rocksdb/table/cuckoo_table_factory.h
Lei Jin 581442d446 option to choose module when calculating CuckooTable hash
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
2014-09-25 13:53:27 -07:00

79 lines
2.5 KiB
C++

// Copyright (c) 2014, 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.
#pragma once
#ifndef ROCKSDB_LITE
#include <string>
#include "rocksdb/table.h"
#include "util/murmurhash.h"
#include "rocksdb/options.h"
namespace rocksdb {
const uint32_t kCuckooMurmurSeedMultiplier = 816922183;
static inline uint64_t CuckooHash(
const Slice& user_key, uint32_t hash_cnt, bool use_module_hash,
uint64_t table_size_, bool identity_as_first_hash,
uint64_t (*get_slice_hash)(const Slice&, uint32_t, uint64_t)) {
#ifndef NDEBUG
// This part is used only in unit tests.
if (get_slice_hash != nullptr) {
return get_slice_hash(user_key, hash_cnt, table_size_);
}
#endif
uint64_t value = 0;
if (hash_cnt == 0 && identity_as_first_hash) {
value = (*reinterpret_cast<const int64_t*>(user_key.data()));
} else {
value = MurmurHash(user_key.data(), user_key.size(),
kCuckooMurmurSeedMultiplier * hash_cnt);
}
if (use_module_hash) {
return value % table_size_;
} else {
return value & (table_size_ - 1);
}
}
// Cuckoo Table is designed for applications that require fast point lookups
// but not fast range scans.
//
// Some assumptions:
// - Key length and Value length are fixed.
// - Does not support Snapshot.
// - Does not support Merge operations.
class CuckooTableFactory : public TableFactory {
public:
explicit CuckooTableFactory(const CuckooTableOptions& table_options)
: table_options_(table_options) {}
~CuckooTableFactory() {}
const char* Name() const override { return "CuckooTable"; }
Status NewTableReader(
const ImmutableCFOptions& ioptions, const EnvOptions& env_options,
const InternalKeyComparator& internal_comparator,
unique_ptr<RandomAccessFile>&& file, uint64_t file_size,
unique_ptr<TableReader>* table) const override;
TableBuilder* NewTableBuilder(const ImmutableCFOptions& options,
const InternalKeyComparator& icomparator, WritableFile* file,
const CompressionType, const CompressionOptions&) const override;
// Sanitizes the specified DB Options.
Status SanitizeDBOptions(const DBOptions* db_opts) const override {
return Status::OK();
}
std::string GetPrintableTableOptions() const override;
private:
const CuckooTableOptions table_options_;
};
} // namespace rocksdb
#endif // ROCKSDB_LITE