mirror of https://github.com/facebook/rocksdb.git
81 lines
2.6 KiB
C++
81 lines
2.6 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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#pragma once
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#include <string>
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#include "rocksdb/options.h"
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#include "rocksdb/table.h"
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#include "util/murmurhash.h"
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namespace ROCKSDB_NAMESPACE {
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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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#if !defined NDEBUG || defined OS_WIN
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// This part is used only in unit tests but we have to keep it for Windows
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// build as we run test in both debug and release modes under Windows.
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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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#else
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(void)get_slice_hash;
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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(), static_cast<int>(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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// - Does not support prefix bloom filters.
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class CuckooTableFactory : public TableFactory {
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public:
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explicit CuckooTableFactory(
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const CuckooTableOptions& table_option = CuckooTableOptions());
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~CuckooTableFactory() {}
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// Method to allow CheckedCast to work for this class
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static const char* kClassName() { return kCuckooTableName(); }
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const char* Name() const override { return kCuckooTableName(); }
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using TableFactory::NewTableReader;
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Status NewTableReader(
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const ReadOptions& ro, const TableReaderOptions& table_reader_options,
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std::unique_ptr<RandomAccessFileReader>&& file, uint64_t file_size,
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std::unique_ptr<TableReader>* table,
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bool prefetch_index_and_filter_in_cache = true) const override;
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TableBuilder* NewTableBuilder(
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const TableBuilderOptions& table_builder_options,
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WritableFileWriter* file) const override;
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std::string GetPrintableOptions() const override;
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private:
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CuckooTableOptions table_options_;
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};
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} // namespace ROCKSDB_NAMESPACE
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