rocksdb/table/iterator.cc

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// 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.
#include "rocksdb/iterator.h"
#include "table/internal_iterator.h"
#include "table/iterator_wrapper.h"
#include "util/arena.h"
namespace rocksdb {
Cleanable::Cleanable() {
cleanup_.function = nullptr;
cleanup_.next = nullptr;
}
Cleanable::~Cleanable() { DoCleanup(); }
Cleanable::Cleanable(Cleanable&& other) {
*this = std::move(other);
}
Cleanable& Cleanable::operator=(Cleanable&& other) {
if (this != &other) {
cleanup_ = other.cleanup_;
other.cleanup_.function = nullptr;
other.cleanup_.next = nullptr;
}
return *this;
}
// If the entire linked list was on heap we could have simply add attach one
// link list to another. However the head is an embeded object to avoid the cost
// of creating objects for most of the use cases when the Cleanable has only one
// Cleanup to do. We could put evernything on heap if benchmarks show no
// negative impact on performance.
// Also we need to iterate on the linked list since there is no pointer to the
// tail. We can add the tail pointer but maintainin it might negatively impact
// the perforamnce for the common case of one cleanup where tail pointer is not
// needed. Again benchmarks could clarify that.
// Even without a tail pointer we could iterate on the list, find the tail, and
// have only that node updated without the need to insert the Cleanups one by
// one. This however would be redundant when the source Cleanable has one or a
// few Cleanups which is the case most of the time.
// TODO(myabandeh): if the list is too long we should maintain a tail pointer
// and have the entire list (minus the head that has to be inserted separately)
// merged with the target linked list at once.
void Cleanable::DelegateCleanupsTo(Cleanable* other) {
assert(other != nullptr);
if (cleanup_.function == nullptr) {
return;
}
Cleanup* c = &cleanup_;
other->RegisterCleanup(c->function, c->arg1, c->arg2);
c = c->next;
while (c != nullptr) {
Cleanup* next = c->next;
other->RegisterCleanup(c);
c = next;
}
cleanup_.function = nullptr;
cleanup_.next = nullptr;
}
void Cleanable::RegisterCleanup(Cleanable::Cleanup* c) {
assert(c != nullptr);
if (cleanup_.function == nullptr) {
cleanup_.function = c->function;
cleanup_.arg1 = c->arg1;
cleanup_.arg2 = c->arg2;
delete c;
} else {
c->next = cleanup_.next;
cleanup_.next = c;
}
}
void Cleanable::RegisterCleanup(CleanupFunction func, void* arg1, void* arg2) {
assert(func != nullptr);
Cleanup* c;
if (cleanup_.function == nullptr) {
c = &cleanup_;
} else {
c = new Cleanup;
c->next = cleanup_.next;
cleanup_.next = c;
}
c->function = func;
c->arg1 = arg1;
c->arg2 = arg2;
}
Status Iterator::GetProperty(std::string prop_name, std::string* prop) {
if (prop == nullptr) {
return Status::InvalidArgument("prop is nullptr");
}
if (prop_name == "rocksdb.iterator.is-key-pinned") {
*prop = "0";
return Status::OK();
}
return Status::InvalidArgument("Unidentified property.");
}
namespace {
class EmptyIterator : public Iterator {
public:
explicit EmptyIterator(const Status& s) : status_(s) { }
virtual bool Valid() const override { return false; }
virtual void Seek(const Slice& /*target*/) override {}
virtual void SeekForPrev(const Slice& /*target*/) override {}
virtual void SeekToFirst() override {}
virtual void SeekToLast() override {}
virtual void Next() override { assert(false); }
virtual void Prev() override { assert(false); }
Slice key() const override {
assert(false);
return Slice();
}
Slice value() const override {
assert(false);
return Slice();
}
virtual Status status() const override { return status_; }
private:
Status status_;
};
template <class TValue = Slice>
class EmptyInternalIterator : public InternalIteratorBase<TValue> {
public:
explicit EmptyInternalIterator(const Status& s) : status_(s) {}
virtual bool Valid() const override { return false; }
virtual void Seek(const Slice& /*target*/) override {}
virtual void SeekForPrev(const Slice& /*target*/) override {}
virtual void SeekToFirst() override {}
virtual void SeekToLast() override {}
virtual void Next() override { assert(false); }
virtual void Prev() override { assert(false); }
Slice key() const override {
assert(false);
return Slice();
}
TValue value() const override {
assert(false);
return TValue();
}
virtual Status status() const override { return status_; }
private:
Status status_;
};
} // namespace
Iterator* NewEmptyIterator() {
return new EmptyIterator(Status::OK());
}
Iterator* NewErrorIterator(const Status& status) {
return new EmptyIterator(status);
}
template <class TValue>
InternalIteratorBase<TValue>* NewErrorInternalIterator(const Status& status) {
return new EmptyInternalIterator<TValue>(status);
}
template InternalIteratorBase<BlockHandle>* NewErrorInternalIterator(
const Status& status);
template InternalIteratorBase<Slice>* NewErrorInternalIterator(
const Status& status);
template <class TValue>
InternalIteratorBase<TValue>* NewErrorInternalIterator(const Status& status,
Arena* arena) {
if (arena == nullptr) {
return NewErrorInternalIterator<TValue>(status);
} else {
auto mem = arena->AllocateAligned(sizeof(EmptyIterator));
return new (mem) EmptyInternalIterator<TValue>(status);
}
}
template InternalIteratorBase<BlockHandle>* NewErrorInternalIterator(
const Status& status, Arena* arena);
template InternalIteratorBase<Slice>* NewErrorInternalIterator(
const Status& status, Arena* arena);
template <class TValue>
InternalIteratorBase<TValue>* NewEmptyInternalIterator() {
return new EmptyInternalIterator<TValue>(Status::OK());
}
template InternalIteratorBase<BlockHandle>* NewEmptyInternalIterator();
template InternalIteratorBase<Slice>* NewEmptyInternalIterator();
template <class TValue>
InternalIteratorBase<TValue>* NewEmptyInternalIterator(Arena* arena) {
if (arena == nullptr) {
return NewEmptyInternalIterator<TValue>();
} else {
auto mem = arena->AllocateAligned(sizeof(EmptyIterator));
return new (mem) EmptyInternalIterator<TValue>(Status::OK());
}
}
template InternalIteratorBase<BlockHandle>* NewEmptyInternalIterator(
Arena* arena);
template InternalIteratorBase<Slice>* NewEmptyInternalIterator(Arena* arena);
} // namespace rocksdb