Summary: Forward iterator puts everything together in a flat structure instead of a hierarchy of nested iterators. this should simplify the code and provide better performance. It also enables more optimization since all information are accessiable in one place. Init evaluation shows about 6% improvement Test Plan: db_test and db_bench Reviewers: dhruba, igor, tnovak, sdong, haobo Reviewed By: haobo Subscribers: sdong, leveldb Differential Revision: https://reviews.facebook.net/D18795main
Lei Jin
11 years ago
parent
f29c62fc6f
commit
388d2054c7
@ -0,0 +1,384 @@ |
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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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#ifndef ROCKSDB_LITE |
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#include "db/forward_iterator.h" |
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#include <string> |
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#include <utility> |
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#include <limits> |
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#include "db/db_impl.h" |
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#include "db/db_iter.h" |
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#include "db/column_family.h" |
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#include "rocksdb/env.h" |
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#include "rocksdb/slice.h" |
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#include "rocksdb/slice_transform.h" |
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#include "table/merger.h" |
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#include "db/dbformat.h" |
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namespace rocksdb { |
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// Usage:
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// LevelIterator iter;
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// iter.SetFileIndex(file_index);
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// iter.Seek(target);
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// iter.Next()
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class LevelIterator : public Iterator { |
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public: |
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LevelIterator(const ColumnFamilyData* const cfd, |
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const ReadOptions& read_options, |
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const std::vector<FileMetaData*>& files) |
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: cfd_(cfd), read_options_(read_options), files_(files), valid_(false), |
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file_index_(std::numeric_limits<uint32_t>::max()) {} |
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void SetFileIndex(uint32_t file_index) { |
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assert(file_index < files_.size()); |
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if (file_index != file_index_) { |
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file_index_ = file_index; |
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file_iter_.reset(cfd_->table_cache()->NewIterator( |
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read_options_, *(cfd_->soptions()), cfd_->internal_comparator(), |
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*(files_[file_index_]), nullptr /* table_reader_ptr */, false)); |
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} |
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valid_ = false; |
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} |
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void SeekToLast() override { |
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status_ = Status::NotSupported("LevelIterator::SeekToLast()"); |
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valid_ = false; |
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} |
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void Prev() { |
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status_ = Status::NotSupported("LevelIterator::Prev()"); |
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valid_ = false; |
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} |
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bool Valid() const override { |
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return valid_; |
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} |
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void SeekToFirst() override { |
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SetFileIndex(0); |
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file_iter_->SeekToFirst(); |
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valid_ = file_iter_->Valid(); |
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} |
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void Seek(const Slice& internal_key) override { |
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assert(file_iter_ != nullptr); |
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file_iter_->Seek(internal_key); |
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valid_ = file_iter_->Valid(); |
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assert(valid_); |
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} |
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void Next() override { |
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assert(valid_); |
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file_iter_->Next(); |
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while (!file_iter_->Valid()) { |
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if (file_index_ + 1 >= files_.size()) { |
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valid_ = false; |
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return; |
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} |
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SetFileIndex(file_index_ + 1); |
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file_iter_->SeekToFirst(); |
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} |
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valid_ = file_iter_->Valid(); |
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} |
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Slice key() const override { |
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assert(valid_); |
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return file_iter_->key(); |
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} |
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Slice value() const override { |
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assert(valid_); |
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return file_iter_->value(); |
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} |
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Status status() const override { |
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return status_; |
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} |
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private: |
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const ColumnFamilyData* const cfd_; |
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const ReadOptions& read_options_; |
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const std::vector<FileMetaData*>& files_; |
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bool valid_; |
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uint32_t file_index_; |
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Status status_; |
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std::unique_ptr<Iterator> file_iter_; |
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}; |
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ForwardIterator::ForwardIterator(Env* const env, DBImpl* db, |
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const ReadOptions& read_options, ColumnFamilyData* cfd) |
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: db_(db), |
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env_(env), |
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read_options_(read_options), |
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cfd_(cfd), |
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prefix_extractor_(cfd->options()->prefix_extractor.get()), |
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user_comparator_(cfd->user_comparator()), |
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immutable_min_heap_(MinIterComparator(&cfd_->internal_comparator())), |
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sv_(nullptr), |
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mutable_iter_(nullptr), |
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current_(nullptr), |
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valid_(false), |
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is_prev_set_(false) {} |
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ForwardIterator::~ForwardIterator() { |
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Cleanup(); |
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} |
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void ForwardIterator::Cleanup() { |
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delete mutable_iter_; |
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for (auto* m : imm_iters_) { |
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delete m; |
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} |
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imm_iters_.clear(); |
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for (auto* f : l0_iters_) { |
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delete f; |
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} |
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l0_iters_.clear(); |
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for (auto* l : level_iters_) { |
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delete l; |
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} |
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level_iters_.clear(); |
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if (sv_ != nullptr && sv_->Unref()) { |
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DBImpl::DeletionState deletion_state; |
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db_->mutex_.Lock(); |
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sv_->Cleanup(); |
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db_->FindObsoleteFiles(deletion_state, false, true); |
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db_->mutex_.Unlock(); |
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delete sv_; |
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if (deletion_state.HaveSomethingToDelete()) { |
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db_->PurgeObsoleteFiles(deletion_state); |
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} |
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} |
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} |
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bool ForwardIterator::Valid() const { |
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return valid_; |
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} |
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void ForwardIterator::SeekToFirst() { |
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if (sv_ == nullptr || |
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sv_ ->version_number != cfd_->GetSuperVersionNumber()) { |
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RebuildIterators(); |
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} |
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SeekInternal(Slice(), true); |
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} |
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void ForwardIterator::Seek(const Slice& internal_key) { |
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if (sv_ == nullptr || |
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sv_ ->version_number != cfd_->GetSuperVersionNumber()) { |
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RebuildIterators(); |
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} |
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SeekInternal(internal_key, false); |
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} |
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void ForwardIterator::SeekInternal(const Slice& internal_key, |
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bool seek_to_first) { |
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// mutable
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seek_to_first ? mutable_iter_->SeekToFirst() : |
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mutable_iter_->Seek(internal_key); |
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// immutable
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// TODO(ljin): NeedToSeekImmutable has negative impact on performance
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// if it turns to need to seek immutable often. We probably want to have
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// an option to turn it off.
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if (seek_to_first || NeedToSeekImmutable(internal_key)) { |
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{ |
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auto tmp = MinIterHeap(MinIterComparator(&cfd_->internal_comparator())); |
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immutable_min_heap_.swap(tmp); |
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} |
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for (auto* m : imm_iters_) { |
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seek_to_first ? m->SeekToFirst() : m->Seek(internal_key); |
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if (m->Valid()) { |
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immutable_min_heap_.push(m); |
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} |
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} |
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auto* files = sv_->current->files_; |
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for (uint32_t i = 0; i < files[0].size(); ++i) { |
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if (seek_to_first) { |
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l0_iters_[i]->SeekToFirst(); |
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} else { |
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// If the target key passes over the larget key, we are sure Next()
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// won't go over this file.
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if (user_comparator_->Compare(ExtractUserKey(internal_key), |
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files[0][i]->largest.user_key()) > 0) { |
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continue; |
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} |
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l0_iters_[i]->Seek(internal_key); |
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} |
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if (l0_iters_[i]->Valid()) { |
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immutable_min_heap_.push(l0_iters_[i]); |
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} |
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} |
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for (int32_t level = 1; level < sv_->current->NumberLevels(); ++level) { |
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if (files[level].empty()) { |
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continue; |
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} |
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assert(level_iters_[level - 1] != nullptr); |
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uint32_t f_idx = 0; |
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if (!seek_to_first) { |
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f_idx = FindFileInRange( |
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files[level], internal_key, 0, files[level].size()); |
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} |
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if (f_idx < files[level].size()) { |
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level_iters_[level - 1]->SetFileIndex(f_idx); |
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seek_to_first ? level_iters_[level - 1]->SeekToFirst() : |
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level_iters_[level - 1]->Seek(internal_key); |
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if (level_iters_[level - 1]->Valid()) { |
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immutable_min_heap_.push(level_iters_[level - 1]); |
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} |
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} |
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} |
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if (seek_to_first || immutable_min_heap_.empty()) { |
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is_prev_set_ = false; |
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} else { |
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prev_key_.SetKey(internal_key); |
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is_prev_set_ = true; |
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} |
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} |
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UpdateCurrent(); |
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} |
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void ForwardIterator::Next() { |
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assert(valid_); |
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if (sv_ == nullptr || |
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sv_ ->version_number != cfd_->GetSuperVersionNumber()) { |
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std::string current_key = key().ToString(); |
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Slice old_key(current_key.data(), current_key.size()); |
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RebuildIterators(); |
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SeekInternal(old_key, false); |
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if (!valid_ || key().compare(old_key) != 0) { |
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return; |
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} |
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} else if (current_ != mutable_iter_) { |
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// It is going to advance immutable iterator
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prev_key_.SetKey(current_->key()); |
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is_prev_set_ = true; |
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} |
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current_->Next(); |
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if (current_->Valid() && current_ != mutable_iter_) { |
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immutable_min_heap_.push(current_); |
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} |
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UpdateCurrent(); |
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} |
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Slice ForwardIterator::key() const { |
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assert(valid_); |
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return current_->key(); |
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} |
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Slice ForwardIterator::value() const { |
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assert(valid_); |
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return current_->value(); |
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} |
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Status ForwardIterator::status() const { |
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if (!status_.ok()) { |
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return status_; |
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} else if (!mutable_iter_->status().ok()) { |
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return mutable_iter_->status(); |
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} |
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return Status::OK(); |
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} |
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void ForwardIterator::RebuildIterators() { |
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// Clean up
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Cleanup(); |
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// New
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sv_ = cfd_->GetReferencedSuperVersion(&(db_->mutex_)); |
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mutable_iter_ = sv_->mem->NewIterator(read_options_); |
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sv_->imm->AddIterators(read_options_, &imm_iters_); |
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const auto& l0_files = sv_->current->files_[0]; |
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l0_iters_.reserve(l0_files.size()); |
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for (const auto* l0 : l0_files) { |
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l0_iters_.push_back(cfd_->table_cache()->NewIterator( |
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read_options_, *cfd_->soptions(), cfd_->internal_comparator(), *l0)); |
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} |
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level_iters_.reserve(sv_->current->NumberLevels() - 1); |
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for (int32_t level = 1; level < sv_->current->NumberLevels(); ++level) { |
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if (sv_->current->files_[level].empty()) { |
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level_iters_.push_back(nullptr); |
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} else { |
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level_iters_.push_back(new LevelIterator(cfd_, read_options_, |
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sv_->current->files_[level])); |
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} |
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} |
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current_ = nullptr; |
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is_prev_set_ = false; |
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} |
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void ForwardIterator::UpdateCurrent() { |
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if (immutable_min_heap_.empty() && !mutable_iter_->Valid()) { |
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current_ = nullptr; |
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} else if (immutable_min_heap_.empty()) { |
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current_ = mutable_iter_; |
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} else if (!mutable_iter_->Valid()) { |
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current_ = immutable_min_heap_.top(); |
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immutable_min_heap_.pop(); |
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} else { |
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current_ = immutable_min_heap_.top(); |
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assert(current_ != nullptr); |
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assert(current_->Valid()); |
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int cmp = cfd_->internal_comparator().InternalKeyComparator::Compare( |
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mutable_iter_->key(), current_->key()) > 0; |
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assert(cmp != 0); |
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if (cmp > 0) { |
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immutable_min_heap_.pop(); |
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} else { |
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current_ = mutable_iter_; |
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} |
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} |
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valid_ = (current_ != nullptr); |
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if (!status_.ok()) { |
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status_ = Status::OK(); |
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} |
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} |
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bool ForwardIterator::NeedToSeekImmutable(const Slice& target) { |
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if (!is_prev_set_) { |
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return true; |
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} |
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Slice prev_key = prev_key_.GetKey(); |
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if (prefix_extractor_ && prefix_extractor_->Transform(target).compare( |
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prefix_extractor_->Transform(prev_key)) != 0) { |
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return true; |
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} |
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if (cfd_->internal_comparator().InternalKeyComparator::Compare( |
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prev_key, target) >= 0) { |
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return true; |
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} |
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if (immutable_min_heap_.empty() || |
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cfd_->internal_comparator().InternalKeyComparator::Compare( |
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target, current_ == mutable_iter_ ? immutable_min_heap_.top()->key() |
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: current_->key()) > 0) { |
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return true; |
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} |
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return false; |
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} |
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uint32_t ForwardIterator::FindFileInRange( |
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const std::vector<FileMetaData*>& files, const Slice& internal_key, |
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uint32_t left, uint32_t right) { |
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while (left < right) { |
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uint32_t mid = (left + right) / 2; |
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const FileMetaData* f = files[mid]; |
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if (cfd_->internal_comparator().InternalKeyComparator::Compare( |
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f->largest.Encode(), internal_key) < 0) { |
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// Key at "mid.largest" is < "target". Therefore all
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// files at or before "mid" are uninteresting.
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left = mid + 1; |
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} else { |
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// Key at "mid.largest" is >= "target". Therefore all files
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// after "mid" are uninteresting.
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right = mid; |
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} |
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} |
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return right; |
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} |
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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@ -0,0 +1,106 @@ |
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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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#pragma once |
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#ifndef ROCKSDB_LITE |
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#include <string> |
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#include <vector> |
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#include <queue> |
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#include "rocksdb/db.h" |
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#include "rocksdb/iterator.h" |
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#include "rocksdb/options.h" |
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#include "db/dbformat.h" |
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namespace rocksdb { |
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class DBImpl; |
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class Env; |
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struct SuperVersion; |
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class ColumnFamilyData; |
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class LevelIterator; |
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class FileMetaData; |
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class MinIterComparator { |
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public: |
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explicit MinIterComparator(const Comparator* comparator) : |
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comparator_(comparator) {} |
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bool operator()(Iterator* a, Iterator* b) { |
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return comparator_->Compare(a->key(), b->key()) > 0; |
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} |
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private: |
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const Comparator* comparator_; |
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}; |
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typedef std::priority_queue<Iterator*, |
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std::vector<Iterator*>, |
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MinIterComparator> MinIterHeap; |
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/**
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* ForwardIterator is a special type of iterator that only supports Seek() |
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* and Next(). It is expected to perform better than TailingIterator by |
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* removing the encapsulation and making all information accessible within |
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* the iterator. At the current implementation, snapshot is taken at the |
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* time Seek() is called. The Next() followed do not see new values after. |
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*/ |
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class ForwardIterator : public Iterator { |
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public: |
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ForwardIterator(Env* const env, DBImpl* db, const ReadOptions& read_options, |
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ColumnFamilyData* cfd); |
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virtual ~ForwardIterator(); |
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void SeekToLast() override { |
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status_ = Status::NotSupported("ForwardIterator::SeekToLast()"); |
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valid_ = false; |
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} |
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void Prev() { |
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status_ = Status::NotSupported("ForwardIterator::Prev"); |
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valid_ = false; |
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} |
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virtual bool Valid() const override; |
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void SeekToFirst() override; |
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virtual void Seek(const Slice& target) override; |
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virtual void Next() override; |
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virtual Slice key() const override; |
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virtual Slice value() const override; |
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virtual Status status() const override; |
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private: |
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void Cleanup(); |
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void RebuildIterators(); |
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void SeekInternal(const Slice& internal_key, bool seek_to_first); |
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void UpdateCurrent(); |
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bool NeedToSeekImmutable(const Slice& internal_key); |
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uint32_t FindFileInRange( |
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const std::vector<FileMetaData*>& files, const Slice& internal_key, |
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uint32_t left, uint32_t right); |
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DBImpl* const db_; |
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Env* const env_; |
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const ReadOptions read_options_; |
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ColumnFamilyData* const cfd_; |
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const SliceTransform* const prefix_extractor_; |
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const Comparator* user_comparator_; |
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MinIterHeap immutable_min_heap_; |
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SuperVersion* sv_; |
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Iterator* mutable_iter_; |
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std::vector<Iterator*> imm_iters_; |
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std::vector<Iterator*> l0_iters_; |
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std::vector<LevelIterator*> level_iters_; |
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Iterator* current_; |
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// internal iterator status
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Status status_; |
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bool valid_; |
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IterKey prev_key_; |
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bool is_prev_set_; |
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}; |
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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