225
226 if (!bg_error_.ok()) {
227 // After a background error, we don't know whether a new version may
228 // or may not have been committed, so we cannot safely garbage collect.
229 return;
230 }
231
232 // Make a set of all of the live files
233 std::set<uint64_t> live = pending_outputs_;
234 versions_->AddLiveFiles(&live);
235
236 std::vector<std::string> filenames;
237 env_->GetChildren(dbname_, &filenames); // Ignoring errors on purpose
238 uint64_t number;
239 FileType type;
240 std::vector<std::string> files_to_delete;
241 for (std::string& filename : filenames) {
242 if (ParseFileName(filename, &number, &type)) {
243 bool keep = true;
244 switch (type) {
245 case kLogFile:
246 keep = ((number >= versions_->LogNumber()) ||
247 (number == versions_->PrevLogNumber()));
248 break;
249 case kDescriptorFile:
250 // Keep my manifest file, and any newer incarnations'
251 // (in case there is a race that allows other incarnations)
252 keep = (number >= versions_->ManifestFileNumber());
253 break;
254 case kTableFile:
255 keep = (live.find(number) != live.end());
256 break;
257 case kTempFile:
258 // Any temp files that are currently being written to must
259 // be recorded in pending_outputs_, which is inserted into "live"
260 keep = (live.find(number) != live.end());
261 break;
262 case kCurrentFile:
263 case kDBLockFile:
264 case kInfoLogFile:
265 keep = true;
266 break;
267 }
268
269 if (!keep) {
270 files_to_delete.push_back(std::move(filename));
271 if (type == kTableFile) {
272 table_cache_->Evict(number);
273 }
274 Log(options_.info_log, "Delete type=%d #%lld\n", static_cast<int>(type),
275 static_cast<unsigned long long>(number));
276 }
277 }
278 }
279
280 // While deleting all files unblock other threads. All files being deleted
281 // have unique names which will not collide with newly created files and
282 // are therefore safe to delete while allowing other threads to proceed.
283 mutex_.Unlock();
284 for (const std::string& filename : files_to_delete) {
285 env_->DeleteFile(dbname_ + "/" + filename);
286 }
287 mutex_.Lock();
288 }
289
290 Status DBImpl::Recover(VersionEdit* edit, bool* save_manifest) {
291 mutex_.AssertHeld();
292
293 // Ignore error from CreateDir since the creation of the DB is
294 // committed only when the descriptor is created, and this directory
295 // may already exist from a previous failed creation attempt.
296 env_->CreateDir(dbname_);
297 assert(db_lock_ == nullptr);
298 Status s = env_->LockFile(LockFileName(dbname_), &db_lock_);
299 if (!s.ok()) {
300 return s;
301 }
302
303 if (!env_->FileExists(CurrentFileName(dbname_))) {
304 if (options_.create_if_missing) {
305 s = NewDB();
306 if (!s.ok()) {
307 return s;
308 }
309 } else {
310 return Status::InvalidArgument(
311 dbname_, "does not exist (create_if_missing is false)");
312 }
313 } else {
314 if (options_.error_if_exists) {
315 return Status::InvalidArgument(dbname_,
316 "exists (error_if_exists is true)");
317 }
318 }
319
320 s = versions_->Recover(save_manifest);
321 if (!s.ok()) {
322 return s;
323 }
324 SequenceNumber max_sequence(0);
325
326 // Recover from all newer log files than the ones named in the
327 // descriptor (new log files may have been added by the previous
328 // incarnation without registering them in the descriptor).
329 //
330 // Note that PrevLogNumber() is no longer used, but we pay
331 // attention to it in case we are recovering a database
332 // produced by an older version of leveldb.
333 const uint64_t min_log = versions_->LogNumber();
334 const uint64_t prev_log = versions_->PrevLogNumber();
335 std::vector<std::string> filenames;
336 s = env_->GetChildren(dbname_, &filenames);
337 if (!s.ok()) {
338 return s;
339 }
340 std::set<uint64_t> expected;
341 versions_->AddLiveFiles(&expected);
342 uint64_t number;
343 FileType type;
344 std::vector<uint64_t> logs;
345 for (size_t i = 0; i < filenames.size(); i++) {
346 if (ParseFileName(filenames[i], &number, &type)) {
347 expected.erase(number);
348 if (type == kLogFile && ((number >= min_log) || (number == prev_log)))
349 logs.push_back(number);
350 }
351 }
352 if (!expected.empty()) {
353 char buf[50];
354 snprintf(buf, sizeof(buf), "%d missing files; e.g.",
355 static_cast<int>(expected.size()));
356 return Status::Corruption(buf, TableFileName(dbname_, *(expected.begin())));
357 }
358
359 // Recover in the order in which the logs were generated
360 std::sort(logs.begin(), logs.end());
361 for (size_t i = 0; i < logs.size(); i++) {
362 s = RecoverLogFile(logs[i], (i == logs.size() - 1), save_manifest, edit,
363 &max_sequence);
364 if (!s.ok()) {
365 return s;
366 }
367
368 // The previous incarnation may not have written any MANIFEST
369 // records after allocating this log number. So we manually
370 // update the file number allocation counter in VersionSet.
371 versions_->MarkFileNumberUsed(logs[i]);
372 }
373
374 if (versions_->LastSequence() < max_sequence) {
375 versions_->SetLastSequence(max_sequence);
376 }
377
378 return Status::OK();
379 }
380
381 Status DBImpl::RecoverLogFile(uint64_t log_number, bool last_log,
382 bool* save_manifest, VersionEdit* edit,
383 SequenceNumber* max_sequence) {
384 struct LogReporter : public log::Reader::Reporter {
385 Env* env;
386 Logger* info_log;
387 const char* fname;
388 Status* status; // null if options_.paranoid_checks==false
389 void Corruption(size_t bytes, const Status& s) override {
390 Log(info_log, "%s%s: dropping %d bytes; %s",
391 (this->status == nullptr ? "(ignoring error) " : ""), fname,
392 static_cast<int>(bytes), s.ToString().c_str());
393 if (this->status != nullptr && this->status->ok()) *this->status = s;
394 }
395 };
396
397 mutex_.AssertHeld();
398
399 // Open the log file
400 std::string fname = LogFileName(dbname_, log_number);
401 SequentialFile* file;
402 Status status = env_->NewSequentialFile(fname, &file);
403 if (!status.ok()) {
404 MaybeIgnoreError(&status);
405 return status;
406 }
407
408 // Create the log reader.
409 LogReporter reporter;
410 reporter.env = env_;
411 reporter.info_log = options_.info_log;
412 reporter.fname = fname.c_str();
413 reporter.status = (options_.paranoid_checks ? &status : nullptr);
414 // We intentionally make log::Reader do checksumming even if
415 // paranoid_checks==false so that corruptions cause entire commits
416 // to be skipped instead of propagating bad information (like overly
417 // large sequence numbers).
418 log::Reader reader(file, &reporter, true /*checksum*/, 0 /*initial_offset*/);
419 Log(options_.info_log, "Recovering log #%llu",
420 (unsigned long long)log_number);
421
422 // Read all the records and add to a memtable
423 std::string scratch;
424 Slice record;
425 WriteBatch batch;
426 int compactions = 0;
427 MemTable* mem = nullptr;
428 while (reader.ReadRecord(&record, &scratch) && status.ok()) {
429 if (record.size() < 12) {
430 reporter.Corruption(record.size(),
431 Status::Corruption("log record too small", fname));
432 continue;
433 }
434 WriteBatchInternal::SetContents(&batch, record);
435
436 if (mem == nullptr) {
437 mem = new MemTable(internal_comparator_);
438 mem->Ref();
439 }
440 status = WriteBatchInternal::InsertInto(&batch, mem);
441 MaybeIgnoreError(&status);
442 if (!status.ok()) {
443 break;
444 }
445 const SequenceNumber last_seq = WriteBatchInternal::Sequence(&batch) +
446 WriteBatchInternal::Count(&batch) - 1;
447 if (last_seq > *max_sequence) {
448 *max_sequence = last_seq;
449 }
450
451 if (mem->ApproximateMemoryUsage() > options_.write_buffer_size) {
452 compactions++;
453 *save_manifest = true;
454 status = WriteLevel0Table(mem, edit, nullptr);
455 mem->Unref();
456 mem = nullptr;
457 if (!status.ok()) {
458 // Reflect errors immediately so that conditions like full
459 // file-systems cause the DB::Open() to fail.
460 break;
461 }
462 }
463 }
464
465 delete file;
466
467 // See if we should keep reusing the last log file.
468 if (status.ok() && options_.reuse_logs && last_log && compactions == 0) {
469 assert(logfile_ == nullptr);
470 assert(log_ == nullptr);
471 assert(mem_ == nullptr);
472 uint64_t lfile_size;
473 if (env_->GetFileSize(fname, &lfile_size).ok() &&
474 env_->NewAppendableFile(fname, &logfile_).ok()) {
475 Log(options_.info_log, "Reusing old log %s \n", fname.c_str());
476 log_ = new log::Writer(logfile_, lfile_size);
477 logfile_number_ = log_number;
478 if (mem != nullptr) {
479 mem_ = mem;
480 mem = nullptr;
481 } else {
482 // mem can be nullptr if lognum exists but was empty.
483 mem_ = new MemTable(internal_comparator_);
484 mem_->Ref();
485 }
486 }
487 }
488
489 if (mem != nullptr) {
490 // mem did not get reused; compact it.
491 if (status.ok()) {
492 *save_manifest = true;
493 status = WriteLevel0Table(mem, edit, nullptr);
494 }
495 mem->Unref();
496 }
497
498 return status;
499 }
500
501 Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit,
502 Version* base) {
503 mutex_.AssertHeld();
504 const uint64_t start_micros = env_->NowMicros();
505 FileMetaData meta;
506 meta.number = versions_->NewFileNumber();
507 pending_outputs_.insert(meta.number);
508 Iterator* iter = mem->NewIterator();
509 Log(options_.info_log, "Level-0 table #%llu: started",
510 (unsigned long long)meta.number);
511
512 Status s;
513 {
514 mutex_.Unlock();
515 s = BuildTable(dbname_, env_, options_, table_cache_, iter, &meta);
516 mutex_.Lock();
517 }
518
519 Log(options_.info_log, "Level-0 table #%llu: %lld bytes %s",
520 (unsigned long long)meta.number, (unsigned long long)meta.file_size,
521 s.ToString().c_str());
522 delete iter;
523 pending_outputs_.erase(meta.number);
524
525 // Note that if file_size is zero, the file has been deleted and
526 // should not be added to the manifest.
527 int level = 0;
528 if (s.ok() && meta.file_size > 0) {
529 const Slice min_user_key = meta.smallest.user_key();
530 const Slice max_user_key = meta.largest.user_key();
531 if (base != nullptr) {
532 level = base->PickLevelForMemTableOutput(min_user_key, max_user_key);
533 }
534 edit->AddFile(level, meta.number, meta.file_size, meta.smallest,
535 meta.largest);
536 }
537
538 CompactionStats stats;
539 stats.micros = env_->NowMicros() - start_micros;
540 stats.bytes_written = meta.file_size;
541 stats_[level].Add(stats);
542 return s;
543 }
544
545 void DBImpl::CompactMemTable() {
546 mutex_.AssertHeld();
547 assert(imm_ != nullptr);
548
549 // Save the contents of the memtable as a new Table
550 VersionEdit edit;
551 Version* base = versions_->current();
552 base->Ref();
553 Status s = WriteLevel0Table(imm_, &edit, base);
554 base->Unref();
555
556 if (s.ok() && shutting_down_.load(std::memory_order_acquire)) {
557 s = Status::IOError("Deleting DB during memtable compaction");
558 }
559
560 // Replace immutable memtable with the generated Table
561 if (s.ok()) {
562 edit.SetPrevLogNumber(0);
563 edit.SetLogNumber(logfile_number_); // Earlier logs no longer needed
564 s = versions_->LogAndApply(&edit, &mutex_);
565 }
566
567 if (s.ok()) {
568 // Commit to the new state
569 imm_->Unref();
570 imm_ = nullptr;
571 has_imm_.store(false, std::memory_order_release);
572 DeleteObsoleteFiles();
573 } else {
574 RecordBackgroundError(s);
575 }
576 }
577
578 void DBImpl::CompactRange(const Slice* begin, const Slice* end) {
579 int max_level_with_files = 1;
580 {
581 MutexLock l(&mutex_);
582 Version* base = versions_->current();
583 for (int level = 1; level < config::kNumLevels; level++) {
584 if (base->OverlapInLevel(level, begin, end)) {
585 max_level_with_files = level;
586 }
587 }
588 }
589 TEST_CompactMemTable(); // TODO(sanjay): Skip if memtable does not overlap
590 for (int level = 0; level < max_level_with_files; level++) {
591 TEST_CompactRange(level, begin, end);
592 }
593 }
594
595 void DBImpl::TEST_CompactRange(int level, const Slice* begin,
596 const Slice* end) {
597 assert(level >= 0);
598 assert(level + 1 < config::kNumLevels);
599
600 InternalKey begin_storage, end_storage;
601
602 ManualCompaction manual;
603 manual.level = level;
604 manual.done = false;
605 if (begin == nullptr) {
606 manual.begin = nullptr;
607 } else {
608 begin_storage = InternalKey(*begin, kMaxSequenceNumber, kValueTypeForSeek);
609 manual.begin = &begin_storage;
610 }
611 if (end == nullptr) {
612 manual.end = nullptr;
613 } else {
614 end_storage = InternalKey(*end, 0, static_cast<ValueType>(0));
615 manual.end = &end_storage;
616 }
617
618 MutexLock l(&mutex_);
619 while (!manual.done && !shutting_down_.load(std::memory_order_acquire) &&
620 bg_error_.ok()) {
621 if (manual_compaction_ == nullptr) { // Idle
622 manual_compaction_ = &manual;
623 MaybeScheduleCompaction();
624 } else { // Running either my compaction or another compaction.
625 background_work_finished_signal_.Wait();
626 }
627 }
628 if (manual_compaction_ == &manual) {
629 // Cancel my manual compaction since we aborted early for some reason.
630 manual_compaction_ = nullptr;
631 }
632 }
633
634 Status DBImpl::TEST_CompactMemTable() {
635 // nullptr batch means just wait for earlier writes to be done
636 Status s = Write(WriteOptions(), nullptr);
637 if (s.ok()) {
638 // Wait until the compaction completes
639 MutexLock l(&mutex_);
640 while (imm_ != nullptr && bg_error_.ok()) {
641 background_work_finished_signal_.Wait();
642 }
643 if (imm_ != nullptr) {
644 s = bg_error_;
645 }
646 }
647 return s;
648 }
649
650 void DBImpl::RecordBackgroundError(const Status& s) {
651 mutex_.AssertHeld();
652 if (bg_error_.ok()) {
653 bg_error_ = s;
654 background_work_finished_signal_.SignalAll();
655 }
656 }
657
658 void DBImpl::MaybeScheduleCompaction() {
659 mutex_.AssertHeld();
660 if (background_compaction_scheduled_) {
661 // Already scheduled
662 } else if (shutting_down_.load(std::memory_order_acquire)) {
663 // DB is being deleted; no more background compactions
664 } else if (!bg_error_.ok()) {
665 // Already got an error; no more changes
666 } else if (imm_ == nullptr && manual_compaction_ == nullptr &&
667 !versions_->NeedsCompaction()) {
668 // No work to be done
669 } else {
670 background_compaction_scheduled_ = true;
671 env_->Schedule(&DBImpl::BGWork, this);
672 }
673 }
674
675 void DBImpl::BGWork(void* db) {
676 reinterpret_cast<DBImpl*>(db)->BackgroundCall();
677 }
678
679 void DBImpl::BackgroundCall() {
680 MutexLock l(&mutex_);
681 assert(background_compaction_scheduled_);
682 if (shutting_down_.load(std::memory_order_acquire)) {
683 // No more background work when shutting down.
684 } else if (!bg_error_.ok()) {
685 // No more background work after a background error.
686 } else {
687 BackgroundCompaction();
688 }
689
690 background_compaction_scheduled_ = false;
691
692 // Previous compaction may have produced too many files in a level,
693 // so reschedule another compaction if needed.
694 MaybeScheduleCompaction();
695 background_work_finished_signal_.SignalAll();
696 }
697
698 void DBImpl::BackgroundCompaction() {
699 mutex_.AssertHeld();
700
701 if (imm_ != nullptr) {
702 CompactMemTable();
703 return;
704 }
705
706 Compaction* c;
707 bool is_manual = (manual_compaction_ != nullptr);
708 InternalKey manual_end;
709 if (is_manual) {
710 ManualCompaction* m = manual_compaction_;
711 c = versions_->CompactRange(m->level, m->begin, m->end);
712 m->done = (c == nullptr);
713 if (c != nullptr) {
714 manual_end = c->input(0, c->num_input_files(0) - 1)->largest;
715 }
716 Log(options_.info_log,
717 "Manual compaction at level-%d from %s .. %s; will stop at %s\n",
718 m->level, (m->begin ? m->begin->DebugString().c_str() : "(begin)"),
719 (m->end ? m->end->DebugString().c_str() : "(end)"),
720 (m->done ? "(end)" : manual_end.DebugString().c_str()));
721 } else {
722 c = versions_->PickCompaction();
723 }
724
725 Status status;
726 if (c == nullptr) {
727 // Nothing to do
728 } else if (!is_manual && c->IsTrivialMove()) {
729 // Move file to next level
730 assert(c->num_input_files(0) == 1);
731 FileMetaData* f = c->input(0, 0);
732 c->edit()->DeleteFile(c->level(), f->number);
733 c->edit()->AddFile(c->level() + 1, f->number, f->file_size, f->smallest,
734 f->largest);
735 status = versions_->LogAndApply(c->edit(), &mutex_);
736 if (!status.ok()) {
737 RecordBackgroundError(status);
738 }
739 VersionSet::LevelSummaryStorage tmp;
740 Log(options_.info_log, "Moved #%lld to level-%d %lld bytes %s: %s\n",
741 static_cast<unsigned long long>(f->number), c->level() + 1,
742 static_cast<unsigned long long>(f->file_size),
743 status.ToString().c_str(), versions_->LevelSummary(&tmp));
744 } else {
745 CompactionState* compact = new CompactionState(c);
746 status = DoCompactionWork(compact);
747 if (!status.ok()) {
748 RecordBackgroundError(status);
749 }
750 CleanupCompaction(compact);
751 c->ReleaseInputs();
752 DeleteObsoleteFiles();
753 }
754 delete c;
755
756 if (status.ok()) {
757 // Done
758 } else if (shutting_down_.load(std::memory_order_acquire)) {
759 // Ignore compaction errors found during shutting down
760 } else {
761 Log(options_.info_log, "Compaction error: %s", status.ToString().c_str());
762 }
763
764 if (is_manual) {
765 ManualCompaction* m = manual_compaction_;
766 if (!status.ok()) {
767 m->done = true;
768 }
769 if (!m->done) {
770 // We only compacted part of the requested range. Update *m
771 // to the range that is left to be compacted.
772 m->tmp_storage = manual_end;
773 m->begin = &m->tmp_storage;
774 }
775 manual_compaction_ = nullptr;
776 }
777 }
778
779 void DBImpl::CleanupCompaction(CompactionState* compact) {
780 mutex_.AssertHeld();
781 if (compact->builder != nullptr) {
782 // May happen if we get a shutdown call in the middle of compaction
783 compact->builder->Abandon();
784 delete compact->builder;
785 } else {
786 assert(compact->outfile == nullptr);
787 }
788 delete compact->outfile;
789 for (size_t i = 0; i < compact->outputs.size(); i++) {
790 const CompactionState::Output& out = compact->outputs[i];
791 pending_outputs_.erase(out.number);
792 }
793 delete compact;
794 }
795
796 Status DBImpl::OpenCompactionOutputFile(CompactionState* compact) {
797 assert(compact != nullptr);
798 assert(compact->builder == nullptr);
799 uint64_t file_number;
800 {
801 mutex_.Lock();
802 file_number = versions_->NewFileNumber();
803 pending_outputs_.insert(file_number);
804 CompactionState::Output out;
805 out.number = file_number;
806 out.file_size = 0;
807 out.smallest.Clear();
808 out.largest.Clear();
809 compact->outputs.push_back(out);
810 mutex_.Unlock();
811 }
812
813 // Make the output file
814 std::string fname = TableFileName(dbname_, file_number);
815 Status s = env_->NewWritableFile(fname, &compact->outfile);
816 if (s.ok()) {
817 compact->builder = new TableBuilder(options_, compact->outfile);
818 }
819 return s;
820 }
821
822 Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
823 Iterator* input) {
824 assert(compact != nullptr);
825 assert(compact->outfile != nullptr);
826 assert(compact->builder != nullptr);
827
828 const uint64_t output_number = compact->current_output()->number;
829 assert(output_number != 0);
830
831 // Check for iterator errors
832 Status s = input->status();
833 const uint64_t current_entries = compact->builder->NumEntries();
834 if (s.ok()) {
835 s = compact->builder->Finish();
836 } else {
837 compact->builder->Abandon();
838 }
839 const uint64_t current_bytes = compact->builder->FileSize();
840 compact->current_output()->file_size = current_bytes;
841 compact->total_bytes += current_bytes;
842 delete compact->builder;
843 compact->builder = nullptr;
844
845 // Finish and check for file errors
846 if (s.ok()) {
847 s = compact->outfile->Sync();
848 }
849 if (s.ok()) {
850 s = compact->outfile->Close();
851 }
852 delete compact->outfile;
853 compact->outfile = nullptr;
854
855 if (s.ok() && current_entries > 0) {
856 // Verify that the table is usable
857 Iterator* iter =
858 table_cache_->NewIterator(ReadOptions(), output_number, current_bytes);
859 s = iter->status();
860 delete iter;
861 if (s.ok()) {
862 Log(options_.info_log, "Generated table #%llu@%d: %lld keys, %lld bytes",
863 (unsigned long long)output_number, compact->compaction->level(),
864 (unsigned long long)current_entries,
865 (unsigned long long)current_bytes);
866 }
867 }
868 return s;
869 }
870
871 Status DBImpl::InstallCompactionResults(CompactionState* compact) {
872 mutex_.AssertHeld();
873 Log(options_.info_log, "Compacted %d@%d + %d@%d files => %lld bytes",
874 compact->compaction->num_input_files(0), compact->compaction->level(),
875 compact->compaction->num_input_files(1), compact->compaction->level() + 1,
876 static_cast<long long>(compact->total_bytes));
877
878 // Add compaction outputs
879 compact->compaction->AddInputDeletions(compact->compaction->edit());
880 const int level = compact->compaction->level();
881 for (size_t i = 0; i < compact->outputs.size(); i++) {
882 const CompactionState::Output& out = compact->outputs[i];
883 compact->compaction->edit()->AddFile(level + 1, out.number, out.file_size,
884 out.smallest, out.largest);
885 }
886 return versions_->LogAndApply(compact->compaction->edit(), &mutex_);
887 }
888
889 Status DBImpl::DoCompactionWork(CompactionState* compact) {
890 const uint64_t start_micros = env_->NowMicros();
891 int64_t imm_micros = 0; // Micros spent doing imm_ compactions
892
893 Log(options_.info_log, "Compacting %d@%d + %d@%d files",
894 compact->compaction->num_input_files(0), compact->compaction->level(),
895 compact->compaction->num_input_files(1),
896 compact->compaction->level() + 1);
897
898 assert(versions_->NumLevelFiles(compact->compaction->level()) > 0);
899 assert(compact->builder == nullptr);
900 assert(compact->outfile == nullptr);
901 if (snapshots_.empty()) {
902 compact->smallest_snapshot = versions_->LastSequence();
903 } else {
904 compact->smallest_snapshot = snapshots_.oldest()->sequence_number();
905 }
906
907 Iterator* input = versions_->MakeInputIterator(compact->compaction);
908
909 // Release mutex while we're actually doing the compaction work
910 mutex_.Unlock();
911
912 input->SeekToFirst();
913 Status status;
914 ParsedInternalKey ikey;
915 std::string current_user_key;
916 bool has_current_user_key = false;
917 SequenceNumber last_sequence_for_key = kMaxSequenceNumber;
918 while (input->Valid() && !shutting_down_.load(std::memory_order_acquire)) {
919 // Prioritize immutable compaction work
920 if (has_imm_.load(std::memory_order_relaxed)) {
921 const uint64_t imm_start = env_->NowMicros();
922 mutex_.Lock();
923 if (imm_ != nullptr) {
924 CompactMemTable();
925 // Wake up MakeRoomForWrite() if necessary.
926 background_work_finished_signal_.SignalAll();
927 }
928 mutex_.Unlock();
929 imm_micros += (env_->NowMicros() - imm_start);
930 }
931
932 Slice key = input->key();
933 if (compact->compaction->ShouldStopBefore(key) &&
934 compact->builder != nullptr) {
935 status = FinishCompactionOutputFile(compact, input);
936 if (!status.ok()) {
937 break;
938 }
939 }
940
941 // Handle key/value, add to state, etc.
942 bool drop = false;
943 if (!ParseInternalKey(key, &ikey)) {
944 // Do not hide error keys
945 current_user_key.clear();
946 has_current_user_key = false;
947 last_sequence_for_key = kMaxSequenceNumber;
948 } else {
949 if (!has_current_user_key ||
950 user_comparator()->Compare(ikey.user_key, Slice(current_user_key)) !=
951 0) {
952 // First occurrence of this user key
953 current_user_key.assign(ikey.user_key.data(), ikey.user_key.size());
954 has_current_user_key = true;
955 last_sequence_for_key = kMaxSequenceNumber;
956 }
957
958 if (last_sequence_for_key <= compact->smallest_snapshot) {
959 // Hidden by an newer entry for same user key
960 drop = true; // (A)
961 } else if (ikey.type == kTypeDeletion &&
962 ikey.sequence <= compact->smallest_snapshot &&
963 compact->compaction->IsBaseLevelForKey(ikey.user_key)) {
964 // For this user key:
965 // (1) there is no data in higher levels
966 // (2) data in lower levels will have larger sequence numbers
967 // (3) data in layers that are being compacted here and have
968 // smaller sequence numbers will be dropped in the next
969 // few iterations of this loop (by rule (A) above).
970 // Therefore this deletion marker is obsolete and can be dropped.
971 drop = true;
972 }
973
974 last_sequence_for_key = ikey.sequence;
975 }
976 #if 0
977 Log(options_.info_log,
978 " Compact: %s, seq %d, type: %d %d, drop: %d, is_base: %d, "
979 "%d smallest_snapshot: %d",
980 ikey.user_key.ToString().c_str(),
981 (int)ikey.sequence, ikey.type, kTypeValue, drop,
982 compact->compaction->IsBaseLevelForKey(ikey.user_key),
983 (int)last_sequence_for_key, (int)compact->smallest_snapshot);
984 #endif
985
986 if (!drop) {
987 // Open output file if necessary
988 if (compact->builder == nullptr) {
989 status = OpenCompactionOutputFile(compact);
990 if (!status.ok()) {
991 break;
992 }
993 }
994 if (compact->builder->NumEntries() == 0) {
995 compact->current_output()->smallest.DecodeFrom(key);
996 }
997 compact->current_output()->largest.DecodeFrom(key);
998 compact->builder->Add(key, input->value());
999
1000 // Close output file if it is big enough
1001 if (compact->builder->FileSize() >=
1002 compact->compaction->MaxOutputFileSize()) {
1003 status = FinishCompactionOutputFile(compact, input);
1004 if (!status.ok()) {
1005 break;
1006 }
1007 }
1008 }
1009
1010 input->Next();
1011 }
1012
1013 if (status.ok() && shutting_down_.load(std::memory_order_acquire)) {
1014 status = Status::IOError("Deleting DB during compaction");
1015 }
1016 if (status.ok() && compact->builder != nullptr) {
1017 status = FinishCompactionOutputFile(compact, input);
1018 }
1019 if (status.ok()) {
1020 status = input->status();
1021 }
1022 delete input;
1023 input = nullptr;
1024
1025 CompactionStats stats;
1026 stats.micros = env_->NowMicros() - start_micros - imm_micros;
1027 for (int which = 0; which < 2; which++) {
1028 for (int i = 0; i < compact->compaction->num_input_files(which); i++) {
1029 stats.bytes_read += compact->compaction->input(which, i)->file_size;
1030 }
1031 }
1032 for (size_t i = 0; i < compact->outputs.size(); i++) {
1033 stats.bytes_written += compact->outputs[i].file_size;
1034 }
1035
1036 mutex_.Lock();
1037 stats_[compact->compaction->level() + 1].Add(stats);
1038
1039 if (status.ok()) {
1040 status = InstallCompactionResults(compact);
1041 }
1042 if (!status.ok()) {
1043 RecordBackgroundError(status);
1044 }
1045 VersionSet::LevelSummaryStorage tmp;
1046 Log(options_.info_log, "compacted to: %s", versions_->LevelSummary(&tmp));
1047 return status;
1048 }
1049
1050 namespace {
1051
1052 struct IterState {
1053 port::Mutex* const mu;
1054 Version* const version GUARDED_BY(mu);
1055 MemTable* const mem GUARDED_BY(mu);
1056 MemTable* const imm GUARDED_BY(mu);
1057
1058 IterState(port::Mutex* mutex, MemTable* mem, MemTable* imm, Version* version)
1059 : mu(mutex), version(version), mem(mem), imm(imm) {}
1060 };
1061
1062 static void CleanupIteratorState(void* arg1, void* arg2) {
1063 IterState* state = reinterpret_cast<IterState*>(arg1);
1064 state->mu->Lock();
1065 state->mem->Unref();
1066 if (state->imm != nullptr) state->imm->Unref();
1067 state->version->Unref();
1068 state->mu->Unlock();
1069 delete state;
1070 }
1071
1072 } // anonymous namespace
1073
1074 Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
1075 SequenceNumber* latest_snapshot,
1076 uint32_t* seed) {
1077 mutex_.Lock();
1078 *latest_snapshot = versions_->LastSequence();
1079
1080 // Collect together all needed child iterators
1081 std::vector<Iterator*> list;
1082 list.push_back(mem_->NewIterator());
1083 mem_->Ref();
1084 if (imm_ != nullptr) {
1085 list.push_back(imm_->NewIterator());
1086 imm_->Ref();
1087 }
1088 versions_->current()->AddIterators(options, &list);
1089 Iterator* internal_iter =
1090 NewMergingIterator(&internal_comparator_, &list[0], list.size());
1091 versions_->current()->Ref();
1092
1093 IterState* cleanup = new IterState(&mutex_, mem_, imm_, versions_->current());
1094 internal_iter->RegisterCleanup(CleanupIteratorState, cleanup, nullptr);
1095
1096 *seed = ++seed_;
1097 mutex_.Unlock();
1098 return internal_iter;
1099 }
1100
1101 Iterator* DBImpl::TEST_NewInternalIterator() {
1102 SequenceNumber ignored;
1103 uint32_t ignored_seed;
1104 return NewInternalIterator(ReadOptions(), &ignored, &ignored_seed);
1105 }
1106
1107 int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes() {
1108 MutexLock l(&mutex_);
1109 return versions_->MaxNextLevelOverlappingBytes();
1110 }
1111
1112 Status DBImpl::Get(const ReadOptions& options, const Slice& key,
1113 std::string* value) {
1114 Status s;
1115 MutexLock l(&mutex_);
1116 SequenceNumber snapshot;
1117 if (options.snapshot != nullptr) {
1118 snapshot =
1119 static_cast<const SnapshotImpl*>(options.snapshot)->sequence_number();
1120 } else {
1121 snapshot = versions_->LastSequence();
1122 }
1123
1124 MemTable* mem = mem_;
1125 MemTable* imm = imm_;
1126 Version* current = versions_->current();
1127 mem->Ref();
1128 if (imm != nullptr) imm->Ref();
1129 current->Ref();
1130
1131 bool have_stat_update = false;
1132 Version::GetStats stats;
1133
1134 // Unlock while reading from files and memtables
1135 {
1136 mutex_.Unlock();
1137 // First look in the memtable, then in the immutable memtable (if any).
1138 LookupKey lkey(key, snapshot);
1139 if (mem->Get(lkey, value, &s)) {
1140 // Done
1141 } else if (imm != nullptr && imm->Get(lkey, value, &s)) {
1142 // Done
1143 } else {
1144 s = current->Get(options, lkey, value, &stats);
1145 have_stat_update = true;
1146 }
1147 mutex_.Lock();
1148 }
1149
1150 if (have_stat_update && current->UpdateStats(stats)) {
1151 MaybeScheduleCompaction();
1152 }
1153 mem->Unref();
1154 if (imm != nullptr) imm->Unref();
1155 current->Unref();
1156 return s;
1157 }
1158
1159 Iterator* DBImpl::NewIterator(const ReadOptions& options) {
1160 SequenceNumber latest_snapshot;
1161 uint32_t seed;
1162 Iterator* iter = NewInternalIterator(options, &latest_snapshot, &seed);
1163 return NewDBIterator(this, user_comparator(), iter,
1164 (options.snapshot != nullptr
1165 ? static_cast<const SnapshotImpl*>(options.snapshot)
1166 ->sequence_number()
1167 : latest_snapshot),
1168 seed);
1169 }
1170
1171 void DBImpl::RecordReadSample(Slice key) {
1172 MutexLock l(&mutex_);
1173 if (versions_->current()->RecordReadSample(key)) {
1174 MaybeScheduleCompaction();
1175 }
1176 }
1177
1178 const Snapshot* DBImpl::GetSnapshot() {
1179 MutexLock l(&mutex_);
1180 return snapshots_.New(versions_->LastSequence());
1181 }
1182
1183 void DBImpl::ReleaseSnapshot(const Snapshot* snapshot) {
1184 MutexLock l(&mutex_);
1185 snapshots_.Delete(static_cast<const SnapshotImpl*>(snapshot));
1186 }
1187
1188 // Convenience methods
1189 Status DBImpl::Put(const WriteOptions& o, const Slice& key, const Slice& val) {
1190 return DB::Put(o, key, val);
1191 }
1192
1193 Status DBImpl::Delete(const WriteOptions& options, const Slice& key) {
1194 return DB::Delete(options, key);
1195 }
1196
1197 Status DBImpl::Write(const WriteOptions& options, WriteBatch* updates) {
1198 Writer w(&mutex_);
1199 w.batch = updates;
1200 w.sync = options.sync;
1201 w.done = false;
1202
1203 MutexLock l(&mutex_);
1204 writers_.push_back(&w);
1205 while (!w.done && &w != writers_.front()) {
1206 w.cv.Wait();
1207 }
1208 if (w.done) {
1209 return w.status;
1210 }
1211
1212 // May temporarily unlock and wait.
1213 Status status = MakeRoomForWrite(updates == nullptr);
1214 uint64_t last_sequence = versions_->LastSequence();
1215 Writer* last_writer = &w;
1216 if (status.ok() && updates != nullptr) { // nullptr batch is for compactions
1217 WriteBatch* write_batch = BuildBatchGroup(&last_writer);
1218 WriteBatchInternal::SetSequence(write_batch, last_sequence + 1);
1219 last_sequence += WriteBatchInternal::Count(write_batch);
1220
1221 // Add to log and apply to memtable. We can release the lock
1222 // during this phase since &w is currently responsible for logging
1223 // and protects against concurrent loggers and concurrent writes
1224 // into mem_.
1225 {
1226 mutex_.Unlock();
1227 status = log_->AddRecord(WriteBatchInternal::Contents(write_batch));
1228 bool sync_error = false;
1229 if (status.ok() && options.sync) {
1230 status = logfile_->Sync();
1231 if (!status.ok()) {
1232 sync_error = true;
1233 }
1234 }
1235 if (status.ok()) {
1236 status = WriteBatchInternal::InsertInto(write_batch, mem_);
1237 }
1238 mutex_.Lock();
1239 if (sync_error) {
1240 // The state of the log file is indeterminate: the log record we
1241 // just added may or may not show up when the DB is re-opened.
1242 // So we force the DB into a mode where all future writes fail.
1243 RecordBackgroundError(status);
1244 }
1245 }
1246 if (write_batch == tmp_batch_) tmp_batch_->Clear();
1247
1248 versions_->SetLastSequence(last_sequence);
1249 }
1250
1251 while (true) {
1252 Writer* ready = writers_.front();
1253 writers_.pop_front();
1254 if (ready != &w) {
1255 ready->status = status;
1256 ready->done = true;
1257 ready->cv.Signal();
1258 }
1259 if (ready == last_writer) break;
1260 }
1261
1262 // Notify new head of write queue
1263 if (!writers_.empty()) {
1264 writers_.front()->cv.Signal();
1265 }
1266
1267 return status;
1268 }
1269
1270 // REQUIRES: Writer list must be non-empty
1271 // REQUIRES: First writer must have a non-null batch
1272 WriteBatch* DBImpl::BuildBatchGroup(Writer** last_writer) {
1273 mutex_.AssertHeld();
1274 assert(!writers_.empty());
1275 Writer* first = writers_.front();
1276 WriteBatch* result = first->batch;
1277 assert(result != nullptr);
1278
1279 size_t size = WriteBatchInternal::ByteSize(first->batch);
1280
1281 // Allow the group to grow up to a maximum size, but if the
1282 // original write is small, limit the growth so we do not slow
1283 // down the small write too much.
1284 size_t max_size = 1 << 20;
1285 if (size <= (128 << 10)) {
1286 max_size = size + (128 << 10);
1287 }
1288
1289 *last_writer = first;
1290 std::deque<Writer*>::iterator iter = writers_.begin();
1291 ++iter; // Advance past "first"
1292 for (; iter != writers_.end(); ++iter) {
1293 Writer* w = *iter;
1294 if (w->sync && !first->sync) {
1295 // Do not include a sync write into a batch handled by a non-sync write.
1296 break;
1297 }
1298
1299 if (w->batch != nullptr) {
1300 size += WriteBatchInternal::ByteSize(w->batch);
1301 if (size > max_size) {
1302 // Do not make batch too big
1303 break;
1304 }
1305
1306 // Append to *result
1307 if (result == first->batch) {
1308 // Switch to temporary batch instead of disturbing caller's batch
1309 result = tmp_batch_;
1310 assert(WriteBatchInternal::Count(result) == 0);
1311 WriteBatchInternal::Append(result, first->batch);
1312 }
1313 WriteBatchInternal::Append(result, w->batch);
1314 }
1315 *last_writer = w;
1316 }
1317 return result;
1318 }
1319
1320 // REQUIRES: mutex_ is held
1321 // REQUIRES: this thread is currently at the front of the writer queue
1322 Status DBImpl::MakeRoomForWrite(bool force) {
1323 mutex_.AssertHeld();
1324 assert(!writers_.empty());
1325 bool allow_delay = !force;
1326 Status s;
1327 while (true) {
1328 if (!bg_error_.ok()) {
1329 // Yield previous error
1330 s = bg_error_;
1331 break;
1332 } else if (allow_delay && versions_->NumLevelFiles(0) >=
1333 config::kL0_SlowdownWritesTrigger) {
1334 // We are getting close to hitting a hard limit on the number of
1335 // L0 files. Rather than delaying a single write by several
1336 // seconds when we hit the hard limit, start delaying each
1337 // individual write by 1ms to reduce latency variance. Also,
1338 // this delay hands over some CPU to the compaction thread in
1339 // case it is sharing the same core as the writer.
1340 mutex_.Unlock();
1341 env_->SleepForMicroseconds(1000);
1342 allow_delay = false; // Do not delay a single write more than once
1343 mutex_.Lock();
1344 } else if (!force &&
1345 (mem_->ApproximateMemoryUsage() <= options_.write_buffer_size)) {
1346 // There is room in current memtable
1347 break;
1348 } else if (imm_ != nullptr) {
1349 // We have filled up the current memtable, but the previous
1350 // one is still being compacted, so we wait.
1351 Log(options_.info_log, "Current memtable full; waiting...\n");
1352 background_work_finished_signal_.Wait();
1353 } else if (versions_->NumLevelFiles(0) >= config::kL0_StopWritesTrigger) {
1354 // There are too many level-0 files.
1355 Log(options_.info_log, "Too many L0 files; waiting...\n");
1356 background_work_finished_signal_.Wait();
1357 } else {
1358 // Attempt to switch to a new memtable and trigger compaction of old
1359 assert(versions_->PrevLogNumber() == 0);
1360 uint64_t new_log_number = versions_->NewFileNumber();
1361 WritableFile* lfile = nullptr;
1362 s = env_->NewWritableFile(LogFileName(dbname_, new_log_number), &lfile);
1363 if (!s.ok()) {
1364 // Avoid chewing through file number space in a tight loop.
1365 versions_->ReuseFileNumber(new_log_number);
1366 break;
1367 }
1368 delete log_;
1369 delete logfile_;
1370 logfile_ = lfile;
1371 logfile_number_ = new_log_number;
1372 log_ = new log::Writer(lfile);
1373 imm_ = mem_;
1374 has_imm_.store(true, std::memory_order_release);
1375 mem_ = new MemTable(internal_comparator_);
1376 mem_->Ref();
1377 force = false; // Do not force another compaction if have room
1378 MaybeScheduleCompaction();
1379 }
1380 }
1381 return s;
1382 }
1383
1384 bool DBImpl::GetProperty(const Slice& property, std::string* value) {
1385 value->clear();
1386
1387 MutexLock l(&mutex_);
1388 Slice in = property;
1389 Slice prefix("leveldb.");
1390 if (!in.starts_with(prefix)) return false;
1391 in.remove_prefix(prefix.size());
1392
1393 if (in.starts_with("num-files-at-level")) {
1394 in.remove_prefix(strlen("num-files-at-level"));
1395 uint64_t level;
1396 bool ok = ConsumeDecimalNumber(&in, &level) && in.empty();
1397 if (!ok || level >= config::kNumLevels) {
1398 return false;
1399 } else {
1400 char buf[100];
1401 snprintf(buf, sizeof(buf), "%d",
1402 versions_->NumLevelFiles(static_cast<int>(level)));
1403 *value = buf;
1404 return true;
1405 }
1406 } else if (in == "stats") {
1407 char buf[200];
1408 snprintf(buf, sizeof(buf),
1409 " Compactions\n"
1410 "Level Files Size(MB) Time(sec) Read(MB) Write(MB)\n"
1411 "--------------------------------------------------\n");
1412 value->append(buf);
1413 for (int level = 0; level < config::kNumLevels; level++) {
1414 int files = versions_->NumLevelFiles(level);
1415 if (stats_[level].micros > 0 || files > 0) {
1416 snprintf(buf, sizeof(buf), "%3d %8d %8.0f %9.0f %8.0f %9.0f\n", level,
1417 files, versions_->NumLevelBytes(level) / 1048576.0,
1418 stats_[level].micros / 1e6,
1419 stats_[level].bytes_read / 1048576.0,
1420 stats_[level].bytes_written / 1048576.0);
1421 value->append(buf);
1422 }
1423 }
1424 return true;
1425 } else if (in == "sstables") {
1426 *value = versions_->current()->DebugString();
1427 return true;
1428 } else if (in == "approximate-memory-usage") {
1429 size_t total_usage = options_.block_cache->TotalCharge();
1430 if (mem_) {
1431 total_usage += mem_->ApproximateMemoryUsage();
1432 }
1433 if (imm_) {
1434 total_usage += imm_->ApproximateMemoryUsage();
1435 }
1436 char buf[50];
1437 snprintf(buf, sizeof(buf), "%llu",
1438 static_cast<unsigned long long>(total_usage));
1439 value->append(buf);
1440 return true;
1441 }
1442
1443 return false;
1444 }
1445
1446 void DBImpl::GetApproximateSizes(const Range* range, int n, uint64_t* sizes) {
1447 // TODO(opt): better implementation
1448 MutexLock l(&mutex_);
1449 Version* v = versions_->current();
1450 v->Ref();
1451
1452 for (int i = 0; i < n; i++) {
1453 // Convert user_key into a corresponding internal key.
1454 InternalKey k1(range[i].start, kMaxSequenceNumber, kValueTypeForSeek);
1455 InternalKey k2(range[i].limit, kMaxSequenceNumber, kValueTypeForSeek);
1456 uint64_t start = versions_->ApproximateOffsetOf(v, k1);
1457 uint64_t limit = versions_->ApproximateOffsetOf(v, k2);
1458 sizes[i] = (limit >= start ? limit - start : 0);
1459 }
1460
1461 v->Unref();
1462 }
1463
1464 // Default implementations of convenience methods that subclasses of DB
1465 // can call if they wish
1466 Status DB::Put(const WriteOptions& opt, const Slice& key, const Slice& value) {
1467 WriteBatch batch;
1468 batch.Put(key, value);
1469 return Write(opt, &batch);
1470 }
1471
1472 Status DB::Delete(const WriteOptions& opt, const Slice& key) {
1473 WriteBatch batch;
1474 batch.Delete(key);
1475 return Write(opt, &batch);
1476 }
1477
1478 DB::~DB() = default;
1479
1480 Status DB::Open(const Options& options, const std::string& dbname, DB** dbptr) {
1481 *dbptr = nullptr;
1482
1483 DBImpl* impl = new DBImpl(options, dbname);
1484 impl->mutex_.Lock();
1485 VersionEdit edit;
1486 // Recover handles create_if_missing, error_if_exists
1487 bool save_manifest = false;
1488 Status s = impl->Recover(&edit, &save_manifest);
1489 if (s.ok() && impl->mem_ == nullptr) {
1490 // Create new log and a corresponding memtable.
1491 uint64_t new_log_number = impl->versions_->NewFileNumber();
1492 WritableFile* lfile;
1493 s = options.env->NewWritableFile(LogFileName(dbname, new_log_number),
1494 &lfile);
1495 if (s.ok()) {
1496 edit.SetLogNumber(new_log_number);
1497 impl->logfile_ = lfile;
1498 impl->logfile_number_ = new_log_number;
1499 impl->log_ = new log::Writer(lfile);
1500 impl->mem_ = new MemTable(impl->internal_comparator_);
1501 impl->mem_->Ref();
1502 }
1503 }
1504 if (s.ok() && save_manifest) {
1505 edit.SetPrevLogNumber(0); // No older logs needed after recovery.
1506 edit.SetLogNumber(impl->logfile_number_);
1507 s = impl->versions_->LogAndApply(&edit, &impl->mutex_);
1508 }
1509 if (s.ok()) {
1510 impl->DeleteObsoleteFiles();
1511 impl->MaybeScheduleCompaction();
1512 }
1513 impl->mutex_.Unlock();
1514 if (s.ok()) {
1515 assert(impl->mem_ != nullptr);
1516 *dbptr = impl;
1517 } else {
1518 delete impl;
1519 }
1520 return s;
1521 }
1522
1523 Snapshot::~Snapshot() = default;
1524
1525 Status DestroyDB(const std::string& dbname, const Options& options) {
1526 Env* env = options.env;
1527 std::vector<std::string> filenames;
1528 Status result = env->GetChildren(dbname, &filenames);
1529 if (!result.ok()) {
1530 // Ignore error in case directory does not exist
1531 return Status::OK();
1532 }
1533
1534 FileLock* lock;
1535 const std::string lockname = LockFileName(dbname);
1536 result = env->LockFile(lockname, &lock);
1537 if (result.ok()) {
1538 uint64_t number;
1539 FileType type;
1540 for (size_t i = 0; i < filenames.size(); i++) {
1541 if (ParseFileName(filenames[i], &number, &type) &&
1542 type != kDBLockFile) { // Lock file will be deleted at end
1543 Status del = env->DeleteFile(dbname + "/" + filenames[i]);
1544 if (result.ok() && !del.ok()) {
1545 result = del;
1546 }
1547 }
1548 }
1549 env->UnlockFile(lock); // Ignore error since state is already gone
1550 env->DeleteFile(lockname);
1551 env->DeleteDir(dbname); // Ignore error in case dir contains other files
1552 }
1553 return result;
1554 }
1555
1556 } // namespace leveldb
1557