mirror of https://github.com/facebook/rocksdb.git
159 lines
4.5 KiB
C++
159 lines
4.5 KiB
C++
// 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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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once
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#include <set>
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#include "table/internal_iterator.h"
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namespace rocksdb {
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// A internal wrapper class with an interface similar to Iterator that
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// caches the valid() and key() results for an underlying iterator.
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// This can help avoid virtual function calls and also gives better
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// cache locality.
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class IteratorWrapper {
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public:
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IteratorWrapper() : iter_(nullptr), iters_pinned_(false), valid_(false) {}
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explicit IteratorWrapper(InternalIterator* _iter)
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: iter_(nullptr), iters_pinned_(false) {
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Set(_iter);
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}
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~IteratorWrapper() {}
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InternalIterator* iter() const { return iter_; }
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// Takes the ownership of "_iter" and will delete it when destroyed.
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// Next call to Set() will destroy "_iter" except if PinData() was called.
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void Set(InternalIterator* _iter) {
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if (iters_pinned_ && iter_) {
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// keep old iterator until ReleasePinnedData() is called
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pinned_iters_.insert(iter_);
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} else {
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delete iter_;
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}
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iter_ = _iter;
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if (iter_ == nullptr) {
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valid_ = false;
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} else {
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Update();
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if (iters_pinned_) {
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// Pin new iterator
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Status s = iter_->PinData();
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assert(s.ok());
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}
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}
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}
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Status PinData() {
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Status s;
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if (iters_pinned_) {
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return s;
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}
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if (iter_) {
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s = iter_->PinData();
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}
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if (s.ok()) {
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iters_pinned_ = true;
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}
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return s;
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}
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Status ReleasePinnedData() {
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Status s;
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if (!iters_pinned_) {
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return s;
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}
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if (iter_) {
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s = iter_->ReleasePinnedData();
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}
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if (s.ok()) {
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iters_pinned_ = false;
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// No need to call ReleasePinnedData() for pinned_iters_
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// since we will delete them
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DeletePinnedIterators(false);
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}
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return s;
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}
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bool IsKeyPinned() const {
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assert(iter_);
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return iters_pinned_ && iter_->IsKeyPinned();
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}
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void DeleteIter(bool is_arena_mode) {
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if (iter_ && pinned_iters_.find(iter_) == pinned_iters_.end()) {
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DestroyIterator(iter_, is_arena_mode);
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}
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DeletePinnedIterators(is_arena_mode);
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}
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// Iterator interface methods
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bool Valid() const { return valid_; }
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Slice key() const { assert(Valid()); return key_; }
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Slice value() const { assert(Valid()); return iter_->value(); }
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// Methods below require iter() != nullptr
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Status status() const { assert(iter_); return iter_->status(); }
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void Next() { assert(iter_); iter_->Next(); Update(); }
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void Prev() { assert(iter_); iter_->Prev(); Update(); }
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void Seek(const Slice& k) { assert(iter_); iter_->Seek(k); Update(); }
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void SeekToFirst() { assert(iter_); iter_->SeekToFirst(); Update(); }
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void SeekToLast() { assert(iter_); iter_->SeekToLast(); Update(); }
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private:
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void Update() {
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valid_ = iter_->Valid();
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if (valid_) {
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key_ = iter_->key();
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}
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}
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void DeletePinnedIterators(bool is_arena_mode) {
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for (auto it : pinned_iters_) {
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DestroyIterator(it, is_arena_mode);
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}
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pinned_iters_.clear();
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}
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inline void DestroyIterator(InternalIterator* it, bool is_arena_mode) {
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if (!is_arena_mode) {
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delete it;
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} else {
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it->~InternalIterator();
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}
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}
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InternalIterator* iter_;
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// If set to true, current and future iterators wont be deleted.
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bool iters_pinned_;
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// List of past iterators that are pinned and wont be deleted as long as
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// iters_pinned_ is true. When we are pinning iterators this set will contain
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// iterators of previous data blocks to keep them from being deleted.
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std::set<InternalIterator*> pinned_iters_;
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bool valid_;
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Slice key_;
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};
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class Arena;
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// Return an empty iterator (yields nothing) allocated from arena.
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extern InternalIterator* NewEmptyInternalIterator(Arena* arena);
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// Return an empty iterator with the specified status, allocated arena.
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extern InternalIterator* NewErrorInternalIterator(const Status& status,
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Arena* arena);
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} // namespace rocksdb
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