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
60 lines
1.9 KiB
C++
60 lines
1.9 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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namespace rocksdb {
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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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// 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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CuckooTableFactory(double hash_table_ratio, uint32_t max_search_depth,
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uint32_t cuckoo_block_size)
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: hash_table_ratio_(hash_table_ratio),
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max_search_depth_(max_search_depth),
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cuckoo_block_size_(cuckoo_block_size) {}
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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 Options& options, const EnvOptions& soptions,
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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 Options& options,
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const InternalKeyComparator& icomparator, WritableFile* file,
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CompressionType compression_type) const override;
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// Sanitizes the specified DB Options.
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Status SanitizeDBOptions(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 double hash_table_ratio_;
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const uint32_t max_search_depth_;
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const uint32_t cuckoo_block_size_;
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};
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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