581442d446
Summary: Using module to calculate hash makes lookup ~8% slower. But it has its benefit: file size is more predictable, more space enffient Test Plan: db_bench Reviewers: igor, yhchiang, sdong Reviewed By: sdong Subscribers: leveldb Differential Revision: https://reviews.facebook.net/D23691
79 lines
2.5 KiB
C++
79 lines
2.5 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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#pragma once
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#ifndef ROCKSDB_LITE
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#include <string>
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#include "rocksdb/table.h"
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#include "util/murmurhash.h"
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#include "rocksdb/options.h"
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namespace rocksdb {
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const uint32_t kCuckooMurmurSeedMultiplier = 816922183;
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static inline uint64_t CuckooHash(
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const Slice& user_key, uint32_t hash_cnt, bool use_module_hash,
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uint64_t table_size_, bool identity_as_first_hash,
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uint64_t (*get_slice_hash)(const Slice&, uint32_t, uint64_t)) {
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#ifndef NDEBUG
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// This part is used only in unit tests.
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if (get_slice_hash != nullptr) {
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return get_slice_hash(user_key, hash_cnt, table_size_);
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}
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#endif
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uint64_t value = 0;
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if (hash_cnt == 0 && identity_as_first_hash) {
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value = (*reinterpret_cast<const int64_t*>(user_key.data()));
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} else {
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value = MurmurHash(user_key.data(), user_key.size(),
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kCuckooMurmurSeedMultiplier * hash_cnt);
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}
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if (use_module_hash) {
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return value % table_size_;
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} else {
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return value & (table_size_ - 1);
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}
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}
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// Cuckoo Table is designed for applications that require fast point lookups
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// but not fast range scans.
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//
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// Some assumptions:
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// - Key length and Value length are fixed.
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// - Does not support Snapshot.
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// - Does not support Merge operations.
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class CuckooTableFactory : public TableFactory {
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public:
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explicit CuckooTableFactory(const CuckooTableOptions& table_options)
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: table_options_(table_options) {}
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~CuckooTableFactory() {}
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const char* Name() const override { return "CuckooTable"; }
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Status NewTableReader(
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const ImmutableCFOptions& ioptions, const EnvOptions& env_options,
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const InternalKeyComparator& internal_comparator,
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unique_ptr<RandomAccessFile>&& file, uint64_t file_size,
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unique_ptr<TableReader>* table) const override;
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TableBuilder* NewTableBuilder(const ImmutableCFOptions& options,
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const InternalKeyComparator& icomparator, WritableFile* file,
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const CompressionType, const CompressionOptions&) const override;
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// Sanitizes the specified DB Options.
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Status SanitizeDBOptions(const DBOptions* db_opts) const override {
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return Status::OK();
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}
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std::string GetPrintableTableOptions() const override;
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private:
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const CuckooTableOptions table_options_;
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};
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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