Squashed 'src/rocksdb/' content from commit 224932d

git-subtree-dir: src/rocksdb
git-subtree-split: 224932d4d0

db/forward_iterator.cc

@@ -0,0 +1,463 @@
+//  Copyright (c) 2013, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under the BSD-style license found in the
+//  LICENSE file in the root directory of this source tree. An additional grant
+//  of patent rights can be found in the PATENTS file in the same directory.
+
+#ifndef ROCKSDB_LITE
+#include "db/forward_iterator.h"
+
+#include <string>
+#include <utility>
+#include <limits>
+#include "db/db_impl.h"
+#include "db/db_iter.h"
+#include "db/column_family.h"
+#include "rocksdb/env.h"
+#include "rocksdb/slice.h"
+#include "rocksdb/slice_transform.h"
+#include "table/merger.h"
+#include "db/dbformat.h"
+
+namespace rocksdb {
+
+// Usage:
+//     LevelIterator iter;
+//     iter.SetFileIndex(file_index);
+//     iter.Seek(target);
+//     iter.Next()
+class LevelIterator : public Iterator {
+ public:
+  LevelIterator(const ColumnFamilyData* const cfd,
+      const ReadOptions& read_options,
+      const std::vector<FileMetaData*>& files)
+    : cfd_(cfd), read_options_(read_options), files_(files), valid_(false),
+      file_index_(std::numeric_limits<uint32_t>::max()) {}
+
+  void SetFileIndex(uint32_t file_index) {
+    assert(file_index < files_.size());
+    if (file_index != file_index_) {
+      file_index_ = file_index;
+      file_iter_.reset(cfd_->table_cache()->NewIterator(
+          read_options_, *(cfd_->soptions()), cfd_->internal_comparator(),
+          files_[file_index_]->fd, nullptr /* table_reader_ptr */, false));
+    }
+    valid_ = false;
+  }
+  void SeekToLast() override {
+    status_ = Status::NotSupported("LevelIterator::SeekToLast()");
+    valid_ = false;
+  }
+  void Prev() {
+    status_ = Status::NotSupported("LevelIterator::Prev()");
+    valid_ = false;
+  }
+  bool Valid() const override {
+    return valid_;
+  }
+  void SeekToFirst() override {
+    SetFileIndex(0);
+    file_iter_->SeekToFirst();
+    valid_ = file_iter_->Valid();
+  }
+  void Seek(const Slice& internal_key) override {
+    assert(file_iter_ != nullptr);
+    file_iter_->Seek(internal_key);
+    valid_ = file_iter_->Valid();
+    assert(valid_);
+  }
+  void Next() override {
+    assert(valid_);
+    file_iter_->Next();
+    while (!file_iter_->Valid()) {
+      if (file_index_ + 1 >= files_.size()) {
+        valid_ = false;
+        return;
+      }
+      SetFileIndex(file_index_ + 1);
+      file_iter_->SeekToFirst();
+    }
+    valid_ = file_iter_->Valid();
+  }
+  Slice key() const override {
+    assert(valid_);
+    return file_iter_->key();
+  }
+  Slice value() const override {
+    assert(valid_);
+    return file_iter_->value();
+  }
+  Status status() const override {
+    if (!status_.ok()) {
+      return status_;
+    } else if (file_iter_ && !file_iter_->status().ok()) {
+      return file_iter_->status();
+    }
+    return Status::OK();
+  }
+
+ private:
+  const ColumnFamilyData* const cfd_;
+  const ReadOptions& read_options_;
+  const std::vector<FileMetaData*>& files_;
+
+  bool valid_;
+  uint32_t file_index_;
+  Status status_;
+  std::unique_ptr<Iterator> file_iter_;
+};
+
+ForwardIterator::ForwardIterator(DBImpl* db, const ReadOptions& read_options,
+                                 ColumnFamilyData* cfd)
+    : db_(db),
+      read_options_(read_options),
+      cfd_(cfd),
+      prefix_extractor_(cfd->options()->prefix_extractor.get()),
+      user_comparator_(cfd->user_comparator()),
+      immutable_min_heap_(MinIterComparator(&cfd_->internal_comparator())),
+      sv_(nullptr),
+      mutable_iter_(nullptr),
+      current_(nullptr),
+      valid_(false),
+      is_prev_set_(false) {}
+
+ForwardIterator::~ForwardIterator() {
+  Cleanup();
+}
+
+void ForwardIterator::Cleanup() {
+  delete mutable_iter_;
+  for (auto* m : imm_iters_) {
+    delete m;
+  }
+  imm_iters_.clear();
+  for (auto* f : l0_iters_) {
+    delete f;
+  }
+  l0_iters_.clear();
+  for (auto* l : level_iters_) {
+    delete l;
+  }
+  level_iters_.clear();
+
+  if (sv_ != nullptr && sv_->Unref()) {
+    DBImpl::DeletionState deletion_state;
+    db_->mutex_.Lock();
+    sv_->Cleanup();
+    db_->FindObsoleteFiles(deletion_state, false, true);
+    db_->mutex_.Unlock();
+    delete sv_;
+    if (deletion_state.HaveSomethingToDelete()) {
+      db_->PurgeObsoleteFiles(deletion_state);
+    }
+  }
+}
+
+bool ForwardIterator::Valid() const {
+  return valid_;
+}
+
+void ForwardIterator::SeekToFirst() {
+  if (sv_ == nullptr ||
+      sv_ ->version_number != cfd_->GetSuperVersionNumber()) {
+    RebuildIterators();
+  }
+  SeekInternal(Slice(), true);
+}
+
+void ForwardIterator::Seek(const Slice& internal_key) {
+  if (sv_ == nullptr ||
+      sv_ ->version_number != cfd_->GetSuperVersionNumber()) {
+    RebuildIterators();
+  }
+  SeekInternal(internal_key, false);
+}
+
+void ForwardIterator::SeekInternal(const Slice& internal_key,
+                                   bool seek_to_first) {
+  // mutable
+  seek_to_first ? mutable_iter_->SeekToFirst() :
+                  mutable_iter_->Seek(internal_key);
+
+  // immutable
+  // TODO(ljin): NeedToSeekImmutable has negative impact on performance
+  // if it turns to need to seek immutable often. We probably want to have
+  // an option to turn it off.
+  if (seek_to_first || NeedToSeekImmutable(internal_key)) {
+    {
+      auto tmp = MinIterHeap(MinIterComparator(&cfd_->internal_comparator()));
+      immutable_min_heap_.swap(tmp);
+    }
+    for (auto* m : imm_iters_) {
+      seek_to_first ? m->SeekToFirst() : m->Seek(internal_key);
+      if (m->Valid()) {
+        immutable_min_heap_.push(m);
+      }
+    }
+
+    Slice user_key;
+    if (!seek_to_first) {
+      user_key = ExtractUserKey(internal_key);
+    }
+    auto* files = sv_->current->files_;
+    for (uint32_t i = 0; i < files[0].size(); ++i) {
+      if (seek_to_first) {
+        l0_iters_[i]->SeekToFirst();
+      } else {
+        // If the target key passes over the larget key, we are sure Next()
+        // won't go over this file.
+        if (user_comparator_->Compare(user_key,
+              files[0][i]->largest.user_key()) > 0) {
+          continue;
+        }
+        l0_iters_[i]->Seek(internal_key);
+      }
+      if (l0_iters_[i]->Valid()) {
+        immutable_min_heap_.push(l0_iters_[i]);
+      }
+    }
+
+    int32_t search_left_bound = 0;
+    int32_t search_right_bound = FileIndexer::kLevelMaxIndex;
+    for (int32_t level = 1; level < sv_->current->NumberLevels(); ++level) {
+      if (files[level].empty()) {
+        search_left_bound = 0;
+        search_right_bound = FileIndexer::kLevelMaxIndex;
+        continue;
+      }
+      assert(level_iters_[level - 1] != nullptr);
+      uint32_t f_idx = 0;
+      if (!seek_to_first) {
+        // TODO(ljin): remove before committing
+        // f_idx = FindFileInRange(
+        //    files[level], internal_key, 0, files[level].size());
+
+        if (search_left_bound == search_right_bound) {
+          f_idx = search_left_bound;
+        } else if (search_left_bound < search_right_bound) {
+          f_idx = FindFileInRange(
+              files[level], internal_key, search_left_bound,
+              search_right_bound == FileIndexer::kLevelMaxIndex ?
+                files[level].size() : search_right_bound);
+        } else {
+          // search_left_bound > search_right_bound
+          // There are only 2 cases this can happen:
+          // (1) target key is smaller than left most file
+          // (2) target key is larger than right most file
+          assert(search_left_bound == (int32_t)files[level].size() ||
+                 search_right_bound == -1);
+          if (search_right_bound == -1) {
+            assert(search_left_bound == 0);
+            f_idx = 0;
+          } else {
+            sv_->current->file_indexer_.GetNextLevelIndex(
+                level, files[level].size() - 1,
+                1, 1, &search_left_bound, &search_right_bound);
+            continue;
+          }
+        }
+
+        // Prepare hints for the next level
+        if (f_idx < files[level].size()) {
+          int cmp_smallest = user_comparator_->Compare(
+              user_key, files[level][f_idx]->smallest.user_key());
+          int cmp_largest = -1;
+          if (cmp_smallest >= 0) {
+            cmp_smallest = user_comparator_->Compare(
+                user_key, files[level][f_idx]->smallest.user_key());
+          }
+          sv_->current->file_indexer_.GetNextLevelIndex(level, f_idx,
+              cmp_smallest, cmp_largest,
+              &search_left_bound, &search_right_bound);
+        } else {
+          sv_->current->file_indexer_.GetNextLevelIndex(
+              level, files[level].size() - 1,
+              1, 1, &search_left_bound, &search_right_bound);
+        }
+      }
+
+      // Seek
+      if (f_idx < files[level].size()) {
+        level_iters_[level - 1]->SetFileIndex(f_idx);
+        seek_to_first ? level_iters_[level - 1]->SeekToFirst() :
+                        level_iters_[level - 1]->Seek(internal_key);
+        if (level_iters_[level - 1]->Valid()) {
+          immutable_min_heap_.push(level_iters_[level - 1]);
+        }
+      }
+    }
+
+    if (seek_to_first || immutable_min_heap_.empty()) {
+      is_prev_set_ = false;
+    } else {
+      prev_key_.SetKey(internal_key);
+      is_prev_set_ = true;
+    }
+  } else if (current_ && current_ != mutable_iter_) {
+    // current_ is one of immutable iterators, push it back to the heap
+    immutable_min_heap_.push(current_);
+  }
+
+  UpdateCurrent();
+}
+
+void ForwardIterator::Next() {
+  assert(valid_);
+
+  if (sv_ == nullptr ||
+      sv_ ->version_number != cfd_->GetSuperVersionNumber()) {
+    std::string current_key = key().ToString();
+    Slice old_key(current_key.data(), current_key.size());
+
+    RebuildIterators();
+    SeekInternal(old_key, false);
+    if (!valid_ || key().compare(old_key) != 0) {
+      return;
+    }
+  } else if (current_ != mutable_iter_) {
+    // It is going to advance immutable iterator
+    prev_key_.SetKey(current_->key());
+    is_prev_set_ = true;
+  }
+
+  current_->Next();
+  if (current_->Valid() && current_ != mutable_iter_) {
+    immutable_min_heap_.push(current_);
+  }
+  UpdateCurrent();
+}
+
+Slice ForwardIterator::key() const {
+  assert(valid_);
+  return current_->key();
+}
+
+Slice ForwardIterator::value() const {
+  assert(valid_);
+  return current_->value();
+}
+
+Status ForwardIterator::status() const {
+  if (!status_.ok()) {
+    return status_;
+  } else if (!mutable_iter_->status().ok()) {
+    return mutable_iter_->status();
+  }
+
+  for (auto *it : imm_iters_) {
+    if (it && !it->status().ok()) {
+      return it->status();
+    }
+  }
+  for (auto *it : l0_iters_) {
+    if (it && !it->status().ok()) {
+      return it->status();
+    }
+  }
+  for (auto *it : level_iters_) {
+    if (it && !it->status().ok()) {
+      return it->status();
+    }
+  }
+
+  return Status::OK();
+}
+
+void ForwardIterator::RebuildIterators() {
+  // Clean up
+  Cleanup();
+  // New
+  sv_ = cfd_->GetReferencedSuperVersion(&(db_->mutex_));
+  mutable_iter_ = sv_->mem->NewIterator(read_options_);
+  sv_->imm->AddIterators(read_options_, &imm_iters_);
+  const auto& l0_files = sv_->current->files_[0];
+  l0_iters_.reserve(l0_files.size());
+  for (const auto* l0 : l0_files) {
+    l0_iters_.push_back(cfd_->table_cache()->NewIterator(
+        read_options_, *cfd_->soptions(), cfd_->internal_comparator(), l0->fd));
+  }
+  level_iters_.reserve(sv_->current->NumberLevels() - 1);
+  for (int32_t level = 1; level < sv_->current->NumberLevels(); ++level) {
+    if (sv_->current->files_[level].empty()) {
+      level_iters_.push_back(nullptr);
+    } else {
+      level_iters_.push_back(new LevelIterator(cfd_, read_options_,
+          sv_->current->files_[level]));
+    }
+  }
+
+  current_ = nullptr;
+  is_prev_set_ = false;
+}
+
+void ForwardIterator::UpdateCurrent() {
+  if (immutable_min_heap_.empty() && !mutable_iter_->Valid()) {
+    current_ = nullptr;
+  } else if (immutable_min_heap_.empty()) {
+    current_ = mutable_iter_;
+  } else if (!mutable_iter_->Valid()) {
+    current_ = immutable_min_heap_.top();
+    immutable_min_heap_.pop();
+  } else {
+    current_ = immutable_min_heap_.top();
+    assert(current_ != nullptr);
+    assert(current_->Valid());
+    int cmp = cfd_->internal_comparator().InternalKeyComparator::Compare(
+        mutable_iter_->key(), current_->key());
+    assert(cmp != 0);
+    if (cmp > 0) {
+      immutable_min_heap_.pop();
+    } else {
+      current_ = mutable_iter_;
+    }
+  }
+  valid_ = (current_ != nullptr);
+  if (!status_.ok()) {
+    status_ = Status::OK();
+  }
+}
+
+bool ForwardIterator::NeedToSeekImmutable(const Slice& target) {
+  if (!is_prev_set_) {
+    return true;
+  }
+  Slice prev_key = prev_key_.GetKey();
+  if (prefix_extractor_ && prefix_extractor_->Transform(target).compare(
+    prefix_extractor_->Transform(prev_key)) != 0) {
+    return true;
+  }
+  if (cfd_->internal_comparator().InternalKeyComparator::Compare(
+        prev_key, target) >= 0) {
+    return true;
+  }
+  if (immutable_min_heap_.empty() ||
+      cfd_->internal_comparator().InternalKeyComparator::Compare(
+          target, current_ == mutable_iter_ ? immutable_min_heap_.top()->key()
+                                            : current_->key()) > 0) {
+    return true;
+  }
+  return false;
+}
+
+uint32_t ForwardIterator::FindFileInRange(
+    const std::vector<FileMetaData*>& files, const Slice& internal_key,
+    uint32_t left, uint32_t right) {
+  while (left < right) {
+    uint32_t mid = (left + right) / 2;
+    const FileMetaData* f = files[mid];
+    if (cfd_->internal_comparator().InternalKeyComparator::Compare(
+          f->largest.Encode(), internal_key) < 0) {
+      // Key at "mid.largest" is < "target".  Therefore all
+      // files at or before "mid" are uninteresting.
+      left = mid + 1;
+    } else {
+      // Key at "mid.largest" is >= "target".  Therefore all files
+      // after "mid" are uninteresting.
+      right = mid;
+    }
+  }
+  return right;
+}
+
+}  // namespace rocksdb
+
+#endif  // ROCKSDB_LITE