andreacavalli/rocksdb
0
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity
8de151bb99
rocksdb/util/hash_linklist_rep.cc
sdong 9c332aa11a HashLinkList memtable switches a bucket to a skip list to reduce performance outliers 
Summary:
In this patch, we enhance HashLinkList memtable to reduce performance outliers when a bucket contains too many entries. We switch to skip list for this case to enable binary search.

Add threshold_use_skiplist parameter to determine when a bucket needs to switch to skip list.

The new data structure is documented in comments in the codes.

Test Plan:
make all check
set threshold_use_skiplist in several tests

Reviewers: yhchiang, haobo, ljin

Reviewed By: yhchiang, ljin

Subscribers: nkg-, xjin, dhruba, yhchiang, leveldb

Differential Revision: https://reviews.facebook.net/D19299
2014-07-01 17:14:15 -07:00

800 lines
27 KiB
C++
Raw Blame History

// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
#ifndef ROCKSDB_LITE
#include "util/hash_linklist_rep.h"
#include <algorithm>
#include "rocksdb/memtablerep.h"
#include "util/arena.h"
#include "rocksdb/slice.h"
#include "rocksdb/slice_transform.h"
#include "port/port.h"
#include "port/atomic_pointer.h"
#include "util/histogram.h"
#include "util/murmurhash.h"
#include "db/memtable.h"
#include "db/skiplist.h"
namespace rocksdb {
namespace {
typedef const char* Key;
typedef SkipList<Key, const MemTableRep::KeyComparator&> MemtableSkipList;
typedef port::AtomicPointer Pointer;
// A data structure used as the header of a link list of a hash bucket.
struct BucketHeader {
Pointer next;
uint32_t num_entries;
explicit BucketHeader(void* n, uint32_t count)
: next(n), num_entries(count) {}
bool IsSkipListBucket() { return next.NoBarrier_Load() == this; }
};
// A data structure used as the header of a skip list of a hash bucket.
struct SkipListBucketHeader {
BucketHeader Counting_header;
MemtableSkipList skip_list;
explicit SkipListBucketHeader(const MemTableRep::KeyComparator& cmp,
Arena* arena, uint32_t count)
: Counting_header(this, // Pointing to itself to indicate header type.
count),
skip_list(cmp, arena) {}
};
struct Node {
// Accessors/mutators for links. Wrapped in methods so we can
// add the appropriate barriers as necessary.
Node* Next() {
// Use an 'acquire load' so that we observe a fully initialized
// version of the returned Node.
return reinterpret_cast<Node*>(next_.Acquire_Load());
}
void SetNext(Node* x) {
// Use a 'release store' so that anybody who reads through this
// pointer observes a fully initialized version of the inserted node.
next_.Release_Store(x);
}
// No-barrier variants that can be safely used in a few locations.
Node* NoBarrier_Next() {
return reinterpret_cast<Node*>(next_.NoBarrier_Load());
}
void NoBarrier_SetNext(Node* x) {
next_.NoBarrier_Store(x);
}
private:
port::AtomicPointer next_;
public:
char key[0];
};
// Memory structure of the mem table:
// It is a hash table, each bucket points to one entry, a linked list or a
// skip list. In order to track total number of records in a bucket to determine
// whether should switch to skip list, a header is added just to indicate
// number of entries in the bucket.
//
//
// +-----> NULL Case 1. Empty bucket
// |
// |
// | +---> +-------+
// | | | Next +--> NULL
// | | +-------+
// +-----+ | | | | Case 2. One Entry in bucket.
// | +-+ | | Data | next pointer points to
// +-----+ | | | NULL. All other cases
// | | | | | next pointer is not NULL.
// +-----+ | +-------+
// | +---+
// +-----+ +-> +-------+ +> +-------+ +-> +-------+
// | | | | Next +--+ | Next +--+ | Next +-->NULL
// +-----+ | +-------+ +-------+ +-------+
// | +-----+ | Count | | | | |
// +-----+ +-------+ | Data | | Data |
// | | | | | |
// +-----+ Case 3. | | | |
// | | A header +-------+ +-------+
// +-----+ points to
// | | a linked list. Count indicates total number
// +-----+ of rows in this bucket.
// | |
// +-----+ +-> +-------+ <--+
// | | | | Next +----+
// +-----+ | +-------+ Case 4. A header points to a skip
// | +----+ | Count | list and next pointer points to
// +-----+ +-------+ itself, to distinguish case 3 or 4.
// | | | | Count still is kept to indicates total
// +-----+ | Skip +--> of entries in the bucket for debugging
// | | | List | Data purpose.
// | | | +-->
// +-----+ | |
// | | +-------+
// +-----+
//
// We don't have data race when changing cases because:
// (1) When changing from case 2->3, we create a new bucket header, put the
// single node there first without changing the original node, and do a
// release store when changing the bucket pointer. In that case, a reader
// who sees a stale value of the bucket pointer will read this node, while
// a reader sees the correct value because of the release store.
// (2) When changing case 3->4, a new header is created with skip list points
// to the data, before doing an acquire store to change the bucket pointer.
// The old header and nodes are never changed, so any reader sees any
// of those existing pointers will guarantee to be able to iterate to the
// end of the linked list.
// (3) Header's next pointer in case 3 might change, but they are never equal
// to itself, so no matter a reader sees any stale or newer value, it will
// be able to correctly distinguish case 3 and 4.
//
// The reason that we use case 2 is we want to make the format to be efficient
// when the utilization of buckets is relatively low. If we use case 3 for
// single entry bucket, we will need to waste 12 bytes for every entry,
// which can be significant decrease of memory utilization.
class HashLinkListRep : public MemTableRep {
public:
HashLinkListRep(const MemTableRep::KeyComparator& compare, Arena* arena,
const SliceTransform* transform, size_t bucket_size,
uint32_t threshold_use_skiplist, size_t huge_page_tlb_size,
Logger* logger, int bucket_entries_logging_threshold,
bool if_log_bucket_dist_when_flash);
virtual KeyHandle Allocate(const size_t len, char** buf) override;
virtual void Insert(KeyHandle handle) override;
virtual bool Contains(const char* key) const override;
virtual size_t ApproximateMemoryUsage() override;
virtual void Get(const LookupKey& k, void* callback_args,
bool (*callback_func)(void* arg,
const char* entry)) override;
virtual ~HashLinkListRep();
virtual MemTableRep::Iterator* GetIterator(Arena* arena = nullptr) override;
virtual MemTableRep::Iterator* GetDynamicPrefixIterator(
Arena* arena = nullptr) override;
private:
friend class DynamicIterator;
size_t bucket_size_;
// Maps slices (which are transformed user keys) to buckets of keys sharing
// the same transform.
port::AtomicPointer* buckets_;
const uint32_t threshold_use_skiplist_;
// The user-supplied transform whose domain is the user keys.
const SliceTransform* transform_;
const MemTableRep::KeyComparator& compare_;
Logger* logger_;
int bucket_entries_logging_threshold_;
bool if_log_bucket_dist_when_flash_;
bool LinkListContains(Node* head, const Slice& key) const;
SkipListBucketHeader* GetSkipListBucketHeader(Pointer* first_next_pointer)
const;
Node* GetLinkListFirstNode(Pointer* first_next_pointer) const;
Slice GetPrefix(const Slice& internal_key) const {
return transform_->Transform(ExtractUserKey(internal_key));
}
size_t GetHash(const Slice& slice) const {
return MurmurHash(slice.data(), slice.size(), 0) % bucket_size_;
}
Pointer* GetBucket(size_t i) const {
return static_cast<Pointer*>(buckets_[i].Acquire_Load());
}
Pointer* GetBucket(const Slice& slice) const {
return GetBucket(GetHash(slice));
}
bool Equal(const Slice& a, const Key& b) const {
return (compare_(b, a) == 0);
}
bool Equal(const Key& a, const Key& b) const { return (compare_(a, b) == 0); }
bool KeyIsAfterNode(const Slice& internal_key, const Node* n) const {
// nullptr n is considered infinite
return (n != nullptr) && (compare_(n->key, internal_key) < 0);
}
bool KeyIsAfterNode(const Key& key, const Node* n) const {
// nullptr n is considered infinite
return (n != nullptr) && (compare_(n->key, key) < 0);
}
Node* FindGreaterOrEqualInBucket(Node* head, const Slice& key) const;
class FullListIterator : public MemTableRep::Iterator {
public:
explicit FullListIterator(MemtableSkipList* list, Arena* arena)
: iter_(list), full_list_(list), arena_(arena) {}
virtual ~FullListIterator() {
}
// Returns true iff the iterator is positioned at a valid node.
virtual bool Valid() const {
return iter_.Valid();
}
// Returns the key at the current position.
// REQUIRES: Valid()
virtual const char* key() const {
assert(Valid());
return iter_.key();
}
// Advances to the next position.
// REQUIRES: Valid()
virtual void Next() {
assert(Valid());
iter_.Next();
}
// Advances to the previous position.
// REQUIRES: Valid()
virtual void Prev() {
assert(Valid());
iter_.Prev();
}
// Advance to the first entry with a key >= target
virtual void Seek(const Slice& internal_key, const char* memtable_key) {
const char* encoded_key =
(memtable_key != nullptr) ?
memtable_key : EncodeKey(&tmp_, internal_key);
iter_.Seek(encoded_key);
}
// Position at the first entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
virtual void SeekToFirst() {
iter_.SeekToFirst();
}
// Position at the last entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
virtual void SeekToLast() {
iter_.SeekToLast();
}
private:
MemtableSkipList::Iterator iter_;
// To destruct with the iterator.
std::unique_ptr<MemtableSkipList> full_list_;
std::unique_ptr<Arena> arena_;
std::string tmp_; // For passing to EncodeKey
};
class LinkListIterator : public MemTableRep::Iterator {
public:
explicit LinkListIterator(const HashLinkListRep* const hash_link_list_rep,
Node* head)
: hash_link_list_rep_(hash_link_list_rep),
head_(head),
node_(nullptr) {}
virtual ~LinkListIterator() {}
// Returns true iff the iterator is positioned at a valid node.
virtual bool Valid() const {
return node_ != nullptr;
}
// Returns the key at the current position.
// REQUIRES: Valid()
virtual const char* key() const {
assert(Valid());
return node_->key;
}
// Advances to the next position.
// REQUIRES: Valid()
virtual void Next() {
assert(Valid());
node_ = node_->Next();
}
// Advances to the previous position.
// REQUIRES: Valid()
virtual void Prev() {
// Prefix iterator does not support total order.
// We simply set the iterator to invalid state
Reset(nullptr);
}
// Advance to the first entry with a key >= target
virtual void Seek(const Slice& internal_key, const char* memtable_key) {
node_ = hash_link_list_rep_->FindGreaterOrEqualInBucket(head_,
internal_key);
}
// Position at the first entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
virtual void SeekToFirst() {
// Prefix iterator does not support total order.
// We simply set the iterator to invalid state
Reset(nullptr);
}
// Position at the last entry in collection.
// Final state of iterator is Valid() iff collection is not empty.
virtual void SeekToLast() {
// Prefix iterator does not support total order.
// We simply set the iterator to invalid state
Reset(nullptr);
}
protected:
void Reset(Node* head) {
head_ = head;
node_ = nullptr;
}
private:
friend class HashLinkListRep;
const HashLinkListRep* const hash_link_list_rep_;
Node* head_;
Node* node_;
virtual void SeekToHead() {
node_ = head_;
}
};
class DynamicIterator : public HashLinkListRep::LinkListIterator {
public:
explicit DynamicIterator(HashLinkListRep& memtable_rep)
: HashLinkListRep::LinkListIterator(&memtable_rep, nullptr),
memtable_rep_(memtable_rep) {}
// Advance to the first entry with a key >= target
virtual void Seek(const Slice& k, const char* memtable_key) {
auto transformed = memtable_rep_.GetPrefix(k);
auto* bucket = memtable_rep_.GetBucket(transformed);
SkipListBucketHeader* skip_list_header =
memtable_rep_.GetSkipListBucketHeader(bucket);
if (skip_list_header != nullptr) {
// The bucket is organized as a skip list
if (!skip_list_iter_) {
skip_list_iter_.reset(
new MemtableSkipList::Iterator(&skip_list_header->skip_list));
} else {
skip_list_iter_->SetList(&skip_list_header->skip_list);
}
if (memtable_key != nullptr) {
skip_list_iter_->Seek(memtable_key);
} else {
IterKey encoded_key;
encoded_key.EncodeLengthPrefixedKey(k);
skip_list_iter_->Seek(encoded_key.GetKey().data());
}
} else {
// The bucket is organized as a linked list
skip_list_iter_.reset();
Reset(memtable_rep_.GetLinkListFirstNode(bucket));
HashLinkListRep::LinkListIterator::Seek(k, memtable_key);
}
}
virtual bool Valid() const {
if (skip_list_iter_) {
return skip_list_iter_->Valid();
}
return HashLinkListRep::LinkListIterator::Valid();
}
virtual const char* key() const {
if (skip_list_iter_) {
return skip_list_iter_->key();
}
return HashLinkListRep::LinkListIterator::key();
}
virtual void Next() {
if (skip_list_iter_) {
skip_list_iter_->Next();
} else {
HashLinkListRep::LinkListIterator::Next();
}
}
private:
// the underlying memtable
const HashLinkListRep& memtable_rep_;
std::unique_ptr<MemtableSkipList::Iterator> skip_list_iter_;
};
class EmptyIterator : public MemTableRep::Iterator {
// This is used when there wasn't a bucket. It is cheaper than
// instantiating an empty bucket over which to iterate.
public:
EmptyIterator() { }
virtual bool Valid() const {
return false;
}
virtual const char* key() const {
assert(false);
return nullptr;
}
virtual void Next() { }
virtual void Prev() { }
virtual void Seek(const Slice& user_key, const char* memtable_key) { }
virtual void SeekToFirst() { }
virtual void SeekToLast() { }
private:
};
};
HashLinkListRep::HashLinkListRep(const MemTableRep::KeyComparator& compare,
Arena* arena, const SliceTransform* transform,
size_t bucket_size,
uint32_t threshold_use_skiplist,
size_t huge_page_tlb_size, Logger* logger,
int bucket_entries_logging_threshold,
bool if_log_bucket_dist_when_flash)
: MemTableRep(arena),
bucket_size_(bucket_size),
// Threshold to use skip list doesn't make sense if less than 3, so we
// force it to be minimum of 3 to simplify implementation.
threshold_use_skiplist_(std::max(threshold_use_skiplist, 3U)),
transform_(transform),
compare_(compare),
logger_(logger),
bucket_entries_logging_threshold_(bucket_entries_logging_threshold),
if_log_bucket_dist_when_flash_(if_log_bucket_dist_when_flash) {
char* mem = arena_->AllocateAligned(sizeof(port::AtomicPointer) * bucket_size,
huge_page_tlb_size, logger);
buckets_ = new (mem) port::AtomicPointer[bucket_size];
for (size_t i = 0; i < bucket_size_; ++i) {
buckets_[i].NoBarrier_Store(nullptr);
}
}
HashLinkListRep::~HashLinkListRep() {
}
KeyHandle HashLinkListRep::Allocate(const size_t len, char** buf) {
char* mem = arena_->AllocateAligned(sizeof(Node) + len);
Node* x = new (mem) Node();
*buf = x->key;
return static_cast<void*>(x);
}
SkipListBucketHeader* HashLinkListRep::GetSkipListBucketHeader(
Pointer* first_next_pointer) const {
if (first_next_pointer == nullptr) {
return nullptr;
}
if (first_next_pointer->NoBarrier_Load() == nullptr) {
// Single entry bucket
return nullptr;
}
// Counting header
BucketHeader* header = reinterpret_cast<BucketHeader*>(first_next_pointer);
if (header->IsSkipListBucket()) {
assert(header->num_entries > threshold_use_skiplist_);
auto* skip_list_bucket_header =
reinterpret_cast<SkipListBucketHeader*>(header);
assert(skip_list_bucket_header->Counting_header.next.NoBarrier_Load() ==
header);
return skip_list_bucket_header;
}
assert(header->num_entries <= threshold_use_skiplist_);
return nullptr;
}
Node* HashLinkListRep::GetLinkListFirstNode(Pointer* first_next_pointer) const {
if (first_next_pointer == nullptr) {
return nullptr;
}
if (first_next_pointer->NoBarrier_Load() == nullptr) {
// Single entry bucket
return reinterpret_cast<Node*>(first_next_pointer);
}
// Counting header
BucketHeader* header = reinterpret_cast<BucketHeader*>(first_next_pointer);
if (!header->IsSkipListBucket()) {
assert(header->num_entries <= threshold_use_skiplist_);
return reinterpret_cast<Node*>(header->next.NoBarrier_Load());
}
assert(header->num_entries > threshold_use_skiplist_);
return nullptr;
}
void HashLinkListRep::Insert(KeyHandle handle) {
Node* x = static_cast<Node*>(handle);
assert(!Contains(x->key));
Slice internal_key = GetLengthPrefixedSlice(x->key);
auto transformed = GetPrefix(internal_key);
auto& bucket = buckets_[GetHash(transformed)];
Pointer* first_next_pointer = static_cast<Pointer*>(bucket.NoBarrier_Load());
if (first_next_pointer == nullptr) {
// Case 1. empty bucket
// NoBarrier_SetNext() suffices since we will add a barrier when
// we publish a pointer to "x" in prev[i].
x->NoBarrier_SetNext(nullptr);
bucket.Release_Store(x);
return;
}
BucketHeader* header = nullptr;
if (first_next_pointer->NoBarrier_Load() == nullptr) {
// Case 2. only one entry in the bucket
// Need to convert to a Counting bucket and turn to case 4.
Node* first = reinterpret_cast<Node*>(first_next_pointer);
// Need to add a bucket header.
// We have to first convert it to a bucket with header before inserting
// the new node. Otherwise, we might need to change next pointer of first.
// In that case, a reader might sees the next pointer is NULL and wrongly
// think the node is a bucket header.
auto* mem = arena_->AllocateAligned(sizeof(BucketHeader));
header = new (mem) BucketHeader(first, 1);
bucket.Release_Store(header);
} else {
header = reinterpret_cast<BucketHeader*>(first_next_pointer);
if (header->IsSkipListBucket()) {
// Case 4. Bucket is already a skip list
assert(header->num_entries > threshold_use_skiplist_);
auto* skip_list_bucket_header =
reinterpret_cast<SkipListBucketHeader*>(header);
skip_list_bucket_header->Counting_header.num_entries++;
skip_list_bucket_header->skip_list.Insert(x->key);
return;
}
}
if (bucket_entries_logging_threshold_ > 0 &&
header->num_entries ==
static_cast<uint32_t>(bucket_entries_logging_threshold_)) {
Info(logger_,
"HashLinkedList bucket %zu has more than %d "
"entries. Key to insert: %s",
GetHash(transformed), header->num_entries,
GetLengthPrefixedSlice(x->key).ToString(true).c_str());
}
if (header->num_entries == threshold_use_skiplist_) {
// Case 3. number of entries reaches the threshold so need to convert to
// skip list.
LinkListIterator bucket_iter(
this, reinterpret_cast<Node*>(first_next_pointer->NoBarrier_Load()));
auto mem = arena_->AllocateAligned(sizeof(SkipListBucketHeader));
SkipListBucketHeader* new_skip_list_header = new (mem)
SkipListBucketHeader(compare_, arena_, header->num_entries + 1);
auto& skip_list = new_skip_list_header->skip_list;
// Add all current entries to the skip list
for (bucket_iter.SeekToHead(); bucket_iter.Valid(); bucket_iter.Next()) {
skip_list.Insert(bucket_iter.key());
}
// insert the new entry
skip_list.Insert(x->key);
// Set the bucket
bucket.Release_Store(new_skip_list_header);
} else {
// Case 5. Need to insert to the sorted linked list without changing the
// header.
Node* first = reinterpret_cast<Node*>(header->next.NoBarrier_Load());
assert(first != nullptr);
// Advance counter unless the bucket needs to be advanced to skip list.
// In that case, we need to make sure the previous count never exceeds
// threshold_use_skiplist_ to avoid readers to cast to wrong format.
header->num_entries++;
Node* cur = first;
Node* prev = nullptr;
while (true) {
if (cur == nullptr) {
break;
}
Node* next = cur->Next();
// Make sure the lists are sorted.
// If x points to head_ or next points nullptr, it is trivially satisfied.
assert((cur == first) || (next == nullptr) ||
KeyIsAfterNode(next->key, cur));
if (KeyIsAfterNode(internal_key, cur)) {
// Keep searching in this list
prev = cur;
cur = next;
} else {
break;
}
}
// Our data structure does not allow duplicate insertion
assert(cur == nullptr || !Equal(x->key, cur->key));
// NoBarrier_SetNext() suffices since we will add a barrier when
// we publish a pointer to "x" in prev[i].
x->NoBarrier_SetNext(cur);
if (prev) {
prev->SetNext(x);
} else {
header->next.Release_Store(static_cast<void*>(x));
}
}
}
bool HashLinkListRep::Contains(const char* key) const {
Slice internal_key = GetLengthPrefixedSlice(key);
auto transformed = GetPrefix(internal_key);
auto bucket = GetBucket(transformed);
if (bucket == nullptr) {
return false;
}
SkipListBucketHeader* skip_list_header = GetSkipListBucketHeader(bucket);
if (skip_list_header != nullptr) {
return skip_list_header->skip_list.Contains(key);
} else {
return LinkListContains(GetLinkListFirstNode(bucket), internal_key);
}
}
size_t HashLinkListRep::ApproximateMemoryUsage() {
// Memory is always allocated from the arena.
return 0;
}
void HashLinkListRep::Get(const LookupKey& k, void* callback_args,
bool (*callback_func)(void* arg, const char* entry)) {
auto transformed = transform_->Transform(k.user_key());
auto bucket = GetBucket(transformed);
auto* skip_list_header = GetSkipListBucketHeader(bucket);
if (skip_list_header != nullptr) {
// Is a skip list
MemtableSkipList::Iterator iter(&skip_list_header->skip_list);
for (iter.Seek(k.memtable_key().data());
iter.Valid() && callback_func(callback_args, iter.key());
iter.Next()) {
}
} else {
auto* link_list_head = GetLinkListFirstNode(bucket);
if (link_list_head != nullptr) {
LinkListIterator iter(this, link_list_head);
for (iter.Seek(k.internal_key(), nullptr);
iter.Valid() && callback_func(callback_args, iter.key());
iter.Next()) {
}
}
}
}
MemTableRep::Iterator* HashLinkListRep::GetIterator(Arena* alloc_arena) {
// allocate a new arena of similar size to the one currently in use
Arena* new_arena = new Arena(arena_->BlockSize());
auto list = new MemtableSkipList(compare_, new_arena);
HistogramImpl keys_per_bucket_hist;
for (size_t i = 0; i < bucket_size_; ++i) {
int count = 0;
auto* bucket = GetBucket(i);
if (bucket != nullptr) {
auto* skip_list_header = GetSkipListBucketHeader(bucket);
if (skip_list_header != nullptr) {
// Is a skip list
MemtableSkipList::Iterator itr(&skip_list_header->skip_list);
for (itr.SeekToFirst(); itr.Valid(); itr.Next()) {
list->Insert(itr.key());
count++;
}
} else {
auto* link_list_head = GetLinkListFirstNode(bucket);
if (link_list_head != nullptr) {
LinkListIterator itr(this, link_list_head);
for (itr.SeekToHead(); itr.Valid(); itr.Next()) {
list->Insert(itr.key());
count++;
}
}
}
}
if (if_log_bucket_dist_when_flash_) {
keys_per_bucket_hist.Add(count);
}
}
if (if_log_bucket_dist_when_flash_ && logger_ != nullptr) {
Info(logger_, "hashLinkedList Entry distribution among buckets: %s",
keys_per_bucket_hist.ToString().c_str());
}
if (alloc_arena == nullptr) {
return new FullListIterator(list, new_arena);
} else {
auto mem = alloc_arena->AllocateAligned(sizeof(FullListIterator));
return new (mem) FullListIterator(list, new_arena);
}
}
MemTableRep::Iterator* HashLinkListRep::GetDynamicPrefixIterator(
Arena* alloc_arena) {
if (alloc_arena == nullptr) {
return new DynamicIterator(*this);
} else {
auto mem = alloc_arena->AllocateAligned(sizeof(DynamicIterator));
return new (mem) DynamicIterator(*this);
}
}
bool HashLinkListRep::LinkListContains(Node* head,
const Slice& user_key) const {
Node* x = FindGreaterOrEqualInBucket(head, user_key);
return (x != nullptr && Equal(user_key, x->key));
}
Node* HashLinkListRep::FindGreaterOrEqualInBucket(Node* head,
const Slice& key) const {
Node* x = head;
while (true) {
if (x == nullptr) {
return x;
}
Node* next = x->Next();
// Make sure the lists are sorted.
// If x points to head_ or next points nullptr, it is trivially satisfied.
assert((x == head) || (next == nullptr) || KeyIsAfterNode(next->key, x));
if (KeyIsAfterNode(key, x)) {
// Keep searching in this list
x = next;
} else {
break;
}
}
return x;
}
} // anon namespace
MemTableRep* HashLinkListRepFactory::CreateMemTableRep(
const MemTableRep::KeyComparator& compare, Arena* arena,
const SliceTransform* transform, Logger* logger) {
return new HashLinkListRep(compare, arena, transform, bucket_count_,
threshold_use_skiplist_, huge_page_tlb_size_,
logger, bucket_entries_logging_threshold_,
if_log_bucket_dist_when_flash_);
}
MemTableRepFactory* NewHashLinkListRepFactory(
size_t bucket_count, size_t huge_page_tlb_size,
int bucket_entries_logging_threshold, bool if_log_bucket_dist_when_flash,
uint32_t threshold_use_skiplist) {
return new HashLinkListRepFactory(
bucket_count, threshold_use_skiplist, huge_page_tlb_size,
bucket_entries_logging_threshold, if_log_bucket_dist_when_flash);
}
} // namespace rocksdb
#endif // ROCKSDB_LITE
Reference in New Issue View Git Blame Copy Permalink