df9069d23f
Summary: In this patch, try to allocate the whole iterator tree starting from DBIter from an arena 1. ArenaWrappedDBIter is created when serves as the entry point of an iterator tree, with an arena in it. 2. Add an option to create iterator from arena for following iterators: DBIter, MergingIterator, MemtableIterator, all mem table's iterators, all table reader's iterators and two level iterator. 3. MergeIteratorBuilder is created to incrementally build the tree of internal iterators. It is passed to mem table list and version set and add iterators to it. Limitations: (1) Only DB::NewIterator() without tailing uses the arena. Other cases, including readonly DB and compactions are still from malloc (2) Two level iterator itself is allocated in arena, but not iterators inside it. Test Plan: make all check Reviewers: ljin, haobo Reviewed By: haobo Subscribers: leveldb, dhruba, yhchiang, igor Differential Revision: https://reviews.facebook.net/D18513
82 lines
2.6 KiB
C++
82 lines
2.6 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 "rocksdb/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), valid_(false) { }
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explicit IteratorWrapper(Iterator* iter): iter_(nullptr) {
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Set(iter);
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}
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~IteratorWrapper() {}
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Iterator* iter() const { return iter_; }
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// Takes ownership of "iter" and will delete it when destroyed, or
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// when Set() is invoked again.
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void Set(Iterator* iter) {
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delete iter_;
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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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}
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}
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void DeleteIter(bool is_arena_mode) {
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if (!is_arena_mode) {
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delete iter_;
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} else {
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iter_->~Iterator();
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}
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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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Iterator* iter_;
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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 Iterator* NewEmptyIterator(Arena* arena);
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// Return an empty iterator with the specified status, allocated arena.
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extern Iterator* NewErrorIterator(const Status& status, Arena* arena);
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} // namespace rocksdb
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