version_set.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/version_set.h"
6
7 #include <stdio.h>
8
9 #include <algorithm>
10
11 #include "db/filename.h"
12 #include "db/log_reader.h"
13 #include "db/log_writer.h"
14 #include "db/memtable.h"
15 #include "db/table_cache.h"
16 #include "leveldb/env.h"
17 #include "leveldb/table_builder.h"
18 #include "table/merger.h"
19 #include "table/two_level_iterator.h"
20 #include "util/coding.h"
21 #include "util/logging.h"
22
23 namespace leveldb {
24
25 static size_t TargetFileSize(const Options* options) {
26 return options->max_file_size;
27 }
28
29 // Maximum bytes of overlaps in grandparent (i.e., level+2) before we
30 // stop building a single file in a level->level+1 compaction.
31 static int64_t MaxGrandParentOverlapBytes(const Options* options) {
32 return 10 * TargetFileSize(options);
33 }
34
35 // Maximum number of bytes in all compacted files. We avoid expanding
36 // the lower level file set of a compaction if it would make the
37 // total compaction cover more than this many bytes.
38 static int64_t ExpandedCompactionByteSizeLimit(const Options* options) {
39 return 25 * TargetFileSize(options);
40 }
41
42 static double MaxBytesForLevel(const Options* options, int level) {
43 // Note: the result for level zero is not really used since we set
44 // the level-0 compaction threshold based on number of files.
45
46 // Result for both level-0 and level-1
47 double result = 10. * 1048576.0;
48 while (level > 1) {
49 result *= 10;
50 level--;
51 }
52 return result;
53 }
54
55 static uint64_t MaxFileSizeForLevel(const Options* options, int level) {
56 // We could vary per level to reduce number of files?
57 return TargetFileSize(options);
58 }
59
60 static int64_t TotalFileSize(const std::vector<FileMetaData*>& files) {
61 int64_t sum = 0;
62 for (size_t i = 0; i < files.size(); i++) {
63 sum += files[i]->file_size;
64 }
65 return sum;
66 }
67
68 Version::~Version() {
69 assert(refs_ == 0);
70
71 // Remove from linked list
72 prev_->next_ = next_;
73 next_->prev_ = prev_;
74
75 // Drop references to files
76 for (int level = 0; level < config::kNumLevels; level++) {
77 for (size_t i = 0; i < files_[level].size(); i++) {
78 FileMetaData* f = files_[level][i];
79 assert(f->refs > 0);
80 f->refs--;
81 if (f->refs <= 0) {
82 delete f;
83 }
84 }
85 }
86 }
87
88 int FindFile(const InternalKeyComparator& icmp,
89 const std::vector<FileMetaData*>& files, const Slice& key) {
90 uint32_t left = 0;
91 uint32_t right = files.size();
92 while (left < right) {
93 uint32_t mid = (left + right) / 2;
94 const FileMetaData* f = files[mid];
95 if (icmp.InternalKeyComparator::Compare(f->largest.Encode(), key) < 0) {
96 // Key at "mid.largest" is < "target". Therefore all
97 // files at or before "mid" are uninteresting.
98 left = mid + 1;
99 } else {
100 // Key at "mid.largest" is >= "target". Therefore all files
101 // after "mid" are uninteresting.
102 right = mid;
103 }
104 }
105 return right;
106 }
107
108 static bool AfterFile(const Comparator* ucmp, const Slice* user_key,
109 const FileMetaData* f) {
110 // null user_key occurs before all keys and is therefore never after *f
111 return (user_key != nullptr &&
112 ucmp->Compare(*user_key, f->largest.user_key()) > 0);
113 }
114
115 static bool BeforeFile(const Comparator* ucmp, const Slice* user_key,
116 const FileMetaData* f) {
117 // null user_key occurs after all keys and is therefore never before *f
118 return (user_key != nullptr &&
119 ucmp->Compare(*user_key, f->smallest.user_key()) < 0);
120 }
121
122 bool SomeFileOverlapsRange(const InternalKeyComparator& icmp,
123 bool disjoint_sorted_files,
124 const std::vector<FileMetaData*>& files,
125 const Slice* smallest_user_key,
126 const Slice* largest_user_key) {
127 const Comparator* ucmp = icmp.user_comparator();
128 if (!disjoint_sorted_files) {
129 // Need to check against all files
130 for (size_t i = 0; i < files.size(); i++) {
131 const FileMetaData* f = files[i];
132 if (AfterFile(ucmp, smallest_user_key, f) ||
133 BeforeFile(ucmp, largest_user_key, f)) {
134 // No overlap
135 } else {
136 return true; // Overlap
137 }
138 }
139 return false;
140 }
141
142 // Binary search over file list
143 uint32_t index = 0;
144 if (smallest_user_key != nullptr) {
145 // Find the earliest possible internal key for smallest_user_key
146 InternalKey small_key(*smallest_user_key, kMaxSequenceNumber,
147 kValueTypeForSeek);
148 index = FindFile(icmp, files, small_key.Encode());
149 }
150
151 if (index >= files.size()) {
152 // beginning of range is after all files, so no overlap.
153 return false;
154 }
155
156 return !BeforeFile(ucmp, largest_user_key, files[index]);
157 }
158
159 // An internal iterator. For a given version/level pair, yields
160 // information about the files in the level. For a given entry, key()
161 // is the largest key that occurs in the file, and value() is an
162 // 16-byte value containing the file number and file size, both
163 // encoded using EncodeFixed64.
164 class Version::LevelFileNumIterator : public Iterator {
165 public:
166 LevelFileNumIterator(const InternalKeyComparator& icmp,
167 const std::vector<FileMetaData*>* flist)
168 : icmp_(icmp), flist_(flist), index_(flist->size()) { // Marks as invalid
169 }
170 bool Valid() const override { return index_ < flist_->size(); }
171 void Seek(const Slice& target) override {
172 index_ = FindFile(icmp_, *flist_, target);
173 }
174 void SeekToFirst() override { index_ = 0; }
175 void SeekToLast() override {
176 index_ = flist_->empty() ? 0 : flist_->size() - 1;
177 }
178 void Next() override {
179 assert(Valid());
180 index_++;
181 }
182 void Prev() override {
183 assert(Valid());
184 if (index_ == 0) {
185 index_ = flist_->size(); // Marks as invalid
186 } else {
187 index_--;
188 }
189 }
190 Slice key() const override {
191 assert(Valid());
192 return (*flist_)[index_]->largest.Encode();
193 }
194 Slice value() const override {
195 assert(Valid());
196 EncodeFixed64(value_buf_, (*flist_)[index_]->number);
197 EncodeFixed64(value_buf_ + 8, (*flist_)[index_]->file_size);
198 return Slice(value_buf_, sizeof(value_buf_));
199 }
200 Status status() const override { return Status::OK(); }
201
202 private:
203 const InternalKeyComparator icmp_;
204 const std::vector<FileMetaData*>* const flist_;
205 uint32_t index_;
206
207 // Backing store for value(). Holds the file number and size.
208 mutable char value_buf_[16];
209 };
210
211 static Iterator* GetFileIterator(void* arg, const ReadOptions& options,
212 const Slice& file_value) {
213 TableCache* cache = reinterpret_cast<TableCache*>(arg);
214 if (file_value.size() != 16) {
215 return NewErrorIterator(
216 Status::Corruption("FileReader invoked with unexpected value"));
217 } else {
218 return cache->NewIterator(options, DecodeFixed64(file_value.data()),
219 DecodeFixed64(file_value.data() + 8));
220 }
221 }
222
223 Iterator* Version::NewConcatenatingIterator(const ReadOptions& options,
224 int level) const {
225 return NewTwoLevelIterator(
226 new LevelFileNumIterator(vset_->icmp_, &files_[level]), &GetFileIterator,
227 vset_->table_cache_, options);
228 }
229
230 void Version::AddIterators(const ReadOptions& options,
231 std::vector<Iterator*>* iters) {
232 // Merge all level zero files together since they may overlap
233 for (size_t i = 0; i < files_[0].size(); i++) {
234 iters->push_back(vset_->table_cache_->NewIterator(
235 options, files_[0][i]->number, files_[0][i]->file_size));
236 }
237
238 // For levels > 0, we can use a concatenating iterator that sequentially
239 // walks through the non-overlapping files in the level, opening them
240 // lazily.
241 for (int level = 1; level < config::kNumLevels; level++) {
242 if (!files_[level].empty()) {
243 iters->push_back(NewConcatenatingIterator(options, level));
244 }
245 }
246 }
247
248 // Callback from TableCache::Get()
249 namespace {
250 enum SaverState {
251 kNotFound,
252 kFound,
253 kDeleted,
254 kCorrupt,
255 };
256 struct Saver {
257 SaverState state;
258 const Comparator* ucmp;
259 Slice user_key;
260 std::string* value;
261 };
262 } // namespace
263 static void SaveValue(void* arg, const Slice& ikey, const Slice& v) {
264 Saver* s = reinterpret_cast<Saver*>(arg);
265 ParsedInternalKey parsed_key;
266 if (!ParseInternalKey(ikey, &parsed_key)) {
267 s->state = kCorrupt;
268 } else {
269 if (s->ucmp->Compare(parsed_key.user_key, s->user_key) == 0) {
270 s->state = (parsed_key.type == kTypeValue) ? kFound : kDeleted;
271 if (s->state == kFound) {
272 s->value->assign(v.data(), v.size());
273 }
274 }
275 }
276 }
277
278 static bool NewestFirst(FileMetaData* a, FileMetaData* b) {
279 return a->number > b->number;
280 }
281
282 void Version::ForEachOverlapping(Slice user_key, Slice internal_key, void* arg,
283 bool (*func)(void*, int, FileMetaData*)) {
284 const Comparator* ucmp = vset_->icmp_.user_comparator();
285
286 // Search level-0 in order from newest to oldest.
287 std::vector<FileMetaData*> tmp;
288 tmp.reserve(files_[0].size());
289 for (uint32_t i = 0; i < files_[0].size(); i++) {
290 FileMetaData* f = files_[0][i];
291 if (ucmp->Compare(user_key, f->smallest.user_key()) >= 0 &&
292 ucmp->Compare(user_key, f->largest.user_key()) <= 0) {
293 tmp.push_back(f);
294 }
295 }
296 if (!tmp.empty()) {
297 std::sort(tmp.begin(), tmp.end(), NewestFirst);
298 for (uint32_t i = 0; i < tmp.size(); i++) {
299 if (!(*func)(arg, 0, tmp[i])) {
300 return;
301 }
302 }
303 }
304
305 // Search other levels.
306 for (int level = 1; level < config::kNumLevels; level++) {
307 size_t num_files = files_[level].size();
308 if (num_files == 0) continue;
309
310 // Binary search to find earliest index whose largest key >= internal_key.
311 uint32_t index = FindFile(vset_->icmp_, files_[level], internal_key);
312 if (index < num_files) {
313 FileMetaData* f = files_[level][index];
314 if (ucmp->Compare(user_key, f->smallest.user_key()) < 0) {
315 // All of "f" is past any data for user_key
316 } else {
317 if (!(*func)(arg, level, f)) {
318 return;
319 }
320 }
321 }
322 }
323 }
324
325 Status Version::Get(const ReadOptions& options, const LookupKey& k,
326 std::string* value, GetStats* stats) {
327 stats->seek_file = nullptr;
328 stats->seek_file_level = -1;
329
330 struct State {
331 Saver saver;
332 GetStats* stats;
333 const ReadOptions* options;
334 Slice ikey;
335 FileMetaData* last_file_read;
336 int last_file_read_level;
337
338 VersionSet* vset;
339 Status s;
340 bool found;
341
342 static bool Match(void* arg, int level, FileMetaData* f) {
343 State* state = reinterpret_cast<State*>(arg);
344
345 if (state->stats->seek_file == nullptr &&
346 state->last_file_read != nullptr) {
347 // We have had more than one seek for this read. Charge the 1st file.
348 state->stats->seek_file = state->last_file_read;
349 state->stats->seek_file_level = state->last_file_read_level;
350 }
351
352 state->last_file_read = f;
353 state->last_file_read_level = level;
354
355 state->s = state->vset->table_cache_->Get(*state->options, f->number,
356 f->file_size, state->ikey,
357 &state->saver, SaveValue);
358 if (!state->s.ok()) {
359 state->found = true;
360 return false;
361 }
362 switch (state->saver.state) {
363 case kNotFound:
364 return true; // Keep searching in other files
365 case kFound:
366 state->found = true;
367 return false;
368 case kDeleted:
369 return false;
370 case kCorrupt:
371 state->s =
372 Status::Corruption("corrupted key for ", state->saver.user_key);
373 state->found = true;
374 return false;
375 }
376
377 // Not reached. Added to avoid false compilation warnings of
378 // "control reaches end of non-void function".
379 return false;
380 }
381 };
382
383 State state;
384 state.found = false;
385 state.stats = stats;
386 state.last_file_read = nullptr;
387 state.last_file_read_level = -1;
388
389 state.options = &options;
390 state.ikey = k.internal_key();
391 state.vset = vset_;
392
393 state.saver.state = kNotFound;
394 state.saver.ucmp = vset_->icmp_.user_comparator();
395 state.saver.user_key = k.user_key();
396 state.saver.value = value;
397
398 ForEachOverlapping(state.saver.user_key, state.ikey, &state, &State::Match);
399
400 return state.found ? state.s : Status::NotFound(Slice());
401 }
402
403 bool Version::UpdateStats(const GetStats& /*stats*/) {
404 // Disable automatic compactions triggered by read seek counters.
405 // The heuristic was tuned for expensive random seeks and can create
406 // severe write amplification on large random-key databases.
407 // Size and manual compactions still run.
408 return false;
409 }
410
411 bool Version::RecordReadSample(Slice internal_key) {
412 ParsedInternalKey ikey;
413 if (!ParseInternalKey(internal_key, &ikey)) {
414 return false;
415 }
416
417 struct State {
418 GetStats stats; // Holds first matching file
419 int matches;
420
421 static bool Match(void* arg, int level, FileMetaData* f) {
422 State* state = reinterpret_cast<State*>(arg);
423 state->matches++;
424 if (state->matches == 1) {
425 // Remember first match.
426 state->stats.seek_file = f;
427 state->stats.seek_file_level = level;
428 }
429 // We can stop iterating once we have a second match.
430 return state->matches < 2;
431 }
432 };
433
434 State state;
435 state.matches = 0;
436 ForEachOverlapping(ikey.user_key, internal_key, &state, &State::Match);
437
438 // Must have at least two matches since we want to merge across
439 // files. But what if we have a single file that contains many
440 // overwrites and deletions? Should we have another mechanism for
441 // finding such files?
442 if (state.matches >= 2) {
443 // 1MB cost is about 1 seek (see comment in Builder::Apply).
444 return UpdateStats(state.stats);
445 }
446 return false;
447 }
448
449 void Version::Ref() { ++refs_; }
450
451 void Version::Unref() {
452 assert(this != &vset_->dummy_versions_);
453 assert(refs_ >= 1);
454 --refs_;
455 if (refs_ == 0) {
456 delete this;
457 }
458 }
459
460 bool Version::OverlapInLevel(int level, const Slice* smallest_user_key,
461 const Slice* largest_user_key) {
462 return SomeFileOverlapsRange(vset_->icmp_, (level > 0), files_[level],
463 smallest_user_key, largest_user_key);
464 }
465
466 int Version::PickLevelForMemTableOutput(const Slice& smallest_user_key,
467 const Slice& largest_user_key) {
468 int level = 0;
469 if (!OverlapInLevel(0, &smallest_user_key, &largest_user_key)) {
470 // Push to next level if there is no overlap in next level,
471 // and the #bytes overlapping in the level after that are limited.
472 InternalKey start(smallest_user_key, kMaxSequenceNumber, kValueTypeForSeek);
473 InternalKey limit(largest_user_key, 0, static_cast<ValueType>(0));
474 std::vector<FileMetaData*> overlaps;
475 while (level < config::kMaxMemCompactLevel) {
476 if (OverlapInLevel(level + 1, &smallest_user_key, &largest_user_key)) {
477 break;
478 }
479 if (level + 2 < config::kNumLevels) {
480 // Check that file does not overlap too many grandparent bytes.
481 GetOverlappingInputs(level + 2, &start, &limit, &overlaps);
482 const int64_t sum = TotalFileSize(overlaps);
483 if (sum > MaxGrandParentOverlapBytes(vset_->options_)) {
484 break;
485 }
486 }
487 level++;
488 }
489 }
490 return level;
491 }
492
493 // Store in "*inputs" all files in "level" that overlap [begin,end]
494 void Version::GetOverlappingInputs(int level, const InternalKey* begin,
495 const InternalKey* end,
496 std::vector<FileMetaData*>* inputs) {
497 assert(level >= 0);
498 assert(level < config::kNumLevels);
499 inputs->clear();
500 Slice user_begin, user_end;
501 if (begin != nullptr) {
502 user_begin = begin->user_key();
503 }
504 if (end != nullptr) {
505 user_end = end->user_key();
506 }
507 const Comparator* user_cmp = vset_->icmp_.user_comparator();
508 for (size_t i = 0; i < files_[level].size();) {
509 FileMetaData* f = files_[level][i++];
510 const Slice file_start = f->smallest.user_key();
511 const Slice file_limit = f->largest.user_key();
512 if (begin != nullptr && user_cmp->Compare(file_limit, user_begin) < 0) {
513 // "f" is completely before specified range; skip it
514 } else if (end != nullptr && user_cmp->Compare(file_start, user_end) > 0) {
515 // "f" is completely after specified range; skip it
516 } else {
517 inputs->push_back(f);
518 if (level == 0) {
519 // Level-0 files may overlap each other. So check if the newly
520 // added file has expanded the range. If so, restart search.
521 if (begin != nullptr && user_cmp->Compare(file_start, user_begin) < 0) {
522 user_begin = file_start;
523 inputs->clear();
524 i = 0;
525 } else if (end != nullptr &&
526 user_cmp->Compare(file_limit, user_end) > 0) {
527 user_end = file_limit;
528 inputs->clear();
529 i = 0;
530 }
531 }
532 }
533 }
534 }
535
536 std::string Version::DebugString() const {
537 std::string r;
538 for (int level = 0; level < config::kNumLevels; level++) {
539 // E.g.,
540 // --- level 1 ---
541 // 17:123['a' .. 'd']
542 // 20:43['e' .. 'g']
543 r.append("--- level ");
544 AppendNumberTo(&r, level);
545 r.append(" ---\n");
546 const std::vector<FileMetaData*>& files = files_[level];
547 for (size_t i = 0; i < files.size(); i++) {
548 r.push_back(' ');
549 AppendNumberTo(&r, files[i]->number);
550 r.push_back(':');
551 AppendNumberTo(&r, files[i]->file_size);
552 r.append("[");
553 r.append(files[i]->smallest.DebugString());
554 r.append(" .. ");
555 r.append(files[i]->largest.DebugString());
556 r.append("]\n");
557 }
558 }
559 return r;
560 }
561
562 // A helper class so we can efficiently apply a whole sequence
563 // of edits to a particular state without creating intermediate
564 // Versions that contain full copies of the intermediate state.
565 class VersionSet::Builder {
566 private:
567 // Helper to sort by v->files_[file_number].smallest
568 struct BySmallestKey {
569 const InternalKeyComparator* internal_comparator;
570
571 bool operator()(FileMetaData* f1, FileMetaData* f2) const {
572 int r = internal_comparator->Compare(f1->smallest, f2->smallest);
573 if (r != 0) {
574 return (r < 0);
575 } else {
576 // Break ties by file number
577 return (f1->number < f2->number);
578 }
579 }
580 };
581
582 typedef std::set<FileMetaData*, BySmallestKey> FileSet;
583 struct LevelState {
584 std::set<uint64_t> deleted_files;
585 FileSet* added_files;
586 };
587
588 VersionSet* vset_;
589 Version* base_;
590 LevelState levels_[config::kNumLevels];
591
592 public:
593 // Initialize a builder with the files from *base and other info from *vset
594 Builder(VersionSet* vset, Version* base) : vset_(vset), base_(base) {
595 base_->Ref();
596 BySmallestKey cmp;
597 cmp.internal_comparator = &vset_->icmp_;
598 for (int level = 0; level < config::kNumLevels; level++) {
599 levels_[level].added_files = new FileSet(cmp);
600 }
601 }
602
603 ~Builder() {
604 for (int level = 0; level < config::kNumLevels; level++) {
605 const FileSet* added = levels_[level].added_files;
606 std::vector<FileMetaData*> to_unref;
607 to_unref.reserve(added->size());
608 for (FileSet::const_iterator it = added->begin(); it != added->end();
609 ++it) {
610 to_unref.push_back(*it);
611 }
612 delete added;
613 for (uint32_t i = 0; i < to_unref.size(); i++) {
614 FileMetaData* f = to_unref[i];
615 f->refs--;
616 if (f->refs <= 0) {
617 delete f;
618 }
619 }
620 }
621 base_->Unref();
622 }
623
624 // Apply all of the edits in *edit to the current state.
625 void Apply(VersionEdit* edit) {
626 // Update compaction pointers
627 for (size_t i = 0; i < edit->compact_pointers_.size(); i++) {
628 const int level = edit->compact_pointers_[i].first;
629 vset_->compact_pointer_[level] =
630 edit->compact_pointers_[i].second.Encode().ToString();
631 }
632
633 // Delete files
634 for (const auto& deleted_file_set_kvp : edit->deleted_files_) {
635 const int level = deleted_file_set_kvp.first;
636 const uint64_t number = deleted_file_set_kvp.second;
637 levels_[level].deleted_files.insert(number);
638 }
639
640 // Add new files
641 for (size_t i = 0; i < edit->new_files_.size(); i++) {
642 const int level = edit->new_files_[i].first;
643 FileMetaData* f = new FileMetaData(edit->new_files_[i].second);
644 f->refs = 1;
645
646 // We arrange to automatically compact this file after
647 // a certain number of seeks. Let's assume:
648 // (1) One seek costs 10ms
649 // (2) Writing or reading 1MB costs 10ms (100MB/s)
650 // (3) A compaction of 1MB does 25MB of IO:
651 // 1MB read from this level
652 // 10-12MB read from next level (boundaries may be misaligned)
653 // 10-12MB written to next level
654 // This implies that 25 seeks cost the same as the compaction
655 // of 1MB of data. I.e., one seek costs approximately the
656 // same as the compaction of 40KB of data. We are a little
657 // conservative and allow approximately one seek for every 16KB
658 // of data before triggering a compaction.
659 //
660 // Note: seek compactions are disabled. See Version::UpdateStats.
661 f->allowed_seeks = static_cast<int>((f->file_size / 16384U));
662 if (f->allowed_seeks < 100) f->allowed_seeks = 100;
663
664 levels_[level].deleted_files.erase(f->number);
665 levels_[level].added_files->insert(f);
666 }
667 }
668
669 // Save the current state in *v.
670 void SaveTo(Version* v) {
671 BySmallestKey cmp;
672 cmp.internal_comparator = &vset_->icmp_;
673 for (int level = 0; level < config::kNumLevels; level++) {
674 // Merge the set of added files with the set of pre-existing files.
675 // Drop any deleted files. Store the result in *v.
676 const std::vector<FileMetaData*>& base_files = base_->files_[level];
677 std::vector<FileMetaData*>::const_iterator base_iter = base_files.begin();
678 std::vector<FileMetaData*>::const_iterator base_end = base_files.end();
679 const FileSet* added_files = levels_[level].added_files;
680 v->files_[level].reserve(base_files.size() + added_files->size());
681 for (const auto& added_file : *added_files) {
682 // Add all smaller files listed in base_
683 for (std::vector<FileMetaData*>::const_iterator bpos =
684 std::upper_bound(base_iter, base_end, added_file, cmp);
685 base_iter != bpos; ++base_iter) {
686 MaybeAddFile(v, level, *base_iter);
687 }
688
689 MaybeAddFile(v, level, added_file);
690 }
691
692 // Add remaining base files
693 for (; base_iter != base_end; ++base_iter) {
694 MaybeAddFile(v, level, *base_iter);
695 }
696
697 #ifndef NDEBUG
698 // Make sure there is no overlap in levels > 0
699 if (level > 0) {
700 for (uint32_t i = 1; i < v->files_[level].size(); i++) {
701 const InternalKey& prev_end = v->files_[level][i - 1]->largest;
702 const InternalKey& this_begin = v->files_[level][i]->smallest;
703 if (vset_->icmp_.Compare(prev_end, this_begin) >= 0) {
704 fprintf(stderr, "overlapping ranges in same level %s vs. %s\n",
705 prev_end.DebugString().c_str(),
706 this_begin.DebugString().c_str());
707 abort();
708 }
709 }
710 }
711 #endif
712 }
713 }
714
715 void MaybeAddFile(Version* v, int level, FileMetaData* f) {
716 if (levels_[level].deleted_files.count(f->number) > 0) {
717 // File is deleted: do nothing
718 } else {
719 std::vector<FileMetaData*>* files = &v->files_[level];
720 if (level > 0 && !files->empty()) {
721 // Must not overlap
722 assert(vset_->icmp_.Compare((*files)[files->size() - 1]->largest,
723 f->smallest) < 0);
724 }
725 f->refs++;
726 files->push_back(f);
727 }
728 }
729 };
730
731 VersionSet::VersionSet(const std::string& dbname, const Options* options,
732 TableCache* table_cache,
733 const InternalKeyComparator* cmp)
734 : env_(options->env),
735 dbname_(dbname),
736 options_(options),
737 table_cache_(table_cache),
738 icmp_(*cmp),
739 next_file_number_(2),
740 manifest_file_number_(0), // Filled by Recover()
741 last_sequence_(0),
742 log_number_(0),
743 prev_log_number_(0),
744 descriptor_file_(nullptr),
745 descriptor_log_(nullptr),
746 dummy_versions_(this),
747 current_(nullptr) {
748 AppendVersion(new Version(this));
749 }
750
751 VersionSet::~VersionSet() {
752 current_->Unref();
753 assert(dummy_versions_.next_ == &dummy_versions_); // List must be empty
754 delete descriptor_log_;
755 delete descriptor_file_;
756 }
757
758 void VersionSet::AppendVersion(Version* v) {
759 // Make "v" current
760 assert(v->refs_ == 0);
761 assert(v != current_);
762 if (current_ != nullptr) {
763 current_->Unref();
764 }
765 current_ = v;
766 v->Ref();
767
768 // Append to linked list
769 v->prev_ = dummy_versions_.prev_;
770 v->next_ = &dummy_versions_;
771 v->prev_->next_ = v;
772 v->next_->prev_ = v;
773 }
774
775 Status VersionSet::LogAndApply(VersionEdit* edit, port::Mutex* mu) {
776 if (edit->has_log_number_) {
777 assert(edit->log_number_ >= log_number_);
778 assert(edit->log_number_ < next_file_number_);
779 } else {
780 edit->SetLogNumber(log_number_);
781 }
782
783 if (!edit->has_prev_log_number_) {
784 edit->SetPrevLogNumber(prev_log_number_);
785 }
786
787 edit->SetNextFile(next_file_number_);
788 edit->SetLastSequence(last_sequence_);
789
790 Version* v = new Version(this);
791 {
792 Builder builder(this, current_);
793 builder.Apply(edit);
794 builder.SaveTo(v);
795 }
796 Finalize(v);
797
798 // Initialize new descriptor log file if necessary by creating
799 // a temporary file that contains a snapshot of the current version.
800 std::string new_manifest_file;
801 Status s;
802 if (descriptor_log_ == nullptr) {
803 // No reason to unlock *mu here since we only hit this path in the
804 // first call to LogAndApply (when opening the database).
805 assert(descriptor_file_ == nullptr);
806 new_manifest_file = DescriptorFileName(dbname_, manifest_file_number_);
807 edit->SetNextFile(next_file_number_);
808 s = env_->NewWritableFile(new_manifest_file, &descriptor_file_);
809 if (s.ok()) {
810 descriptor_log_ = new log::Writer(descriptor_file_);
811 s = WriteSnapshot(descriptor_log_);
812 }
813 }
814
815 // Unlock during expensive MANIFEST log write
816 {
817 mu->Unlock();
818
819 // Write new record to MANIFEST log
820 if (s.ok()) {
821 std::string record;
822 edit->EncodeTo(&record);
823 s = descriptor_log_->AddRecord(record);
824 if (s.ok()) {
825 s = descriptor_file_->Sync();
826 }
827 if (!s.ok()) {
828 Log(options_->info_log, "MANIFEST write: %s\n", s.ToString().c_str());
829 }
830 }
831
832 // If we just created a new descriptor file, install it by writing a
833 // new CURRENT file that points to it.
834 if (s.ok() && !new_manifest_file.empty()) {
835 s = SetCurrentFile(env_, dbname_, manifest_file_number_);
836 }
837
838 mu->Lock();
839 }
840
841 // Install the new version
842 if (s.ok()) {
843 AppendVersion(v);
844 log_number_ = edit->log_number_;
845 prev_log_number_ = edit->prev_log_number_;
846 } else {
847 delete v;
848 if (!new_manifest_file.empty()) {
849 delete descriptor_log_;
850 delete descriptor_file_;
851 descriptor_log_ = nullptr;
852 descriptor_file_ = nullptr;
853 env_->DeleteFile(new_manifest_file);
854 }
855 }
856
857 return s;
858 }
859
860 Status VersionSet::Recover(bool* save_manifest) {
861 struct LogReporter : public log::Reader::Reporter {
862 Status* status;
863 void Corruption(size_t bytes, const Status& s) override {
864 if (this->status->ok()) *this->status = s;
865 }
866 };
867
868 // Read "CURRENT" file, which contains a pointer to the current manifest file
869 std::string current;
870 Status s = ReadFileToString(env_, CurrentFileName(dbname_), ¤t);
871 if (!s.ok()) {
872 return s;
873 }
874 if (current.empty() || current[current.size() - 1] != '\n') {
875 return Status::Corruption("CURRENT file does not end with newline");
876 }
877 current.resize(current.size() - 1);
878
879 std::string dscname = dbname_ + "/" + current;
880 SequentialFile* file;
881 s = env_->NewSequentialFile(dscname, &file);
882 if (!s.ok()) {
883 if (s.IsNotFound()) {
884 return Status::Corruption("CURRENT points to a non-existent file",
885 s.ToString());
886 }
887 return s;
888 }
889
890 bool have_log_number = false;
891 bool have_prev_log_number = false;
892 bool have_next_file = false;
893 bool have_last_sequence = false;
894 uint64_t next_file = 0;
895 uint64_t last_sequence = 0;
896 uint64_t log_number = 0;
897 uint64_t prev_log_number = 0;
898 Builder builder(this, current_);
899
900 {
901 LogReporter reporter;
902 reporter.status = &s;
903 log::Reader reader(file, &reporter, true /*checksum*/,
904 0 /*initial_offset*/);
905 Slice record;
906 std::string scratch;
907 while (reader.ReadRecord(&record, &scratch) && s.ok()) {
908 VersionEdit edit;
909 s = edit.DecodeFrom(record);
910 if (s.ok()) {
911 if (edit.has_comparator_ &&
912 edit.comparator_ != icmp_.user_comparator()->Name()) {
913 s = Status::InvalidArgument(
914 edit.comparator_ + " does not match existing comparator ",
915 icmp_.user_comparator()->Name());
916 }
917 }
918
919 if (s.ok()) {
920 builder.Apply(&edit);
921 }
922
923 if (edit.has_log_number_) {
924 log_number = edit.log_number_;
925 have_log_number = true;
926 }
927
928 if (edit.has_prev_log_number_) {
929 prev_log_number = edit.prev_log_number_;
930 have_prev_log_number = true;
931 }
932
933 if (edit.has_next_file_number_) {
934 next_file = edit.next_file_number_;
935 have_next_file = true;
936 }
937
938 if (edit.has_last_sequence_) {
939 last_sequence = edit.last_sequence_;
940 have_last_sequence = true;
941 }
942 }
943 }
944 delete file;
945 file = nullptr;
946
947 if (s.ok()) {
948 if (!have_next_file) {
949 s = Status::Corruption("no meta-nextfile entry in descriptor");
950 } else if (!have_log_number) {
951 s = Status::Corruption("no meta-lognumber entry in descriptor");
952 } else if (!have_last_sequence) {
953 s = Status::Corruption("no last-sequence-number entry in descriptor");
954 }
955
956 if (!have_prev_log_number) {
957 prev_log_number = 0;
958 }
959
960 MarkFileNumberUsed(prev_log_number);
961 MarkFileNumberUsed(log_number);
962 }
963
964 if (s.ok()) {
965 Version* v = new Version(this);
966 builder.SaveTo(v);
967 // Install recovered version
968 Finalize(v);
969 AppendVersion(v);
970 manifest_file_number_ = next_file;
971 next_file_number_ = next_file + 1;
972 last_sequence_ = last_sequence;
973 log_number_ = log_number;
974 prev_log_number_ = prev_log_number;
975
976 // See if we can reuse the existing MANIFEST file.
977 if (ReuseManifest(dscname, current)) {
978 // No need to save new manifest
979 } else {
980 *save_manifest = true;
981 }
982 }
983
984 return s;
985 }
986
987 bool VersionSet::ReuseManifest(const std::string& dscname,
988 const std::string& dscbase) {
989 if (!options_->reuse_logs) {
990 return false;
991 }
992 FileType manifest_type;
993 uint64_t manifest_number;
994 uint64_t manifest_size = 0;
995 if (!ParseFileName(dscbase, &manifest_number, &manifest_type) ||
996 manifest_type != kDescriptorFile ||
997 !env_->GetFileSize(dscname, &manifest_size).ok() ||
998 // Make new compacted MANIFEST if old one is too big
999 manifest_size >= TargetFileSize(options_)) {
1000 return false;
1001 }
1002
1003 assert(descriptor_file_ == nullptr);
1004 assert(descriptor_log_ == nullptr);
1005 Status r = env_->NewAppendableFile(dscname, &descriptor_file_);
1006 if (!r.ok()) {
1007 Log(options_->info_log, "Reuse MANIFEST: %s\n", r.ToString().c_str());
1008 assert(descriptor_file_ == nullptr);
1009 return false;
1010 }
1011
1012 Log(options_->info_log, "Reusing MANIFEST %s\n", dscname.c_str());
1013 descriptor_log_ = new log::Writer(descriptor_file_, manifest_size);
1014 manifest_file_number_ = manifest_number;
1015 return true;
1016 }
1017
1018 void VersionSet::MarkFileNumberUsed(uint64_t number) {
1019 if (next_file_number_ <= number) {
1020 next_file_number_ = number + 1;
1021 }
1022 }
1023
1024 void VersionSet::Finalize(Version* v) {
1025 // Precomputed best level for next compaction
1026 int best_level = -1;
1027 double best_score = -1;
1028
1029 for (int level = 0; level < config::kNumLevels - 1; level++) {
1030 double score;
1031 if (level == 0) {
1032 // We treat level-0 specially by bounding the number of files
1033 // instead of number of bytes for two reasons:
1034 //
1035 // (1) With larger write-buffer sizes, it is nice not to do too
1036 // many level-0 compactions.
1037 //
1038 // (2) The files in level-0 are merged on every read and
1039 // therefore we wish to avoid too many files when the individual
1040 // file size is small (perhaps because of a small write-buffer
1041 // setting, or very high compression ratios, or lots of
1042 // overwrites/deletions).
1043 score = v->files_[level].size() /
1044 static_cast<double>(config::kL0_CompactionTrigger);
1045 } else {
1046 // Compute the ratio of current size to size limit.
1047 const uint64_t level_bytes = TotalFileSize(v->files_[level]);
1048 score =
1049 static_cast<double>(level_bytes) / MaxBytesForLevel(options_, level);
1050 }
1051
1052 if (score > best_score) {
1053 best_level = level;
1054 best_score = score;
1055 }
1056 }
1057
1058 v->compaction_level_ = best_level;
1059 v->compaction_score_ = best_score;
1060 }
1061
1062 Status VersionSet::WriteSnapshot(log::Writer* log) {
1063 // TODO: Break up into multiple records to reduce memory usage on recovery?
1064
1065 // Save metadata
1066 VersionEdit edit;
1067 edit.SetComparatorName(icmp_.user_comparator()->Name());
1068
1069 // Save compaction pointers
1070 for (int level = 0; level < config::kNumLevels; level++) {
1071 if (!compact_pointer_[level].empty()) {
1072 InternalKey key;
1073 key.DecodeFrom(compact_pointer_[level]);
1074 edit.SetCompactPointer(level, key);
1075 }
1076 }
1077
1078 // Save files
1079 for (int level = 0; level < config::kNumLevels; level++) {
1080 const std::vector<FileMetaData*>& files = current_->files_[level];
1081 for (size_t i = 0; i < files.size(); i++) {
1082 const FileMetaData* f = files[i];
1083 edit.AddFile(level, f->number, f->file_size, f->smallest, f->largest);
1084 }
1085 }
1086
1087 std::string record;
1088 edit.EncodeTo(&record);
1089 return log->AddRecord(record);
1090 }
1091
1092 int VersionSet::NumLevelFiles(int level) const {
1093 assert(level >= 0);
1094 assert(level < config::kNumLevels);
1095 return current_->files_[level].size();
1096 }
1097
1098 const char* VersionSet::LevelSummary(LevelSummaryStorage* scratch) const {
1099 // Update code if kNumLevels changes
1100 static_assert(config::kNumLevels == 7, "");
1101 snprintf(scratch->buffer, sizeof(scratch->buffer),
1102 "files[ %d %d %d %d %d %d %d ]", int(current_->files_[0].size()),
1103 int(current_->files_[1].size()), int(current_->files_[2].size()),
1104 int(current_->files_[3].size()), int(current_->files_[4].size()),
1105 int(current_->files_[5].size()), int(current_->files_[6].size()));
1106 return scratch->buffer;
1107 }
1108
1109 uint64_t VersionSet::ApproximateOffsetOf(Version* v, const InternalKey& ikey) {
1110 uint64_t result = 0;
1111 for (int level = 0; level < config::kNumLevels; level++) {
1112 const std::vector<FileMetaData*>& files = v->files_[level];
1113 for (size_t i = 0; i < files.size(); i++) {
1114 if (icmp_.Compare(files[i]->largest, ikey) <= 0) {
1115 // Entire file is before "ikey", so just add the file size
1116 result += files[i]->file_size;
1117 } else if (icmp_.Compare(files[i]->smallest, ikey) > 0) {
1118 // Entire file is after "ikey", so ignore
1119 if (level > 0) {
1120 // Files other than level 0 are sorted by meta->smallest, so
1121 // no further files in this level will contain data for
1122 // "ikey".
1123 break;
1124 }
1125 } else {
1126 // "ikey" falls in the range for this table. Add the
1127 // approximate offset of "ikey" within the table.
1128 Table* tableptr;
1129 Iterator* iter = table_cache_->NewIterator(
1130 ReadOptions(), files[i]->number, files[i]->file_size, &tableptr);
1131 if (tableptr != nullptr) {
1132 result += tableptr->ApproximateOffsetOf(ikey.Encode());
1133 }
1134 delete iter;
1135 }
1136 }
1137 }
1138 return result;
1139 }
1140
1141 void VersionSet::AddLiveFiles(std::set<uint64_t>* live) {
1142 for (Version* v = dummy_versions_.next_; v != &dummy_versions_;
1143 v = v->next_) {
1144 for (int level = 0; level < config::kNumLevels; level++) {
1145 const std::vector<FileMetaData*>& files = v->files_[level];
1146 for (size_t i = 0; i < files.size(); i++) {
1147 live->insert(files[i]->number);
1148 }
1149 }
1150 }
1151 }
1152
1153 int64_t VersionSet::NumLevelBytes(int level) const {
1154 assert(level >= 0);
1155 assert(level < config::kNumLevels);
1156 return TotalFileSize(current_->files_[level]);
1157 }
1158
1159 int64_t VersionSet::MaxNextLevelOverlappingBytes() {
1160 int64_t result = 0;
1161 std::vector<FileMetaData*> overlaps;
1162 for (int level = 1; level < config::kNumLevels - 1; level++) {
1163 for (size_t i = 0; i < current_->files_[level].size(); i++) {
1164 const FileMetaData* f = current_->files_[level][i];
1165 current_->GetOverlappingInputs(level + 1, &f->smallest, &f->largest,
1166 &overlaps);
1167 const int64_t sum = TotalFileSize(overlaps);
1168 if (sum > result) {
1169 result = sum;
1170 }
1171 }
1172 }
1173 return result;
1174 }
1175
1176 // Stores the minimal range that covers all entries in inputs in
1177 // *smallest, *largest.
1178 // REQUIRES: inputs is not empty
1179 void VersionSet::GetRange(const std::vector<FileMetaData*>& inputs,
1180 InternalKey* smallest, InternalKey* largest) {
1181 assert(!inputs.empty());
1182 smallest->Clear();
1183 largest->Clear();
1184 for (size_t i = 0; i < inputs.size(); i++) {
1185 FileMetaData* f = inputs[i];
1186 if (i == 0) {
1187 *smallest = f->smallest;
1188 *largest = f->largest;
1189 } else {
1190 if (icmp_.Compare(f->smallest, *smallest) < 0) {
1191 *smallest = f->smallest;
1192 }
1193 if (icmp_.Compare(f->largest, *largest) > 0) {
1194 *largest = f->largest;
1195 }
1196 }
1197 }
1198 }
1199
1200 // Stores the minimal range that covers all entries in inputs1 and inputs2
1201 // in *smallest, *largest.
1202 // REQUIRES: inputs is not empty
1203 void VersionSet::GetRange2(const std::vector<FileMetaData*>& inputs1,
1204 const std::vector<FileMetaData*>& inputs2,
1205 InternalKey* smallest, InternalKey* largest) {
1206 std::vector<FileMetaData*> all = inputs1;
1207 all.insert(all.end(), inputs2.begin(), inputs2.end());
1208 GetRange(all, smallest, largest);
1209 }
1210
1211 Iterator* VersionSet::MakeInputIterator(Compaction* c) {
1212 ReadOptions options;
1213 options.verify_checksums = options_->paranoid_checks;
1214 options.fill_cache = false;
1215
1216 // Level-0 files have to be merged together. For other levels,
1217 // we will make a concatenating iterator per level.
1218 // TODO(opt): use concatenating iterator for level-0 if there is no overlap
1219 const int space = (c->level() == 0 ? c->inputs_[0].size() + 1 : 2);
1220 Iterator** list = new Iterator*[space];
1221 int num = 0;
1222 for (int which = 0; which < 2; which++) {
1223 if (!c->inputs_[which].empty()) {
1224 if (c->level() + which == 0) {
1225 const std::vector<FileMetaData*>& files = c->inputs_[which];
1226 for (size_t i = 0; i < files.size(); i++) {
1227 list[num++] = table_cache_->NewIterator(options, files[i]->number,
1228 files[i]->file_size);
1229 }
1230 } else {
1231 // Create concatenating iterator for the files from this level
1232 list[num++] = NewTwoLevelIterator(
1233 new Version::LevelFileNumIterator(icmp_, &c->inputs_[which]),
1234 &GetFileIterator, table_cache_, options);
1235 }
1236 }
1237 }
1238 assert(num <= space);
1239 Iterator* result = NewMergingIterator(&icmp_, list, num);
1240 delete[] list;
1241 return result;
1242 }
1243
1244 Compaction* VersionSet::PickCompaction() {
1245 Compaction* c;
1246 int level;
1247
1248 // We prefer compactions triggered by too much data in a level over
1249 // the compactions triggered by seeks.
1250 const bool size_compaction = (current_->compaction_score_ >= 1);
1251 const bool seek_compaction = (current_->file_to_compact_ != nullptr);
1252 if (size_compaction) {
1253 level = current_->compaction_level_;
1254 assert(level >= 0);
1255 assert(level + 1 < config::kNumLevels);
1256 c = new Compaction(options_, level);
1257
1258 // Pick the first file that comes after compact_pointer_[level]
1259 for (size_t i = 0; i < current_->files_[level].size(); i++) {
1260 FileMetaData* f = current_->files_[level][i];
1261 if (compact_pointer_[level].empty() ||
1262 icmp_.Compare(f->largest.Encode(), compact_pointer_[level]) > 0) {
1263 c->inputs_[0].push_back(f);
1264 break;
1265 }
1266 }
1267 if (c->inputs_[0].empty()) {
1268 // Wrap-around to the beginning of the key space
1269 c->inputs_[0].push_back(current_->files_[level][0]);
1270 }
1271 } else if (seek_compaction) {
1272 level = current_->file_to_compact_level_;
1273 c = new Compaction(options_, level);
1274 c->inputs_[0].push_back(current_->file_to_compact_);
1275 } else {
1276 return nullptr;
1277 }
1278
1279 c->input_version_ = current_;
1280 c->input_version_->Ref();
1281
1282 // Files in level 0 may overlap each other, so pick up all overlapping ones
1283 if (level == 0) {
1284 InternalKey smallest, largest;
1285 GetRange(c->inputs_[0], &smallest, &largest);
1286 // Note that the next call will discard the file we placed in
1287 // c->inputs_[0] earlier and replace it with an overlapping set
1288 // which will include the picked file.
1289 current_->GetOverlappingInputs(0, &smallest, &largest, &c->inputs_[0]);
1290 assert(!c->inputs_[0].empty());
1291 }
1292
1293 SetupOtherInputs(c);
1294
1295 return c;
1296 }
1297
1298 // Finds the largest key in a vector of files. Returns true if files it not
1299 // empty.
1300 bool FindLargestKey(const InternalKeyComparator& icmp,
1301 const std::vector<FileMetaData*>& files,
1302 InternalKey* largest_key) {
1303 if (files.empty()) {
1304 return false;
1305 }
1306 *largest_key = files[0]->largest;
1307 for (size_t i = 1; i < files.size(); ++i) {
1308 FileMetaData* f = files[i];
1309 if (icmp.Compare(f->largest, *largest_key) > 0) {
1310 *largest_key = f->largest;
1311 }
1312 }
1313 return true;
1314 }
1315
1316 // Finds minimum file b2=(l2, u2) in level file for which l2 > u1 and
1317 // user_key(l2) = user_key(u1)
1318 FileMetaData* FindSmallestBoundaryFile(
1319 const InternalKeyComparator& icmp,
1320 const std::vector<FileMetaData*>& level_files,
1321 const InternalKey& largest_key) {
1322 const Comparator* user_cmp = icmp.user_comparator();
1323 FileMetaData* smallest_boundary_file = nullptr;
1324 for (size_t i = 0; i < level_files.size(); ++i) {
1325 FileMetaData* f = level_files[i];
1326 if (icmp.Compare(f->smallest, largest_key) > 0 &&
1327 user_cmp->Compare(f->smallest.user_key(), largest_key.user_key()) ==
1328 0) {
1329 if (smallest_boundary_file == nullptr ||
1330 icmp.Compare(f->smallest, smallest_boundary_file->smallest) < 0) {
1331 smallest_boundary_file = f;
1332 }
1333 }
1334 }
1335 return smallest_boundary_file;
1336 }
1337
1338 // Extracts the largest file b1 from |compaction_files| and then searches for a
1339 // b2 in |level_files| for which user_key(u1) = user_key(l2). If it finds such a
1340 // file b2 (known as a boundary file) it adds it to |compaction_files| and then
1341 // searches again using this new upper bound.
1342 //
1343 // If there are two blocks, b1=(l1, u1) and b2=(l2, u2) and
1344 // user_key(u1) = user_key(l2), and if we compact b1 but not b2 then a
1345 // subsequent get operation will yield an incorrect result because it will
1346 // return the record from b2 in level i rather than from b1 because it searches
1347 // level by level for records matching the supplied user key.
1348 //
1349 // parameters:
1350 // in level_files: List of files to search for boundary files.
1351 // in/out compaction_files: List of files to extend by adding boundary files.
1352 void AddBoundaryInputs(const InternalKeyComparator& icmp,
1353 const std::vector<FileMetaData*>& level_files,
1354 std::vector<FileMetaData*>* compaction_files) {
1355 InternalKey largest_key;
1356
1357 // Quick return if compaction_files is empty.
1358 if (!FindLargestKey(icmp, *compaction_files, &largest_key)) {
1359 return;
1360 }
1361
1362 bool continue_searching = true;
1363 while (continue_searching) {
1364 FileMetaData* smallest_boundary_file =
1365 FindSmallestBoundaryFile(icmp, level_files, largest_key);
1366
1367 // If a boundary file was found advance largest_key, otherwise we're done.
1368 if (smallest_boundary_file != NULL) {
1369 compaction_files->push_back(smallest_boundary_file);
1370 largest_key = smallest_boundary_file->largest;
1371 } else {
1372 continue_searching = false;
1373 }
1374 }
1375 }
1376
1377 void VersionSet::SetupOtherInputs(Compaction* c) {
1378 const int level = c->level();
1379 InternalKey smallest, largest;
1380
1381 AddBoundaryInputs(icmp_, current_->files_[level], &c->inputs_[0]);
1382 GetRange(c->inputs_[0], &smallest, &largest);
1383
1384 current_->GetOverlappingInputs(level + 1, &smallest, &largest,
1385 &c->inputs_[1]);
1386
1387 // Get entire range covered by compaction
1388 InternalKey all_start, all_limit;
1389 GetRange2(c->inputs_[0], c->inputs_[1], &all_start, &all_limit);
1390
1391 // See if we can grow the number of inputs in "level" without
1392 // changing the number of "level+1" files we pick up.
1393 if (!c->inputs_[1].empty()) {
1394 std::vector<FileMetaData*> expanded0;
1395 current_->GetOverlappingInputs(level, &all_start, &all_limit, &expanded0);
1396 AddBoundaryInputs(icmp_, current_->files_[level], &expanded0);
1397 const int64_t inputs0_size = TotalFileSize(c->inputs_[0]);
1398 const int64_t inputs1_size = TotalFileSize(c->inputs_[1]);
1399 const int64_t expanded0_size = TotalFileSize(expanded0);
1400 if (expanded0.size() > c->inputs_[0].size() &&
1401 inputs1_size + expanded0_size <
1402 ExpandedCompactionByteSizeLimit(options_)) {
1403 InternalKey new_start, new_limit;
1404 GetRange(expanded0, &new_start, &new_limit);
1405 std::vector<FileMetaData*> expanded1;
1406 current_->GetOverlappingInputs(level + 1, &new_start, &new_limit,
1407 &expanded1);
1408 if (expanded1.size() == c->inputs_[1].size()) {
1409 Log(options_->info_log,
1410 "Expanding@%d %d+%d (%ld+%ld bytes) to %d+%d (%ld+%ld bytes)\n",
1411 level, int(c->inputs_[0].size()), int(c->inputs_[1].size()),
1412 long(inputs0_size), long(inputs1_size), int(expanded0.size()),
1413 int(expanded1.size()), long(expanded0_size), long(inputs1_size));
1414 smallest = new_start;
1415 largest = new_limit;
1416 c->inputs_[0] = expanded0;
1417 c->inputs_[1] = expanded1;
1418 GetRange2(c->inputs_[0], c->inputs_[1], &all_start, &all_limit);
1419 }
1420 }
1421 }
1422
1423 // Compute the set of grandparent files that overlap this compaction
1424 // (parent == level+1; grandparent == level+2)
1425 if (level + 2 < config::kNumLevels) {
1426 current_->GetOverlappingInputs(level + 2, &all_start, &all_limit,
1427 &c->grandparents_);
1428 }
1429
1430 // Update the place where we will do the next compaction for this level.
1431 // We update this immediately instead of waiting for the VersionEdit
1432 // to be applied so that if the compaction fails, we will try a different
1433 // key range next time.
1434 compact_pointer_[level] = largest.Encode().ToString();
1435 c->edit_.SetCompactPointer(level, largest);
1436 }
1437
1438 Compaction* VersionSet::CompactRange(int level, const InternalKey* begin,
1439 const InternalKey* end) {
1440 std::vector<FileMetaData*> inputs;
1441 current_->GetOverlappingInputs(level, begin, end, &inputs);
1442 if (inputs.empty()) {
1443 return nullptr;
1444 }
1445
1446 // Avoid compacting too much in one shot in case the range is large.
1447 // But we cannot do this for level-0 since level-0 files can overlap
1448 // and we must not pick one file and drop another older file if the
1449 // two files overlap.
1450 if (level > 0) {
1451 const uint64_t limit = MaxFileSizeForLevel(options_, level);
1452 uint64_t total = 0;
1453 for (size_t i = 0; i < inputs.size(); i++) {
1454 uint64_t s = inputs[i]->file_size;
1455 total += s;
1456 if (total >= limit) {
1457 inputs.resize(i + 1);
1458 break;
1459 }
1460 }
1461 }
1462
1463 Compaction* c = new Compaction(options_, level);
1464 c->input_version_ = current_;
1465 c->input_version_->Ref();
1466 c->inputs_[0] = inputs;
1467 SetupOtherInputs(c);
1468 return c;
1469 }
1470
1471 Compaction::Compaction(const Options* options, int level)
1472 : level_(level),
1473 max_output_file_size_(MaxFileSizeForLevel(options, level)),
1474 input_version_(nullptr),
1475 grandparent_index_(0),
1476 seen_key_(false),
1477 overlapped_bytes_(0) {
1478 for (int i = 0; i < config::kNumLevels; i++) {
1479 level_ptrs_[i] = 0;
1480 }
1481 }
1482
1483 Compaction::~Compaction() {
1484 if (input_version_ != nullptr) {
1485 input_version_->Unref();
1486 }
1487 }
1488
1489 bool Compaction::IsTrivialMove() const {
1490 const VersionSet* vset = input_version_->vset_;
1491 // Avoid a move if there is lots of overlapping grandparent data.
1492 // Otherwise, the move could create a parent file that will require
1493 // a very expensive merge later on.
1494 return (num_input_files(0) == 1 && num_input_files(1) == 0 &&
1495 TotalFileSize(grandparents_) <=
1496 MaxGrandParentOverlapBytes(vset->options_));
1497 }
1498
1499 void Compaction::AddInputDeletions(VersionEdit* edit) {
1500 for (int which = 0; which < 2; which++) {
1501 for (size_t i = 0; i < inputs_[which].size(); i++) {
1502 edit->DeleteFile(level_ + which, inputs_[which][i]->number);
1503 }
1504 }
1505 }
1506
1507 bool Compaction::IsBaseLevelForKey(const Slice& user_key) {
1508 // Maybe use binary search to find right entry instead of linear search?
1509 const Comparator* user_cmp = input_version_->vset_->icmp_.user_comparator();
1510 for (int lvl = level_ + 2; lvl < config::kNumLevels; lvl++) {
1511 const std::vector<FileMetaData*>& files = input_version_->files_[lvl];
1512 while (level_ptrs_[lvl] < files.size()) {
1513 FileMetaData* f = files[level_ptrs_[lvl]];
1514 if (user_cmp->Compare(user_key, f->largest.user_key()) <= 0) {
1515 // We've advanced far enough
1516 if (user_cmp->Compare(user_key, f->smallest.user_key()) >= 0) {
1517 // Key falls in this file's range, so definitely not base level
1518 return false;
1519 }
1520 break;
1521 }
1522 level_ptrs_[lvl]++;
1523 }
1524 }
1525 return true;
1526 }
1527
1528 bool Compaction::ShouldStopBefore(const Slice& internal_key) {
1529 const VersionSet* vset = input_version_->vset_;
1530 // Scan to find earliest grandparent file that contains key.
1531 const InternalKeyComparator* icmp = &vset->icmp_;
1532 while (grandparent_index_ < grandparents_.size() &&
1533 icmp->Compare(internal_key,
1534 grandparents_[grandparent_index_]->largest.Encode()) >
1535 0) {
1536 if (seen_key_) {
1537 overlapped_bytes_ += grandparents_[grandparent_index_]->file_size;
1538 }
1539 grandparent_index_++;
1540 }
1541 seen_key_ = true;
1542
1543 if (overlapped_bytes_ > MaxGrandParentOverlapBytes(vset->options_)) {
1544 // Too much overlap for current output; start new output
1545 overlapped_bytes_ = 0;
1546 return true;
1547 } else {
1548 return false;
1549 }
1550 }
1551
1552 void Compaction::ReleaseInputs() {
1553 if (input_version_ != nullptr) {
1554 input_version_->Unref();
1555 input_version_ = nullptr;
1556 }
1557 }
1558
1559 } // namespace leveldb
1560