7f71448388
Summary: This implements a cache friendly version of Cuckoo Hash in which, in case of collission, we try to insert in next few locations. The size of the neighborhood to check is taken as an input parameter in builder and stored in the table.
Test Plan:
make check all
cuckoo_table_{db,reader,builder}_test
Reviewers: sdong, ljin
Reviewed By: ljin
Subscribers: leveldb
Differential Revision: https://reviews.facebook.net/D22455
78 lines
3.0 KiB
C++
78 lines
3.0 KiB
C++
// Copyright (c) 2014, 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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#ifndef ROCKSDB_LITE
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#include "table/cuckoo_table_factory.h"
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#include "db/dbformat.h"
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#include "table/cuckoo_table_builder.h"
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#include "table/cuckoo_table_reader.h"
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#include "util/murmurhash.h"
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namespace rocksdb {
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extern const uint32_t kMaxNumHashTable = 64;
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extern uint64_t GetSliceMurmurHash(const Slice& s, uint32_t index,
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uint64_t max_num_buckets) {
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static constexpr uint32_t seeds[kMaxNumHashTable] = {
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816922183, 506425713, 949485004, 22513986, 421427259, 500437285,
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888981693, 847587269, 511007211, 722295391, 934013645, 566947683,
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193618736, 428277388, 770956674, 819994962, 755946528, 40807421,
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263144466, 241420041, 444294464, 731606396, 304158902, 563235655,
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968740453, 336996831, 462831574, 407970157, 985877240, 637708754,
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736932700, 205026023, 755371467, 729648411, 807744117, 46482135,
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847092855, 620960699, 102476362, 314094354, 625838942, 550889395,
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639071379, 834567510, 397667304, 151945969, 443634243, 196618243,
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421986347, 407218337, 964502417, 327741231, 493359459, 452453139,
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692216398, 108161624, 816246924, 234779764, 618949448, 496133787,
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156374056, 316589799, 982915425, 553105889 };
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return MurmurHash(s.data(), s.size(), seeds[index]) % max_num_buckets;
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}
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Status CuckooTableFactory::NewTableReader(const Options& options,
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const EnvOptions& soptions, const InternalKeyComparator& icomp,
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std::unique_ptr<RandomAccessFile>&& file, uint64_t file_size,
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std::unique_ptr<TableReader>* table) const {
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std::unique_ptr<CuckooTableReader> new_reader(new CuckooTableReader(options,
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std::move(file), file_size, icomp.user_comparator(), GetSliceMurmurHash));
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Status s = new_reader->status();
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if (s.ok()) {
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*table = std::move(new_reader);
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}
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return s;
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}
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TableBuilder* CuckooTableFactory::NewTableBuilder(
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const Options& options, const InternalKeyComparator& internal_comparator,
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WritableFile* file, CompressionType compression_type) const {
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return new CuckooTableBuilder(file, hash_table_ratio_, kMaxNumHashTable,
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max_search_depth_, internal_comparator.user_comparator(),
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cuckoo_block_size_, GetSliceMurmurHash);
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}
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std::string CuckooTableFactory::GetPrintableTableOptions() const {
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std::string ret;
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ret.reserve(2000);
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const int kBufferSize = 200;
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char buffer[kBufferSize];
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snprintf(buffer, kBufferSize, " hash_table_ratio: %lf\n",
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hash_table_ratio_);
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ret.append(buffer);
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snprintf(buffer, kBufferSize, " max_search_depth: %u\n",
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max_search_depth_);
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ret.append(buffer);
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return ret;
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}
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TableFactory* NewCuckooTableFactory(double hash_table_ratio,
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uint32_t max_search_depth, uint32_t cuckoo_block_size) {
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return new CuckooTableFactory(
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hash_table_ratio, max_search_depth, cuckoo_block_size);
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}
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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