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rocksdb/memtable/vectorrep.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).
//
#ifndef ROCKSDB_LITE
#include "rocksdb/memtablerep.h"
#include <unordered_set>
#include <set>
#include <memory>
#include <algorithm>
#include <type_traits>
#include "db/memtable.h"
#include "memory/arena.h"
#include "memtable/stl_wrappers.h"
#include "port/port.h"
#include "util/mutexlock.h"
namespace ROCKSDB_NAMESPACE {
namespace {
using namespace stl_wrappers;
class VectorRep : public MemTableRep {
public:
VectorRep(const KeyComparator& compare, Allocator* allocator, size_t count);
// Insert key into the collection. (The caller will pack key and value into a
// single buffer and pass that in as the parameter to Insert)
// REQUIRES: nothing that compares equal to key is currently in the
// collection.
void Insert(KeyHandle handle) override;
// Returns true iff an entry that compares equal to key is in the collection.
bool Contains(const char* key) const override;
void MarkReadOnly() override;
size_t ApproximateMemoryUsage() override;
void Get(const LookupKey& k, void* callback_args,
bool (*callback_func)(void* arg, const char* entry)) override;
~VectorRep() override {}
class Iterator : public MemTableRep::Iterator {
class VectorRep* vrep_;
std::shared_ptr<std::vector<const char*>> bucket_;
std::vector<const char*>::const_iterator mutable cit_;
const KeyComparator& compare_;
std::string tmp_; // For passing to EncodeKey
bool mutable sorted_;
void DoSort() const;
public:
explicit Iterator(class VectorRep* vrep,
std::shared_ptr<std::vector<const char*>> bucket,
const KeyComparator& compare);
// Initialize an iterator over the specified collection.
// The returned iterator is not valid.
// explicit Iterator(const MemTableRep* collection);
~Iterator() override{};
// Returns true iff the iterator is positioned at a valid node.
bool Valid() const override;
// Returns the key at the current position.
// REQUIRES: Valid()
const char* key() const override;
// Advances to the next position.
// REQUIRES: Valid()
void Next() override;
// Advances to the previous position.
// REQUIRES: Valid()
void Prev() override;
// Advance to the first entry with a key >= target
void Seek(const Slice& user_key, const char* memtable_key) override;
// Advance to the first entry with a key <= target
void SeekForPrev(const Slice& user_key, const char* memtable_key) override;
// Position at the first entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
void SeekToFirst() override;
// Position at the last entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
void SeekToLast() override;
};
// Return an iterator over the keys in this representation.
MemTableRep::Iterator* GetIterator(Arena* arena) override;
private:
friend class Iterator;
using Bucket = std::vector<const char*>;
std::shared_ptr<Bucket> bucket_;
mutable port::RWMutex rwlock_;
bool immutable_;
bool sorted_;
const KeyComparator& compare_;
};
void VectorRep::Insert(KeyHandle handle) {
auto* key = static_cast<char*>(handle);
WriteLock l(&rwlock_);
assert(!immutable_);
bucket_->push_back(key);
}
// Returns true iff an entry that compares equal to key is in the collection.
bool VectorRep::Contains(const char* key) const {
ReadLock l(&rwlock_);
return std::find(bucket_->begin(), bucket_->end(), key) != bucket_->end();
}
void VectorRep::MarkReadOnly() {
WriteLock l(&rwlock_);
immutable_ = true;
}
size_t VectorRep::ApproximateMemoryUsage() {
return
sizeof(bucket_) + sizeof(*bucket_) +
bucket_->size() *
sizeof(
std::remove_reference<decltype(*bucket_)>::type::value_type
);
}
VectorRep::VectorRep(const KeyComparator& compare, Allocator* allocator,
size_t count)
: MemTableRep(allocator),
bucket_(new Bucket()),
immutable_(false),
sorted_(false),
compare_(compare) {
bucket_.get()->reserve(count);
}
VectorRep::Iterator::Iterator(class VectorRep* vrep,
std::shared_ptr<std::vector<const char*>> bucket,
const KeyComparator& compare)
: vrep_(vrep),
bucket_(bucket),
cit_(bucket_->end()),
compare_(compare),
sorted_(false) { }
void VectorRep::Iterator::DoSort() const {
// vrep is non-null means that we are working on an immutable memtable
if (!sorted_ && vrep_ != nullptr) {
WriteLock l(&vrep_->rwlock_);
if (!vrep_->sorted_) {
std::sort(bucket_->begin(), bucket_->end(), Compare(compare_));
cit_ = bucket_->begin();
vrep_->sorted_ = true;
}
sorted_ = true;
}
if (!sorted_) {
std::sort(bucket_->begin(), bucket_->end(), Compare(compare_));
cit_ = bucket_->begin();
sorted_ = true;
}
assert(sorted_);
assert(vrep_ == nullptr || vrep_->sorted_);
}
// Returns true iff the iterator is positioned at a valid node.
bool VectorRep::Iterator::Valid() const {
DoSort();
return cit_ != bucket_->end();
}
// Returns the key at the current position.
// REQUIRES: Valid()
const char* VectorRep::Iterator::key() const {
assert(sorted_);
return *cit_;
}
// Advances to the next position.
// REQUIRES: Valid()
void VectorRep::Iterator::Next() {
assert(sorted_);
if (cit_ == bucket_->end()) {
return;
}
++cit_;
}
// Advances to the previous position.
// REQUIRES: Valid()
void VectorRep::Iterator::Prev() {
assert(sorted_);
if (cit_ == bucket_->begin()) {
// If you try to go back from the first element, the iterator should be
// invalidated. So we set it to past-the-end. This means that you can
// treat the container circularly.
cit_ = bucket_->end();
} else {
--cit_;
}
}
// Advance to the first entry with a key >= target
void VectorRep::Iterator::Seek(const Slice& user_key,
const char* memtable_key) {
DoSort();
// Do binary search to find first value not less than the target
const char* encoded_key =
(memtable_key != nullptr) ? memtable_key : EncodeKey(&tmp_, user_key);
cit_ = std::equal_range(bucket_->begin(),
bucket_->end(),
encoded_key,
[this] (const char* a, const char* b) {
return compare_(a, b) < 0;
}).first;
}
// Advance to the first entry with a key <= target
void VectorRep::Iterator::SeekForPrev(const Slice& /*user_key*/,
const char* /*memtable_key*/) {
assert(false);
}
// Position at the first entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
void VectorRep::Iterator::SeekToFirst() {
DoSort();
cit_ = bucket_->begin();
}
// Position at the last entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
void VectorRep::Iterator::SeekToLast() {
DoSort();
cit_ = bucket_->end();
if (bucket_->size() != 0) {
--cit_;
}
}
void VectorRep::Get(const LookupKey& k, void* callback_args,
bool (*callback_func)(void* arg, const char* entry)) {
rwlock_.ReadLock();
VectorRep* vector_rep;
std::shared_ptr<Bucket> bucket;
if (immutable_) {
vector_rep = this;
} else {
vector_rep = nullptr;
bucket.reset(new Bucket(*bucket_)); // make a copy
}
VectorRep::Iterator iter(vector_rep, immutable_ ? bucket_ : bucket, compare_);
rwlock_.ReadUnlock();
for (iter.Seek(k.user_key(), k.memtable_key().data());
iter.Valid() && callback_func(callback_args, iter.key()); iter.Next()) {
}
}
MemTableRep::Iterator* VectorRep::GetIterator(Arena* arena) {
char* mem = nullptr;
if (arena != nullptr) {
mem = arena->AllocateAligned(sizeof(Iterator));
}
ReadLock l(&rwlock_);
// Do not sort here. The sorting would be done the first time
// a Seek is performed on the iterator.
if (immutable_) {
if (arena == nullptr) {
return new Iterator(this, bucket_, compare_);
} else {
return new (mem) Iterator(this, bucket_, compare_);
}
} else {
std::shared_ptr<Bucket> tmp;
tmp.reset(new Bucket(*bucket_)); // make a copy
if (arena == nullptr) {
return new Iterator(nullptr, tmp, compare_);
} else {
return new (mem) Iterator(nullptr, tmp, compare_);
}
}
}
} // anon namespace
MemTableRep* VectorRepFactory::CreateMemTableRep(
const MemTableRep::KeyComparator& compare, Allocator* allocator,
const SliceTransform*, Logger* /*logger*/) {
return new VectorRep(compare, allocator, count_);
}
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE