rocksdb/table/iterator_wrapper.h
Yi Wu 662ce62044 Reduce iterator key comparison for upper/lower bound check (2nd attempt) (#5468)
Summary:
This is a second attempt for https://github.com/facebook/rocksdb/issues/5111, with the fix to redo iterate bounds check after `SeekXXX()`. This is because MyRocks may change iterate bounds between seek.

See https://github.com/facebook/rocksdb/issues/5111 for original benchmark result and discussion.

Closes https://github.com/facebook/rocksdb/issues/5463.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5468

Test Plan: Existing rocksdb tests, plus myrocks test `rocksdb.optimizer_loose_index_scans` and `rocksdb.group_min_max`.

Differential Revision: D15863332

fbshipit-source-id: ab4aba5899838591806b8673899bd465f3f53e18
2019-07-02 11:48:46 -07:00

135 lines
3.6 KiB
C++

// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#include <set>
#include "table/internal_iterator.h"
namespace rocksdb {
// A internal wrapper class with an interface similar to Iterator that caches
// the valid() and key() results for an underlying iterator.
// This can help avoid virtual function calls and also gives better
// cache locality.
template <class TValue = Slice>
class IteratorWrapperBase {
public:
IteratorWrapperBase() : iter_(nullptr), valid_(false) {}
explicit IteratorWrapperBase(InternalIteratorBase<TValue>* _iter)
: iter_(nullptr) {
Set(_iter);
}
~IteratorWrapperBase() {}
InternalIteratorBase<TValue>* iter() const { return iter_; }
// Set the underlying Iterator to _iter and return
// previous underlying Iterator.
InternalIteratorBase<TValue>* Set(InternalIteratorBase<TValue>* _iter) {
InternalIteratorBase<TValue>* old_iter = iter_;
iter_ = _iter;
if (iter_ == nullptr) {
valid_ = false;
} else {
Update();
}
return old_iter;
}
void DeleteIter(bool is_arena_mode) {
if (iter_) {
if (!is_arena_mode) {
delete iter_;
} else {
iter_->~InternalIteratorBase<TValue>();
}
}
}
// Iterator interface methods
bool Valid() const { return valid_; }
Slice key() const {
assert(Valid());
return result_.key;
}
TValue value() const {
assert(Valid());
return iter_->value();
}
// Methods below require iter() != nullptr
Status status() const { assert(iter_); return iter_->status(); }
void Next() {
assert(iter_);
valid_ = iter_->NextAndGetResult(&result_);
assert(!valid_ || iter_->status().ok());
}
void Prev() { assert(iter_); iter_->Prev(); Update(); }
void Seek(const Slice& k) {
TEST_SYNC_POINT("IteratorWrapper::Seek:0");
assert(iter_);
iter_->Seek(k);
Update();
}
void SeekForPrev(const Slice& k) {
assert(iter_);
iter_->SeekForPrev(k);
Update();
}
void SeekToFirst() { assert(iter_); iter_->SeekToFirst(); Update(); }
void SeekToLast() { assert(iter_); iter_->SeekToLast(); Update(); }
bool MayBeOutOfLowerBound() {
assert(Valid());
return iter_->MayBeOutOfLowerBound();
}
bool MayBeOutOfUpperBound() {
assert(Valid());
return result_.may_be_out_of_upper_bound;
}
void SetPinnedItersMgr(PinnedIteratorsManager* pinned_iters_mgr) {
assert(iter_);
iter_->SetPinnedItersMgr(pinned_iters_mgr);
}
bool IsKeyPinned() const {
assert(Valid());
return iter_->IsKeyPinned();
}
bool IsValuePinned() const {
assert(Valid());
return iter_->IsValuePinned();
}
private:
void Update() {
valid_ = iter_->Valid();
if (valid_) {
assert(iter_->status().ok());
result_.key = iter_->key();
result_.may_be_out_of_upper_bound = true;
}
}
InternalIteratorBase<TValue>* iter_;
IterateResult result_;
bool valid_;
};
using IteratorWrapper = IteratorWrapperBase<Slice>;
class Arena;
// Return an empty iterator (yields nothing) allocated from arena.
template <class TValue = Slice>
extern InternalIteratorBase<TValue>* NewEmptyInternalIterator(Arena* arena);
} // namespace rocksdb