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use concatenating iterator for level-0 if there is no overlap

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This commit is contained in:
luohaha 2020-10-19 00:23:39 +08:00
parent 1454924aac
commit 17b5d5a064
2 changed files with 23 additions and 7 deletions
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22
db/version_set.cc
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@ -228,10 +228,16 @@ Iterator* Version::NewConcatenatingIterator(const ReadOptions& options,
void Version::AddIterators(const ReadOptions& options,
std::vector<Iterator*>* iters) {
// Merge all level zero files together since they may overlap
for (size_t i = 0; i < files_[0].size(); i++) {
iters->push_back(vset_->table_cache_->NewIterator(
options, files_[0][i]->number, files_[0][i]->file_size));
if (OverlapInLevel0()) {
// Merge all level zero files together since they overlap
for (size_t i = 0; i < files_[0].size(); i++) {
iters->push_back(vset_->table_cache_->NewIterator(
options, files_[0][i]->number, files_[0][i]->file_size));
}
} else {
if (!files_[0].empty()) {
iters->push_back(NewConcatenatingIterator(options, 0));
}
}
// For levels > 0, we can use a concatenating iterator that sequentially
@ -725,6 +731,11 @@ class VersionSet::Builder {
f->smallest) < 0);
}
f->refs++;
if (level == 0 && !files->empty() && !v->OverlapInLevel0()) {
if (vset_->icmp_.Compare(files->at(files->size() - 1)->largest, f->smallest) >= 0) {
v->SetOverlapInLevel0();
}
}
files->push_back(f);
}
}
@ -1218,13 +1229,12 @@ Iterator* VersionSet::MakeInputIterator(Compaction* c) {
// Level-0 files have to be merged together. For other levels,
// we will make a concatenating iterator per level.
// TODO(opt): use concatenating iterator for level-0 if there is no overlap
const int space = (c->level() == 0 ? c->inputs_[0].size() + 1 : 2);
Iterator** list = new Iterator*[space];
int num = 0;
for (int which = 0; which < 2; which++) {
if (!c->inputs_[which].empty()) {
if (c->level() + which == 0) {
if (c->level() + which == 0 && c->input_version_->OverlapInLevel0()) {
const std::vector<FileMetaData*>& files = c->inputs_[which];
for (size_t i = 0; i < files.size(); i++) {
list[num++] = table_cache_->NewIterator(options, files[i]->number,

8
db/version_set.h
View File

@ -114,6 +114,10 @@ class Version {
// Return a human readable string that describes this version's contents.
std::string DebugString() const;
bool OverlapInLevel0() const { return overlap_in_level0_; }
void SetOverlapInLevel0() { overlap_in_level0_ = true; }
private:
friend class Compaction;
friend class VersionSet;
@ -128,7 +132,8 @@ class Version {
file_to_compact_(nullptr),
file_to_compact_level_(-1),
compaction_score_(-1),
compaction_level_(-1) {}
compaction_level_(-1),
overlap_in_level0_(false) {}
Version(const Version&) = delete;
Version& operator=(const Version&) = delete;
@ -162,6 +167,7 @@ class Version {
// are initialized by Finalize().
double compaction_score_;
int compaction_level_;
bool overlap_in_level0_;
};
class VersionSet {